Effective charge separation towards enhanced photocatalytic activity via compositing reduced graphene oxide with two-phase anatase/brookite TiO2

•H2 production is greatly enhanced with rGO-anatase/brookite TiO2 composite photocatalyst.•More effective charge separation occurs when anatase/brookite TiO2 is coupled with rGO.•More cathodic conduction band potential of brookite is contributing to the high H2 production.•The roles of effective charge separation and conduction band position have been elucidated.

In this paper, we synthesized composites consisting of reduced graphene oxide (rGO) and two-phase anatase/brookite TiO2 particles. Results showed that with the addition of rGO to anatase/brookite TiO2, the photocatalytic H2 production from aqueous methanol solution over Pt loaded catalyst is greatly enhanced. This is attributed to effective charge separation leading to the inhibition of photogenerated electron–hole recombination as evidenced from photoluminescence (PL) spectroscopic measurement. Moreover, with the rGO – anatase/brookite TiO2 composite, the H2 production is 2.3 times the amount of H2 produced by rGO – P25 TiO2 (which consists of anatase and rutile particles) composite. The comparison illustrates the importance of the conduction band potential position. As the conduction band potential of brookite TiO2 is more cathodic than anatase and rutile TiO2, it is energetically more favorable for reductive hydrogen production. Through the concept of compositing rGO with two-phase semiconductor photocatalyst, our work has elucidated the importance of effective charge transfer as well as conduction band potential position in photocatalytic hydrogen generation.