Metal oxides are a promising material for designing highly
active
and selective catalysts for the electrochemical reduction of carbon
dioxide (CO2RR). Here, we designed a Cu/ceria catalyst
with high selectivity of methane production at single-atomic Cu active
sites. Using this, we report favorable design concepts that push the
product selectivity of methane formation by combining detailed structural
analysis, density functional theory (DFT), in situ Raman spectroscopy,
and electrochemical measurements. We demonstrate that a higher concentration
of oxygen vacancies on the catalyst surface, resulting from more available
Cu+ sites, enables high selectivity for methane formation
during CO2RR and can be controlled by the calcination temperature.
The DFT calculation and in situ Raman studies indicate that pH controls
the surface termination; a more alkaline pH generates hydroxylated
surface motifs with more active sites for the hydrogen evolution reaction.
These findings provide insights into designing an efficient metal
oxide electrocatalyst by controlling the atomic structure via the
reaction environment and synthesis conditions.