2D/2D V2C mediated porous g-C3N4 heterojunction with the role of monolayer/multilayer MAX/MXene structures for stimulating photocatalytic CO2 reduction to fuels

Abstract

2D vanadium carbide (V2C) MXene nanosheets coupled 2D porous g-C3N4 (PCN) was designed and tested for photocatalytic CO2 reduction under visible light. Controlled coupling g-C3N4 with V2C MXene resulted in higher visible light absorption and efficient charge separation. Comparatively, V2C MXene found more favorable than V2AlC MAX due to more proficient charge separation. Highest performance was achieved with optimized 15%-V2C/g-C3N4, in which CO and CH4 generation rates of 151 and 205 µmol g−1, respectively, were attained. This enhancement was significantly higher than using V2AlC/g-C3N4 and pure g-C3N4 samples due to higher conductivity and large CO2 adsorption capacity. The performance of V2C/g-C3N4 composite was further examined under a variety of conditions such as pressure, catalyst loading, and reducing agents. With increasing pressure, higher yield of CO and CH4 was attained due to increased reactant adhesion to the catalyst surface, whereas increasing catalyst loading has adverse effects. Water was the best reducing agent for CO evolution, while the methanol–water system enhanced CH4 generation. Furthermore, the stability of composite lasted for several cycles without showing any obvious deterioration. The potential outcomes are assigned to a porous structure with intimate contact, effective charge carrier separation and porous 2D g-C3N4 transporting electrons towards MXene surface. This study shows that 2D V2C MXene could be a potential carrier for constructing 2D/2D heterojunctions in photocatalytic CO2 reduction to produce useful solar fuel.