Electrochemical Conversion of CO2 to Syngas with Controllable CO/H2 Ratios over Co and Ni Single-Atom Catalysts.

The electrochemical CO2 reduction reaction (CO2 RR) 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 CO2 RR 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 CO2 RR. 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 CO2 RR activity with tunable CO/H2 ratios.