Tuning the subsurface oxygen of Ag2O-derived Ag nanoparticles to achieve efficient CO2 electroreduction to CO

Abstract

Electrochemical CO2 reduction reaction (CO2RR) to value-added chemicals at low cost is highly attractive in mitigating the environmental issues caused by excessive greenhouse gasses emission. In this work, Ag2O-derived Ag nanoparticles (OD-Ag NPs) with the optimized subsurface oxygen were obtained through steering the reducing current density (ire) upon in situ Galvano-statically reducing Ag2O NPs to metallic Ag, and it is found that the OD-Ag NPs thus obtained exhibit high catalytic activity and selectivity towards CO production. Specifically, the OD-Ag NPs derived from an intermediate ire of ‒1 mA⋅cm‒2 achieve the high Faradaic efficiencies (FECO) of over 90% in a wide potential window over 450 mV, whereas either smaller (‒0.1 mA⋅cm‒2) or larger (‒10 mA⋅cm‒2) ire reduces the overall CO2RR performance. This suggests that tuning the ire to change the subsurface oxygen of oxide-derived catalysts is beneficial to improve their selectivity. Theoretical DFT calculations and analysis rationalize the experimental observation, and reveal that the outstanding performance of the OD-Ag NPs benefits from the suitable concentration of subsurface oxygen which not only enhances the adsorption of intermediate *COOH, but also optimizes the free energy of the reaction pathways.