In Situ-Fabricated In₂S₃-Reduced Graphene Oxide Nanosheet Composites for Enhanced CO₂ Electroreduction to Formate

The use of renewable electricity to catalyze carbon dioxide reduction is a promising method for CO2 utilization. However, the lack of highly efficient catalysts for CO2 reduction seriously limits its industrial applications. As a prototype, an ultrathin indium sulfide nanosheet (In2S3 NS) was synthesized and fabricated in situ on reduced graphene oxide (RGO) to obtain an In2S3–RGO composite. Induced by the two-dimensional (2D) structure of graphene oxide, the thickness of the In2S3 NSs was reduced from 30.2 to 3.9 nm. Simultaneously, the (440) plane of In2S3 NSs was preferentially grown parallel to the graphene plane, which was proven to possess a higher selectivity in catalyzing CO2 electroreduction to formate than the (111) and (311) planes by density functional theory calculations. Attributed to the 2D structure and full exposure of the (440) planes, a large electrochemically active surface area and high density of optimum active sites were both realized on the In2S3–RGO hybrids, leading to 91% faradaic efficiency of formate at −1.2 V versus The reversible hydrogen electrode in 0.1 M KHCO3 is 3.5 times that of bulk In2S3 (26%). Our work provides an effective way to prepare 2D transition metal catalysts with controllable crystal face exposure for specific reactions.