Mechanistic Insights for the Electrocatalytic CO2 Reduction on M2C-Type MXenes

Two-dimensional (2D) transition-metal carbides (MXenes) without termination groups have been recognized as excellent electrocatalysts for the CO2 reduction reaction (CO2RR) due to their abundant metal active sites, while the harsh synthesis conditions hinder the mechanism exploration of the CO2RR. In this work, nine M2C-type MXenes (M = Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W) were selected to explore their CO2 capture and conversion performance by density functional theory (DFT) calculation. Results show that all nine M2C can effectively adsorb and activate CO2 and tend to generate HCOOH thermodynamically. Among them, V2C and Cr2C with a low limiting potential (UL) show excellent CO2 reduction performance. Further calculation reveals that V2C has the highest catalytic selectivity due to a high UL of hydrogen evolution reaction (HER) and a positive UL(CO2) – UL(H2) value. Our results demonstrate that V2C may be the best candidate for the electrocatalytic reduction of CO2 to HCOOH and provide insights into the design of M2C-type MXenes for CO2RR electrocatalysts with high activity and selectivity.