Owing to the synergistic effects of ultrastable substrate of 1D sodium titanate (NTO) nanowires, high‐capacity promoter of 2D MoS2 nanosheets as well as the 2D conductive carbon matrix, the resulting 1D/2D–2D hybrid demonstrates excellent high‐rate capacity and super‐durable cyclability, delivering a stable capacity of up to 425.5 mAh g−1 at 200 mA g−1. Even at an ultrafast charging/discharging process within 80 s, the capacity can be maintained at 201 mAh g−1 after 16 000 cycles with only 0.0012% capacity loss per cycle, one of the best high‐rate capacities and cyclabilities for NTO‐based hybrid composites. The present work highlights the designing protocol of hierarchical nanoarchitectures with stable substrate and high‐capacity electrodes for next‐generation energy storage applications.There is an ever‐increasing demand for rechargeable batteries with fast charging, long cycling, high safety, and low cost in new energy storage systems. Herein, a heterogeneous architecture composed of MoS However, the insulating nature and relatively sluggish reaction kinetics limit the electrochemical performances of layered sodium titanates. Several strategies have been adopted to solve those shortcomings, including nanostructuring, hydrogenation, and compositing with carbon materials. Compared with bulk materials, nanosized materials, especially 1D nanostructure, can shorten ionic diffusion path, improve the contact area between electrode and electrolyte, as well as relieve the stress caused by structural volume expansion during electrochemical reactions, leading to high‐rate capacity and cyclability enhancement.With the rapid development of electronic vehicles (EVs) all around the world, the limited lithium reserves could not support the huge revolution process from fuel vehicles to EVs. 2 ≤ n ≤ , such as2, as a typical conversion‐type anode, has been widely studied for high‐capacity Li+ and Na+ storage.2, as well as conductivity enhancement with some carbonaceous materials is advisable for ideal advanced anodes, but it is still a great challenge.Layered MoS2 nanosheets coupled with carbon nanosheets. The as‐resulting core/shell NTO/MoS2‐C composite possessed multiple structural features. For one thing, the 1D layered sodium titanates act as stable core substrates and the epitaxially aligned MoS2–carbon coupled interface nanosheets can effectively enlarge the capability of Na+ storage; for another, external 2D carbon heterogeneous structures not only can prevent the aggregation of 1D NTO substrates and high‐capacity promoter MoS2, but also improve the electronic conductivity of the whole nanoarchitectures. As a result, the nanocomposites exhibit significantly enhanced sodium ion storage compared to pure NTO nanowires. Qualitative leap in specific capacities shows about 10 times improvement at 200 mA g−1, and 30 times improvement at 8000 mA g−1. Even at ultrafast charging/discharging process within 80 s (8000 mA g−1), the novel architecture can sustain more than 16 000 cycles with merely 0.0012% capacity loss per cycle, demonstrating it could be an ideal high‐rate and long‐cycling host for SIBs. This work would give an enlightenment by designing hierarchical architectures with stable substrates and high‐capacity electrodes for next‐generation energy storage applications.In this work, we rationally designed and synthesized a hierarchical core/shell nanoarchitecture composed of 1D NTO nanowires core and MoSFigure2Ti2O5·H2O) substrate can be synthesized by a simple hydrothermal process.2Ti2O5·H2O nanowires exhibit a large length‐diameter ratio. Then, heterogeneous architectures assembled by 1D Na2Ti2O5·H2O/2D‐Mo‐polydopamine (PDA) nanosheets (denoted as Na2Ti2O5·H2O/Mo‐PDA) can be fabricated by a polymerization process , and the 2D–2D Mo‐PDA were densely packed on the surface of 1D Na2Ti2O5·H2O substrate. Finally, phase transformation and carbonization processes were performed via thermal treatment. During this process, the core Na2Ti2O5·H2O nanowires converted into sodium titanate, and the external Mo‐PDA nanosheets simultaneously transformed to MoS2 nanosheets and conductive‐carbon nanosheets, leading to the formation of core/shell hybrids (denoted as NTO/MoS2‐C).2‐C was initially analyzed by X‐ray diffraction (XRD). As shown in Figure2Ti9O19 phase (JCPDS No. 33‐1293) and MoS2 phase (JCPDS No. 75‐1539). There are no obvious signals about other species. It is proposed that the 2D carbon precursor is grown on the surface of NTO during the polymerization process, and then convert to conductive carbon nanosheets during calcination process. According to elemental analysis from inductively coupled plasma mass spectroscopy (ICP‐MS), the contents of MoS2 and NTO in NTO/MoS2‐C are 33.4 and 41.3 wt%, respectively. It is rational to believe that the content of the carbon species is about 25.3 wt%. In addition, typical D peak (1360 cm−1) and G (1560 cm−1) peaks in Raman spectroscopy analysis  further indicate an amorphous feature of the carbon structure.The phase composition of NTO/MoS2‐C