Fabrication of Bi-BiOCl/MgIn2S4 heterostructure with step-scheme mechanism for carbon dioxide photoreduction into methane

Abstract Step-scheme (S-scheme) Bi-BiOCl/MgIn2S4 heterostructure (BBOC/MIS) was successfully fabricated via NaBH4 reduction and facile in-situ hydrothermal process and applied in photocatalytic CO2 reduction. A part of BBOC ultrathin nanosheets processed by ultrasonication exfoliation was grown on the surfaces of MIS marigold microflower. Another part of BBOC and MIS exhibited as the core and shell of BBOC/MIS, respectively. The morphology, band alignment, optical and electronic characteristics of photocatalysts were comprehensively studied via diverse characterization methods. The S-scheme BBOC/MIS heterojunction possessed superior photocatalytic performance and well reusability to primarily convert CO2 into CH4 with high efficiency under the simulated solar light irradiation without using any sacrificial agent in water. Experimental results displayed that the 6% BBOC/MIS sample behaved the optimal photocatalytic performance in photocatalytic reduction of CO2, and its maximum CH4 production rate could reach up to 4.29 μmol g−1 h−1, which was about 7.56 times as high as that of unadulterated MIS. The enhanced photocatalytic performance of BBOC/MIS could be attributed to the improved visible light response and highly-efficient separation of the photogenerated electron-hole pairs between BBOC and MIS through the S-scheme heterojunction interface. In addition, the metal Bi acted as the bridge connecting the BOC and MIS to facilitate the charge transfer, which greatly promoted the CO2 photocatalytic reduction to CH4.