Zinc-Modified Copper Catalyst for Efficient (Photo-)Electrochemical CO2 Reduction with High Selectivity of HCOOH Production

(Photo-)electrochemical carbon dioxide (CO2) reduction has gained significant importance as it has the potential to yield valuable organic products by utilizing renewable energy. Here, CuZn alloy catalysts fabricated by the electrodeposition method were evaluated as efficient catalysts for selective CO2 reduction to HCOOH. By varying the concentration of zinc (Zn) in CuZn bimetallic catalysts, the Faradaic efficiency and partial current density of HCOOH on CuZn-0.5 were enhanced nearly 4 and 5 times, respectively, as compared to Cu foil. Furthermore, we developed a photoelectrochemical cell system for CO2 reduction by using the CuZn-0.5 catalyst as the cathode and BiVO4 as the photoanode. HCOOH formation was maximized with approximately 60% Faradaic efficiency under simulated sunlight, which is among the highest for copper-based cathodes. The higher selectivity of CuZn originates from the synergistic effect of Cu and Zn. The reaction process is further studied by in situ Raman and density functional theory calculations. This work can provide a detailed understanding of developing a catalyst with highly selective HCOOH formation.