Microwave-assisted hydrothermal synthesis of graphene based Au–TiO2 photocatalysts for efficient visible-light hydrogen production

Abstract

The construction and application of visible-light-driven photocatalysts falls in the central focus for the efficient utilization of renewable solar energy, which provides unprecedented opportunities for addressing the increasing concerns on energy and environmental sustainability. Herein, graphene based Au–TiO₂ photocatalysts were fabricated by a simple, one-step microwave-assisted hydrothermal method, using Degussa P25 TiO₂ powder (P25), graphene oxide and HAuCl₄ aqueous solution as the raw materials. The effects of graphene introduction and gold loading on the photocatalytic hydrogen production rates of the as-prepared samples in a methanolic aqueous solution were investigated. The results indicated that Au–TiO₂–graphene composite had a significantly increased visible light absorption and enhanced photocatalytic H₂-production activity compared to the Au–TiO₂ composite. In comparison, the pure TiO₂, graphene–TiO₂ and graphene–Au had no appreciable visible-light-driven H₂ production. The enhanced photocatalytic H₂-production activity of the Au–TiO₂–graphene composite is ascribed to (1) the load of the Au nanoparticles which broadens the visible light response of TiO₂ due to the surface plasmon resonance (SPR) effect, and (2) the introduction of graphene, which functions as rapid electron transfer units, facilitating the space separation of photoelectron and hole pairs. The proposed H₂-production activity enhancement mechanism was further confirmed by the transient photocurrent response and electrochemical impedance spectroscopy (EIS) experiments.