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

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.