Constructing functionalized plasmonic gold/titanium dioxide nanosheets with small gold nanoparticles for efficient photocatalytic hydrogen evolution.

Small plasmonic Au nanoparticles (NPs)-decorated with TiO nanosheets were fabricated to improve the photocatalytic performance. The Au/TiO nanosheets with Au NPs of different sizes ranging from ∼3 nm to 28 nm were prepared by using hydrothermally obtained TiO nanosheets as substrate via urea and light reduction method. During synthesis, the obtained Au NPs through urea reduction treatment in different calcination temperatures possessed smaller size (∼3-13 nm) than those of the light reduction method (∼28 nm). The introduced Au NPs were tightly loaded on the surface of TiO nanosheets through in situ growth reduction process of chloroauric acid. The emergence of smaller Au NPs promoted the photocatalytic performance over Au/TiO nanosheets. The as-prepared Au/TiO nanosheets with small Au NP sizes of ∼3-5 nm showed the highest photocatalytic rate of hydrogen production (∼230 µmol·h) under xenon lamp illumination, exceeding more than twice that of Au/TiO nanosheets with loading of larger Au NPs (∼28 nm). The favorable constituents and combination of Au/TiO nanosheets provided large surface adsorptive sites for reactant adsorption, introduced plasmonic effects and formed Schottky barrier junction via surface plasmon resonance. The Schottky barrier height was lower due to the presence of smaller Au NPs, thereby enhancing the charge separation through the Schottky transfer hub to neighboring TiO nanosheets. The synergistic effect between the plasmonic hot carrier-driven Au NPs and TiO nanosheets was discussed. The photocatalytic mechanism was also proposed for the fabrication of visible light-restricted photocatalysts with smaller Au NPs.