Fast and spontaneous reduction of gold ions over oxygen-vacancy-rich TiO2: A novel strategy to design defect-based composite photocatalyst Original Research Article

A novel strategy has been developed for spontaneous reduction of gold ions on the TiO2 with oxygen vacancies (TiO2-OV) to obtain defect-based composite photocatalyst, during which neither additional reducing agents nor surfactants are required. The as-formed metallic gold nanoparticles are partially embedded into the surface of TiO2 resulting from the binding with OV on the TiO2 surface. Such an intimate interfacial contact between gold nanoparticles and TiO2 can contribute to improving the separation and transport of charge carriers photogenerated from Au-TiO2-OV hybrids under visible light irradiation as well as stabilizing gold nanoparticles on TiO2. It is revealed that the electron transfer from OV states of TiO2-OV to gold ions is responsible for the spontaneous formation of metallic gold nanoparticles. The results show that Au-TiO2-OV shows enhanced visible light photoactivity toward Rhodamine B (RhB) degradation compared to the original TiO2 and TiO2-OV. The wavelength dependent photoactivity analysis further clarifies that the surface plasmon resonance (SPR) due to the excitation of gold nanoparticles under visible light irradiation is the driving force for the enhanced visible light photoactivity. It is hoped that our current work would provide a simple, fast strategy to synthesize defect-based composite photocatalysts for target applications.