Although the superior performance of Cu–Zn bimetallic sites toward multicarbon C2+ products has been established, the dynamic surface reconstruction has not been fully understood. Herein, Zn‐doped Cu2O nano‐octahedrons are used to investigate the effect of the dynamic stability by the leaching and redeposition on CO2RR. Correlative characterizations confirm the Zn leaching from Zn‐doped Cu2O, which is redeposited at the surface of the catalysts, leading to dynamic stability and abundant Cu–Zn bimetallic sites at the surface. The reconstructed Zn‐doped Cu2O catalysts achieve a high Faradaic efficiency (FE) of C2+ products (77% at –1.1 V versus reversible hydrogen electrode (RHE)). Additionally, similar dynamic stability is also discovered in Al‐doped Cu2O for CO2RR, proving its universality in amphoteric metal‐doped catalysts. Mechanism analyses reveal that the OHC–CHO pathway can be the C–C coupling processes on bare Cu2O and Zn‐doped Cu2O, and the introduction of Zn to Cu can efficiently lower the energy barrier for CO2RR to C2H4. This research provides profound insight into unraveling surface dynamic reconstruction of amphoteric metal‐containing electrocatalysts and can guide rational design of the high‐performance electrocatalysts for CO2RR.The recognition of the surface reconstruction of the catalysts during electrochemical CO 2O is redeposited at the surface of the catalysts in electrocatalytic CO2 reduction, leading to dynamic stability and abundant Cu–Zn bimetallic sites at the surface, which achieves a high Faradaic efficiency of C2+ products. Similar dynamic stability is also discovered in Al‐doped Cu2O for CO2 reduction, proving its universality in amphoteric metal‐doped catalysts.Zn leaching from Zn‐doped Cu Conversion of CO2 to hydrocarbons and/or oxygenates is a promising strategy to alleviate CO2 emission. Electrochemical CO2 reduction (CO2RR), which converts CO2 into fuels and chemical feedstocks driven by renewable energies, has gained significant attention in the past decades. Among the various products generated from CO2RR, multicarbon (C2+) products  are highly desirable due to their high direct utilization values. However, the CO2RR performance of copper‐based electrocatalysts, the only family of electrocatalysts capable of efficiently generating C2+ products from CO2RR, has been greatly limited by competing hydrogen evolution reaction, C1 products  and slow reaction kinetics.The concentration of carbon dioxide , attributed to the formation of a favorable Cu coordination environment that enhances C–C dimerization. These reports indicate that doping amphoteric metals to Cu could improve the selectivity of C2+ products from CO2RR by providing the abundant Cu‐amphoteric metal sites for C–C dimerization.Various strategies have been employed to enhance the selectivity and activity of Cu‐based catalysts for COrivation,4 crys The process of component leaching and redeposition, which can cause surface reconstructions, has not received adequate attention. For instance, recently, the concomitant leaching and redeposition of the Fe active sites in NiFe‐layered double hydroxides was demonstrated after manipulating both electrode and electrolyte components for electrocatalytic water oxidation, highlighting the effect of dynamic surface stability on the structure–catalytic activity relationship. Nevertheless, such dynamic stability formed by component leaching and redeposition in electrocatalytic CO2RR has been seldom reported. Considering the predominantly used alkaline electrolyte and the higher local pH at the electrode surface during CO2RR operation, the dissolution of the aforementioned amphoteric metals of Zn/Al or amphoteric oxides of ZnO/Al2O3 doped in Cu/Cu2O can be reasonably anticipated, and the underlying corresponding redeposition of these amphoteric metals/oxides could lead to dynamic stability at the surface, which is important for mechanism research but often overlooked in literature.Surface reconstructions of catalysts during electrocatalytic reactions  are ubiquitous and crucial for understanding the real active sites.10 The2O nano‐octahedrons to investigate the dynamic surface reconstruction of catalysts under CO2RR. The leaching and redeposition of Zn in CO2RR form a dynamic stability at the surface of Cu2O through the co‐effect of the strong alkaline electrolyte and applied negative potentials. Meanwhile, the ratio of active Cu0 is increased with the Zn‐rich surface of the dynamically reconstructed catalysts. The presence of Zn in Cu2O can stabilize the Cu0 and provides abundant Cu–Zn sites near the surface of the catalysts through the leaching and redeposition mechanism, which further improves the selectivity of C2+ products for CO2RR. Consequently, the optimized catalyst exhibits a FE of 77% for C2+ products at –1.1 V versus reversible hydrogen electrode . Additionally, the behavior of another amphoteric metal, Al, has also been verified to show similar dynamic leaching and redeposition in Al‐doped Cu2O catalysts during CO2RR, indicating the ubiquity of the dynamic stability of the amphoteric metal‐doped electrocatalysts for CO2RR. In situ attenuated total reflection Fourier‐transform infrared spectroscopy (ATR–FTIR) results and density functional theory (DFT) calculations reveal that the reduction of CO2 to C2H4 occurs via the OHC–CHO pathway on Cu2O and Zn‐doped Cu2O, and the reaction free energy of the rate‐determining step (RDS) on Zn‐doped Cu2O is lower than that on bare Cu2O catalysts, which leads to an improvement in the performance of CO2 reduction to C2H4 formation. These findings provide insights into the surface reconstruction of amphoteric metal‐based electrocatalysts, and suggest avenues for the further development of high‐performance electrocatalysts for CO2RR.Herein, we employ Zn‐doped Cu22O nano‐octahedrons precursor were prepared via low‐temperature chemical synthesis. To optimized the catalysts, the Zn content in the total amount of metals (Zn + Cu) was varied to 1 at%, 5 at% and 25 at% and investigated as Cu2O–Zn‐1%, Cu2O–Zn‐5% and Cu2O–Zn‐25% respectively. The X‐ray diffraction (XRD) patterns of the bare precursor Cu2O and precursor Zn‐doped Cu2O catalysts are presented in Figure 2O. The Raman spectra of precursor Zn‐doped Cu2O  when the doping ratio of Zn increases to 5 and 25 at%. The control sample was also prepared by following the same synthesis protocol without the Cu precursor, and its XRD pattern  with the small peaks of Cu2+ (933.5 eV). In addition, Cu LMM spectra  is dominant in all the as‐prepared catalysts, with only a small amount of metallic Cu0 (918.6 eV) present. Based on the Zn 2p spectra  and Auger electron spectroscopy (AES). The Cu 2p spectra of the four catalysts, depicted in Figures a Figure  further  present.17 Bas2O, Cu2O–Zn‐1%, and Cu2O–Zn‐5% are observed by scanning electron microscopy  are obtained at –1.0 V, and the total current density does not increase when the potential is more negative than –1.0 V due to the mass transport limitations. Eight products from CO2RR are detected, including C2H4, EtOH, CO and H2 etc.  was measured under different potentials after 30 min electrocatalysis by ICP–MS, as shown in Figure 2+ ion concentration in the electrolyte showing a volcano‐type relationship with the applied negative potentials, reaching the peak concentration at –0.7 V. This trend is ascribed to the combined effects of the applied negative potentials and higher local pH at the surface of the electrodes, which are favorable for Zn redeposition and leaching, respectively. Besides, the time‐dependent Zn2+ concentration in electrolyte under the potential of –0.9 V  can be easily dissolved in strong alkaline electrolyte due to its nature as an amphoteric metal (oxide). In this regard, the present study conducted an investigation into the dissolution of Zn during the CO2RR by CuV Figure  also conR Figure  also shom KOH with 0.2 × 10−3m Zn2+ was used as the electrolyte for the bare Cu2O. The deposited Zn onto the electrode was detected by ICP–MS again, and the relative deposition of Zn was calculated by the reduction of Zn2+ concentration in the 1 m KOH with 0.2 × 10−3m Zn2+ electrolyte. Figure 2O after CO2RR confirm the depositional process of Zn2+ in CO2RR as well, supporting the dynamic surface reconstruction of Cu2O–Zn catalysts via the leaching and redeposition of Zn.Moreover, to confirm the expected redeposition of Zn ions at the surface of catalysts in CO2RR, 1 2O–Zn after such leaching and redeposition process in electrocatalysis, the bulk and surface atomic fractions of Cu and Zn before and after CO2RR were detected by ICP–MS and XPS, respectively. As shown in Figure 2O–Zn series catalysts are almost consistent with the nominal fractions. However, the atomic fractions of Zn at the surface are much higher than those of the bulk of the Zn‐doped Cu2O catalysts, indicating that the Zn could be preferentially segregated to the surface, which can be attributed to the surface energy minimization principle by the lower surface energy of Zn. After CO2RR, the atomic fraction of Zn in the bulk decreases slightly, which may originate from the leaching of Zn or ZnO in strong alkaline electrolyte and higher local pH , indicating that a significant portion of Zn have either leaching in the strong alkaline electrolyte or highly dispersed. Notably, the surface chemical states of Cu2O–Zn series catalysts differ significantly from those in the bulk after CO2RR. As shown in Figure 0 on the bare Cu2O and Cu2O–Zn‐1% catalysts after the electrocatalysis, instead, the peaks of Cu+ are dominant at the surface of these two samples, while a small Cu0 peak is present on Cu2O–Zn‐5%, and Cu2O–Zn‐25% displays the highest intensity of Cu0 peak. These data suggest that Zn doping can increase the ratio of Cu0 at the reconstructed surface via the dynamic stability. Moreover, the potential‐dependent Cu LMM spectra  is prepared. As shown in Figure 2O–Zn‐5% shows the higher FE of CO (above 20%) compared with the Cu2O catalyst due to the isolated Zn sites (without Cu–Zn binding), and the max C2+ products selectivity is only 54.2% at –1.1 V. Here, it is noted that the products after a short time of 10‐min electrolysis are collected to avoid the impact of reconstruction. However, after potentiostatic activation at –1.0 V for 1 h, the leaching and redeposition progress of Zn induces the excellent CO2RR performance with a C2+ products FE of 65.5%, much higher than that of the fresh physical‐mixed Cu2O–Zn‐5% and bare Cu2O catalysts  and EDS‐mapping images Figure 5b,c, theR Figure  provideds Figure . At moreproducts,26 so 2O–Zn‐5% catalyst during CO2RR is investigated under different potentials by quasi‐operando XRD . These results reveal the potential for amphoteric metal (oxide) catalysts to provide rich surface bimetallic sites through the dynamic stability of leaching and redeposition, indicating that the electrochemical surface reconstruction of these catalysts cannot be ignored for electrocatalytic reactions.Furthermore, in order to generalize the findings of the dynamic stability of surface reconstruction to other amphoteric metal‐doped catalysts, 5 at% Al‐doped Cu2O–Zn catalyst, in situ ATR–FTIR was conducted to detect the adsorbed intermediates on Cu2O–Zn‐5% during the CO2RR. As shown in Figure −1 corresponds to the stretching vibration of CO2, and the peak around 1617 cm−1 belongs to the deformation band of H2O. With the negative shift of potential, the peaks appeared at 1250 and 1390 cm−1 can be attributed to the OH deformation and C–O stretch of *COOH, respectively, which is generally considered a crucial intermediate in the production of various products. The peak at 2088 cm−1 that emerges with the negative shift of potential is attributed to the C≡O stretching mode of linearly bonded CO species (*COL), showing a trend of first increasing and then decreasing. This result indicates the initial formation of CO intermediates and subsequent transmutation into other hydrocarbons at more negative bias. Moreover, the increased peak of stretching of adsorbed *CHO intermediate (1750 cm−1) suggests that the possible C–C coupling for formation of C2H4 could occur via the OC–CHO pathway or OHC–CHO pathway on Cu2O–Zn‐5% catalyst.To gain further insight into the reaction mechanism on Cud of H2O.28 Wit2O in Figure 2O surface, indicating the charge transferred from Zn to Cu. This can result in the Cu+ reduced to a lower valence state and causing an easier reduction reaction on the Cu site, which agrees well with the XPS result after CO2RR . Similar results are obtained for the Zn‐doped Cu2O catalyst. On the basis of these kinetic energy barriers, it is concluded that the reduction of CO2 to C2H4 primarily occurs via the OHC–CHO pathway.The calculated charge density difference of the Zn‐doped CuR Figure . In ordes Figure . In addi32O nano‐octahedrons are prepared and used for investigating the leaching and redeposition process of the amphoteric metal for CO2RR. Cu2O–Zn‐5% shows excellent activity and selectivity for CO2RR toward C2+ products , while the productions of CO and H2 are significantly inhibited. Moreover, the leaching and redeposition mechanism of Zn, which is influenced by the strong alkaline electrolyte and the reduction potentials, has been confirmed. The reconstructed surface of Zn‐doped Cu2O catalysts provided abundant Cu–Zn sites, as evidenced by the increased surface atomic ratio of Zn. Meanwhile, the ratio of metallic Cu0 in Zn‐doped Cu2O catalysts increases by the increased reconstructed‐surface Zn, leading to more Cu0/Cu+ interfaces and improved selectivity of C2+ products. Similar observations can be made with Al‐doped Cu2O from CO2RR as well. In situ ATR–FTIR and DFT calculations reveal that the C–C coupling processes on bare Cu2O and Cu2O–Zn primarily occur through the OHC–CHO pathway, and the introduction of Zn into Cu could efficiently lower the energy barrier for CO2RR to C2H4. This study not only presents an effective strategy for designing efficient Cu‐based catalysts for CO2RR to C2+ products, but also sheds new light on the surface reconstruction of amphoteric metal‐doped Cu2O catalysts.In this study, Zn‐doped CuThe authors declare no conflict of interest.Supporting InformationClick here for additional data file.


