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 TiO hollow spheres (Cu/TiO), was designed for efficient photocatalytic overall water splitting (POWS) under both ultraviolet (UV) and visible (Vis) light. This Cu/TiO photocatalyst possesses excellent POWS performance under Vis light at the highest level among the reported TiO-based photocatalysts. Interestingly, the metal/semiconductor junction formed between Cu and TiO enables controlled water-oxidation product selectivity (HO or O) via different reaction pathways regulated by irradiation wavelengths. Under UV light, the electrons excited in TiO are captured by Cu NPs through the Cu/TiO Schottky interface for H production, with the photoholes in TiO producing HO through a two-electron process; whilst under Vis light, Cu NPs act as plasmon to inject hot electrons to TiO for H production, while O 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.