Theoretical screening of single-atom electrocatalysts of MXene-supported 3d-metals for efficient nitrogen reduction

Single-atom catalysts (SACs) with metal atoms embedded in MXenes are potentially low-cost, highly efficient, and environment-friendly electrocatalysts for ammonia production due to their high stability, unique electronic structure, and the highest atom utilization. Here, density functional theory calculations are carried out to systematically investigate the geometries, stability, electronic properties of SACs with the 3d-transition metal M (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn) atoms embedded in the Ti defect sites of Ti2CO2 (denoted as M1@Ti2CO2). A highly stable V1@Ti2CO2 catalyst has been found to show excellent catalytic performance for N2 reduction reaction to produce NH3 after screening the 3d transition metals. The results show that V1@Ti2CO2 can not only strongly adsorb N2, but also exhibits an excellent Nitrogen reduction reaction (NRR) catalytic activity with a limiting potential of only −0.20 V and a high ability to suppress the competing hydrogen evolution reaction. The excellent NRR catalytic activity of V1@Ti2CO2 is attributed to the strong covalent metal-support interaction that leads to superb N2 adsorption ability of V atom. Furthermore, the embedded V single atoms facilitate electron transfer, thus improving the catalytic performance for NRR. These results demonstrate that V1@Ti2CO2 is a potentially promising 2D material for building robust electrocatalyst for NRR.