The resulting broad or narrow spans for the energy bands caused by spin states lead to different OAR chemistries. By tuning the Li/Ni antisite defects to be dispersive rather than aggregative, the threshold voltage for triggering OAR is obviously elevated, and the generation of bulk‐O2‐like species and O2 release at phase transition nodes is fundamentally restrained. The OAR is regulated from irreversible to reversible, fundamentally addressing structural degradation and heterogeneity. This study reveals the interaction of the Li/Ni antisite defect/OAR chemistry/chemo‐mechanical heterogeneity and presents some insights into the design of high‐performance NRLO cathodes.Despite the low cost and high capacity of Ni‐rich layered oxides (NRLOs), their widespread implementation in electric vehicles is hindered by capacity decay and O release. These issues originate from chemo‐mechanical heterogeneity, which is mainly related to oxygen anion redox (OAR). However, what to tune regarding OAR in NRLOs and how to tune it remains unknown. In this study, a close correlation between the OAR chemistry and Li/Ni antisite defects is revealed. Experiments and calculations show the opposite effects of aggregative and dispersive Li/Ni antisite defects on the NiO The aspects of oxygen anion redox (OAR) that should be tuned in Ni‐rich cathodes for improved performance and means of doing so is not clearly elucidated. Herein, a basic factor of spin state that influences OAR is discovered. Distinct spin states result from aggregative and dispersive Li/Ni disorder. The mechanism of spin states in tuning OAR chemistry is revealed. A high Ni content enables LiNixCoyMn1−x−yO2 to have a high specific capacity and a low proportion of expensive and toxic Co. However, the critical issues of rapid capacity decay and safety concerns plague this series of cathodes. Following extensive studies, a consensus has been reached that the chemo‐mechanical heterogeneity of grains accounts for electrode failure. Surface reconstruction, uneven Li depletion, intragranular nanopores, and internal void spaces were observed in the oxides. Grey et al. revealed that the lattice strain between the reconstructed surface and bulk layered structure induces the fatigue process of the cathode. Furthermore, the heterogeneity of Ni‐rich layered oxides originates from the inhomogeneous chemical reactions in the cathodes. Efforts have been made to perform surface modification and bulk doping, as well as to realize single‐crystalline particles. Although improvements have been achieved to some extent, the practical electrode performance remains far from satisfactory for large‐scale commercialization, and the underlying mechanism for addressing the heterogeneity and degradation of LiNixCoyMn1−x−yO2 cathodes remains to be clearly elucidated.The widespread implementation of electric vehicles (EVs) is essential for decarbonization, which presently calls for advanced cathodes with low cost and high capacity. Ni‐rich transition metal (TM) layered oxides , correlations between the complex OAR behaviors and cathode heterogeneity have been proven. Issues of O release and phase degradation, spreading from the surface to the bulk of the cathode grains, initiate cathode heterogeneity.17 ThexCoyMn1−x−yO2. Pristine and cycled Ni‐rich cathodes have been proven to exhibit Li/Ni antisite disorders. Extensive research on Li/Ni antisite defects has been conducted, and the detrimental and beneficial effects of Li/Ni disorder have recently been debated. The different effects may be due to the different characteristics of the Li/Ni antisite defects, which were overlooked in these works. Different Li/Ni disorders should have varied effects on the local crystal and electronic structure near the defects, and the overall structural properties of the material will also change accordingly. Previous studies have shown that the microstructure plays an important role in OAR chemistry through band structure regulation. Obviously, Li/Ni antisite defects with specific characteristics should exhibit an influence. However, the relationship between Li/Ni antisite defects with different local structures and the OAR reaction path/reaction rate/reversibility remains unclear. Therefore, it is important to explore the influence mechanisms of specific Li/Ni mixing on the OAR chemistry to realize a fundamental solution for chemo‐mechanical heterogeneity.Li/Ni antisite defects are basic and unavoidable structural defects in LiNi0.8Co0.1Mn0.1O2 with characteristics of aggregative or dispersive Li/Ni antisite defects was designed and synthesized. The OAR was tuned from irreversible to reversible by changing the spin states of the Li/Ni antisite defects. By utilizing both experimental and calculation techniques, the fundamental correlations between the OAR chemistry and Li/Ni antisite defects were fully elucidated for the first time. The aggregative Li/Ni antisite defect shows an elevated Ni spin state and an expanded span for the energy bands. The elevated Ni spin state quickens Ni oxidation and compels some electrons in the O2p band to participate in charge compensation with delithiation. Abundant bulk‐O2‐like species are generated in the lattice at nodes for phase changes of H1→M, M→H2, and H2→H3  with simultaneous O2 gas release and remarkable NiO6 distortions, which contribute to severe heterogeneity. In contrast, Ni exhibits a relatively low spin state in dispersive Li/Ni antisite‐defected LiNi0.8Co0.1Mn0.1O2. O oxidation is largely inhibited by producing only a small amount of (O2)n−. After discharge, (O2)n− was completely reduced to lattice O2−, whereas the bulk‐O2‐like species were only partly reduced to O−. Thus, OAR reversibility and heterogeneity were fundamentally improved. The modulated cathode showed enhanced electrochemical kinetics, a high capacity at 0.1 C (>200 mAh g−1), and good capacity retention at 0.2 C (93.8%@100 cycles). Some insights into the interaction between Li/Ni antisite defect/OAR chemistry/chemo‐mechanical heterogeneity were revealed, shedding light on OAR tuning for high‐performance Ni‐rich cathodes.In this study, LiNi22.10.8Co0.1Mn0.1O2 cathodes are labeled 811‐A and 811‐D, respectively. Precursors with different Ni distributions were designed to synthesize the two cathodes. A schematic of the synthesis process is provided in Figure + etching and elevated the relative Ni content on the surface of the precursor for 811‐D by Ni reprecipitation. Scanning electron microscopy (SEM) images showed that the morphologies of the two precursors were almost identical  was used to probe the compositions of the precursor surfaces. The results showed that the prepared precursors conformed to our design % and 2.39(4)%, respectively. O vacancies appeared in 811‐A but not in 811‐D. This finding is supported by another report that a high Li/Ni antisite defect ratio induces the formation of O defects. The XPS results indicate that the O vacancies were mainly located on the surface of 811‐A, as demonstrated by the shifts in the depth spectra  testing at 4 K, verifies this point  and Ni(Co/Mn)—O stretching (A1g) were observed at Raman shifts of ≈500 and 550 cm−1, respectively. In the LiNixCoyMn1−x−yO2 cathodes, these two peaks widen because of the slightly different peak positions for different TM elements. In Figure −1, a peak representing a cation antisite defect was distinctly observed in the spectrum of 811‐A but not in that of 811‐D. In Figure Raman spectroscopy with different lasers was used to explore 811‐A and 811‐D further at various depths Figure . The detThe surface structural features of the two materials were explored using spherical aberration‐corrected scanning transmission electron microscopy (AC‐STEM). The bright‐spot array represents the TM layer, whereas the interlayer with a dark appearance represents the Li layer. For 811‐D Figure , the ful2.2Figure dQ/dV curves indicate the differences in the redox peaks of the two materials  for the two samples is at the same level in most electrochemical states, except in the charge voltage intervals of 3.7–3.9 and 4.3–4.5 V. This change in DLi+ was related to the different redox behaviors of the two materials. Electrochemical impedance spectroscopy (EIS) was additionally performed to explore the impedance . In the pristine state, the inelastic peak of 811‐A is wider than that of 811‐D, which implies an enlarged energy band span for 811‐A  spectra were used to elucidate the O redox reactions of 811‐A and 811‐D Figure 3a,b, usiFigure 32 All As shown in Figure  A large vibrational frequency implies a strong O—O interaction, which reflects a short O—O distance. The vibrational frequency for 4.5 V charged 811‐A is 0.189 eV (corresponding to 1520 cm−1), whereas that for 4.5 V charged 811‐D is 0.181 eV (corresponding to 1460 cm−1). The O—O interactions and shorter O—O distances of the O oxidized species for 811‐A than for 811‐D are demonstrated by these values. The different vibrational frequencies were verified using Raman spectroscopy n−.The vibrational peaks near 0 eV are caused by the O—O interactions. The amplitudes and frequencies of the vibration peaks convey information about the content and character of the O‐oxidized species.35 As  Figure − in 811‐A. For 811‐D, the elastic peaks are almost identical for the pristine and discharged electrodes, indicating improved reversibility for the O redox. The restrained change in the elastic peaks for the charged 811‐D electrodes verified the alleviated OAR in 811‐D. The elastic peaks and OAR fingerprint peaks indicate a related loss–gain relationship, which can be interpreted as indicating that O holes transform into other oxidized species at a deep charge. This finding is consistent with previously reported theoretical calculations of the lattice O redox path.The relative area of the elastic peak in the O–K‐edge RIXS spectra reflects the O‐hole content.36 FigNext, the soft‐synchrotron X‐ray absorption spectroscopy (XAS) spectra of the O–K‐edge in the total electron yield (TEY) and total fluorescence yield (TFY) modes for pristine and 4.5 V charged electrodes were tested. For the TEY spectra  and Ni(Co/Mn)—O stretching (A1g) peaks reflect the structural features of Ni(Co/Mn)O6 octahedrons. Both materials exhibit broad peaks in the spectra of the pristine electrodes —O, which is derived from the unequal variation of cell parameters a and b. The 3.9 V charged 811‐D maintains a spectral shape similar to that of pristine 811‐D. When charging to 4.5 V, the elevated Eg peak in the 811‐A spectrum indicates that the O—O reverse vibration along the c‐axis is enhanced owing to the shrinkage in parameter c. This finding indicates that with delithiating, 811‐A experiences a faster structural change than 811‐D at depths of ≈100 nm for the particles.A Raman experiment with a 633 nm laser was conducted. To detect the structural properties accurately, multiple points on each sample were selected for testing. The shapes, shifts, and relative intensities of the O—Ni(Co/Mn)—O bending Eg and NiEg and NiEg and Ni evolutions accompanied by (de)lithiation of 811‐A and 811‐D were revealed by Rietveld refinement lithiation was subsequently probed by in situ XRD Figure . A fatigt Figure . Some spFigure The local environment of Ni was probed using XANES spectroscopy Figure 5a,b. A q2‐weighted Fourier transform magnitudes from the XANES results for 811‐A and 811‐D are shown in Figure The k2.512Ni10Mn1Co1O24 model was used to represent 811‐D, and a disordered (Li10Ni2)(Li2Ni8Mn1Co1)O24 model with a periodic Li/Ni disorder‐Li/Ni order‐Li/Ni disorder configuration was used to represent 811‐A. The NiO6 octahedral transformations in Li12Ni10Mn1Co1O24 and (Li10Ni2)(Li2Ni8Mn1Co1)O24 with delithiation were calculated (Li2Ni8Mn1Co1)O24 was more discrete than that in Li12Ni10Mn1Co1O24, which signified greater structural distortion of (Li10Ni2)(Li2Ni8Mn1Co1)O24. This result is consistent with the experimental results. Simultaneously, the evolution of the electronic structure of Li12Ni10Mn1Co1O24 and (Li10Ni2)(Li2Ni8Mn1Co1)O24 with different amounts of intercalated Li was probed through the density of states (DOS).First‐principles calculations were performed to investigate the mechanism of Li/Ni antisite defects in OAR chemistry. For feasible computation, a normal Lid Figure 6a. The N12Ni10Mn1Co1O24 are almost symmetric, which is related to the electron configuration. In total, 90% of Ni cations in Li12Ni10Mn1Co1O24 appear as Ni3+ with an electron configuration of t2g6eg1 in the pristine state. Upon delithiation, they are gradually oxidized to Ni4+ with an electron configuration of t2g6eg0. Under these conditions, the numbers of up‐spin and down‐spin electrons are largely equal, resulting in similar up‐spin and down‐spin states. The up‐spin and down‐spin states of Ni in pristine (Li10Ni2)(Li2Ni8Mn1Co1)O24 are evidently different (Li2Ni8Mn1Co1)O24, a signal of enhanced electron density appears near the Fermi level on the DOS of O, which enhances the electrochemical activity of O. This behavior does not occur for Li12Ni10Mn1Co1O24. Combined with the crystal orbital overlap population (COOP), part of the eg* state near the Fermi level in delithiated (Li10Ni2)(Li2Ni8Mn1Co1)O24 is more intense than that in delithiated Li12Ni10Mn1Co1O24 (Li2Ni8Mn1Co1)O24.Structural distortion influences the electronic structure of materials by affecting crystal field band splitting. As illustrated in Figure Figure eg* band. Owing to the electronic state enhancement at the Fermi level, 811‐A shows deeper Ni oxidation than 811‐D at relatively low charge voltages. Simultaneously, because 811‐A has a longer O2p band span than 811‐D, the Fermi level approaches the O2p band at a lower charge voltage for 811‐A than for 811‐D. Thus, the triggered O2p→Ni eg* charge transfer and resulting O redox reaction appear earlier for 811‐A than for 811‐D. Second, the spin state of Ni influences the structural distortion. Because Ni in the high‐spin state increases the complexity of the structure and charge compensation of 811‐A, a more obvious distortion for 811‐A than for 811‐D is demonstrated with delithiating. In particular, in the phase transitions H1→M, M→H2, and H2→H3, when the lattice displacement is easily formed, the structural distortion is intensified. This phenomenon could causes the O2p band to exceed the Fermi level, leading to sharp O→Ni charge transfer and O2 release and resulting in a structural‐phase‐transition‐dependent OAR. O2 release and abundant bulk‐O2‐like species are observed in the H1→M, M→H2, and H2→H3 phase transitions in 811‐A. The O2 release and structural degradation finally account for the severe chemomechanical heterogeneity of the cathode. This result supports that of a previous study that indicated that lattice displacement is the cause of the lattice O reaction. Dispersive Li/Ni disorder does not significantly influence the NiO6 octahedron, which restrains the OAR during phase transitions by reducing the intertwining between the O2p and eg* states.Based on the above results and discussions, a full understanding of the interactions of the Li/Ni antisite defect/OAR chemistry/chemo‐mechanical heterogeneity was obtained, as shown in The form of Li/Ni disorder (dispersive or aggregative) and degree of Li/Ni disorder are difficult to discuss separately. When the Li/Ni disorder degree is high, the Li/Ni mixing defects appear in an aggregated state, whereas when the Li/Ni disorder degree is low, the Li/Ni mixing defects appear in a dispersed state. Owing to the significant effect on the structure, electronic state changes caused by the aggregative Li/Ni disorder appear, inducing the production of high‐spin‐state Ni and ultimately promoting the OAR during charging and discharging. However, the electronic state changes caused by dispersive Li/Ni disorder are diluted by the surrounding chemical environment and thus cannot be fully manifested. Therefore, dispersive Li/Ni disorder does not promote the OAR.36 distortion and obvious competitive electron stripping between the O2p and eg* bands occurred at nodes for the H1→M, M→H2, and H2→H3 phase changes. This behavior contributed to the abundant generation of bulk‐O2‐like species and O2 gas release in the corresponding states, which led to severe heterogeneity. In contrast, 811‐D exhibited a restrained OAR with dispersive Li/Ni antisite defects and a relatively low Ni spin state. O oxidation was restricted by the production of a small amount of (O2)n−. After discharge, (O2)n− was completely reduced to lattice O2−, whereas the bulk‐O2‐like species were only partly reduced to O−. Thus, OAR reversibility and heterogeneity were fundamentally improved. Enhanced electrochemical kinetics, a high capacity at 0.1 C (>200 mAh g−1), and a good capacity retention at 0.2 C (93.8%@100 cycles) were delivered by 811‐D. This study revealed the critical functional mechanisms of different Li/Ni antisite defect characteristics on the OAR chemistry and chemo‐mechanical heterogeneity of LiNi0.8Co0.1Mn0.1O2. The insights regarding the importance of modulating Li/Ni antisite defects in tuning the OAR chemistry and restraining heterogeneity are applicable to other Ni‐rich layered cathodes as well.In this work, we revealed a correlation between the OAR chemistry and Li/Ni antisite defects in Ni‐rich oxide cathodes for the first time. Distinct OAR chemistry was demonstrated using a cathode with aggregative or dispersive Li/Ni antisite defects. The characteristics of Li/Ni antisite defects play a decisive role in influencing the OAR chemistry by varying the Ni spin states and energy band spans. Specifically, 811‐A with aggregative Li/Ni antisite defects and an elevated Ni spin state exhibited an enlarged energy band span. Upon delithiation, severe NiO42C2O4·2H2O  was dissolved in 80 mL distilled water to serve as the precipitating agent solution. It was added dropwise into an aqueous solution (50 mL) containing 0.08 mol NiSO4·6H2O , 0.01 mol CoSO4·7H2O , and 0.01 mol MnSO4·5H2O  with stirring. A green precipitate was obtained and washed with distilled water three times and with ethanol twice. Drying the green powder yielded the 811‐D precursor.To prepare the precursor for 811‐D, coprecipitation with a single precipitation time was adopted. First, 0.08 mol H4·6H2O and 0.001 H2C2O4·2H2O were re‐fed into the solution for the second precipitation. Washing and drying the green powder yielded the 811‐D precursor.To produce the precursor for 811‐A, coprecipitation with two precipitations was adopted. The first precipitation event was the same as that described above. After the formation of the green precipitate, 0.001 NiSO2O . The mixed powders were calcined at 900 °C for 12 h in air.To form the 811‐D and 811‐A, the precursors of 811‐D and 811‐A were each uniformly mixed with 5% beyond the stoichiometric amount of LiOH·H The morphology of the samples was observed with a scanning electron microscope (Hitachi SU8010). The valence states of the elements in the samples were probed by X‐ray photoelectron spectroscopy . A HORIBA LabRAM Odyssey was used to collect Raman spectra with wavelengths of 532 and 633 nm. An aberration‐corrected scanning transmission electron microscope JEM ARM200F  equipped with two CEOS  probe aberration correctors was used to probe the structure at the atomic scale. The X‐band electron spin resonance spectra were obtained by a Bruker E500 spectrometer at 4 K. Time‐of‐flight secondary ion mass spectrometry analysis was conducted on a PHI nanoTOF II Time‐of‐Flight SIMS with a 30 keV Bi analysis ion beam. The chemical compositions of the materials were measured by an inductively coupled plasma optical emission spectrometer (Agilent 730). DEMS was conducted using a cell with gas inlet and outlet ports. Ar carrier gas was flown at a constant rate (0.2 mL min−1) through the cell and into a quadrupole mass spectrometer (Hiden HPR‐20).The XRD data were collected using an X‐ray diffractometer . The neutron powder diffraction experiments were conducted on an MPI from China Spallation Neutron Source (CSNS).42 The−2. The electrolyte consisted of 1.15 m LiPF6 in ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate (1:2:2 vol%). A Celgard 2400 was used as the separator. The cells (CR2025) were assembled in an Ar‐filled glove box . Galvanostatic charging and discharging tests were performed using the NEWARE system. The cells were tested in an electrochemical window of 3.0–4.5 V (vs Li/Li+) unless otherwise stated. EIS and GITT were performed using an electrochemical workstation (Auto Lab). The 1 C capacity was defined as 200 mA g−1.The electrochemical performance of the samples was tested using CR2025 coin cells. First, 80 wt% active material, 10 wt%), super P carbon (10 wt%), and polyvinylidene fluoride were mixed evenly with N‐methyl pyrrolidinone. The slurry was deposited on Al foil and dried under a vacuum at 110 °C for 12 h. The typical loading of the active material was 2.5–3.0 mg cm The hard XAS experiments were performed at beamlines 4B9A and 1W1B of the Beijing Synchrotron Radiation Facility. A double‐crystal monochromator was used in this study. The metal foil was measured before the XAS measurements to ensure that the data were calibrated in the case of any drift in the monochromator position. The electrodes were measured in transmission mode. Soft XAS was conducted at beamline 02B02 of Shanghai Synchrotron Radiation Facility (SSRF).The RIXS data were collected at the PEAXIS beamline of the synchrotron BESSY II at Helmholtz‐Zentrum Berlin.43 Theπ × 0.04 Å−1 was adopted for the Uniform G‐centered k‐point meshes and Methfessel–Paxton electronic smearing. A cut‐off energy of 500 eV was used for the simulation. Convergence of the total energy to within 1 meV per atom was ensured. Structural relaxation continued until the atomic force was less than 1 meV Å−1, and the total stress tensor was within 0.01 GPa of the target value. The Coulomb interactions of the on‐site were described by calculating all the elementary reaction steps using the DFT+U approach, and the U terms of Mn‐3d, Ni‐3d, and Co‐3d were 5.0, 7.0, and 5.5 eV, respectively. The crystal orbital overlap population was calculated using the LOBSTER package with the same parameters used in the DOS calculations.The density functional theory (DFT) calculations were performed using the Vienna Ab initio simulation package. The exchange and correlation functions were described by the generalized gradient approximation function with Perdew–Burke–Ernzerhof. A resolution of 2The Li/Ni disorder degrees for the surfaces of 811‐A and 811‐D were obtained from the peak area ratio of the line intensity in the Li layer/line intensity in the TM layer. The line intensities for the Li and TM layers were obtained from randomly selected areas of the Li and TM layers in the aberration‐corrected scanning transmission electron microscopy images using Digital Micrograph software.The authors declare no conflict of interest.Supporting InformationClick here for additional data file.


