Cobalt−Iron Oxide Nanosheets for High‐Efficiency Solar‐Driven CO2−H2O Coupling Electrocatalytic Reactions

Abstract Solar‐driven electrochemical overall CO 2 splitting (OCO 2 S) offers a promising route to store sustainable energy; however, its extensive implementation is hindered by the sluggish kinetics of two key reactions (i.e., CO 2 reduction reaction and oxygen evolution reaction (CO 2 RR and OER, respectively)). Here, as dual‐functional catalysts, Co 2 FeO 4 nanosheet arrays having high electrocatalytic activities toward CO 2 RR and OER are developed. When the catalyst is applied to a complete OCO 2 S system driven by a triple junction GaInP 2 /GaAs/Ge photovoltaic cell, it shows a high photocurrent density of ≈13.1 mA cm −2 , corresponding to a remarkably high solar‐to‐CO efficiency of 15.5%. Density functional theory studies suggest that the Co sites in Co 2 FeO 4 are favorable to the formation of *COOH and *O intermediates and thus account for its efficient bifunctional activities. The results will facilitate future studies for designing highly effective electrocatalysts and devices for OCO 2 S.