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Intercalation-type layered oxides have been widely explored as cathode materials for aqueous zinc-ion batteries (ZIBs). Although high-rate capability has been achieved based on the pillar effect of various intercalants for widening interlayer space, an in-depth understanding of atomic orbital variations induced by intercalants is still unknown. Herein, we design an NH 4 + -intercalated vanadium oxide (NH 4 + -V 2 O 5 ) for high-rate ZIBs, together with deeply investigating the role of the intercalant in terms of atomic orbital. Besides extended layer spacing, our X-ray spectroscopies reveal that the insertion of NH 4 + could promote electron transition to 3 d xy state of V t 2 g orbital in V 2 O 5 , which significantly accelerates the electron transfer and Zn-ion migration, further verified by DFT calculations. As results, the NH 4 + -V 2 O 5 electrode delivers a high capacity of 430.0 mA h g −1 at 0.1 A g −1 , especially excellent rate capability (101.0 mA h g −1 at 200 C), enabling fast charging within 18 s. Moreover, the reversible V t 2 g orbital and lattice space variation during cycling are found via ex-situ soft X-ray absorption spectrum and in-situ synchrotron radiation X-ray diffraction, respectively. This work provides an insight at orbital level in advanced cathode materials.

Anodic oxygen evolution reaction (OER) is the key bottleneck for water electrolysis technique owing to its sluggish reaction kinetics. Interfacial engineering on the rationally designed heterostructure can regulate the electronic states efficiently for intrinsic activity improvement. Here, we report a co-phosphorization approach to construct a VPO4-Ni2P heterostructure on nickel foam with strongly chemical binding, wherein phosphate acts as electronic modifier for Ni2P electrocatalyst. Profiting from the interfacial interaction, it is uncovered that electron shifts from Ni2P to VPO4 to render valence increment in Ni species. Such an electronic manipulation rationalizes the chemical affinities of various oxygen intermediates in OER pathway, giving a substantially reduced energy barrier. As a result, the advanced VPO4-Ni2P heterostructure only requires an overpotential of 289 mV to deliver a high current density of 350 mA/cm2 for OER in alkaline electrolyte, together with a Tafel slope as low as 28 mV/dec. This work brings fresh insights into interfacial engineering for advanced electrocatalyst design.

Single-atom catalysts (SACs) that can achieve maximum atom utilization and provide well-defined active sites in energy conversion reactions have attracted much attention in the past decade. In general, the local structures of active sites in SACs largely determine their catalytic activity and selectivity. Therefore, identifying the local environments of active sites in specific SACs is essential to understand their catalytic functions in various reactions. Recent research works have demonstrated that synchrotron-radiation spectroscopic characterization methods possess unparalleled capacity in the identification of local environments of SACs due to their wide energy regulation window and high resolution. In this review, we aim to discuss the practical applications of some ex/in situ synchrotron-radiation spectroscopic techniques in recently reported advanced SACs. The experimental analyses from various techniques, such as X-ray absorption spectroscopy (XAS), photoemission spectroscopy (PES) and Fourier-transform infrared spectroscopy (FTIR), are highlighted. The built structure-activity relationships towards identified active sites are also discussed. Finally, a summary of spectral imputs and related significance is made and the research perspectives are suggested.

Interface engineering of zinc metal anodes is a promising remedy to relieve their inferior stability caused by dendrite growth and side reactions. Nevertheless, the low affinity and additional weight of the protective coating remain obstacles to their further implementation. Here, aroused by DFT simulation, self-assembled monolayers (SAMs) are selectively constructed to enhance the stability of zinc metal anodes in dilute aqueous electrolytes. It is found that the monolayer thiol molecules relatively prefer to selectively graft onto the unstable zinc crystal facets through strong Zn-S chemical interactions to engineer a covalent interface, enabling the uniform deposition of Zn

