Guiding Electrochemical Carbon Dioxide Reduction toward Carbonyls Using Copper Silver Thin Films with Interphase Miscibility
Steering the selectivity of Cu-based electrochemical CO2 reduction (CO2R) catalysts toward targeted products will serve to improve the technoeconomic outlook of technologies based on this process. Using physical vapor deposition as a tool to overcome thermodynamic miscibility limitations, CuAg thin films with nonequilibrium Cu/Ag alloying were prepared for CO2R performance evaluation. In comparison to pure Cu, the CuAg thin films showed significantly higher activity and selectivity toward liquid carbonyl products, including acetaldehyde and acetate. Suppressed activity and selectivity toward hydrocarbons and the competing hydrogen evolution were also demonstrated on CuAg thin films, with a greater degree of suppression observed at increasing nominal Ag compositions. Compositional-dependent CO2R trends coupled with physical characterization and density functional theory suggest that significant miscibility of Ag into the Cu-rich phase of the catalyst underpinned the observed CO2R trends through tuning of adsorbate and reaction intermediate binding energies on the surface.