How To Boost Thermo–Photo Synergistic Water Splitting on TiO 2 ? A Water Trapping Strategy via Heterostructure Design

Thermo-photocatalytic overall water splitting has attracted considerable interest for utilizing solar energy. However, at elevated temperatures, the reaction rate is limited by inefficient contact between the catalyst and the vaporized water molecules. Herein, we report a catalyst (n-La-TiO2) with up to sixfold enhanced water splitting efficiency compared to that of pure TiO2 through loading La2O3 onto TiO2. TEM at the atomic level revealed that the La species were preferentially intercalated at the interfaces of fine TiO2 grains, forming sharp heterostructures of La2O3–TiO2. In situ characterization from XRD, XPS, and IR further unveiled an interface water stabilization mechanism through La(OH)3 formation and decomposition within the heterostructure of n-La-TiO2 at an elevated temperature. Additional density functional theory (DFT) calculations demonstrated that the built-in electric field of the La2O3–TiO2 heterostructure facilitated carrier transportation to the La interface layer toward a minimized energy barrier for the hydrogen evolution reaction (HER). The comprehensive mechanistic studies explained the highly active interface sites at high temperature. The final optimized 2-La-TiO2 catalyst achieved a H2 evolution rate of 35.92 μmol·gcat–1·h–1 at 400 °C without sacrificial agents. This study provides broader insights and ideas for the design and development of catalysts for the thermo-photocatalytic overall water splitting.