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

Photocatalytic H-2 evolution from water splitting using catalysts has proven to be a promising strategy. In photocatalytic H-2 evolution, a hydrogen evolution cocatalyst is necessary. The cocatalyst should be inexpensive and efficient. In this work, a hollow Co-2(OH)(3)Cl/cobalt carbide/reduced graphene oxide (RGO) composite was fabricated as a cocatalyst via the one-step thermal treatment at low temperature (300 degrees C and 350 degrees 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 H-2 evolution activity than the catalysts prepared at high temperature (500 degrees C and 600 degrees C), which mainly consist of CoO/Co/cobalt carbide/RGO. This enhanced activity is ascribed to the formation of highly dispersed cobalt carbide and Co-2(OH)(3)Cl, the effective electron transfer between them, and the ability of Co-2(OH)(3)Cl to efficiently convey electrons from excited dye molecules. The highest apparent quantum yield of dye-sensitized photocatalytic H-2 evolution obtained using our catalyst was 28.3% at 420 nm. The possible mechanism is also discussed.