Efficient photocatalytic overall water vapor splitting over amorphous Ni(OH)₂/Ni₂B heterojunctions

Developing efficient photocatalysts for solar-driven overall water vapor splitting is crucial for sustainable hydrogen production. However, current photocatalytic efficiencies are limited by inadequate hygroscopicity, sluggish proton transport, and rapid recombination of photogenerated electron-hole pairs. Here, we report the successful synthesis of an amorphous Ni(OH)₂/Ni₂B heterojunction material with a core-shell structure by regulating the reducing environment during the formation of nickel boride. This material exhibits highly efficient overall water vapor splitting performance without any cocatalysts. Under simulated solar irradiation, the optimized sample achieves a hydrogen production rate of 976 micromol·g^-1·h^-1, with near-stoichiometric evolution of hydrogen and oxygen, an apparent quantum yield of 5.4 %, and a solar-to-hydrogen conversion efficiency of 3.8 %. The enhanced performance is attributed to the unique amorphous/amorphous heterojunction structure that promotes effective charge separation, the abundant surface hydroxyl groups that improve proton transport and hygroscopicity, and the formation of photo-induced frustrated Lewis pairs (FLPs). Our findings shed light on the critical role of amorphous structures and surface chemistry in boosting photocatalytic activity, paving the way for the rational design of advanced photocatalysts for overall water vapor splitting.