Single-atom catalysts (SACs) have great potential in electrocatalysis.Their performance can be rationally optimized by tailoring the metal atoms,a djacent coordinative dopants, and metal loading. However,doing so is still agreat challenge because of the limited synthesis approach and insufficient understanding of the structure-property relationships.H erein, we report an ew kind of Mo SACw ith au nique O,S coordination and ah igh metal loading over 10 wt %. The isolation and local environment was identified by high-angle annular dark-field scanning transmission electron microscopy and extended X-ray absorption fine structure.T he SACs catalyze the oxygen reduction reaction (ORR) via a2 e À pathway with ah igh H 2 O 2 selectivity of over 95 %i n0 .10 m KOH. The critical role of the Mo single atoms and the coordination structure was revealed by both electrochemical tests and theoretical calculations. Figure 4. Reaction mechanism of single Mo atom supported by O,Sdoped graphene substrate. a) Free energy diagram of 2e À ORR on three investigated substrates at equilibriumpotential of the reaction. b) Atomic configuration of OOH* adsorption on Mo-O 3 S-C. c) Atomic configuration of OOH* adsorptiono nMo-S 4 -C.

The electrochemical carbon dioxide reduction reaction to syngas with controlled CO/H 2 ratios has been studied on Pd-based bimetallic hydrides using a combination of in situ characterization and density functional theory calculations. When compared with pure Pd hydride, the bimetallic Pd hydride formation occurs at more negative potentials for Pd-Ag, Pd-Cu, and Pd-Ni. Theoretical calculations show that the choice of the second metal has a more significant effect on the adsorption strength of *H than *HOCO, with the free energies between these two key intermediates (i.e., ΔG(*H)–ΔG(*HOCO)) correlating well with the carbon dioxide reduction reaction activity and selectivity observed in the experiments, and thus can be used as a descriptor to search for other bimetallic catalysts. The results also demonstrate the possibility of alloying Pd with non-precious transition metals to promote the electrochemical conversion of CO 2 to syngas.

The electrochemical CO2 reduction reaction (CO2RR) to yield synthesis gas (syngas, CO and H2) has been considered as a promising method to realize the net reduction in CO2 emission. However, it is challenging to balance the CO2RR activity and the CO/H2 ratio. To address this issue, nitrogen‐doped carbon supported single‐atom catalysts are designed as electrocatalysts to produce syngas from CO2RR. While Co and Ni single‐atom catalysts are selective in producing H2 and CO, respectively, electrocatalysts containing both Co and Ni show a high syngas evolution (total current >74 mA cm−2) with CO/H2 ratios (0.23–2.26) that are suitable for typical downstream thermochemical reactions. Density functional theory calculations provide insights into the key intermediates on Co and Ni single‐atom configurations for the H2 and CO evolution. The results present a useful case on how non‐precious transition metal species can maintain high CO2RR activity with tunable CO/H2 ratios.