Microenvironment Evolution at Triple-phase Interface on the CO2RR Process of Hydrophobic Oxide-derived Copper

Abstract The local microenvironment of electricity-powered CO2 electroreduction reaction (CO2RR) surrounding the catalyst-electrolyte-gas triple-phase interface plays a crucial role in catalytic activity and selectivity as it affects reaction pathways and species transport. However, it still needs to be explored and understood regarding the impact of microenvironment evolution on the CO2RR performance. We report here a hydrophobic oxide-derived copper foam with villous nanowires on the surface that demonstrates significant suppressed HER and enhanced C2+ selectivity in H-type cell. In-situ 3D Raman mapping and in-situ Raman spectra investigation on micro-environmental species reveal that high local pH and fast CO2 mass transfer were simultaneously allowed in the microenvironment of the triple-phase interface because of the special hydrophobic structure. On this mechanism, the material reaches a minimum H2 Faradaic efficiency (FE) of 6.6% and maximum C2+ FE of 74.4% at the current density of 300 mA cm-2 in a flow cell under acidic conditions (pH=4) without an additional gas-diffusion layer (GDL). This study not only highlighted the importance of the microenvironment but also provided an effective method for tuning the triple-phase interface of CO2RR and demonstrated a promising application of the pure metal foam-based GDEs.