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.
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