Theoretical considerations on activity of the alectrochemical CO₂ reduction on metal single-atom catalysts with asymmetrical active sites

Abstract

Electrochemical CO2 reduction to higher-value hydrocarbons beyond C1 products has attracted much attention recently. Single-atom catalysts (SACs) are regarded as promising CO2 reduction electrocatalysts. However, most SACs only show activity to C1 products. In this work, we considered the activity and the synergetic effect of dual active sites for metal SACs supported on graphitic carbon nitride (g-C3N4) as CO2 reduction electrocatalysts. Density functional theory (DFT) calculations are employed. First, by using the adsorption energies of CO* on the metal site and that of H* on the nitrogen site as bi-descriptors, we predicted seven out of 14 metal centers have the propensity to generate beyond CO products. To further evaluate the catalyst activity on beyond CO product formation, we established reaction pathways towards ethylene through M/N or M/C. Ru has the best performance (the limiting potential is −0.90 V) by taking M/N as active sites. A dual volcano-shaped plot is built up based on the CO adsorption energies on metal sites, which can be used to indicate whether M/C or M/N shows better performance for a specific metal center. Our work shed light on developing criteria to guide the design of CO2 reduction electrocatalysts with dual active sites.