were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is clearly to see that rambling nanosheet‐like structures are uniformly grown around the NTO nanowires  crystal planes of MoS2 . Linear scanning analysis . In XPS full spectrum  and 3d5/2 peaks (229.6 eV) are both consistent with the Mo (IV) oxidation state of MoS23/2 (161.8 eV) and S 2p1/2 band (162.8 eV) can be assigned to S2− in MoS2.s spectrum  as well as a relatively low coulombic efficiency (CE) of about 61.8% . The reversible reductive peaks ≈0.7 V and below 0.5 V could be mainly attributed to the initial intercalation of Na+ into the MoS2 interlayer (Equation 1), and the conversion reaction from NaxMoS2 into metallic Mo nanoparticles and Na2S2 (Equation 3),2S to S.2 and NTO. However, based on the CV curves of pure NTO materials , it is obvious that the peaks at 0.2 and 0.6 V correspond to the redox couple of Ti4+/Ti3+ during sodiation/desodiation process (Equation 4).[qv: 3b] After the second scan, the peak position and peak shape of the CV curves were well maintained and overlapped, indicating an excellent electrochemical reaction reversibility in the electrochemical process. The reversible electrochemical reactions in the material can be expressed as follows:The heterogeneous NTO/MoS2‐C, MoS2‐C, and NTO electrode materials  were also tested for constant current charge and discharge at current densities of 200, 500, 1000, 2000, 4000, and 8000 mA g−1 , the NTO/MoS2‐C electrode material released a stable capacity of up to 425.5 mAh g−1. When the current density increased from 500 to 4000 mA g−1, the specific capacity of the material decreased from 383.6 to 348.4, 311.5, and 279.4 mAh g−1 , there is almost no capacity for pure NTO nanowires. MoS2‐C, however, exhibited a quite satisfactory specific capacity: from 594.1 to 366.5 mA g−1 when the current densities increased from 200 to 8000 mA g−1. This phenomenon could be attributed to higher content of the promoter MoS2 in MoS2‐C compared with that in NTO/MoS2‐C hybrid, together with higher specific surface area of MoS2‐C (259.9 m2 g−1) compared with that of NTO/MoS2‐C (176.0 m2 g−1) . More MoS2 component and larger specific surface area give rise to relatively high capacity.Herein, the NTO/MoS2‐C nanospheres was superior to NTO/MoS2‐C and pure NTO nanowires. As shown in Figure 2‐C is 435.1 mA g−1 at 2000 mA g−1, which is also much higher than that of NTO/MoS2‐C. However, the specific capacity of MoS2‐C declines quickly after 500 cycles. In contrast, NTO/MoS2‐C shows more stable cyclability and even no capacity decay from 1000 to 2100 cycles. Compared to NTO/MoS2‐C and MoS2‐C, the capacity for NTO material shows an excellent cycling stability with almost no capacity decay for thousands of cycles, implying an ideal stable substrate for the high‐capacity promoter. It is proposed that the superiority of the design and protocol of NTO/MoS2‐C nanoarchitecture: the NTO substrate is quite useful for the whole architecture and NTO/MoS2‐C illustrates the best trade‐off for electrochemical performances in consideration of 1) low capacity but stable NTO substrate and 2) high capacity but unstable MoS2. As a result, the NTO/MoS2‐C electrode material exhibits an initial discharge specific capacity of up to 252.5 mAh g−1 at 8000 mA g−1 due to the uniform dispersion of the large‐capacity MoS2 nanosheets on 2D carbon conductive networks. The capacity was still maintained at 79.7% (capacity fade of only 0.0012% per cycle) after 16 000 super‐long cycles . As a comparison, the specific capacities of MoS2‐C are relatively high for the first several cycles (≈300 mAh g−1) but decrease gradually for the next 5000 cycles with the fading rate of 0.013% per cycle . By comparing the electrochemical performances with some recent reported works about NTO materials and MoS2‐based composites, NTO/MoS2‐C ranks as one of the best anodes for SIBs , reflecting the design superiority of 1D/2D–2D architecture proposed in this work.Capacity and cyclic stability are two critical factors to emulate the electrode materials. It has been demonstrated that structural synergetic advantages are favored for high‐rate capacity and long‐term cyclability. In order to exhibit the superiority of hybrid structure, cyclic stability of various samples was also carefully investigated. At the beginning of the test, the capacity of MoSi = bav (where a and b are adjustable parameters).Figurev)–log(i) plot analysis of the three electrodes from CV curves at different current densities . NTO substrate exhibits the relatively low b value (0.72), indicating that the electrochemical kinetic is mixed with surface‐controlled redox reaction and diffusion‐controlled redox reaction. For MoS2‐C, the b value is very close to 1 (0.97). It is a typical surface‐controlled redox process, which can make the most use of high‐capacity property of nano‐MoS2. The b value of NTO/MoS2‐C, as a result, shows intermediate value between 0.72 and 0.97, leading to the best cyclability and capacity combination. To have better understanding about the contribution of