Modulating CO<sub>2</sub> Electroreduction Activity on Mo<sub>2</sub>C and Promoting C<sub>2</sub> Product by Grain Boundary Engineering: Insights from First-Principles Calculations
Yuxing Lin, Fangqi Yu, Lei Li, Yameng Li, Rao Huang, Yu‐Hua Wen
Abstract
Recently, two-dimensional transition-metal carbides and/or nitrides (MXenes) have attracted extensive interest owing to their promising applications in electrochemistry, especially in electrocatalysis for the CO 2 reduction reaction (CO 2 RR). However, there still exist challenges in developing MXene electrocatalysts with high activity and selectivity. Grain boundaries (GBs) could potentially provide active sites for chemical reactions, and their existence may be helpful for improving various electrocatalytic performances of MXenes. In this work, we constructed nine types of GBs in the Mo 2 C monolayer and employed density functional theory (DFT) calculations to systematically investigate their effects on the conversion efficiency of CO 2 and the diversity of CO 2 RR products. Our study reveals that the presence of different valence states of Mo atoms at the GBs breaks the symmetry of CO 2 adsorption on Mo 2 C, which promotes the activation of CO 2 and diversifies the CO 2 RR products. Especially, these GBs exhibited remarkably low limiting potentials for C 1 products, e.g., −0.29 V for CH 4 on 5|7c GB, −0.31 V for CH 3 OH on 4|8 GB, and −0.55 V for HCOOH on 4|4a GB. Furthermore, the reduced potential barriers at the GBs, such as 0.26 eV for 5|7b GB and 0.13 eV for 8|8b GB, facilitate the C–C coupling and promote the formation of C 2 products. These findings demonstrate that the introduction of GBs can enhance both the electrocatalytic activity of Mo 2 C for the CO 2 RR and the diversity of CO 2 RR products, therefore paving the way for designing and advancing high-efficiency MXene electrocatalysts through GB engineering.