N-doped carbon-based single-atom catalysts (NC-SACs) are widely researched in various electrochemical reactions due to high metal atom utilization and catalytic activity. The catalytic activity of NC-SACs originates from the coordinating structure between single metal site (M) and the doped nitrogen (N) in carbon matrix by forming M-Nx-C structure (1≤ x≤ 4). The M-N4-C structure is widely considered to be the most stable and effective catalytic site. However, there is no in-depth research for the “x” modulation in Pt-Nx-C structure and the corresponding catalytic properties. Herein, atomically dispersed Pt on N-doped carbon (Pt-NC) with Pt-Nx-C structure (1≤ x≤ 4), as a research model, is fabricated by a ZIF-8 template and applied to catalytic oxygen reduction. Different carbonization temperatures are used to control N loss, and then modulate the N coordination of Pt-Nx-C structure. The Pt-NC has the predictable low half-wave potential (E1/2) of 0.72 V vs RHE compared to the Pt/C 20% of 0.81V due to low Pt content. Remarkably, the Pt-NC shows a high onset potential (1.10 V vs RHE, determined for j = -0.1 mA cm2) and a high current density of 5.2 mA cm−2, more positive and higher than that of Pt/C 20% (0.96 V) and 4.9 mA cm−2, respectively. As the structural characterization and DFT simulation confirmed, the reducing Pt-N coordination number induces low valence of Pt atoms and low free energy of oxygen reduction, which is responsible for the improved catalytic activity. Furthermore, the Pt-NC shows high mass activity (172 times higher than that of Pt/C 20%), better stability and methanol crossover resistance.

The phase transformation of catalysts has been extensively observed in heterogeneous catalytic reactions that hinder the long cycling catalysis, and it remains a big challenge to precisely control the active phase during the complex conditions in electrochemical catalysis. Here, we theoretically predict that carbon-based support could achieve the phase engineering regulation of catalysts by suppressing specific phase transformation. Taken single-walled carbon nanotube (SWCNT) as typical support, combined with calculated E-pH (Pourbaix) diagram and advanced synchrotron-based characterizations technologies prove there are two different active phases source from cobalt selenide which demonstrate that the feasibility of using support effect regulating the potential advantageous catalysts. Moreover, it is worth noting that the phase engineering derived Co3O4-SWCNT exhibits a low overpotential of 201 mV for delivering the current density of 10 mA/cm2 in electrocatalytic oxygen evolution reaction (OER). Also, it reaches a record current density of 529 mA/cm2 at 1.63 V (vs. RHE) in the electrocatalytic urea oxidation reaction (UOR), overwhelming most previously reported catalysts.

Amidst the development of photoelectrochemical (PEC) CO2 conversion toward practical application, the production of high-value chemicals beyond C1 compounds under mild conditions is greatly desired yet challenging. Here, through rational PEC device design by combining Au-loaded and N-doped TiO2 plate nanoarray photoanode with Zn-doped Cu2O dark cathode, efficient conversion of CO2 to CH3COOH has been achieved with an outstanding Faradaic efficiency up to 58.1% (91.5% carbon selectivity) at 0.5 V vs. Ag/AgCl. Temperature programmed desorption and in situ Raman spectra reveal that the Zn-dopant in Cu2O plays multiple roles in selective catalytic CO2 conversion, including local electronic structure manipulation and active site modification, which together promote the formation of intermediate *CH2/*CH3 for C–C coupling. Apart from that, it is also unveiled that the sufficient electron density provided by the Au-loaded and N-doped TiO2 plate nanoarray photoanode plays an equally important role by initiating multi-electron CO2 reduction. This work provides fresh insights into the PEC system design to reach the multi-electron reduction reaction and facilitate the C–C coupling reaction toward high-value multicarbon (C2+) chemical production via CO2 conversion.

Despite acknowledgment of structural reconstruction of materials following oxygen evolution reaction (OER) reaction, the role of support during the reconstruction process has been ignored. Given this, we directly in situ transform the residual iron present in raw single-walled carbon nanotubes (SWCNT) into Fe2O3 and thus build Fe2O3-CNT as the model system. Intriguingly, an anomalous self-optimization occurred on SWCNT and the derived components show satisfactory electrochemical performance. Soft X-ray absorption spectroscopy (sXAS) analysis and theory calculation correspondingly indicate that self-optimization yields stronger interaction between SWCNT and Fe2O3 nanoparticles, where the electrons migrate from Fe2O3 to optimized SWCNT. Such polarization will generate a positive charge center and thus boost the OER activity. This finding directly observes the self-optimization of support effect, providing a new perspective for OER and related electrochemical reactions.

Carbonaceous materials present the promising anode candidates for sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs), however, the poor rate performance and low capacity due to limited interlayer spacing greatly impact their practical application. Herein, we report soybean roots-derived mesoporous hard carbon constructed by N, P co-doping (NPDCs) with enlarged interlayer distance and more active sites for high-performance SIBs and PIBs. As a result, the optimized NPDC achieves an excellent cyclic stability (197 mA g−1 after 2000 cycles at 2.0 A g−1) for SIBs, superior rate capability (a high reversible capacity of 179 mAh g−1 at 5.0 A g−1) for PIBs. Kinetic and first-principles calculation studies further demonstrate the dual-doping improves the Na (K) ions diffusion and adsorption as well as electrons transport. This work provides a facile and sustainable strategy to realize advanced carbon-based materials with heteratoms doping in application for energy storage devices.