Pour sand into a container and only the grains near the top surface move. The collective motion associated with the translational and rotational energy of the grains in a thin flowing layer is quickly dissipated as friction through multibody interactions. Alternatively, consider what will happen to a bed of particles if one applies a torque to each individual particle. In this paper, we demonstrate an experimental system where torque is applied at the constituent level through a rotating magnetic field in a dense bed of microrollers. The net result is the grains roll uphill, forming a heap with a negative angle of repose. Two different regimes have been identified related to the degree of mobility or fluidisation of the particles in the bulk. Velocimetry of the near surface flowing layer reveals the collective motion of these responsive particles scales in a similar way to flowing bulk granular flows. A simple granular model that includes cohesion accurately predicts the apparent negative coefficient of friction. In contrast to the response of active or responsive particles that mimic thermodynamic principles, this system results in macroscopic collective behavior that has the kinematics of a purely dissipative granular system. Kinetic energy put into a granular medium as a collective is typically dissipated as friction. The situation is different when forces are applied to the individual particles. An experiment now shows that when torques are applied to particles in a dense bed of microrollers, the grains roll uphill. Note that dipole interactions are not referring to those typically seen on the colloidal scale, but instead refer to the macroscopic dipole of the magnetic material forming the cap of each particle. The impact of increasing the effective interparticle particle friction by increasing magnetic strength, (β/β0)2 > 1, is detailed below. The frequency of magnet rotation, Ω, is chosen within the wide range of rotation rates for which the observed phenomena do not deviate greatly from that reported herein. Also important, the rolling velocity of a single microroller in dilute conditions is independent of the field strength  ≈ 0.45 which is a direct measure of particle friction. The dynamic angles of repose of microrollers, plotted as—tan (θ) vs. (β/β0)2, display two distinct regimes 2 just above 1, these samples have vanishingly thin flowing layers and take a very long time to reach steady state (Supplementary Movie θ). Experiments with increasing values of (β/β0)2 causes the magnitude of tan (θ) to reach a minimum negative value (β/β0)2 ≈ 9. This is a result of the increased fraction of mobile/fluidised particles as the fluidised fraction χ → 1 2 beyond the point where χ = 1, the magnitude of the uphill dynamic angle of repose increases. This transition coincides closely with the point at which the degree of fluidisation in the bed is 1 (Supplementary Movie β/β0)2 ~ 9, as indicated by the greyscale colourmap of the data points in Fig. Δ/2a = 9.5, where the fluidised layer formed has a thickness equal to that of the depth of the bed at (β/β0)2 ~ 2.9–3.5 where the stress associated with the particle-wall interactions at the bottom of the bed likely play a more significant role. Movies of the fluidisation fraction and flow motion for (β/β0)2 ≪ 9 (Supplementary Movie β/β0)2 < 9 (Supplementary Movie β/β0)2 > 9 2 and bed depths. The velocity measured at the midpoint of the free surface is scaled by single particle rotation rate, vx/2aΩ, and plotted against the normalised depth into the sample, y/2a, with the uphill direction defined as positive values of vx  of steady-state heaping was performed at varying field strengths, 0.5 5 The driving force in this study, localised torque introduced at the particle scale, and for microroller “critters” has been demonstrated as a linear combination of rotation rate producing a constant local shear, similar to that observed in Fig. Δ/2a, and all field strengths, excluding the strongest magnetic field, (β/β0)2 = 29, were collapsed with For gravity driven flows, it is common to scale the velocity by the driving force, }γ° Fig. . Note thβ/β0)2 increases for low field strength and plateaus to 18. For small (β/β0)2, the flowing layer thickness is very small, thus transporting very little material uphill. This analysis is for the top-most layer of flow rather than the transition regime deeper within the granular bed where normal stress increases, eventually resulting in stagnation deep in the granular bed. These particles at the free surface experience essentially no granular pressure from above and can move in a more synchronized motion with the magnet. Combining the results of Fig. 19 has developed a constitutive equation that relates the coefficient of friction to the shear rate,μmax and μmin are the maximum and minimum angles observed, I is the inertia number I0 is a fitting parameter for the observed plateau in the coefficient of friction. In the topmost regime of the flowing layer where changes in σyy are small and ρ is roughly constant, μ(I) rheology simplifies to a Bagnold profile with a linear dependance on μmax and μmax are the maximum and minimum angles observed for each depth. The lone fitting parameter in this system, α, is used to scale the magnitude of cohesion due to dipole-dipole attractions, proportional to (β/β0)2. Figure α = 7.6 × 10−3. Cohesion is necessary to overcome lubrication force imparted between freely rotating particles. Similar to active systems that can demonstrate negative viscosity20, this system has a negative coefficient of friction. Energy is injected at the microscale, resulting in local shear that is dissipated in the resulting kinematics that follow granular behaviour.From Fig. Alternatively, with a higher field strength, the flowing layer is deeper and there is more local dissipation through frictional contacts. The work associated with the flow of these rolling particles is larger because of the weight of the granular media through the flowing layer. The plateau of 22. The observed flowing layer arises from imparting internal stress conditions at the particle-level rather than large-scale stresses from body and surface forces on the bulk and boundaries of the granular bed. This suggests an ergodic set of reversed cause-effect relationships could exist between driven and dissipative systems21.In summary, the emergent behaviour observed from imparting torque on individual particles is the granular behaviour as is expected in gravity driven flows. A rotating set of magnets imparts localised torque that results in particle rotation. Importantly, this suggests that the responding macroscale stress and related kinematics of a broader class of responsive systems on the granular scale could be described using the insights already obtained for gravity-driven flows. This localised control of particle scale torque allows for a robust set of experimental controls of granular behaviour that could only be considered in simulations where fictitious physical forces could be imparted on the system. The negative coefficient of friction that includes cohesion accurately predicts the negative angle of repose. This result also shines light on the broader consideration of local vs. nonlocal stress in granular media38–53 µm  polymethyl methacrylate microparticles were purchased from syringia lab supplies. 190 Proof ethanol was purchased from Fisher.4 ×1000 G neodymium magnets (60  ×10 × 3 mm) were purchased from MIKEDE. Imaging was performed with a USB Jiusion WIFI Digital Microscope F210. Programmable Lego-EV3 and motor. A PTFE stoppered Cuvette  was purchased from FireFlySci. Kindle E-reader purchased from Amazon. Table-mounted supports and brackets were purchased from ThorLabs. Magnetic field strength was measured with a Senjie SJ200 Teslameter, accuracy 1%, precision 0.1 mT.23. The dried films were coated with 100 nm of Fe by physical vapour deposition using an Eddy SC 20 E-Beam Evaporator. PMMA coatings were placed in the evaporation chamber with Fe pellets, then sealed and held at high vacuum . The cap thickness was monitored in-situ with a calibrated crystal balance. The resulting Fe capped Janus particle films had 100 nm coatings on the exposed hemispheres. Film substrates were cut into small sections and sonicated in ethanol for 10 s to remove the Janus particles. The ethanol was subsequently evaporated to leave dried magnetic Janus particles.Sub-monolayer films of 38–53 µm  diameter PMMA particles were prepared on a roll-to-roll scale by automated Langmuir-BlodgettSee Janus particles were suspended in a small amount of ethanol in a clean glass vial. A magnet was used to separate Janus particles from any uncoated PMMA particles as well as dust. The ethanol, uncoated particles and dust were removed using a glass pipette and replace with fresh ethanol. This process was repeated 4 times to ensure samples were clean. Janus particles were then dried in a weighing boat and subsequently 5 samples were prepared with increasing masses of Janus particles suspended in ethanol (2 mL).h = 25, 27.5, 30, 32.5, 35, 37.5, 40, 42.5, 45 and 60 mm from the magnet surface. hmax = 60 mm. The rotation rate of the magnetic wheel was set to 1.2 rpm, equivalent to 2.4 Hz (cycles) (1 rotation = 4 N–S pole switches). When the magnetic rotation was activated, the system was allowed to reach a steady-state or until 3 ×105 ° of rotation was attained. Subsequently, a 10 srecording at steady-state was taken. All slope analysis and PIV was performed on the 10 s steady state recordings. The distance between the cuvette and the magnetic surface was the only parameter changed between measurements and samples, with cuvette position and orientation fixed for all experiments, and the motorized magnet moved further/closer with the use of an adjustable height stand.Before every sample loading, the magnet was centred at 0° (North). Samples were transferred to a glass cuvette and were subsequently loaded into the experimental apparatus and allowed to settle for 2 min at the maximum height of the set-up. Samples were then agitated with a vibrating motor to give a flattened granular bed. The distance measured was from the base of the cuvette  pixel ROI was cropped parallel to the heap surface in the steady-state. These were saved as image sequences. Velocity flow fields were generated using PIVLab scripts in MatlabSupplementary InformationPeer Review FileDescription of Additional Supplementary FilesSupplementary Movie 1Supplementary Movie 2Supplementary Movie 3Supplementary Movie 4Source Data