surface‐controlled redox current (Ic) and diffusion‐controlled redox current (Id), the total peak current of one electrode i = bav can be described by the following equations: i = Ic + Id = k1v + k2v1/2, or i v−1/2 = k1v1/2 + k2. Therefore, the coefficients k1 and k2 can be calculated by linear fitting of the cathode and anode peaks of i v−1/2 versus v1/2 . This cathodic process could be regarded as a typical solid solution behavior. Such a solid solution electrochemical reaction is conducive to the super high‐rate capability due to the elimination of nucleation‐and‐growth kinetics of two‐phase transformations.The charge storage mechanism of three electrode materials was further investigated by sweep voltammetry, the current obeys a power‐law relationship with the sweep rate: 2 Figure b, and coRct, obtained from the semicircle at the high‐medium frequency region) of the NTO/MoS2‐C electrode is smaller than those of MoS2‐C and NTO, implying an improved electronic conductivity of the NTO/MoS2‐C with novel 1D/2D–2D hierarchical architectures. To further illustrate the chemical diffusion coefficient of Na+, galvanostatic intermittent titration technique (GITT) was conducted, according to which the sodium diffusion coefficient (DNa) can be calculated as follows:DNa (cm2 s−1) is the chemical diffusion coefficient of the mobile material, VM is the molar volume of the active material (31.63 cm3 mol−1 for MoS2), and A (cm2) is the total contact area between the electrolyte and the electrode. F is the Faraday constant, iZ is the valence of the substance, I0 (A) is the applied constant current, (dE /dδ) is determined by the quasi‐equilibrium potential against the stoichiometry concentration of Na+ in one electrode , t is the time during constant current pulse and L (cm) is the thickness of the electrode. Based on the above equation, the Na+ diffusion coefficient calculated on the GITT curves . The phenomenon may be caused by the differences of contribution ratios of the diffusion‐controlled current during charging and discharging. Just as mentioned above, the anodic (charging) process of NTO/MoS2‐C electrode is mixed by pseudocapacitive current and diffusion‐controlled current compared with mainly diffusion‐controlled current of cathodic (discharging) process. The diffusion‐controlled current is obviously illustrated between 1.5 and 2.0 V, in which region the nucleation‐and‐growth kinetics of two‐phase transformations reduce the ionic diffusion coefficient. This interesting result shows that it is easier to achieve a satisfactory capacity during the discharging process in a half cell (the charging process in a full cell), thus making the NTO/MoS2‐C a very promising anode for fast charging batteries. Because of the layered structure of NTO with large interlayer spacing for ionic transport, the DNa of NTO substrate show about one order of magnitude higher than those of MoS2‐C, especially in the voltage range of 1–2 V 3 materials as the cathode and NTO/MoS2‐C as the anode. As shown in Figure S17 (Supporting Information), due to the irreversible reactions in both electrodes together with limited sodium ions in full cells, the electrochemical performances are not as satisfactory as those in half cells, especially for the beginning several cycles. However, the high‐rate capacity and cyclability became relatively stable after those cycles. The results not only demonstrate the fast‐electrochemical kinetics of NTO/MoS2‐C as an anode for SIBs, but also emphasize the significance of high CE as well as matched working potential of one electrode when serving in full batteries.To investigate the electron conductivity among the three electrodes, electrochemical impedance spectroscopy (EIS) was conducted . The charge‐transfer resistance , the NTO/MoS2‐C electrode materials released a stable specific capacity of up to 425.5 mAh g−1. Even at a large rate of 8000 mA g−1, the NTO/MoS2‐C composite retained a reversible specific capacity of 201.1 mAh g−1 after 16 000 cycles. The charge storage mechanism and chemical diffusion coefficient analysis imply that NTO/MoS2‐C can be an ideal and promising host for high‐power battery systems. This work highlights the design protocol and synthesis strategy of the hierarchical architecture and exhibits their broad prospects in energy storage applications.In summary, a heterogeneous architecture of 1D/2D‐2D NTO/MoSThe authors declare no conflict of interest.SupplementaryClick here for additional data file.


