Formation of flaky carbon nitride and beta-Indium sulfide heterojunction with efficient separation of charge carriers for enhanced photocatalytic carbon dioxide reduction

The flaky carbon nitride containing nitrogen defects (NDCN) could effectively perform the photocatalytic reduction of carbon dioxide (CO2) due to its abundant active sites. Reducing the recombination of electrons and holes was also a method of semiconductor photocatalyst design. A nanosphere ball-flower Indium sulfide (In2S3) was synthesized via a simple hydrothermal approach, and then calcined to obtain the β-In2S3/NDCN heterojunction photocatalyst and applied for CO2 photocatalytic reduction. The best total yield (carbon monoxide, CO: 20.32 μmol·g-1·h-1; methane, CH4: 2.12 μmol·g-1·h-1) could be obtained at the optimized 20% β-In2S3/NDCN under near room temperature and pressure and without using any sacrificial agents or promoters, almost 1.7 times higher compared with NDCN. The composite catalyst still exhibited excellent stability after four cycles. The improvement of excellent performance was due to not only the enhancement of fine CO2 adsorption/activation and the light absorption ability, but also attributed to the formation of heterojunction, which accelerated the effective separation of electrons and holes. This work might provide a novel approach to design carbon nitride heterojunction photocatalysts with nitrogen defects for CO2 utilization.