Copper-Graphene-TiO2 Hybrid Materials for Photocatalytically Assisted H2 Generation
Hydrogen, as energy carrier, is a zero-emission fuel. Being green and clean, it is considered to play an important role in energy and environmental issues. Photocatalytic water splitting is a process used to generate hydrogen from the dissociation of water. Titanium dioxide is still the archetype material for photocatalytic water splitting. However, because of the fast recombination of the photo-generated exciton, the yield of the reaction is typically low. In this work, we have modified the surface of titanium dioxide with copper and copper/graphene to sensitise it to visible light, and to increase the spatial charge carrier separation, thus extending the quantum yield of H2 production from methanol/water mixtures. Results showed that, in the analysed system, exists an optimum amount of copper plus graphene (i.e. 0.5 mol% copper plus 0.5 wt% graphene) to grant a two-fold increase in the photocatalytic hydrogen generation compared to that of bare titania. That system proved itself to be complex and dynamic. This was attributed to the increased spatial charge carrier separation exploited by graphene (under 365 and 405 nm irradiation), and to the continuous reduction of Cu(II) to Cu(I) due to IFCT that has proven to be an excellent visible-light sensitiser in the copper/graphene-titania system.
Hybrid titania-copper-graphene materials could therefore be exploited in the field of light-to-energy applications.