Intervertebral disk (IVD) degeneration is a prevalent age‐associated musculoskeletal disorder and a major cause of chronic low back pain. Aging is the main risk factor for the disease, but the molecular mechanisms regulating IVD homeostasis during aging are unknown. The aim of this study was to investigate the function of FOXO, a family of transcription factors linked to aging and longevity, in IVD aging and age‐related degeneration. Conditional deletion of all FOXO isoforms  in IVD using the Col2a1Cre and AcanCreER mouse resulted in spontaneous development of IVD degeneration that was driven by severe cell loss in the nucleus pulposus (NP) and cartilaginous endplates (EP). Conditional deletion of individual FOXO in mature mice showed that FOXO1 and FOXO3 are the dominant isoforms and have redundant functions in promoting IVD homeostasis. Gene expression analyses indicated impaired autophagy and reduced antioxidant defenses in the NP of FOXO‐deficient IVD. In primary human NP cells, FOXO directly regulated autophagy and adaptation to hypoxia and promoted resistance to oxidative and inflammatory stress. Our findings demonstrate that FOXO are critical regulators of IVD homeostasis during aging and suggest that maintaining or restoring FOXO expression can be a therapeutic strategy to promote healthy IVD aging and delay the onset of IVD degeneration. This represents the most common musculoskeletal disorder and a major cause of disability . Col2a1‐Cre−/−; Foxo1fl/fl; Foxo3fl/fl; and Foxo4fl/fl littermates (Col2a1Cre−/−) were used as controls. FOXO deletion was confirmed by gene expression analysis in NP and AF of lumbar IVD from 2‐month‐old mice .To model and study the consequences of the reduced expression of FOXO in NP, AF, and EP of degenerated IVD  and 7 (P7) . Starting at 1 month of age, lumbar IVD from Col2a1Cre‐FOXO KO mice exhibited a mild enlargement of the NP and a modest increase in disk height , suggesting that FOXO1 is the predominant isoform in the regulation of postnatal cell proliferation and differentiation. Reduced cellularity and mild degenerative changes were also observed in the EP of mice with FOXO1 deletion . However, these changes were less severe than those in Col2a1Cre‐FOXO KO mice, indicating compensation by FOXO3 or FOXO4. On the other hand, Col2a1Cre‐FOXO3 KO and Col2a1Cre‐FOXO4 KO mice did not show any structural abnormalities in IVD up to 6 months of age. However, degenerative changes were observed in lumbar IVD from Col2a1Cre‐FOXO3 KO mice, but not Col2a1Cre‐FOXO4 KO, at 12 months . These changes more severe at 18 months recapitulated histological hallmarks of age‐related disk degeneration such as decreased NP cellularity, decreased disk height, abnormal AF organization, and ossification of the EP and resulted in increased histopathological scores . These results suggest that FOXO3 is dispensable for normal IVD postnatal development, likely due to compensation by FOXO1, but is essential for IVD homeostasis, and its deletion results in accelerated IDD during aging.2.2−/− control mice were injected with 5‐bromo‐2'‐deoxyuridine (BrdU) intraperitoneally for five consecutive days. Quantification of BrdU labeling by immunohistochemistry showed a significant increase in proliferating cells in the NP of Col2a1Cre‐FOXO KO mice as compared to control mice  at 4 months of age  and X (Col10a1) was increased in the AF of Col2a1Cre‐FOXO KO mice when compared with controls at 4 months of age  and AcanCreER+/−; Foxo1fl/fl; Foxo3fl/fl; and Foxo4fl/fl (AcanCreER‐FOXO KO) mice were injected with tamoxifen, and FOXO expression was assessed 2 weeks later by qPCR analysis . Unlike the results in the Col2a1‐Cre model, the reduction in FOXO expression upon tamoxifen administration in the AcanCreER model was more marked in the NP than in the AF, consistent with higher aggrecan expression in NP than in AF  and autophagy‐related genes  in the NP of 2‐month‐old FOXO mutant mice  dUTP Nick‐End Labeling (TUNEL) analysis revealed higher numbers of apoptotic cells in the EP of Col2a1Cre‐FOXO KO mice at 4 months and in the NP and EP at 6 months of age when compared with control littermates  showed no differences in FOXO3 levels . In addition, hypoxia increased the expression of autophagic genes  and autophagic activity as evidenced by decreased protein levels of p62 and increased levels of lipidated LC3 (LC3‐II)  Figure b–c. In a) Figure , this inSESN3, SOD2, and MAP1LC3, whereas siFOXO1 + 3‐transfected cells also showed lower levels of BECN1 and PRKAA2  in serum‐free media for 24 hr. Simultaneous knockdown of FOXO1 and FOXO3 resulted in a significant decrease in cell viability upon H2O2 or TNF‐α or IL‐1β stimulation  or constitutively active FOXO1 (Ad‐FOXO1‐AAA) and treated with IL‐1β for 6 hr. IL‐1β stimulation increased expression of IL6, PTGS2, ADAMTS5, MMP1, MMP3, and MMP13  were used as controls. For FOXO deletion in skeletally mature mice, 4‐month‐old mice AcanCreER; Foxo1fl/fl; Foxo3fl/fl; and Foxo4fl/fl mice were injected with tamoxifen  intraperitoneally at 1.5 mg/10 g body weight for five consecutive days.Col2a1‐Cre transgenic mice . Macroscopic assessment was performed according to Thompson grading , aggrecan , or LC3 . Then, samples were incubated with secondary fluorescent antibodies  and visualized under a fluorescence microscope. Five IVD samples per experimental group were analyzed. The number of LC3 puncta was quantified in 20 cells randomly selected in the NP, and data are expressed as average number of LC3 puncta per cell.4.6n = 3 mice per group) for five consecutive days. Immunohistochemical detection of BrdU‐positive cells