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Sulfur is an important electrode material in metal−sulfur batteries. It is usually coupled with metal anodes and undergoes electrochemical reduction to form metal sulfides. Herein, we demonstrate, for the first time, the reversible sulfur oxidation process in AlCl3/carbamide ionic liquid, where sulfur is electrochemically oxidized by AlCl4− to form AlSCl7. The sulfur oxidation is: 1) highly reversible with an efficiency of ~94%; and 2) workable within a wide range of high potentials. As a result, the Al−S battery based on sulfur oxidation can be cycled steadily around ~1.8 V, which is the highest operation voltage in Al−S batteries. The study of sulfur oxidation process benefits the understanding of sulfur chemistry and provides a valuable inspiration for the design of other high-voltage metal−sulfur batteries, not limited to Al−S configurations. The sulfur cathode in metal-sulfur batteries normally undergoes electrochemical reduction to form metal sulfides. Here, the authors demonstrate the electrochemical oxidation of sulfur in ionic liquid for high-voltage aluminium-sulfur batteries. [ABSTRACT FROM AUTHOR]

The C–C coupling kinetic variations are observed on Cu alloys with Pt, Pd, or Au surface sites. The OC–COH coupling is kinetically more favorable than OC–CHO coupling, which originates from increased reactivity of adsorbed *CO species. Linear energy relations for C–C association/dissociation could simplify the energetic evaluation for C2 production. [ABSTRACT FROM AUTHOR]

Monitoring and controlling the reconstruction of materials under working conditions is crucial for the precise identification of active sites, elucidation of reaction mechanisms, and rational design of advanced catalysts. Herein, a Bi‐based metal–organic framework (Bi‐MOF) for electrochemical CO2 reduction is selected as a case study. In situ Raman spectra combined with ex situ electron microscopy reveal that the intricate reconstruction of the Bi‐MOF can be controlled using two steps: 1) electrolyte‐mediated dissociation and conversion of Bi‐MOF to Bi2O2CO3, and 2) potential‐mediated reduction of Bi2O2CO3 to Bi. The intentionally reconstructed Bi catalyst exhibits excellent activity, selectivity, and durability for formate production, and the unsaturated surface Bi atoms formed during reconstruction become the active sites. This work emphasizes the significant impact of pre‐catalyst reconstruction under working conditions and provides insight into the design of highly active and stable electrocatalysts through the regulation of these processes. [ABSTRACT FROM AUTHOR]

Recent studies have shown that single‐atom catalysts (SACs) have significantly better catalytic activity and selectivity for the electrochemical CO2 reduction reaction (CRR) compared to their bulk metal and nanostructured counterparts. However, there are few relevant articles reviewing SACs for the CRR, despite their importance in the field. Herein, the scope of this review is the recent development of single‐atom 3d‐block transition metal catalysts (metal = Mn, Fe, Co, Ni, Cu, Zn) and their application as electrocatalysts for the CRR. The recent representative works by metal are summarized. Results show that 1) Ni and Fe SACs exhibit superior catalytic performance for CO evolution; 2) Co, Mn, Zn SACs are less reported due to their relative inertness for the CRR; 3) Cu SACs have ordinary catalytic activity for the CRR, however, C2 products are observed in a few reports. Point (3) is attractive to the prospective study of CO2 to highly reduced products. Finally, some suggestions for the future development of SACs for the CRR are briefly proposed. [ABSTRACT FROM AUTHOR]

Electrochemical conversion of CO2 into ethane is seldom observed because of the generally higher selectivity towards methane, ethylene, and ethanol. Consequently, little experimental evidence for its reaction mechanism exists and thus remains largely unknown. Now, by combining electrochemistry with in situ X‐ray absorption fine‐structure and in situ Raman techniques, iodide‐derived copper (ID‐Cu) and oxide‐derived copper (OD‐Cu) systems were studied to obtain a deeper understanding of the CO2 to ethane mechanism. With trace iodine species on the surface and positively charged Cu species, production of ethane is significantly more favored on ID‐Cu compared to OD‐Cu, with higher selectivity and faster kinetics. For the first time, it is experimentally found that the formation of ethane follows the same pathway to ethylene and ethanol, and better stabilization of the late stage ethoxy intermediate can steer the reaction to ethane over ethanol. [ABSTRACT FROM AUTHOR]

The electrochemical nitrogen reduction reaction (NRR) is a promising alternative to the energy‐intensive Haber–Bosch process for ammonia synthesis. Among the possible electrocatalysts, bismuth‐based materials have shown unique NRR properties due to their electronic structures and poor hydrogen evolution activity. However, identification of the active sites and reaction mechanism is still difficult due to structural and chemical changes under reaction potentials. Herein, in situ Raman spectroscopy, complemented by electron microscopy, is employed to investigate the structural and chemical transformation of the Bi species during the NRR. Nanorod‐like bismuth‐based metal–organic frameworks are reduced in situ and fragment into densely contacted Bi0 nanoparticles under the applied potentials. The fragmented Bi0 nanoparticles exhibit excellent NRR performance in both neutral and acidic electrolytes, with an ammonia yield of 3.25 ± 0.08 µg cm−2 h−1 at −0.7 V versus reversible hydrogen electrode and a Faradaic efficiency of 12.11 ± 0.84% at −0.6 V in 0.10 m Na2SO4. Online differential electrochemical mass spectrometry detects the production of NH3 and N2H2 during NRR, suggesting a possible pathway through two‐step reduction and decomposition. This work highlights the importance of monitoring and optimizing the electronic and geometric structures of the electrocatalysts under NRR conditions. [ABSTRACT FROM AUTHOR]

