Constructing a B4C3/MoS2 heterojunction through interfacial coupling for enhancing optical absorption and photocatalytic H2 evolution activity: A hybrid theoretical study

A single photocatalyst has poor photocatalytic performance while combining two or more materials to form a heterostructure can effectively improve photocatalytic efficiency. A single-molecule layer B4C3 and MoS2 was selected to construct the heterojunctions used in visible-light hydrogen production in photocatalysts. The electronic properties and optical characteristics of the heterojunctions composed of MoS2 and B3C4 were calculated based on the density functional theory (DFT). The MoS2/B4C3 (MSBC) van der Waals (vdW) heterojunction has an indirect bandgap (Eg=1.525 V), while the B4C3/MoS2(BCMS) vdW heterostructure has a direct bandgap (Eg=1.510 V). They possess an energy band with the intrinsic type, which allows them to efficiently separate photo-generated carriers to improve the longevity of photogenerated electrons. The positions of the band edges in the heterojunctions of MSBC and BCMS can meet the requirements for decomposing water into hydrogen. In the MSBC and BCMS heterostructures, B4C3 monolayers carry negative charges while MoS2 monolayers carry positive charges, so an electric field is created at the contact surface of MSBC or BCMS heterojunction spontaneously. The BCMS and MSBC heterostructures have different solar to hydrogen (STH) efficiencies, which are 12.3% for BCMS (pH=0) and 1.24% for MSBC (pH=7). These results provide theoretical guidance for the composition of high-performance photocatalysts used in visible-light hydrogen production.