was performed using a primary antibody against BrdU  as indicated above. The number of positive cells was quantified in the NP of L4/L5 IVD under 20× magnification. Proliferation rate was expressed as the ratio of the total number of BrdU‐positive cells to the total number of NP cells in the L4/L5 IVD.To evaluate the rate of cell proliferation, injections of 100 mg/kg of BrdU (Sigma‐Aldrich) were administered intraperitoneally to 3‐week‐old mice (n = 5 mice per group) and visualized under fluorescence microscopy. The number of positive cells was quantified in the NP and EP of L4/L5 IVD, and data were expressed as the ratio of TUNEL‐positive cells to the total number of DAPI‐positive cells in the L4/L5 disk.To assess the apoptotic cell death, TUNEL staining was performed using in situ cell death detection kit  in lumbar spine samples  filled with 5% CO2% and 1% O2. For the evaluation of autophagic activity, cells were incubated in the presence or absence of 25 µM chloroquine  for 24 hr. All experiments using human cells were performed at least three times in duplicate. A detailed description of gene knockdown, overexpression, and cell viability experiments is provided as Supporting information.Human NP cells were isolated following the protocol described by Sakai et al.  and main4.8Mouse lumbar spine samples were collected at 2 and 4 months of age. NP and AF from all lumbar IVD were resected separately for each mouse and homogenized in QIAzol Lysis Reagent . RNA was isolated using Direct‐zol RNA miniprep kit . RNA quality was assessed by measuring the 260/280 absorbance ratio. All RNA samples used in this study had a 260/280 ratio > 1.8. Gene expression was measured by real‐time PCR using predesigned TaqMan gene expression assays (Thermo Fisher Scientific). At least four samples were analyzed in duplicate for each experimental condition.4.9Protein extraction and Western blotting were performed as described previously . All data were tested for normal distribution using the Kolmogorov–Smirnov test. Statistical comparisons between more than two groups were assessed by one‐way analysis of variance (ANOVA) followed by a post hoc Tukey's test. Comparisons between two groups were assessed by an unpaired, two‐tailed t‐test after testing for equal variance using an F‐test. All statistical analyses were performed using prism 6 software (GraphPad Software). p‐Values less than 0.05 were considered significant.All data are reported as the mean ± standard deviation (4.11All mouse studies were approved by the Scripps Institutional Animal Care and Use Committee and performed in accordance with ARRIVE guidelines and with attention to the standards reported by the NIH‐NINDS designed to enhance animal study transparency and reproducibility.The authors have declared that no conflict of interest exists.OA and ML designed the study; OA, TM, MO, KM, and SM performed experiments; OA, DS, KM, HA, and ML analyzed the data; OA and ML wrote and edited the manuscript. All authors reviewed and approved the final version of the manuscript. Click here for additional data file.


Here we show that this reaction occurs readily when CO2 ions scatter from solid surfaces in a two-step sequential collision process at hyperthermal incidence energies. The produced O2 is preferentially ionized by charge transfer from the surface over the predominant atomic oxygen product, leading to direct detection of both O2+ and O2−. First-principles simulations of the collisional dynamics reveal that O2 production proceeds via strongly-bent CO2 configurations, without visiting other intermediates. Bent CO2 provides dynamic access to the symmetric dissociation of CO2 to C+O2 with a calculated yield of 1 to 2% depending on molecular orientation. This unexpected collision-induced transformation of individual CO2 molecules provides an accessible pathway for generating O2 in astrophysical environments and may inspire plasma-driven electro- and photo-catalytic strategies for terrestrial CO2 reduction.The intramolecular conversion of CO Carbon dioxide can dissociate via different pathways depending on the amount of available energy. Here the authors investigate carbon dioxide collisions with metal substrates and observe a pathway producing molecular oxygen, which might explain the presence of oxygen in abiotic environments. The recent discovery of abundant O2 in the coma of comet 67P/CG6 has rekindled interest in abiotic reactions, occurring in extreme environments, which release O2 from compounds, such as H2O, CO2, CO, silicates, and metal oxides. Such reactions may offer competing explanations for the origin of O2 in comets, in the upper atmosphere of Mars, and in Earth’s prebiotic atmosphere9. They may also present alternative ways for resource utilization related to space travel, such as generation of O2 from CO2 for making Mars habitable. Finally, new strategies for CO2 activation may be inspired by such reactions.Although plentiful in modern Earth’s atmosphere, molecular oxygen is extremely rare in space. Only trace amounts have