Investigation of Electrocatalytic CO2 Reduction on MXene Materials via First-Principles Simulations

Computational studies of CO₂ reduction to yield various products were carried out on the basal plane and edges of different MXene materials. The impact of vacancies upon Mo₂TiC₂T_x, W₂TiC₂T_x, and Ti₃C₂T_x (T_x = O and OH) was also examined for both edge and basal sites. Initial calibrations were carried out to generate surfaces with optimal oxide/hydroxide ratios and proper termination sites upon which various vacancy sites were explored to ensure an accurate model of the surfaces’ resting states. From this work, Mo₂TiC₂O was determined to exhibit the lowest theoretical overpotential for methane as determined by volcano plot analyses. At a large enough vacancy concentration, the CO₂ reduction reaction (CO₂RR) is predicted to outcompete the hydrogen evolution reaction (HER) as the predominant reaction on the surface. When examining the edge of Mo₂TiC₂O, stronger CO₂ binding was exhibited to such an extent that the reaction was predicted to terminate after the generation of formate on the edge.