Construction of Bi2WO6/RGO/g-C3N4 2D/2D/2D hybrid Z-scheme heterojunctions with large interfacial contact area for efficient charge separation and high-performance photoreduction of CO2 and H2O into solar fuels

We have rationally constructed a hybrid heterojunction comprising of Bi2WO6, reduced graphene oxide, and g-C3N4 (BWO/RGO/CN) with a 2D/2D/2D configuration for efficient photoreduction to generate solar fuels. These heterojunctions displayed dramatically improved performance towards CO2 reduction to generate CO and CH4 under visible-light irradiation, compared to the base material (CN), P25 as reference, as well as binary BWO/CN and RGO/CN heterojunctions. Particularly, the BWO/RGO/CN heterojunctions with 1 wt. % RGO and 15 wt. % BWO achieved record performance in the yields of carbonaceous products (CO + CH4) compared to other synthesized catalysts, with a selectivity of 92% against H2. The remarkable photocatalytic performance was mainly attributed to the unique 2D/2D/2D architecture that creates large interfacial contact between the constituent materials for rapid charge transfer, to hinder the direct recombination of photoinduced electrons and holes. Notably, RGO played two significant roles: as a supporter to capture the electrons from CN, and as a redox mediator to promote the Z-scheme charge transfer between CN and BWO. The result is a greater extent of charge separation in the present BWO/RGO/CN heterojunction system, as evidenced by the photoluminescence, photocurrent responses, and electron microscopy findings. More importantly, the heterojunctions displayed excellent stability during recycling tests with no obvious loss in the generation of CO and CH4 from photoreduction of CO2. This interesting interfacial engineering approach presented herein offers a promising route for the rational design of a new class of layered multicomponent heterojunctions with 2D/2D/2D architecture for various applications in environmental protection and solar energy conversion.