The increased importance of RNA‐based therapeutics comes with a need to develop next‐generation stimuli‐responsive systems capable of binding, transporting and releasing RNA oligomers. In this work, we describe triazolium‐based amphiphiles capable of siRNA binding and enzyme‐responsive release of the nucleic acid payload. In aqueous medium, the amphiphile self‐assembles into nanocarriers that can disintegrate upon the addition of esterase. Key to the molecular design is a self‐immolative linker that is anchored to the triazolium moiety and acts as a positively‐charged polar head group. We demonstrate that addition of esterase leads to a degradation cascade of the linker, leaving the neutral triazole compound unable to form complexes and therefore releasing the negatively‐charged siRNA. The reported molecular design and overall approach may have broad utility beyond this proof‐of‐principle study, because the underlying CuAAC “click” chemistry allows bringing together three groups very efficiently as well as cleaving off one of the three groups under the mild action of an esterase enzyme. Self‐assembled triazolium‐based amphiphiles lose the ability to bind siRNA upon addition of esterase, due to the degradation of the polar head group and conversion to a neutral triazole. After a bumpy road paved with hopes and failures, patients can today benefit from small interfering RNA (siRNA) drugs1, 2 aThe success of these RNA‐based therapeutics relies largely on the development of lipid nanoparticle nanovectors such as micelleplexes12, 13However, these multi‐component formulations must be preserved at (ultra)low temperatures for storage and distribution to preserve their structure  biodegradable lipid nanoparticles that degrade at the acidic pH found in late endosomes or in the intracellular reductive environment,38, 39Herein, we report the synthesis of amphiphiles with positively charged triazolium head groups that self‐assemble into vesicular structures and are able to complex siRNA. After addition of a stimulus (here: esterase) the polar head group of the amphiphiles degrades irreversibly by forming a neutral triazole and siRNA gets released.A wide range of self‐immolative linkers have been used in stimuli‐responsive drug delivery systems.51, 52The first consideration when designing the specific self‐immolative linker was the choice of a stimulus for its cleavage. We decided to use porcine liver esterase as trigger due to its commercial availability and overexpression of esterases in cancer cells.59, 606, C8, C12 or C14) containing either one or no unsaturated bond, resulting in three compounds: 6TC6C, 8’TC12C and 14TC12C  exhibited the highest CAC (2.5±0.1 mM), which we deemed too high for the purposes of drug delivery. Due to their longer hydrophobic tails, compounds 8’TC12C and 14TC12C did however show CACs three orders of magnitude lower , which is why we pursued these two compounds further. The addition of siRNA  did not have a pronounced effect on the CAC (Table S1).To study the aggregation behavior of the compounds, the critical aggregation concentration (CAC) was determined  was performed to obtain the average size of the aggregates, and ζ‐potential measurements indicated on the surface charge of those nanoassemblies. Solutions of the compounds in PBS at concentrations higher than the CAC (30 μM) revealed nanoassemblies with a hydrodynamic diameter of 173±25 and 185±5 nm and ζ‐potentials of 35.0±5.6 and 33.4±3.3 mV, for 8’TC12C (210 μM) and 14TC12C (300 μM) into spherical assemblies with diameters of 140–280 nm  and 160–375 nm (14TC12C) was confirmed by transmission electron microscopy (TEM) . Confocal fluorescence microscopy using a lipophilic styryl membrane dye showed, at concentrations of 300 μM in Dulbecco's Modified Eagle Medium (DMEM), the formation of spherical aggregates of average diameter around 900 nm for 8’TC12C and somewhat larger, less well‐defined aggregates for 14TC12C . Further, 14TC12C showed less ability to be stained compared to 8’TC12C. It needs to be noted that the average size of the nanocarriers lies below the detection limit of optical microscopy and therefore the consistent DLS and TEM data are more reliable regarding (average) size.The aggregation of compounds 8’TC12C and 14TC12C (above the CAC) and from 210 to 840 μM for 6TC6C (below the CAC). Both 8’TC12C and 14TC12C showed partial complexation of siRNA at N/P=5 and a complete complexation was found at N/P=10  at different N/P ratios (molar ratio of positively‐charged triazolium nitrogen atoms per negatively‐charged phosphodiester in siRNA). The final concentration of the triazolium compounds ranged from 21 to 210 μM for 8’TC12C and 14TC12C (see below), thereby indicating that siRNA complexation has little effect on the size and surface charge of the nanoassemblies, suggesting that the load preferentially fills their inner volume which is predetermined by the amphiphilic self‐assembly of the triazolium compounds. In support of this conclusion, the determination of the CAC in presence of siRNA showed no changes , confirming the absence of any templating role of the siRNA in this case.DLS and ζ‐potential analyses showed nanoassemblies formed at N/P=10 with hydrodynamic diameters of 182±36 and 184±25 nm, and ζ‐potentials of 34.3±4.7 and 25.3±4.2 mV, for 8’TC12C aggregates were treated with labelled siRNA. Striking differences in the complexation mode of siRNA were detected, however, between 8’TC12C and 14TC12C, with superficial binding dominating with 8’TC12C (suggesting liposome structure) and internal binding occurring with 14TC12C (suggesting nanoparticle structure).The morphologies of the siRNA complexes were visualized by confocal fluorescence microscopy using a fluorophore‐labeled siRNA Figure . No sign8’TC12C and 14TC12C in the absence and presence of esterase. We chose porcine liver esterase (4 Units per μmol triazolium), PBS buffer (pH 7.2) as solvent, and the temperature was set to 37 °C. After four hours, the organic compounds were extracted from the aqueous phase using ethyl acetate and a 1H NMR spectrum was recorded after removal of the solvent  to 7.23 (a’) ppm. Additionally, the signal of the benzyl moiety (b) at 5.67 ppm decreased and a new peak at 4.61 ppm arose, which can be attributed to the formation of 4‐hydroxybenzyl alcohol (b’). The ratio between triazolium 8’TC12C and triazole 8’T*C12C appears to be 15 : 85 – hence an 85 % conversion of the enzymatic reaction is deduced. It should be noted, that a full conversion is not necessarily needed to realize our release concept, because any concentration of residual triazolium below the CAC will lead to disintegration of the aggregates. When the reaction was performed using 14TC12C, only a conversion of around 8 % was observed, even when the reaction was run for 24 h . In light of the kinetic profile observed by NMR spectroscopy, gel electrophoresis and ethidium bromide displacement assay (see below), we propose that the triazole compound 14T*C12C with longer tails leads to product inhibition. Notably, in all four reactions the signal corresponding to the triazolium proton shows a slight shift compared to the starting material  due to counterion exchange during the reaction. In all cases, the signal corresponding to the methyl group of the mesylate counterion has disappeared .Upon addition of esterase, however, new peaks occurred in the 8’TC12C and 14TC12C with siRNA (N/P=10) were treated with esterase (4 U/μmol) and incubated at 37 °C for different time intervals. After four hours, only a weak siRNA release was observed when using 14TC12C. However, in the case of 8’TC12C a complete release of siRNA was reached already after 30 minutes  was added to a solution of siRNA (0.5 μM) and EthBr (5 μM) in PBS to obtain a final concentration of the triazolium compounds of 210 μM (above CAC). A significant decrease of the fluorescence emission intensity was observed over a period of three hours, when the compounds were added as a DMSO solution . Hence, when DMSO is used as a solvent, the rate of either nanoparticle assembly or siRNA complexation is slowed down. In these assays, we observed no pronounced difference in the complexation ability between compounds 8’TC12C and 14TC12C, which is in line with the results obtained by gel electrophoresis (see above).SiRNA complexation and release were further studied by a fluorescence displacement assay with ethidium bromide (EthBr). The dye shows high fluorescence emission at 590 nm upon intercalation into siRNA. The addition of an siRNA complexing agent leads to a decrease of the emission due to the expulsion of EthBr. A dimethyl sulfoxide (DMSO) solution of compound n Figure . When ch8’TC12C. Of note, typically an intensity increase would be expected in such an assay, because the release of siRNA should lead to regeneration of the EthBr/siRNA complex. We propose that our finding of decreased emission upon siRNA release is due to the precipitation of the triazole products 8’T*C12C and 14T*C12C which could remove the EthBr dye effectively from the solution . Given the molecular structures, it is reasonable to assume that the flat EthBr dye would co‐precipitate with the triazole compounds. As a control experiment, we measured the fluorescence of the EthBr/siRNA complex in the absence of the amphiphile and found that the intensity was not changing when adding esterase to the complex . Overall, the EthBr assay is valuable as a complement to gel electrophoresis, because it shows in real time that siRNA release is completed after 15 to 30 minutes. Such a kinetic profile is of interest, because it matches the process of maturation of endosomes in endocytotic cell penetration.In contrast, differences between both compounds were found when studying siRNA release. Even though the kinetics of siRNA release were almost identical in both reactions (completion after 15 minutes), the outcome was different. The decrease of fluorescence intensity was much more pronounced with 8’TC12C, DLS showed a strong decrease in size (hydrodynamic diameter of 2.1±0.4 nm) along with negligible ζ‐potential (−1.03±0.97 mV), which is in agreement with the 85 % enzymatic transformation of the cationic triazolium into the neutral triazole 8’T*C12C  were added to the pre‐assembled aggregates, thus confirming that only amphiphile 8’TC12C undergoes effective esterase‐induced disassembly and therefore allows the release of siRNA.To complete this proof‐of‐principle study, the esterase‐induced transformations were monitored by DLS and ζ‐potential measurements Table . After i6TC6C) showed a CAC too high to be relevant in drug delivery, two other compounds (8’TC12C and 14TC12C) exhibited micromolar CACs and were therefore studied in more detail. While both compounds showed similar siRNA complexation behavior, the siRNA release was much more efficient for compound 8’TC12C. We propose that the reason for this finding is that the two long aliphatic chains in the lipophilic product 14T*C12C lead to product inhibition, for instance via persistent binding to the esterase's active site. Product inhibition on the same magnitude was not observed for compound 8’TC12C, in which one aliphatic chain is only roughly half as long (C8 vs. C14). This delivery system may therefore allow the selective release of siRNA in cells showing a high concentration of esterase, for example in cancer cells. Future work will focus on mixed compositions with additional phospholipids, fine‐tuning of lipophilicity and in vitro studies.We report the design of a new type of amphiphile that is accessible via CuAAC “click” reaction and features a positively charged triazolium head group capable of the formation of self‐assembled nanocarriers and thereby the complexation of siRNA. At the polar head group, a self‐immolative linker is attached to a triazolium moiety in such a way that addition of esterase leads to the formation of a neutral triazole compound that is unable to form aggregates and therefore releases the siRNA load. Whereas one specific compound  should be addressed to the authors.Supporting InformationClick here for additional data file.


