Hierarchical TiO2 spheres decorated with Au nanoparticles for visible light hydrogen production

Abstract

Hierarchical TiO₂ spheres composed of nanosheets are successfully synthesized via a simple solvothermal route. TiO₂ spheres with high surface area (∼100 m² g⁻¹) exhibit excellent photocatalytic activity. Au nanoparticles are loaded on the surface of TiO₂ nanosheets through anchor molecules – thiolglycolic acid. The LSPR absorption band at ∼550 nm of Au nanoparticles is clearly observed in the diffusion reflective UV-Vis spectra. H₂ production results show that the TiO₂ spheres have higher photocatalytic activity than commercial P25 TiO₂. After loading with Au nanoparticles, TiO₂–Au spheres display a 27.6 μmol (g⁻¹ h⁻¹) H₂ production rate under visible light irradiation (λ > 420 nm) because the localized surface plasmon resonance (LSPR) of Au nanoparticles enhances the visible light absorption. Furthermore, the H₂ production rate could be improved to 92.4 μmol (g⁻¹ h⁻¹) for TiO₂ spheres loaded with both Au and Pt nanoparticles. Based on these results, we propose a possible mechanism. Under UV light, TiO₂ absorbs UV light and generates excited electrons, passing to Au nanoparticles for H₂ production. In the case of visible light irradiation, the hot electrons are generated from Au nanoparticles due to the LSPR effect. And then the hot electrons are transferred from the Au nanoparticles to TiO₂ and cocatalyst Pt nanoparticles for H₂ generation.