Theoretical prediction of metal-doped high C/N-ratio CxN3 (x=7, 10, 13, 19) as single-atom catalysts for CO2RR

The development of efficient catalysts for the electrocatalytic carbon dioxide reduction reaction (CO2RR) has emerged as a primary focus in contemporary research. In this study, a series of single-atom catalysts are constructed by doping Ru, Rh, and Pd into CxN3 (x = 7, 10, 13, 19), denoted as M-CxN3. Density functional theory (DFT) methods are employed to systematically investigate the CO2RR catalytic activity and mechanism on MCxN3. The catalysts are found to exhibit thermodynamic, electrochemical, and dynamic stability, as evidenced by formation energy calculations, dissolution potential assessments, and first principles molecular dynamics simulations. Gibbs free energy calculations reveal that Ru-CxN3 demonstrates exceptional catalytic selectivity towards HCOOH production, with optimal catalytic activity observed at low limiting potentials (x = 7: -0.36 V, x = 10: -0.33 V, x = 13: -0.30 V, and x = 19: -0.18 V). Furthermore, Ru-CxN3 effectively suppresses the competitive hydrogen evolution reaction (HER). Linear relationships between the Gibbs free energy change of the key intermediate *OCHO and the catalyst d band center, as well as the integration crystal orbital Hamiltonian population (ICOHP), indicate that Ru doping and higher C/N-ratios in CxN3 enhance catalytic performance for CO2RR. This computational study provides comprehensive guidance and insights for the experimental synthesis and exploration of CO2RR electrocatalysts.