Theoretical investigation of defective MXenes as potential electrocatalysts for CO reduction toward C2 products

Abstract

Electrochemical CO₂/CO conversion to valuable chemical products is an attractive strategy for storage of clean energy and control of greenhouse gas emission. Currently, CO₂ reduction to CO is relatively mature, whereas the deep reduction and further conversion of CO into multi-carbon products, such as ethylene (C₂H₄) and ethanol (C₂H₅OH), are highly challenging. Based on the density functional theory (DFT) calculations, we explored the possibility of CO reduction reaction (CORR), to obtain C₂ products, with defective MXenes in which the defect is created by removing two neighboring oxygen atoms on the surface. Our results revealed that the dual-oxygen vacancy in defective Mo₂TiC₂O₂ (labeled as Mo₂TiC₂O₂-2O_V) can offer a unique environment that confines and enriches the active *COH species, significantly promoting the reduction process as well as C–C bond coupling. The thermodynamic barrier of the potential-determining step (PDS) for Mo₂TiC₂O₂-2O_V is 0.32 eV with promising selectivity of C₂ products over the competing hydrogen evolution reaction (HER). This work provides a feasible strategy for designing MXene-based electrocatalysts for highly efficient CO₂/CO reduction to C₂ products.