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 CO 2 reduction reaction (CO 2 RR) due to their abundant metal active sites, while the harsh synthesis conditions hinder the mechanism exploration of the CO 2 RR. In this work, nine M 2 C-type MXenes (M = Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W) were selected to explore their CO 2 capture and conversion performance by density functional theory (DFT) calculation. Results show that all nine M 2 C can effectively adsorb and activate CO 2 and tend to generate HCOOH thermodynamically. Among them, V 2 C and Cr 2 C with a low limiting potential ( U L ) show excellent CO 2 reduction performance. Further calculation reveals that V 2 C has the highest catalytic selectivity due to a high U L of hydrogen evolution reaction (HER) and a positive U L (CO 2 ) – U L (H 2 ) value. Our results demonstrate that V 2 C may be the best candidate for the electrocatalytic reduction of CO 2 to HCOOH and provide insights into the design of M 2 C-type MXenes for CO 2 RR electrocatalysts with high activity and selectivity.