It was analyzed by UV‐Vis, NMR, IR and Raman spectroscopy. Its crystal structure was redetermined by X‐ray diffraction, and its space group was corrected to Pnma. Quantum‐chemical calculations were performed for the band assignment of the vibrational spectra. A monoclinic polymorph of BrF5 was quantum chemically predicted and then observed as its low‐temperature modification in space group P21/c by single crystal X‐ray diffraction. BrF5 reacts with the alkali metal fluorides AF  to form alkali metal hexafluoridobromates(V), A[BrF6] the crystal structures of which have been determined. Both compounds crystallize in the K[AsF6] structure type . For the species [BrF6]+, BrF5, [BrF6]−, and [IF6]−, the chemical bonds and lone pairs on the heavy atoms were investigated by means of intrinsic bond orbital analysis.BrF Taking a closer look: We present the photochemical synthesis of BrF5, its high‐ and low‐temperature crystal structures, its reactions with some alkali metal fluorides and a discussion of the free valence electron pairs on the bromine atoms of the BrF5 molecules and [BrF6]− anions by using intrinsic bond orbitals. The existence of the hypothetical BrF7 molecule has not yet been proven as attempts of a further oxidation of BrF5 resulted in the formation of the [BrF6]+ cation known for the compounds [BrF6][AsF6] and [BrF6][Sb2F11].Bromine pentafluoride is one of the most reactive halogen fluorides, probably outperformed in its reactivity only by ClF3.4, 5 B53 at 473 K in a platinum or copper vessel . To the best of our knowledge, the crystal structure of BrF5 represents a new structure type. The formation of oligomeric molecular structures, as known for other pentafluorides such as MoF5 (mS48), that is rings of Mo4F20, RuF5 (mP48), differently shaped Ru4F20 rings, or AuF5 (oP48), Au2F10 dimers, does not occur., are formed  is already known,6] and Rb[BrF6] have not been reported. Suitable crystals of these compounds were obtained by slow cooling of a saturated solution of the respective alkali metal fluoride in BrF5 warmed to about 373 K in an air bath.While the crystal structure of Cs[BrF6] and Rb[BrF6] crystallize isotypic to Cs[BrF6]6] structure type in the trigonal crystal system, space group R3‾, with the lattice parameters a=7.4450(14), c=7.287(2) Å, V=349.80(17) Å3, Z=3, at T=100 K for K[BrF6] and a=7.576(3), c=7.568(5) Å, V=376.2(4) Å3, Z=3, at T=100 K for Rb[BrF6]. The compounds have already been studied by Bougon and co‐workers using powder X‐ray diffraction methods,R3‾and R3‾m have been proposed. Accordingly, two possible structure types were considered, the K[AsF6] type in R3‾and the Ba[SiF6] type in R3‾m. We can clearly exclude space group R3‾m as a refinement of the crystal structures in that space group leads to a striking elongation of the displacement ellipsoids of the fluorine atoms perpendicular to the m mirror plane. The crystal structure of the compounds in space group R3‾is shown in Figure 6] as an example. Details of the structure solutions and refinements are given in Table K− anion with point group symmetry S6. As already discussed by Seppelt and co‐workers for the crystal structure of Cs[BrF6], the lone pair of the Br atom within the [BrF6]− anion seems to show no stereochemical activity.b, 3‾.) are 12‐fold coordinated by fluorine atoms in a cuboctahedron‐like environment.The bromine atoms reside on position 3a 3‾. and ar6]− anions of Cs[BrF6] of 1.854(1) Å by X‐ray diffraction on single crystals and 1.847(1) Å by powder neutron diffraction.6] and 1.8623(15) Å for Rb[BrF6], respectively, and quantum chemically calculated a Br−F bond length of 1.868 Å for the [BrF6]− anion in the gas phase and of both circa 1.864 Å for the calculated crystal structures of K[BrF6] and Rb[BrF6]. While the observed Br−F bond lengths agree within the tripled standard uncertainties for the Rb and Cs compounds, the Br−F bond length is slightly longer in the determined crystal structure of the K compound. The observed bond lengths agree with those quantum chemically calculated for the solids and the Br−F bonds are longest in the gas‐phase [BrF6]− anion, as may be expected.Seppelt and co‐workers observed a Br−F bond length within the [BrF6]− anion shows ideal octahedral symmetry, the selected F−Br−F bond angles within the [BrF6]− anions of the quantum chemically calculated crystal structures of K[BrF6] and Rb[BrF6] are 91.77° and 91.30°, respectively. Therefore, observed and quantum chemically calculated values agree. Based on these findings we conclude that the influence of the K+ cations on the molecular structure of the [BrF6]− anions is seemingly the strongest and weakest for the Cs+ cations, as might have been expected on the basis of Pearson's concept of hard and soft acids and bases.Observed selected F−Br−F bond angles are 91.79(6)° within the potassium, 91.47(8)° within the rubidium, and 90.8(1)° within the cesium compound (91.3° by powder neutron diffraction). While the calculated gas‐phase [BrF6] and Rb[BrF6], three bands were observed corresponding to the Raman active vibrations of the octahedron‐like [BrF6]− anion. The Raman spectra are shown in Figure The bulk phases of the samples were analyzed by Raman spectroscopy. For both, KBrF and Rb− molecules, population analyses were carried out at the DFT‐PBE0/TZVP level of theory by using intrinsic atomic orbitals (IAOs) and the bonding was analyzed with the aid of IBOs.− anion in hO symmetry, that is, an “ideal” octahedron is obtained with no signs of stereochemical activity of the Br lone pair. The Br atom shows a positive partial charge of +2.32 e− which is by 0.04 e− lower compared to the Br atom within the BrF5 molecule. The F atoms show negative partial charges of −0.55 e−. Figure 6]− anion.Quantum‐chemical calculations lead to a true local minimum for the [BrF6]− anion become even more polarized compared to the BrF5 molecule and the Br atom no longer contributes with its 4 s orbital to the Br−F bonds but only with its p orbitals. The lone pair of the Br atom is completely 4 s‐like and therefore shows the absence of any stereochemical activity.The Br−F bonds in the [BrF6]+ cation, where there is no Br lone pair, for comparison and found a true local minimum for hO symmetry, as expected from the literature.[We calculated the [BrF6]+ cation the Br−F bonds are less polarized in comparison to [BrF6]− and also in comparison to the BrF5 molecule. The contribution of the Br 4 s orbital to the Br−F bond has increased to 37 %.In the [BrF6]+, BrF5, and [BrF6]−, the F atoms always contribute more or less the same to the Br−F bonds, circa 11 % with their 2 s and about 89 % with the respective 2p orbital. The 4 s orbital contribution to the Br−F bonds goes from 37 % in the [BrF6]+ cation down to 20 % for Br−Fap and 3 % for Br−Feq in the BrF5 molecule, and reaches 0 % in [BrF6]−. The 4p orbital contributions follow the inverted trend, the Br−F bonds are strongest p‐like in [BrF6]− and least in [BrF6]+.For the species discussed here, [BrF6]− anion had been discussed previously by different researchers. Christe and co‐workers reasoned well‐founded that “in a rigid molecule the space requirement of a sterically active free valence electron pair slightly exceeds that of a fluorine ligand”,6]− are not octahedral as there is enough space around the I atom for the lone pair to become active because I atoms can adopt coordination numbers up to eight with F ligands, for example, in [IF8]− anions. “In [BrF6]− there is little or no room left for a seventh ligand and, therefore, the free valence electron pair should be sterically inactive” they concluded.The stereochemical inactivity of the lone pair of the Br atom within the [BrF6]− anion shows that its molecular structure is not a local minimum in point group hO. Following the imaginary mode of 39i cm−1 leads to molecular structures in point groups Cv2 and sC that are also no local minima. Finally, a true local minimum in point group C1 is reached, and overall the energy lowered by 14 kJ mol−1 compared to the ideal hO symmetry. The IBOs of the I lone pair and the I−F bonds of the [IF6]− anion in its energy minimum are shown in Figure A quantum‐chemical calculation of the [IFx orbital contribution. It therefore shows some stereochemical activity in contrast to the Br lone pair of the [BrF6]− anion. Both reasons for the stereochemical inactivity of the Br lone pair of the [BrF6]− anion given by Seppelt or Christe are valid and in agreement with our quantum chemical findings.The I lone pair is essentially 5 s‐orbital‐like with 93 % 5 s and 7 % 5p5 was synthesized at room temperature by the photochemical reaction of BrF3 with F2. UV‐Vis spectra of BrF5 and F2 were recorded to identify the region of suitable wavelength, 300 to 400 nm, to photodissociate F2 but not the product BrF5. BrF5 can be obtained in yields above 90 % with respect to the starting material BrF3 and pure on the basis of NMR, IR and Raman spectroscopy. NMR spectra of BrF5 were taken at various temperatures. Quantum‐chemical calculations aided in the determination of the new low‐temperature modification and allowed the band assignment of the recorded IR and Raman spectra. By treating BrF5 with KF and RbF, crystals of the compounds K[BrF6] and Rb[BrF6], respectively, were obtained and their crystal structures determined. The chemical bonds and the lone pairs on the Br atoms within the molecules [BrF6]+, BrF5, and [BrF6]− were investigated by using intrinsic bond orbitals. These show that the contribution of the 4 s orbitals of the Br atoms to the Br−F bonds decreases to zero in the octahedral [BrF6]− anion where the Br lone pair is purely 4 s‐orbital‐like. In the [IF6]− molecule, which is not octahedral, the 5p orbitals contribute to the I lone pair, making it stereochemically active.BrFGeneral: All operations were performed on a Monel metal Schlenk line, which was passivated with fluorine and ClF3 at various temperatures and pressures before use. The alkali metal fluorides were purchased from Merck, purified according to literature procedures,−3 mbar) at circa 393 K for several times and then filled up to a pressure of 4 bar with diluted F2  for 16 h in order to saturate the polymer with fluorine.Reaction vessels were made out of fluoropolymer  and sealed with a bellows valve made out of Monel or stainless steel. The vessels were baked out in vacuum  must be handled with appropriate protective gear with ready access to proper emergency treatment procedures in the event of contact. The aforementioned are potent oxidative fluorinators that are only stable under the rigorously anhydrous conditions employed in the experimental procedures outlined in the Experimental Section. They react vigorously to explosively upon hydrolysis or contact with organic materials. The utmost precautions must be taken when disposing of these materials and their derivatives.5 in PFA vesselsPreparation of BrF: When only small amounts of BrF5 around 1 g are required, the reaction can be performed in a reaction vessel with a volume of 50 to 80 mL made out of PFA or FEP and equipped with a stainless‐steel valve.3 was loaded into the reaction vessel (V=74 mL) and diluted fluorine  was added. After irradiating the reaction mixture with a UV LED  for 6 h, the reaction vessel was cooled to 77 K and all volatiles were pumped off. The vessel was then allowed to warm to room temperature and diluted fluorine  was added again. This process was repeated for three times. After the third addition of F2 a slight excess (5.37 mmol) with respect to Br was reached. The liquid completely decolorized upon irradiation, which can be attributed to the absence of BrF3. Bromine pentafluoride  was obtained as a colorless liquid. As BrF5, like ClF5,For a typical synthesis 692 mg (5.08 mmol) BrF5 in a stainless‐steel reactorPreparation of BrF: For the preparation of larger amounts of circa 60 g BrF5 per batch, a stainless‐steel (1.4571) reactor  and undiluted fluorine  was added. The reaction mixture was irradiated with a UV LED  for 12 h during which the pressure dropped to circa 400 mbar. The F2 pressure was then again increased to 1 bar and the process was repeated until the reaction mixture completely decolorized after 9.5 d of irradiation. Bromine pentafluoride  was obtained as a colorless liquid.r Figure  with sapPreparation ofA6]  : Samples were filled and sealed in quartz capillaries inside the glovebox and were then placed under the Raman microscope for data acquisition.Infrared spectroscopy: The gas‐phase IR spectrum of BrF5 was recorded on a Bruker Tensor 37 FTIR with a resolution of 4 cm−1 using a passivated measuring cell manufactured from 316 L stainless steel, equipped with diamond or BaF2 windows. IR spectra of solids were recorded on a Bruker alpha FTIR spectrometer using the ATR Diamond module with a resolution of 4 cm−1. The spectrometer was located inside a glovebox (MBraun) under argon atmosphere. The spectra were processed with the OPUS software package.Single‐crystal X‐ray diffraction: A crystal of K[BrF6] or Rb[BrF6], respectively, was selected under pre‐dried perfluorinated oil (Fomblin YR‐1800) and mounted using a MiTeGen loop. Intensity data of a suitable crystal were recorded with an IPDS 2 diffractometer (Stoe & Cie). The diffractometer was operated with MoKα radiation  and equipped with an image plate detector. In case of K[BrF6], split reflections were observed for several crystals, which indicated non‐merohedral twinning. Evaluation, integration and reduction of the diffraction data was carried out using the X‐Area software suite.F2 (SHELXL‐2018/3).[6] only the non‐overlapping reflections of the major twin component were used. The data were initially refined with the HKLF5 format option in SHELXL‐2018/3 with all reflections (overlapping reflections and non‐overlapping reflections of three twin components).3‾and the overlapping reflections were merged in point group 1. The final refinement was carried out against the detwinned dataset (created by SHELXL with the LIST 8 option as an FCF file and converted to an HKL file with HKLF5Tools).For the structure solution of K), 2193269 (for HT‐BrF5 at 200 K), 2193270 (for HT‐BrF5 at 150 K), 2193271 (for LT‐BrF5), 2193272 (for HT‐BrF5 at 180 K), 2193273 (for Rb[BrF6])2193268  in Debye‐Scherrer geometry. The diffractometer was operated with CuKα1radiation  and equipped with a MYTHEN 1 K detector. The sample was cooled to 180 K using a capillary cooling system (Osford Cryosystems). Diffraction data of the resulting polycrystalline material were collected in eight subsequent runs in a range of 15 to 71 °2θ with an irradiation time of 80 s per 1°. Due to ice formation on the surface of the capillary during the measurement only the first tree runs were used for the refinement.5 was frozen directly inside of the capillary, making it impossible to grind the sample before measurement. Therefore, various different directions of crystal growth are to be expected. The same phenomenon was observed when trying to obtain single crystals of the compound. In this case, the preferred orientation was also clearly visible in the diffraction image . The geometry of CFCl3 was also optimized and it was used as the NMR reference species for 19F NMR chemical shifts. The 19F NMR chemical shift calculations were carried out at the optimized geometries with weighted core‐valence basis sets (cc‐pwCVTZ).−, COF2, and COF3− at the CCSD(T)/cc‐pVTZ level of theory and used the COF2 reference system with an experimental FIA of 208.08 kJ mol−1 to estimate the FIA at an absolute scale.5, Rb[BrF6], and K[BrF6] were investigated with hybrid density functional methods (DFT‐PBE0) and K[BrF6] the experimental setup of T=298.15 K and λ=532 nm was considered. For the simulation of the spectra a pseudo‐Voigt band profile (50 : 50 Lorentzian/Gaussian) with a FWHM of 8 cm−1 was used. Assignment of the vibrational bands was done with the visualization tool CRYSPLOT.All solid‐state calculations were performed with the CRYSTAL17DFT‐PBE0)71, 72The authors declare no conflict of interest.1As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re‐organized for online delivery, but are not copy‐edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors.Supporting InformationClick here for additional data file.


