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-TiO 2 ) with up to sixfold enhanced water splitting efficiency compared to that of pure TiO 2 through loading La 2 O 3 onto TiO 2 . TEM at the atomic level revealed that the La species were preferentially intercalated at the interfaces of fine TiO 2 grains, forming sharp heterostructures of La 2 O 3 –TiO 2 . 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-TiO 2 at an elevated temperature. Additional density functional theory (DFT) calculations demonstrated that the built-in electric field of the La 2 O 3 –TiO 2 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-TiO 2 catalyst achieved a H 2 evolution rate of 35.92 μmol·g cat –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.