been found elsewhere in our solar system2 proceeds via multiple pathways depending on available energy. The partial dissociation reaction, CO2 → CO + O (3P or 1D), has the lowest energy requirement (5.43 or 7.56 eV)10; it has been extensively studied in photochemistry and in heterogeneous catalysis under thermal activation conditions12. Full dissociation to C + O + O involves the cleavage of both C–O bonds and requires 16.46 eV. Other pathways may be possible at intermediate energies, such as the exotic reaction: CO2 → C(3P) + O2(1Σg), which entails extensive intramolecular rearrangement of the CO2 molecule. Calculations have suggested that this reaction proceeds on the ground-state potential energy surface, by first forming a cyclic CO2 intermediate [c-CO2(1A1)], which then rearranges into a collinear COO(1Σ+) intermediate on its way to dissociation into C + O210. The first step in this channel involves bending of the CO2 molecule to bring the two O atoms in close proximity, which requires close to 6 eV of internal energy13.The dissociation of CO2 can bend the molecule as a first step to O2 production. Indeed, pioneering experiments employing VUV photo-excitation16 and electron attachment18 have shown that dissociation of CO2 into C(3P) + O2(X3Σg−) is possible, as evidenced by the detection of the complementary atomic C+ or C− fragment. Further confirmation of the exotic pathway, however, remained elusive as neutral or ionized O2 products were not detected. Using ion-beam scattering methods and numerical simulation techniques, we demonstrate here a different way to drive the direct reduction of CO2 to O2 with in situ detection of ionized O2 products. The process involves a previously unknown intramolecular reaction pathway, which occurs in energetic CO2 ion–surface collisions with a surprising lack of dependence on either the nature of the surface or the surface temperature. As such, the reaction may be relevant for astrophysical environments, such as comets, moons, and planets with CO2 atmospheres.Although inaccessible by thermal activation, transitions to electronically excited and anionic states of CO2 in hyperthermal CO2+/Au collisions by plotting kinetic energy distributions of three scattered molecular ion products: CO2+, O2+, and O2− for various CO2+ incidence energies (E0). Very weak signal of scattered CO2+ is detected for E0 < 80 eV  and increase monotonically with E0 over a larger range than scattered CO2+. The O2 ion signal intensity exhibits a maximum at E0 ~ 100 eV. Above that, only the O2+ distribution develops a shoulder  from physical sputtering.We first demonstrate the formation of O eV Fig. . The CO2rved Fig.. The O2+2 ion products is surprising. Neither sputtering of surface O2 nor O-atom abstraction reactions  can explain their formation, because both mechanisms would produce O2 at much lower exit energies (see the section “Methods”). A remaining possibility to be explored here is dynamic formation of O2 through dissociation of CO2. Dynamic partial and full dissociation of CO2 is in fact consistent with the other detected products, including CO+, CO−, O+, O−, and C+  allows calculation of the kinematic factor, defined as the fraction of incident energy retained by a scattered product exiting the surface. In the simplest possible model, CO2+ scatters as a whole molecule, i.e., a hard sphere with atomic mass of 44 Da. Under this assumption, BCT predicts a kinematic factor of 0.6349, which fits the data poorly , kinematic analysis of the exit energy data provides strong evidence for impulsive dissociation of the CO2 molecule24. Assuming delayed fragmentation of the CO2 parent24, the kinematic factors of the CO, O, and (possibly) O2 daughter products can be calculated from energy conservation to be 0.5724, 0.5008, and 0.2862, respectively. These factors are used as fixed slopes in one-parameter fittings of the respective data points (adjustable intercept). We find that the calculated slopes fit the O2±, CO±, and O− ion exit data very well  simulations.Although the kinematic analysis indicates conclusively that some CO2 on Au(111) are performed in the experimental scattering geometry, with CO2 evolving on the ground singlet potential energy surface under the assumption that incoming CO2+ ions are neutralized before the hard collision. Facile neutralization occurs via resonant electron tunneling26 from the metal surface to the molecular cation because the molecular level of CO2 (−13.8 eV) lies well within the occupied band of Au (−5.3 to −15.3 eV). Electron transfer from and to the surface is explicitly included in the simulations to also account for ionization of neutral collision products. The calculated exit energies of the products are plotted in Fig. 2+ has a calculated slope of 0.713 vs. the experimental value of 0.787. Negligible CO2 is found to survive for E0 > 80 eV, consistent with the lack of experimental signal at these energies. All other calculated slopes agree well with the experimental values; for instance, compare the slope of 0.54 ± 0.02 vs. the