Mesoporous plasmonic Au–TiO2 nanocomposites for efficient visible-light-driven photocatalytic water reduction

The mesoporous Au–TiO2 nanocomposites with different Au concentrations were prepared via a co-polymer assisted sol–gel method. The structures have been characterized by powder X-Ray diffraction, N2 adsorption–desorption isotherms, diffuse reflectance UV–Vis spectroscopy, X-ray photoemission spectroscopy, transmission electron microscopy. Most generated Au nanoparticles were embedded in the mesoporous TiO2 matrix. The prepared Au–TiO2 nanocomposites exhibit remarkable visible-light activity for H2 evolution from photocatalytic water reduction in the presence of ascorbic acid as the electron donor. By comparing with Pt–TiO2 samples, we found that the visible-light activity of the Au–TiO2 nanocomposites could be partially contributed by the defects/impurity states in the TiO2 matrix, while the gold surface plasmons could significantly enhance the weak visible-light excitation of TiO2 matrix. In addition, further studies by controlling irradiation wavelengths suggest that some plasmon-excited electrons could transfer from Au nanoparticles to the contacting TiO2 to reduce water for H2 generation. We believe that these Au–TiO2 nanocomposites as well as the mechanistic studies would have considerable impact on future development of metal-semiconductor hybrid photocatalysts for efficient solar hydrogen production.