It is revealed that the Ru‐O‐Fe1 structure is formed between the atomically dispersed Fe atoms and the surrounding Ru sites through electron interaction, and this structure could act as the ultra‐high activity driving force center of oxygen reduction/evolution reaction (ORR/OER). Specifically, the Ru‐O‐Fe1 structure enhances the reaction kinetics of ORR to a certain extent, and optimizes the morphology of discharge products by reducing the adsorption energy of catalyst for O2 and LiO2; while during the OER process, the Ru‐O‐Fe1 structure not only greatly enhances the reaction kinetics of OER, but also catalyzes the efficient decomposition of the discharge products Li2O2 by the favorable electron transfer between the active sites and the discharge products. Hence, LOBs based on FeSA‐RuO2/HPCS cathodes show an ultra‐low over‐potential, high discharge capacity and superior durability.It is significant to develop catalysts with high catalytic activity and durability to improve the electrochemical performances of lithium‐oxygen batteries (LOBs). While electronic metal‐support interaction (EMSI) between metal atoms and support has shown great potential in catalytic field. Hence, to effectively improve the electrochemical performance of LOBs, atomically dispersed Fe modified RuO 2 is designed as an efficient catalyst for Li‐O2 battery. The Ru‐O‐Fe1 structure formed in this catalyst changes the coordination environment of Ru sites and modulates the electronic structure, thus promoting the growth and decomposition of Li2O2 and significantly enhancing the kinetics of oxygen reduction reaction/oxygen evolution reaction reaction.Based on the electronic metal‐support interaction criterion, an atomically dispersed Fe‐modified RuO Recently developed rechargeable Li‐O2 batteries (LOBs) have attracted extensive attention and research due to their extremely high theoretical energy density (≈3500 Wh kg−1), and it even considered as an ideal power system for new electric vehicles. In general, a typical LOB consists of a lithium metal anode, a separator, a porous O2 cathode, and an organic electrolyte with dissolved organic/inorganic lithium salts. It is generally believed that the high specific energy of LOBs comes from the electrochemical reaction between reaction gas (O2) and lithium ions on the cathode surface . As the main region of discharge–charge reaction, the pore structure, catalytic activity and durability of O2 cathodes can directly determine the electrochemical performance of LOBs to a large extent. In terms of the cathodes, however, there are some challenges that need to be addressed in order to make LOBs practical. Among them, the slow oxygen reduction reaction/oxygen evolution reaction (ORR/OER) kinetics, and the insulated and insoluble discharge products Li2O2, are the most intractable and pressing challenges. Hence, cathodes with ultra‐high catalytic activity and durability can often significantly improve the electrochemical performance of LOBs. Moreover, the ideal LOBs cathode materials should have high specific surface area and appropriate pore structure to provide enough channels and space for ion/gas transport and discharge products accumulation. So the development of cathodes with high catalytic activity, durability and suitable pore structure is of great significance for the practical application of LOBs.Nowadays, growing of the market for electric vehicles and various electronic products has stimulated the development of efficient and sustainable energy conversion and storage technologies.2, 32 catalysts with rutile structure exhibit excellent catalytic activity for LOBs and ability to regulate the growth pathway of discharge products, so RuO2 is recognized as the benchmark catalyst in LOBs and has been widely studied. But objectively speaking, the ORR/OER catalytic activity and durability of RuO2‐based catalysts still have room for improvement. Recently, some reports claim that the incorporation of transition metals can modulate the intrinsic electrocatalytic properties of metal oxides by improving its reactive electron surface distribution/coordination environment. This is mainly due to the interaction between the introduced component and the support material that regulates the electronic structure at the catalyst surface, and this phenomenon is known as the electronic metal‐support interaction (EMSI) or strong metal‐support interaction (SMSI). Many reports have shown that catalysts based on EMSI/SMSI criterion designs tend to show increased catalytic activity/durability and powerful functionality. For example, Xin et al. found that SMSI between Ru nanoparticles and MoO3 could optimize the electronic structure on the surface of Ru nanoparticles, thus enhancing the catalytic activity and selectivity of the catalyst for CO2 hydrogenation. Hou et al. demonstrated that W atoms deposited on the surface of PdO nanoparticles could form Pd‐O‐W1 structure, so as to optimize the oxygen activation pathway and reaction mechanism of methane combustion at low temperature. Using the electronic interaction between Mn atoms and RuO2, Zhou et al. identified the single atom Mn site and the modulated Ru site as excellent ORR and OER active sites respectively, which enabled the Zn‐air battery based on this catalyst to display extraordinary electrochemical performance. Although the catalysts designed based on EMSI/SMSI criterion have been successfully used in many fields, there are few reports on LOBs. Hence, it is significant to study the practicality and application potential of catalysts designed based on SMSI/EMSI criterion in LOBs field.RuO studied.23 But2 nanoparticles (NPs) and forming a Ru‐O‐Fe1 structure. The obtained catalyst is supported by hierarchical porous carbon shell (HPCS), and marked as FeSA‐RuO2/HPCS. Experimental results not only confirm the atomic dispersion of Fe species on FeSA‐RuO2 NPs, but also clearly analyze the interactions between the introduced Fe atoms and RuO2. These interactions including the formation of Ru‐O‐Fe1 structure, redistribution of the surface electronic structures, the elongation of Ru—O bond and the change of coordination environment of Ru atoms. Density functional theory (DFT) calculation is used to deeply understand the mechanism of FeSA‐RuO2/HPCS cathode in LOBs. For the ORR process, compared with RuO2, the doping of Fe atom leads to a slight negative shift in the d‐band center of the FeSA‐RuO2, which further results in its anti‐bonding orbital being lower than the Fermi level (Ef), thus weakening the adsorption of O2 and LiO2 on FeSA‐RuO2. The moderate adsorption energy of the FeSA‐RuO2/HPCS cathode for O2 and LiO2 can optimize the growth pathway of discharge products, at the same time, the Ru‐O‐Fe1 structure can also improve the reaction kinetics of ORR. While during the OER process, the Ru‐O‐Fe1 structure can significantly improve the reaction kinetics of OER and reduce the resistance of O2 and LiO2 in the desorption process. In addition, there is a strong favorable electron transfer between the Ru‐O‐Fe1 structure and the discharge products Li2O2, these factors together promote the efficient decomposition of the discharge products during the charging process. Therefore, LOBs based on FeSA‐RuO2/HPCS cathodes exhibit extraordinary electrochemical performances, including an excellent round‐trip efficiency, high discharge capacity and impressive cycle life (232 cycles). Additionally, FeSA‐RuO2/HPCS cathodes also exhibit amazing durability during battery operation. This work not only reveals the beneficial effect of electron interaction between Fe atoms and RuO2 on ORR/OER, but also confirms the great potential of catalysts designed based on EMSI/SMSI criterion in LOBs.Hence, a novel strategy is proposed in this work, which can deposit atomically dispersed Fe atoms onto ultrafine RuO2 as the cathode of Li‐O2 or Li‐CO2 batteries, HPCS have advantages such as hollow spherical shell with thin shell, abundant pore and 3D cross‐linking structure, which can provide a large number of fast channels for gas/ions and have enough space to store discharge products. Subsequently, HPCS supported Ru NPs are prepared by liquid‐phase reduction method, and a small amount of Fe(acac)3 is added to deposit atomically dispersed Fe species on the surface of Ru NPs (FeRu NPs/HPCS). Finally, the FeRu NPs/HPCS sample is calcined in air for 30 min at 250 °C to obtain FeSA‐RuO2/HPCS. The whole synthesis process is as observed in Figure3, three FeSA‐RuO2/HPCS samples  with different Fe content are prepared. In addition, Fe2O3/HPCS and RuO2/HPCS samples are also synthesized for comparison. The surface morphology of these samples is identified by the scanning electron microscopy (SEM) technique . TEM images confirm the semi‐open spherical shell and thin shell characteristics of HPCS  and (211) planes of rutile RuO2, respectively  and (100) planes,33 resSA‐RuO2/HPCS sample in detail. Among the three samples with different Fe contents, FeSA‐RuO2/HPCS containing 0.19 wt% Fe species show the best catalytic activity for LOB (see below), so select it for HAADF‐STEM test. As observed in FigureSA‐RuO2 NPs are tightly and evenly loaded on the carbon shell. The particle size of FeSA‐RuO2 NPs ranges from 2 to 8 nm, and some NPs are slightly agglomerated. The aberration‐corrected HAADF‐STEM (AC‐HAADF‐STEM) images show that some dark spots (highlighted in red circles) are dispersed on the surface of bright RuO2 NPs, which should be attributed to the atomically dispersed Fe atoms  and therefore appears as dark spots. EDX elemental mapping is also performed to analyze the elemental distribution of the FeSA‐RuO2/HPCS sample. As expected, the high‐magnification EDX analysis results also indicate that Fe species are atomically dispersed in the FeSA‐RuO2/HPCS samples  and energy‐dispersive X‐ray (EDX) elemental mapping techniques are used to further analyze the microscopic morphology of the Fes Figure . Accordis Figure . Notably4+ (463.39 and 486.08 eV) for RuO2/HPCS. And with the increase of Fe content in FeSA‐RuO2/HPCS, the binding energy of each peak has more and more obvious negative shift, as shown in Figure 2, resulting in an increase in the electron density of the Ru sites in FeSA‐RuO2. The O 1s XPS spectra  and hydroxyl group, respectively, as shown in Figure 2O3/HPCS . Remarkably, due to the low content of Fe, no Fe 2p related XPS signals in the three FeSA‐RuO2/HPCS samples . The Ru 3p XPS spectra  was carried out to probe the electronic state and coordination environment of Fe and Ru elements. As the Fe K‐edge X‐ray absorption near edge structure (XANES) profiles observed in FigureSA‐RuO2/HPCS situates between those of FePc and Fe2O3, confirming the presence of Fe species with valance between +2 and +3. While the Ru K‐edge XANES results show that the absorption edge position of Ru element in FeSA‐RuO2/HPCS is slightly lower than that of RuO2  k2‐weighted extended X‐ray absorption fine structure (EXAFS) spectra in R space. The EXAFS spectra of FeSA‐RuO2/HPCS , which is caused by the bonding of the doped Fe atom and the surrounding Ru atoms with the same O atom. In addition, it is also observed that the bond length of the Ru—O bond (1.53 Å) in FeSA‐RuO2/HPCS is slightly stretched compared to commercial RuO2 (1.50 Å), which contributes to charge redistribution on FeSA‐RuO2.To further understand the interactions of Fe species and RuO2 Figure . This inS Figure  exhibitsa Figure . This scSA‐RuO2/HPCS. Due to the