experimental value of 0.57 for the O2− line. These results indicate broad agreement between the simulations and the scattering kinematics.MD trajectories for the scattering of CO2− ions over O−, resulting from the exponential dependence of the ionization probability on the coupling to the metal surface . As the center-of-mass distance to the surface, –Au increases steeply. During this encounter, one of the O atoms of CO2 strikes a surface Au atom, giving rise to the first peak in the –Au curve (inset II). This collision occurs before –Au curve (inset III), which occurs after the apsis. As a result of the impulsive energy transfer during the collision, the rebounding CO2 undergoes substantial intramolecular rearrangement portrayed by the bond distance evolution in Fig. rCO, simultaneously increase, reaching a point along the trajectory where CO2 acquires a triangular configuration with nearly equal bond lengths . This strongly bent CO2 intermediate (inset IV) has a significant amount of internal energy, 2 molecule (inset V). The complete CO2 collision trajectory discussed in Fig. 2 depicted by this representative trajectory proceeds by delayed fragmentation following the two-step sequential collision of CO2 with the surface. This mechanism is consistent with the assumptions of the kinematic model used earlier to explain the experimental data in Fig. An ensemble of 20,000 CO O2 Fig. . Prior tion Fig. . Select 2 at E0 = 56.4 eV are shown in Fig. 2 (6%) survives the collision in correspondence with experimental detection. Approximately 5% of all trajectories lead to the strongly bent intermediate state—the precursor to O2 formation—which is characterized by C–O and O–O bond orders exceeding 0.7. This intermediate state fragments primarily via partial dissociation (51%) followed again by complete dissociation, albeit now with a higher yield (33%). Remarkably, one in eight (13%) of the strongly bent CO2 molecules produces O2. The overall neutral yield of the symmetric dissociation channel, CO2 → C + O2, amounts to 0.6% at E0 = 56.4 eV. Upon increasing incidence energy, the neutral O2 yield obtained from the ensemble of isotropically oriented incident CO2 molecules reaches 0.8 ± 0.2% for E0 ~ 70 ± 15 eV , the fraction of O2-producing trajectories increases to ~2%  but also because the collisional mechanism occurs via a delayed fragmentation of a single CO2 intermediate, i.e., without visiting the linear COO state. The collisional mechanism also differs fundamentally from that taking place in electron-attachment experiments17, where the CO2 bends spontaneously on the anionic potential energy surface. Instead, the bent CO2 state is accessed on the neutral surface via collisional energy transfer. Furthermore, while the collisional interconversion of CO2 to O2 has comparable efficiency to activation via high-energy photons and higher efficiency than via electron attachment, it is a much simpler process. Importantly, our mechanism is independent of surface temperature and generic to surface composition  as long as: (i) the surface contains atoms heavier than the constituents of CO2 and (ii) surface charging is mitigated when CO2 ions are used. Finally, we note that an analogous dissociation reaction: OCS → C + SO, previously reported27 for OCS+ collisions on Ag(111), was speculated to occur via a sharply bent excited state, such as the OCS(3A), activated either by neutralization prior to impact or by the energetic collision with the surface. However, the basic mechanistic features of the latter process—including whether it involves unimolecular collisions or Eley–Rideal reactions with surfaced-absorbed O or S atoms—were not addressed.The mechanism reported here is distinct from previously proposed mechanisms for CO2 reaction may be relevant in astrochemical environments with abundant CO2 and prevalent solar wind. Solar ultraviolet light photo-ionizes CO2 molecules readily, producing ions which are then picked up by the solar wind and accelerated to hyperthermal energies29. Collisions of these fast ions with the surfaces of dust particles or other astrophysical bodies can activate the dissociation. Such interactions may affect dynamically the composition of cometary comae, contributing to the abundance of the super-volatiles O2 and CO. Production of O2 from CO2 was explicitly disregarded in the coma of comet 67P early on (pre-perihelion) during the Rosetta mission, owing to the low abundance of CO2 and poor correlation between O2 and CO2 fluxes6. However, the situation may warrant reexamination in the post-perihelion phase, when CO2 can reach abundancies as high as 32% relative to H2O, a 10-fold increase versus pre-perihelion30. The precise level of contribution to the O2 abundance in the coma cannot be determined without CO2 ion energy and flux data. Nevertheless, the number is likely small for collisional encounters on dust and cometary surfaces. Even at low yield, however, contribution to the measured O2 abundance may be disproportionate if the CO2 reaction occurs close to the point of