Oxygen induced promotion of electrochemical reduction of CO2 via co-electrolysis.

Harnessing renewable electricity to drive the electrochemical reduction of CO2 is being intensely studied for sustainable fuel production and as a means for energy storage. Copper is the only monometallic electrocatalyst capable of converting CO2 to value-added products, e.g., hydrocarbons and oxygenates, but suffers from poor selectivity and mediocre activity. Multiple oxidative treatments have shown improvements in the performance of copper catalysts. However, the fundamental underpinning for such enhancement remains controversial. Here, we combine reactivity, in-situ surface-enhanced Raman spectroscopy, and computational investigations to demonstrate that the presence of surface hydroxyl species by co-electrolysis of CO2 with low concentrations of O2 can dramatically enhance the activity of copper catalyzed CO2 electroreduction. Our results indicate that co-electrolysis of CO2 with an oxidant is a promising strategy to introduce catalytically active species in electrocatalysis.