Design of type-II heterojunction MoS2/gC3N4/graphene ternary nanocomposite for photocatalytic CO2 reduction to hydrocarbon fuels: In aqueous solvents with a sacrificial donor

Abstract

MoS2/gCN/graphene ternary nanocomposites were synthesized using the ultrasonication-assisted calcination method, and different amounts of gCN were loaded to prepare the ternary nanocomposites. The hybrid MoS2/gCN/graphene ternary nanocomposites showed significant responses to an incident light source, and electrochemical analysis indicated that the junctions of the rose-like MoS2, metal-free gC3N4, and 2D graphene positively changed the electronic structure without changing the internal crystal and electronic structures of each unary nanocomposite, thus offering an effective separation of the electron–hole pairs. Therefore, this process provides abundant photoinduced electrons for CO2/CH3OH and holes for the water oxidation reactions, which can in turn be employed for the photoreduction of CO2. In addition, the charge-carrier mechanism of the ternary nanocomposites was labeled as type-II heterojunction. The use of an aqueous solvent with a basic salt and donor scavenger enhanced the Type-II heterojunction photocatalytic CO2 reduction because of the efficient supply of hydrated CO2 molecules and the large number of electrons required for the complex reduction reaction of CO2 to alcohol. Control of the external and internal factors for photocatalytic CO2 reduction further increased the selectivity for the reduction of CO2 and CH3OH. This work demonstrates the successful integration of gCN, graphene, and rose-like MoS2 with enhanced catalytic activity. Moreover, this work is expected to be of great importance in the development of photocatalyst materials for CO2 reduction while allowing advanced tunable chemical and structural properties of the metal-free gCN and rose-like MoS2.