measurement. For example, we have verified experimentally that the reaction takes place on indium–tin oxide (ITO), a man-made material found on Rosetta’s thermal insulation and solar panels. Thus, CO2 collisions on the spacecraft’s exposed surfaces can change the composition of the surrounding gaseous halo with unknown repercussions for mass spectrometric measurements31.The intramolecular CO2-dominated atmosphere; likewise, orbiting satellites/spacecraft or high-speed space debris32 will encounter neutral or photoionized CO2 in Mars’ upper ionosphere. In these situations, the target surface is moving against a stagnant CO2 atmosphere with correspondingly high velocities, driving the partial transformation of CO2 into O2. Indeed, O2 abundances in the 1000’s of parts per million measured at Mars33 may contain significant contributions from such processes.Similar collisional processes may have occurred in early Earth when projectiles, such as meteorites, traversed through its CO2 is relatively small in the current study, a combination of collisional activation with photoexcitation, electron attachment, and Eley–Rideal reactions in a plasma reactor may result in a process that could be promising for CO2 reduction strategies, as well as plasma-driven continuous O2 production in CO2 atmospheres.Finally, although the yield of O34. The CO2+ ion beam was extracted from an inductively coupled plasma, struck in a reactor held at 2 mTorr using a CO2/Ar/Ne gas mixture supplied with 500 W RF power at 13.56 MHz. Ions were delivered to a grounded surface at 45° incidence angle; typical beam currents of 5–15 μA were spread over a ~3 mm spot. Beam energy was varied between 40 and 200 eV by externally adjusting the plasma potential. The beam energy distribution had a Gaussian shape with a FWHM of ~5 eV. Typical target surfaces were polycrystalline Au foils (5 N), sputter-cleaned with an Ar+ ion gun before each run. Scattered ion products, exiting at an angle of 45° in the scattering plane, were energy-resolved and mass-resolved using an electrostatic ion energy analyzer and a quadruple mass spectrometer, respectively. All ions were detected using a channel electron multiplier, biased as appropriate to detect positive or negative ions. Differences in detector bias precluded a direct comparison of signal intensities between product ions of different charge polarities. All collected signals were normalized to the beam current measured on the sample.All experiments were carried out in a custom-made low-energy ion scattering apparatus2 scattering from Au(111) surface were propagated on a potential energy surface represented as a sum of the CO2 electronic energy, the molecule–surface interaction energy, and the interatomic potential of the metal atoms. The CO2 energy of the ground singlet electronic state was modeled by a self-consistent-charge tight-binding model, the molecule–surface interaction energy was described by a Tersoff–Brenner reactive force field, and the interatomic metal interactions were represented by an embedded-atom potential. Both the tight-binding model and reactive force field were specifically parameterized for the CO2–Au system on datasets consisting, respectively, of 689 and 930 ab initio energies with mean absolute errors of 0.42 and 0.48 eV, which are small compared to the translational and internal energies involved in the collisions. Finite-temperature tight-binding calculations were used to alleviate concerns about the multi-reference nature of the dissociating scattering products. Non-adiabatic transition probabilities presented in Supplementary Fig. x and y directions. Trajectories were initiated with fixed incidence angle of 45° and with center-of-mass of the CO2 molecules at 5.5 Å above an energy-minimized gold surface, and they were terminated after the scattering products had left the surface region. The trajectories were averaged over molecular orientation and surface unit cell, and 0.2 eV thermal ro-vibrational energy was attributed to the internal degrees of freedom of CO2. 20,000 trajectories were computed for each incidence energy and all scattering products were collected for final analysis. The probability for ion formation depended exponentially on the inverse of the normal component of the center-of-mass velocity and the coupling to the metal, and the exit velocities of the ions were corrected for the ionization energies.MD trajectories of CO2 from the surface and (2) abstraction of atomic O from the surface to form the hypothetical radical •CO3 via an Eley–Rideal reaction, followed up by spontaneous dissociation to CO + O2. Sputtering can be discounted for two reasons: (a) sputtering requires typically higher E0 to induce the collision cascade—indeed, there is some evidence of sputtering in the O2+ energy distributions for E0 > 100 eV, forming a low-energy shoulder to the main peak  sputtering of Oeak Fig.  and (b)  eV Fig. . Moreoveons Fig. . SimilarSupplementary InformationPeer Review FileDescription of Additional Supplementary FilesSupplementary Video 1