Photoelectrochemical CO2 Reduction via Cu2O/CuFeO2 Hierarchical nanorods photocatalyst

Although cuprous oxide, Cu2O, has attracted attention as a promising p‐type semiconductor material for carbon dioxide reduction (CO2RR) photocatalysts, serious stability problems have always occurred due to photocorrosion. In this work, we fabricated hierarchical‐structured photocathodes with CuFeO2 on Cu2O nanorods by spray pyrolysis and oxygen‐controlled heat treatment to improve the stability of Cu2O from a thermodynamic perspective. Field‐emission scanning electron microscopy, field‐emission transmission electron microscopy and X‐ray diffraction confirmed that the Cu2O/CuFeO2 hierarchical nanorod structure was successfully fabricated. It was observed that the photocathodes show enhanced stability as the Fe content increases. Therefore, we report that the CuFeO2 layer enhances the stability of the Cu2O nanorod photocathode. A photocathode with a Cu : Fe atomic ratio of 1.52 : 1 has a current density of 1.1 mA/cm2 at 0.35 VRHE even after 10 linear voltage sweep repetitions, a decrease of only 8 % compared to the current density at the first sweep. Additionally, formate and acetate were produced during the CO2RR, exhibiting faradaic efficiencies (FEs) of 21.6 % and 68.6 %, respectively. Strength through iron: Newly fabricated Cu2O/CuFeO2 hierarchical nanorods have been applied as a photocatalyst for carbon dioxide reduction. They show high stability and current density and the photocathodes show enhanced stability as the ratio of Fe increases.