Self-healing redox chemistry in Cu-TiO₂ photocatalysts for enhanced hydrogen production

Hydrogen production from sunlight and abundant feedstock is central to a sustainable energy future, yet most efficient photocatalysts rely on costly noble metals. Here we report a scalable one-pot synthesis of CuO_x-TiO₂ photocatalysts that achieve a methanol-assisted hydrogen evolution rate of 30.6 mmol g^-1 h^-1, among the highest reported for Cu-based systems. The optimized 12% CuO_x-TiO₂ maintains >90% activity retention over 50 h and performs reproducibly at the gram scale, underscoring its industrial potential. Spectroscopic and computational analyses uncover a dynamic CuO ⇆ Cu₂O ⇆ Cu⁰ cycle and a previously unrecognized corrosion-healing redox loop, in which transient Cu(OH)₂ is continuously reduced back to Cu₂O by methanol-derived intermediates. This self-healing mechanism stabilizes the active Cu₂O phase, suppresses deactivation, and sustains long-term performance. Density functional theory reveals near-optimal hydrogen adsorption free energy (ΔG_H* = -0.06 eV) on Cu-TiO₂(101), comparable to Pt(111), confirming copper's potential as a low-cost alternative to noble metals. These findings establish redox self-healing catalysis as a powerful design principle for durable, scalable, and earth-abundant photocatalysts for solar hydrogen production.