Mesoporous plasmonic Au-TiO ₂ nanocomposites for efficient visible-light-driven photocatalytic water reduction

The mesoporous Au-TiO ₂ 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, N ₂ adsorption-desorption isotherms, diffuse reflectance UV-Vis spectroscopy, X-ray photoemission spectroscopy, transmission electron microscopy. Most generated Au nanoparticles were embedded in the mesoporous TiO ₂ matrix. The prepared Au-TiO ₂ nanocomposites exhibit remarkable visible-light activity for H ₂ evolution from photocatalytic water reduction in the presence of ascorbic acid as the electron donor. By comparing with Pt-TiO ₂ samples, we found that the visible-light activity of the Au-TiO ₂ nanocomposites could be partially contributed by the defects/impurity states in the TiO ₂ matrix, while the gold surface plasmons could significantly enhance the weak visible-light excitation of TiO ₂ matrix. In addition, further studies by controlling irradiation wavelengths suggest that some plasmon-excited electrons could transfer from Au nanoparticles to the contacting TiO ₂ to reduce water for H ₂ generation. We believe that these Au-TiO ₂ nanocomposites as well as the mechanistic studies would have considerable impact on future development of metal-semiconductor hybrid photocatalysts for efficient solar hydrogen production.