WT contour plots with intensity maximums located at coordinates of  are closely related to the path length R and atomic number Z, WT‐EXAFS spectra could provide momentous clues for identifying coordination structures. As shown in Figure SA‐RuO2/HPCS shows an intensity maximum at , which is very close in both wave vector k and bond length R relative to Fe2O3 , indicating that Fe species are mainly anchored to FeSA‐RuO2 NPs by Fe‐O bond. Moreover, Fe2O3 also has an apparent maximum intensity attributed to the Fe—Fe bond at , while FeSA‐RuO2/HPCS does not, which further confirms the atomic dispersion of Fe species. And as observed in Figure SA‐RuO2/HPCS shows an intensity maximum at , but the abscissa value representing the path length R is obviously different from RuO2 , which further confirmed that the introduction of Fe species changed the Ru‐O bond length. Note that, in RuO2 sample, a peak attributed to the Ru—Ru bond (Ru‐O‐Ru structure in RuO2) is shown at , while in FeSA‐RuO2/HPCS sample, this peak is missing, but a new peak appears at , which should be attributed to the Ru‐Fe bond (Ru‐O‐Fe1 structure in FeSA‐RuO2 NPs). The corresponding fitting curves of EXAFS spectra of FeSA‐RuO2/HPCS in R space and k space are shown in Figure SA‐RuO2/HPCS sample is about 2.01 Å, which is longer than the mean Ru—O bond distance of RuO2 sample (1.98 Å). To sum up, the overall analysis of XPS and XAS results indicate that the introduced Fe species are atomically dispersed and formed a Ru‐O‐Fe1 structure on FeSA‐RuO2 NPs. In addition, the introduction of Fe atoms increases the electron density of the Ru sites in RuO2, and slightly stretches the Ru—O bond.Wavelet transform (WT) analysis is further conducted to study the Fe and Ru K‐edge EXAFS oscillations of Feructures.39 As SA‐RuO2 NPs, the formation energies of Fe atoms at different positions in RuO2 crystal structure are analyzed by DFT simulations. It is shown that, of all possible locations, Fe atoms are most likely to be anchored on FeSA‐RuO2 NPs by replacing the Ru sites on the surface of RuO2 crystals due to thermodynamic advantages , which is also confirmed by the discharge–charge over‐potential in Figure −1 current density and 500 mAh g−1 cut‐off capacity, LOBs based on HPCS, Fe2O3/HPCS, and RuO2/HPCS cathodes show over‐potentials of 1.71, 1.16, and 0.83 V, respectively , Fe2O3/HPCS (17 004 mAh g−1), and HPCS (6391 mAh g−1) cathodes. In addition, the Coulomb efficiencies of LOBs based on HPCS and Fe2O3/HPCS cathodes are 33.14% and 71.52%, respectively, while both RuO2/HPCS and FeSA‐RuO2/HPCS cathodes achieve Coulomb efficiencies of 100% at a low charging potential. It is worth noting that the terminal charging potential of the RuO2/HPCS cathode is 4.20 V, while the terminal charging potential of the FeSA‐RuO2/HPCS cathode is only 3.80 V. Even under higher current densities (300 mA g−1), FeSA‐RuO2/HPCS retained a satisfactory depth discharge capacity (16 202 mAh g−1), while the discharge capacity of other cathodes decreased sharply  and the first‐cycle terminal over‐potential is only 0.68 V, as shown in Figure SA‐RuO2/HPCS cathode always show highest discharge potential and lowest charge potential than other cathodes in the same cycle period. Even at the 232th cycle, the terminal charge potential is only about 4.0 V. The impressive cyclic stability not only further confirms the excellent catalytic activity of FeSA‐RuO2/HPCS cathode for LOBs, but also indicates its outstanding durability. To further highlight the catalytic activity and durability of FeSA‐RuO2/HPCS cathode, the electrochemical performances of LOBs based on FeSA‐RuO2/HPCS cathode were compared with some reported RuO2‐based and single atom catalysts‐based LOBs, as shown in Figure SA‐RuO2/HPCS cathode show electrochemical performances that far exceed those previously reported.Cycle stability is recognized as one of the most important criteria to measure the electrochemical performance of LOBs,44 so Figure2O3/HPCS, RuO2/HPCS, and FeSA‐RuO2/HPCS cathodes all present similar cross‐linked semi‐open carbon shell morphology . The discharge products on FeSA‐RuO2/HPCS cathode coexist in two forms, making the space inside the carbon shell more fully utilized, which perfectly explains why the deep discharge capacity of FeSA‐RuO2/HPCS cathode is much larger  under the same conditions, as shown in y Figure . Accordie Figure . Accordir Figure . In the S Figure .2O2 (JCPDS 07–0115) appeared on all the cathodes, and the corresponding diffraction peaks disappeared after recharged. It is noteworthy that although the four cathodes discharge at the same cut‐off capacity, their diffraction peaks intensity of discharge products shows significant differences. Specifically, the diffraction peaks intensity of discharge products Li2O2 is in the order of HPCS > Fe2O3/HPCS > RuO2/HPCS > FeSA‐RuO2/HPCS, which indicates that the discharge products on the FeSA‐RuO2/HPCS cathode has the worst crystallinity. The results of the high‐resolution Li 1s XPS spectra of the different cathodes after discharge also show that the proportion order of the amorphous discharge products (Li2O2‐x) is FeSA‐RuO2/HPCS > RuO2/HPCS > Fe2O3/HPCS > HPCS  are more likely to be catalyzed during OER process than that of well‐crystallinity discharge products (Li2O2). Corresponding electrochemical impedance tests confirmed that the impedance values of all cathodes increased significantly after discharge and returned to near original values after charging (except for HPCS cathodes), as observed in Figure 2O3/HPCS, RuO2/HPCS, and FeSA‐RuO2/HPCS cathodes , the ratio of the transferred electrons to the gas in the OER process should be 2:1, and O2 should be detected as the only gaseous product. However, the obvious CO2 gas product were detected in LOBs based on HPCS and Fe2O3/HPCS cathodes during OER, implying that more unsatisfied reactions are occurring. In stark contrast, LOBs based on RuO2/HPCS and FeSA‐RuO2/HPCS cathodes, only O2 is detected and more O2 is released on the FeSA‐RuO2/HPCS cathode, indicating that it has the best catalytic activity for LOBs among these cathodes.Then, XRD and XPS measurements were used to further investigate the composition of the discharge products on different cathodes. As shown in Figure allinity.20 The As for Fe2O3/HPCS cathode, after 10 cycles, some fine granular discharge products can be observed on its surface , only trace discharge products residues were observed on its surface  were still observed on the FeSA‐RuO2/HPCS cathode, further highlighting the excellent durability of this catalyst  used in this work were basically consistent with previous work, and the electrochemical properties and discharge products of LOBs based HPCS cathodes are also very close to our previous work, only catalytic components loaded on HPCS were considered. Hence, to simulate the active sites of Fe2O3/HPCS, RuO2/HPCS and FeSA‐RuO2 /HPCS cathodes in LOBs, three models  were established. By comparing the adsorption energy (ΔEAds) of the reaction gas O2 and the reaction intermediate LiO2 at different catalytic active sites, the reason for the difference in the morphology of the discharge products at different cathodes was analyzed. Figure2 and LiO2). It was found that the adsorption energy of Fe2O3, RuO2, and Ru‐O‐Fe1 for the reaction gas O2 are −1.18, −1.49, and −0.99 eV, respectively, while their adsorption energies for reaction intermediate LiO2 are −1.63, −1.49, and −0.60 eV, respectively. In LOBs field, the adsorption energy of catalysts for reactants  has a great influence on the growth pathway of discharge products. For active sites Fe2O3 and RuO2, both of them have high adsorption energy for O2 and LiO2, so discharge products of Fe2O3/HPCS and RuO2/HPCS cathodes tend to form sheet‐like Li2O2 through the surface‐adsorption growth pathway , as observed in Figure 2O3 site and Li2O2*, the electron transfer between RuO2 and Ru‐O‐Fe1 sites and Li2O2* is much stronger, and there is a clear cyan region (electron density loss) around Li2O2*. Specifically, for the adsorbed Li2O2*, Fe2O3 tends to transfer a small number of electrons (0.01 e) to Li2O2*, which is undoubtedly not conducive to the conversion process of Li2O2*. While adsorbed Li2O2* tends to transfer its electrons to the active sites RuO2 and Ru‐O‐Fe1, and the number of electron transfer between Ru‐O‐Fe1 and Li2O2* (0.10 e) is larger than that between RuO2 and Li2O2* (0.06 e). The increased electron transfer indicates that during charging, adsorbed Li2O2* can transfer its electrons to the active site of Ru‐O‐Fe1 more efficiently and promote the conversion process from Li2O2* to LiO2*, thus greatly enhancing the reaction kinetics on the active site Ru‐O‐Fe1. We also calculated the charge transfer between the active sites and the reaction intermediate LiO2* (adsorption state), as shown in Figure 2* and the active sites Fe2O3, RuO2, and Ru‐O‐Fe1 is −0.64, −0.50, and −0.45 eV, respectively. Although these active sites tends to transfer electrons to LiO2*, the charge transfer between Ru‐O‐Fe1 and LiO2* in the three active site models is the smallest, which further supports the best catalytic activity of FeSA‐RuO2/HPCS cathode.It has been reported that in many electrocatalytic reaction systems,59 ele2 and Ru‐O‐Fe1 sites, the spin‐resolved density of states (DOS) of Fe2O3, RuO2, and FeSA‐RuO2 are calculated , which is not conducive to its adsorption. Furthermore, according to the partial density of states, the introduction of Fe atoms regulated the DOS of RuO2, so Fe atoms significantly contributed to the valence band and conduction band of the FeSA‐RuO2 system.To reveal the physical origin of the difference in catalytic activity between RuOd Figure . It is fi level EF, which i level EF, which 2O2)2 clusters at different over‐potentials for the three models. Then, the theoretical over‐potential obtained from gibbs free energy was studied and their catalytic activity was further analyzed. Here, UDC, UC, and UEQ represent discharge voltage, charge voltage and equilibrium potential, respectively. Discharge (ORR) and charge (OER) over‐potential are defined as ΔORR = UEQ − UDC and ΔOER = UC − UEQ, respectively. While the overall over‐potential is defined as ΔO = UC − UDC. For active site Fe2O3, the calculated ΔORR/ΔOER value is 1.07/1.38 V , high discharge capacity (23 628 mAh g−1) and impressive cycle life (232 cycles). The potential factors of the extraordinary catalytic activity and durability for FeSA‐RuO2/HPCS cathode are generalized as follows. First, the atom‐dispersed Fe atoms form Ru‐O‐Fe1 structure through electron interaction with RuO2, and improve the electron distribution of the original RuO2. Second, Ru‐O‐Fe1 sites optimize the morphology of discharge products and accelerate the decomposition of the discharge products by modulating the adsorption energy of the reactants (O2 and LiO2). Third, favorable electron transfer between the Ru‐O‐Fe1 sites and the discharge products can promote the decomposition of Li2O2. Last, the Ru‐O‐Fe1 sites as the powerful driving force center can significantly enhance the ORR/OER reaction kinetics of LOBs. This work not only confirms the feasibility of the catalysts designed based on EMSI criteria in LOBs field, but also provides some reference value for the design of LOBs catalysts with extraordinary catalytic activity and durability.In summary, RuOThe authors declare no conflict of interest.Supporting InformationClick here for additional data file.