Cu-based electrocatalysts have provoked much attention for their high activity and selectivity in carbon dioxide (CO2) conversion into multi-carbon hydrocarbons. However, during the electrochemical reaction, Cu catalysts inevitably undergo surface reconstruction whose impact on CO2 conversion performance remains contentious. Here we report that polycrystalline Cu nanoparticles (denoted as Cu-s) with rich high-index facets, derived from Cu2−xS through desulphurization and surface reconstruction, offer an excellent platform for investigating the role of surface reconstruction in electrocatalytic CO2 conversion. During the formation of Cu-s catalyst, the two stages of desulphurization and surface reconstruction can be clearly resolved by in situ X-ray absorption spectroscopy and OH− adsorption characterizations, which are well correlated with the changes in electrocatalytic performance. It turns out that the high CO2 conversion performance, achieved by the Cu-s catalyst (Faradic efficiency of 68.6% and partial current density of 40.8 mA/cm2 in H-cell toward C2H4 production), is attributed to the increased percentage of high-index facets in Cu-s during the surface reconstruction. Furthermore, the operando electrochemical Raman spectroscopy further reveals that the conversion of the CO2 into the C2H4 on Cu-s is intermediated by the production of *COCHO. Our findings manifest that the surface reconstruction is an effective method for tuning the reaction intermediate of the CO2 conversion toward high-value multicarbon (C2+) chemicals, and highlight the significance of in situ characterizations in enhancing the understanding of the surface structure and its role in electrocatalysis.

This work was financially supported by the Australian Research Council (FL170100154, DP160104866, and DP190103472). Y.H.Z. acknowledges financial support from Zhejiang Provincial Natural Science Foundation of China (LR18B030003), National Natural Science Foundation of China (51701181, 21771161), and the Thousand Talents Program for Distinguished Young Scholars. J.S. was supported by the Chinese CSC Scholarship Program. DFT computations were performed by using services offered from the National Computational Infrastructure (NCI) and Phoenix High Performance Computing, which are supported by the Australian Government and the University of Adelaide. XAS measurements were conducted at the Beijing Synchrotron Radiation Facility (1W1B, BSRF)

Broadly, the oxygen evolution reaction (OER) has been deeply understood as a significant part of energy conversion and storage. Nevertheless, the anions in the OER catalysts have been neglected for various reasons such as inactive sites, dissolution, and oxidation, amongst others. Herein, we applied a model catalyst s-Ni(OH)2 to track the anionic behavior in the catalyst during the electrochemical process to fill this gap. The advanced operando synchrotron radiation Fourier transform infrared (SR-FTIR) spectroscopy, synchrotron radiation photoelectron spectroscopy (SRPES) depth detection and differential X-ray absorption fine structure (Δ-XAFS) spectrum jointly point out that some oxidized sulfur species (SO42−) will self-optimize new Ni–S bonds during OER process. Such amazing anionic self-optimization (ASO) behavior has never been observed in the OER process. Subsequently, the optimization-derived component shows a significantly improved electrocatalytic performance (activity, stability, etc.) compared to reference catalyst Ni(OH)2. Theoretical calculation further suggests that the ASO process indeed derives a thermodynamically stable structure of the OER catalyst, and then gives its superb catalytic performance by optimizing the thermodynamic and kinetic processes in the OER, respectively. This work demonstrates the vital role of anions in the electrochemical process, which will open up new perspectives for understanding OER and provide some new ideas in related fields (especially catalysis and chemistry).

Vacancy engineering has attracted intensive attention owing to its great influence on the performance of photocatalysts. So far it still remains a big challenge to controllably modulate various vacancies co-existing in a photocatalyst and unveil the resultant influence mechanism. Herein, the model catalysts of ZnS nanoplates with vacancy defects of VS and VZn–VS–VZn are successfully prepared via a facile annealing approach and are systematically investigated by various techniques. The ZnS nanoplates with more VS defects show much higher photoreduction activity than those with more VZn–VS–VZn defects. The detailed mechanism is elucidated based on the influence of different vacancy defects on the adsorption and activation of the reactants and desorption of the reduction products, as well as on the separation of charge carriers. The reason that ZnS with different majority defects exhibits different photoreduction selectivity is explained according to the differences in the adsorption/desorption among CO2, H2O, H2 and CO.

