Function-switchable metal/semiconductor junction enables efficient photocatalytic overall water splitting with selective water oxidation products

A novel metal/semiconductor photocatalyst, Cu nanoparticles (NPs) modified TiO₂ hollow spheres (Cu/TiO₂), was designed for efficient photocatalytic overall water splitting (POWS) under both ultraviolet (UV) and visible (Vis) light. This Cu/TiO₂ photocatalyst possesses excellent POWS performance under Vis light at the highest level among the reported TiO₂-based photocatalysts. Interestingly, the metal/semiconductor junction formed between Cu and TiO₂ enables controlled water-oxidation product selectivity (H₂O₂ or O₂) via different reaction pathways regulated by irradiation wavelengths. Under UV light, the electrons excited in TiO₂ are captured by Cu NPs through the Cu/TiO₂ Schottky interface for H₂ production, with the photoholes in TiO₂ producing H₂O₂ through a two-electron process; whilst under Vis light, Cu NPs act as plasmon to inject hot electrons to TiO₂ for H₂ production, while O₂ is produced by hot holes on Cu NPs via a four-electron process. This rational design of function-switchable metal/semiconductor junction may be helpful to understand the mechanisms for POWS with desired gas/liquid water-oxidation products.