Well-designed 2D vanadium carbide (V2C) MXenes supported LaCoO3/g-C3N4 heterojunction for highly efficient and stable photocatalytic CO2 reduction to CO and CH4

Abstract

The fabrication of heterostructure photocatalysts, incorporating co-catalysts to replace noble metals, is a challenging task aimed at enhancing the efficient separation and transfer of photo-induced electrons and holes. Herein, well-designed 2D V2C MXenes cocatalyst-assisted LaCoO3 perovskite-based g-C3N4 composite was investigated for photocatalytic CO2 reduction to cleaner fuels. As a novel cocatalyst, V2C MXene exhibits remarkable potential in forming intimate contact with LaCoO3/g-C3N4 heterojunction, enabling higher visible light absorbance and proficient charge carrier separation. With the optimized LaCoO3/g-C3N4/V2C heterojunction, CH4 and CO yield rates of 332 and 171 µmol g−1 h−1 were obtained with their selectivity of 34% and 66%, respectively. This substantially higher photocatalytic activity for CO2 reduction with CH4 as the main product was 11.85, 11.10, and 6.91 times greater than LaCoO3, g-C3N4, and LaCoO3/g-C3N4, respectively. The performance of the composite was further investigated under various operating parameters such as the effect of sacrificial reagent, catalyst loading and pressure. The highest CO and CH4 generation rates were achieved with a pressure of 0.4 bars, which was due to the increased rate of CO2 attachment over the V2C-assisted nanotexture. Among the water, methanol and hydrogen sacrificial reagents, the highest photoactivity was achieved with H2, 1.33 folds more than using water for CH4 production, due to involving CO2 methanation reaction with efficient charge carrier generation. Thus, V2C MXene can be used as a promising cocatalyst to replace noble metals and would be used for photocatalytic CO2 reduction to solar fuels and can also be used for other solar energy applications.