Cu2O/CeO2 Photo‐electrochemical Water Splitting: A Nanocomposite with an Efficient Interfacial Transmission Path under the Co‐action of a p–n Heterojunction and Micro‐mesocrystals

Abstract Cu2O is an ideal p‐type material for photo‐electrochemical (PEC) hydrogen evolution, although serious electron–hole recombination and photocorrosion restrict its further improvement for PEC activity. In this work, CeO2 nanoparticles (NPs) self‐assemble on the surface of Cu2O octahedra, thus successfully forming a Cu2O/CeO2 structure in which p–n heterojunctions and micro‐mesocrystals (m‐MCs) work together. The optimum Cu2O/CeO2 composite, without the use of any cocatalyst, exhibits a fivefold higher photocurrent density (4.63 mA cm−2 at 0 V vs. the reversible hydrogen electrode) than that of Cu2O octahedra, which is better than most Cu2O‐based photocathodes without cocatalyst and even comparable with advanced Cu2O‐based photocathodes. The hydrogen production of the optimal Cu2O/CeO2 (Faradaic efficiency of ∼100 %) is 17.5 times higher than that of pure Cu2O octahedra, and the photocurrent shows almost no decay under the 12 h stability test. The delicately designed Cu2O/CeO2 structure in this work provides reference and inspiration for the design of cathodes materials.