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 (O_V), 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.