The ambiguous mechanism of electrocatalysts for the oxygen evolution reaction (OER) greatly hinders their industrial applications toward renewable and clean energy conversion. Here, we elaborately prepared a cobalt sulfide catalyst to perform a comprehensive study of the OER performance under neutral/alkaline conditions. The combination of synchrotron-based operando X-ray spectroscopic investigations and electron microscopy observations captured a chameleon-like structural self-optimization on the cobalt sulfide oxygen evolution electrocatalyst in both neutral and alkaline electrolytes. Driven by the actual working conditions (pH gradient, electrical potential, etc.), distinct catalytic sites could be activated dramatically. In particular, the CoOOH supported on a single-walled carbon nanotube (CoOOH-SWCNT) with residual S species was identified as the true catalyst under alkaline conditions rather than the entirely transformed CoOOH-SWCNT, while the oxygenated CoS-SWCNT (O-CoS-SWCNT) was formed as the true catalyst under neutral conditions. Undoubtedly, such a mechanism of opening different locks with different keys and its microstructural advantages together guarantee the high catalytic activity in different electrolytes. This work provides a promising catalyst as well as sheds light on the very essence of the structural self-optimization process of catalysts. It makes a significant contribution to the advancement of OER relevant studies in the future while providing new ideas for the fields of chemistry and catalysis.

Buffer reactions can prevent changes induced by external causes. Here, we demonstrate the significant buffer role of a very small amount of Mn in a self-optimized cathode for an aqueous Zn-ion battery. Our operando X-ray characterization studies reveal that the dissolution of most of the Mn in MnV2O4 during the first charging cycle induces atomic re-arrangement to form a disordered vanadium oxide phase with 0.88 at% Mn. Interestingly, the residual Mn ions exhibit voluntary migration between tetrahedral and octahedral sites during Zn2+ de/intercalation. This Mn migration not only stabilizes the main structure of the vanadium-based electrode, but also modulates the Fermi surface of V 3d against excessive drift. As result, the optimized cathode delivers an excellent capacity of 610.2 mA h g−1 at 0.2 A g−1 and long-term cycling stability over 4000 cycles. This buffer contribution via tunable metal ions exhibits high potential for applications in long-life metal-ion batteries and related fields.

Enhancing activity and stability of iridium- (Ir-) based oxygen evolution reaction (OER) catalysts is of great significance in practice. Here, we report a vacancy-rich nickel hydroxide stabilized Ir single-atom catalyst (Ir

Vacancies enhance proton conductivity Proton-exchange membranes (PEMs) allow for the transport of protons while acting as electrical insulators and ensuring that reactants are kept apart; therefore, they are a key component in devices such as low-temperature fuel cells. PEMs are typically made from polymers or materials embedded in a polymer matrix and need to operate in conditions of very high humidity. Starting with an inorganic, layered material, CdPS 3 , Qian et al. show that the removal of a small amount of cadmium introduces vacancies that greatly increase the proton conductivity of the PEMs (see the Perspective by Wang and He). The process works for manganese-based membranes as well, and high lithium ion transport was also observed. Science , this issue p. 596 ; see also p. 525

The development of highly active and reliable photocatalysts for solar hydrogen (H2) production requires the thorough and in-depth understanding of the atomic-level structure/composition-performanc...

Understanding the metal-support interactions in heterogeneous catalysis is critical yet complicated to tailor-design the catalysts with desirable properties. Exemplified with Pt-catalyzed ammonia borane (AB) hydrolysis, a dramatic increase of 20 folds in the catalytic activity is achieved by engineering the Pt-carbon interactions via adopting four different carbon materials (AC, CNT, f-CNF and p-CNF) as the catalyst supports. Multiple characterization techniques reveal that the Pt-carbon electronic interactions, including electron transfer and interfacial bonding, are deemed to be mainly responsible for the remarkable enhancement in the hydrogen generation rate. The molar ratio of electron-withdrawing group to electron-donating group (nEWG/nEDG) is further identified as a descriptor of catalyst in terms of Pt binding energy, which exhibits an almost linear relationship with the catalytic activity. Moreover, a comparison of Pt catalyst pre-treatments, i.e., H2 and AB reduction as well as Ar calcination, suggests that the Pt-O-C linkages within the Pt-carbon interactions are highly stable yet inferior to this reaction. As a result, combining the merits of the highest Pt binding energy as well as the minimum Pt-O-C linkages, the Pt/p-CNF delivers the highest catalytic activity. The insights presented here could shed new lights on the nature of Pt-carbon interactions, which could be extended to the design and manipulation of other metal-carbon catalysts.