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.