Covalently functionalized graphene by thiourea for enhancing H2-evolution performance of TiO2 photocatalyst

Graphene as a well-known electron cocatalyst can enhance the hydrogen-production performance of photocatalysts due to its excellent conductivity. For highly efficient graphene-modified TiO₂ photocatalyst, besides the speedy electron transfer via graphene, it is significant to raise the interfacial hydrogen-generation reaction rate on the graphene surface. In this paper, thiourea (TU) can covalently functionalize graphene and act as effective H⁺-adsorbed active sites to improve the hydrogen-production efficiency of graphene-modified TiO₂ (TiO₂/rGO-TU). The TiO₂/rGO-TU sample was successfully prepared by a facile nucleophilic substitution reaction between the thiol (-SH) of thiourea and carboxyl (-COOH) of graphene. The TiO₂/rGO-TU could possess the maximum H₂-generation rate of 241.83 μmol h^?1 g^?1, which was 2.33 and 6.60 times greater than that of TiO₂/rGO and TiO₂, respectively. The enhanced photocatalytic activity of TiO₂/rGO-TU can be ascribed to the synergistic effect of graphene and thiourea, namely, the graphene functions as a cocatalyst to capture the photoexcited electrons of TiO₂ and the thiourea acts as effectual H⁺-adsorbed active sites to promote interfacial hydrogen generation. This study presents a feasible strategy for developing grephene-based photocatalysts for prospective applications in the hydrogen-production field.