Assessing Efficiencies of Infrared and Visible Active Janus MXenes in CO₂ to Methane Conversion by Photocatalysis

Photocatalytic reduction of CO2 is a green process to produce useful hydrocarbons. Quasi two-dimensional Janus MXenes have recently turned out to be excellent photocatalysts in water splitting reactions. In this work, using precise density functional theory calculations, we have assessed the efficiencies of Janus MXenes Sc2COX, Hf2COX (X = S, Se), Zr2COS, and ZrHfCO2 in the conversion of CH4 from CO2. By examining the reaction energetics, the limiting potentials, the interfacial charge transfers, and rates of adsorption–desorption of products, we find that Sc2COS stands out as the only catalyst that can enable the CO2 reduction reaction spontaneously with the help of photogenerated electrons, while others require extra energy for the same. We also found that the reactions cannot take place under ambient conditions. A small pressure of the order of MPa is required for the reactions to take place at room temperature. This comprehensive analysis provides useful insights into the prediction of new photocatalysts for CO2 reduction reactions.