Facile synthesis of Co2(OH)3Cl/cobalt carbide/reduced graphene oxide composites for enhanced dye-sensitized photocatalytic H2 evolution

Abstract

Photocatalytic H₂ evolution from water splitting using catalysts has proven to be a promising strategy. In photocatalytic H₂ evolution, a hydrogen evolution cocatalyst is necessary. The cocatalyst should be inexpensive and efficient. In this work, a hollow Co₂(OH)₃Cl/cobalt carbide/reduced graphene oxide (RGO) composite was fabricated as a cocatalyst via the one-step thermal treatment at low temperature (300 °C and 350 °C) of CoCl₂/graphene oxide (GO). Cobalt carbide was formed based on the strong interaction between GO and Co²⁺. GO not only provides the carbon source for cobalt carbide, but also acts as a soft template of a hollow structure and promotes the distribution of active species. The obtained sample exhibits a much higher dye-sensitized photocatalytic H₂ evolution activity than the catalysts prepared at high temperature (500 °C and 600 °C), which mainly consist of CoO/Co/cobalt carbide/RGO. This enhanced activity is ascribed to the formation of highly dispersed cobalt carbide and Co₂(OH)₃Cl, the effective electron transfer between them, and the ability of Co₂(OH)₃Cl to efficiently convey electrons from excited dye molecules. The highest apparent quantum yield of dye-sensitized photocatalytic H₂ evolution obtained using our catalyst was 28.3% at 420 nm. The possible mechanism is also discussed.