Hydroxyl functionalised 2D/2D Ti2CTx MXene @ g-C3N4 photocatalyst confer selectivity for CO2 reduction to ethanol

Abstract

Production of solar biofuel where CO₂ is reduced to hydrocarbon by harnessing sunlight through photocatalyst has attracted tremendous attention in recent years. In this study, titanium carbide MXene (Ti₂CT_x), a noble metal-free co-catalyst, was combined with graphitic carbon nitride (g-C₃N₄) to make a composite wherein 2D Ti₂CTx was synthesized following modified MILD process followed by hydrothermal assisted co-polymerization with g-C₃N₄ resulting in the formation of hydroxyl functionalised Ti₂C(OH)₂ @ g-C₃N₄ composite (TiGCN). As Ti₂C(OH)₂ MXene being an efficient electron-coupled proton donor, the TiGCN exhibited high selectivity for CO₂ adsorption and direct reduction to ethanol. Engineering the selective reduction of CO₂ capability of TiGCN to ethanol, a C2 compound, was facilitated by OH terminalization imparted via ethanol-assisted sono-chemical processing. Our findings reveal that the loading of OH terminalized Ti₂C(OH)₂ at 0.8 wt% in g-C₃N₄ resulted in highest photocatalytic CO₂ reduction, yielding 784 µmol gcat⁻¹h⁻¹ of ethanol. We further discuss the possible reaction mechanism of C2 conversion.