Solid-State Proton Donors in Hydroxyl-Rich Ni3Ge2O5(OH)4 for Solar-Driven Hydrogen Evolution.

The hydrogen evolution reaction (HER) through water splitting is one of the most promising solutions to global energy and environmental challenges. In this study, using hydroxyl-rich Ni3Ge2O5(OH)4 as a photocatalyst, a novel, kinetically self-activated solar-driven gas-solid system for H2 production was demonstrated, where solid-state lattice hydroxyls (Ni-OH) serve as proton donors due to their low reaction barrier. The sustainable regeneration of Ni-OH is achieved through gaseous H2O molecule dissociation at the resultant oxygen vacancies (OV), which plays a critical role in enhancing proton activity. Under 5 h of testing, the system achieved a cocatalyst-free H2 yield of 311.8 μmol g-1 at the gas-solid interface, approximately 35 times higher than that of the triphasic system, and even 3.4 and 2.1 times higher than H2O splitting systems using triethanolamine or methanol as sacrificial agents, respectively. This work provides valuable insights into the design of advanced photocatalysts and the development of sustainable H2 production systems.