The intrinsic activity descriptor of TM-N₃-C single-atom catalysts for electrochemical CO₂ reduction: a DFT study

Developing catalysts for the high efficiency of CO2 utilization and conversion is a hot topic and has attracted significant interest. Using systematic density functional theory (DFT) calculations, the stability and catalytic performance of TM-N-3-C catalysts are determined by the element of the metal site and influenced by the local environment around TM atoms during CO2RR, which is mainly attributed to tailoring the electronic structure of the active center and its coordinated atoms. The influence of inherent features of the catalyst on properties was clarified. It is worth noting that an intrinsic descriptor (Psi) of activity and selectivity for CO2-to-CH4 was assembled by inherent characteristics of electrocatalysts, such as the number of valence electrons (V), electronegativity (chi), and Hirshfeld charges (Q); the elevation altitude (H) from TM center to N-3-C substrate; average bond length (d) of the TM atom and the nearest neighbor atoms; and metal-coordinated number (N). The volcano-shaped physical curves were established between Psi and the limiting potential, and three promising TM-N-3-C (Ru-II, Rh-II, and Pd-II) with moderate V-M, Q(M), d, and H, and larger chi(M) are distributed close to the summit of the volcano curve. This study is meaningful for understanding the mechanism of electrocatalytic CO2 reduction and the design of efficient electrocatalysts for CO2RR.