Facile fabrication of a noble metal-free photocatalyst: TiO2 nanotube arrays covered with reduced graphene oxide

One-dimensional TiO2 nanotubes arrays (TNT) are the subject of great current interest among the photocatalysis research community, however the relatively large bandgap that provides TiO2 with its excellent corrosion stability severely limits its absorption of solar spectrum energy. To increase the optical absorption of TiO2 while maintaining its otherwise commendable properties a number of approaches have been investigated including doping with non-metal or noble metal co-catalysts such as platinum, coupling with low band gap semiconductors, and the synthesis of carbon-based TiO2 composites. During the past few years graphene-based TiO2 nanostructures have been found to offer improved photoelectrochemical properties, with graphene enhancing light absorption as well as promoting rapid charge transfer. With the aim of replacing expensive noble metal co-catalysts, herein we report a noble metal-free novel nanostructured photocatalytic material fabricated using a facile synthesis approach, comprising a one-dimensional array of TNT covered with a reduced graphene oxide-TiO2 nanoparticles (rGO-TiO2 NP) composite. The novel nanostructure exhibits significantly improved photocurrent density and photochemical activity via conversion of CO2 into methane under simulated solar light irradiation. The improved performance appears due to the combined effect of enhanced light absorption and effective charge separation promoted by the rGO.