Cost‐effective carbon‐based catalysts are promising for catalyzing the electrochemical N2 reduction reaction (NRR). However, the activity origin of carbon‐based catalysts towards NRR remains unclear, and regularities and rules for the rational design of carbon‐based NRR electrocatalysts are still lacking. Based on a combination of theoretical calculations and experimental observations, chalcogen/oxygen group element (O, S, Se, Te) doped carbon materials were systematically evaluated as potential NRR catalysts. Heteroatom‐doping‐induced charge accumulation facilitates N2 adsorption on carbon atoms and spin polarization boosts the potential‐determining step of the first protonation to form *NNH. Te‐doped and Se‐doped C catalysts exhibited high intrinsic NRR activity that is superior to most metal‐based catalysts. Establishing the correlation between the electronic structure and NRR performance for carbon‐based materials paves the pathway for their NRR application. [ABSTRACT FROM AUTHOR]

Low concentration tin bronze alloys show high selectivity for CO2 electroreduction to CO, while high concentration tin bronze alloys show high selectivity for formate. The tin surface sites appear to control selectivity by influencing the binding characteristics toward the first reaction intermediate on copper-based alloys. [ABSTRACT FROM AUTHOR]

The electrochemical reduction of CO2 to useful molecules offers an elegant technological solution to current energy security and sustainability issues because it sequesters carbon from the atmosphere, provides an energy storage solution for intermittent renewable sources, and can be used to produce fuels and industrial chemicals. Nanostructured carbon materials have been extensively used to catalyse some key electrochemical processes because of their excellent electrical conductivity, chemical stability, and abundant active sites. This progress report focuses on nanostructured carbon materials, namely graphene materials, carbon nanotubes, porphyrin materials, nanodiamond, and glassy carbon, which have recently shown promise as high performing CO2 reduction electrocatalysts and supports. Along with discussion regarding materials synthesis, structural characterisation, and electrochemical performance characterisation techniques used, this report will discuss the findings of recent computational CO2RR studies which have been key to elucidating active sites and reaction mechanisms, and developing strategies to break conventional scaling relationships. Lastly, challenges and future perspective of these carbon-based materials for CO2 reduction applications will be given. Much work is still required to realise the commercial viability of the technology, but advanced experimental techniques coupled with theoretical calculations are expected to facilitate future development of the technology. [ABSTRACT FROM AUTHOR]

The electrochemical reduction of CO2 to useful molecules offers an elegant technological solution to current energy security and sustainability issues because it sequesters carbon from the atmosphere, provides an energy storage solution for intermittent renewable sources, and can be used to produce fuels and industrial chemicals. Nanostructured carbon materials have been extensively used to catalyse some key electrochemical processes because of their excellent electrical conductivity, chemical stability, and abundant active sites. This progress report focuses on nanostructured carbon materials, namely graphene materials, carbon nanotubes, porphyrin materials, nanodiamond, and glassy carbon, which have recently shown promise as high performing CO2 reduction electrocatalysts and supports. Along with discussion regarding materials synthesis, structural characterisation, and electrochemical performance characterisation techniques used, this report will discuss the findings of recent computational CO2RR studies which have been key to elucidating active sites and reaction mechanisms, and developing strategies to break conventional scaling relationships. Lastly, challenges and future perspective of these carbon-based materials for CO2 reduction applications will be given. Much work is still required to realise the commercial viability of the technology, but advanced experimental techniques coupled with theoretical calculations are expected to facilitate future development of the technology. [ABSTRACT FROM AUTHOR]

Low concentration tin bronze alloys show high selectivity for CO2 electroreduction to CO, while high concentration tin bronze alloys show high selectivity for formate. The tin surface sites appear to control selectivity by influencing the binding characteristics toward the first reaction intermediate on copper-based alloys. [ABSTRACT FROM AUTHOR]

Review: 210 refs. [ABSTRACT FROM AUTHOR]

• Reaction mechanisms for C 2 H 4 production on Cu-C 3 N 4 were studied thoroughly, 17 possible pathways are investigated. • The asymmetrical active sites enable C 2 production from CRR. • The combination of Cu/C as active sites present a higher activity than Cu/N from the thermodynamic perspectives. Electrochemical reduction of CO 2 requires catalysts beyond Cu with high activity and selectivity to produce C 2 products. Different from many single-atom catalysts that show high performance in obtaining C 1 products, Cu supported on carbon nitride (Cu-C 3 N 4) has shown a unique capability to generate C 2 products by providing asymmetrical active sites. Herein, we study 17 possible pathways and reaction mechanisms of CO 2 reduction toward ethylene – a featured C 2 product, on Cu-C 3 N 4. The possible reaction intermediates along with different reaction pathways on three active sites of Cu-C 3 N 4 (Cu, C, and N) were obtained by density functional theory (DFT) computations. The most probable reaction pathway toward C 2 H 4 production is 1.08 eV at open circuit conditions, which is benefited by the synergistic effect of both Cu and C active sites. Comparing with other pathways utilizing Cu/N and C/N active sites, the carbon atom provides a perfect settling centre for the first CO 2 after reduction by Cu and leaves Cu vacant for the second CO 2 reduction. Our study provides reaction mechanism insights for C 2 production on Cu-C 3 N 4 and sheds light on designing electrocatalysts with dual active sites. [ABSTRACT FROM AUTHOR]