Nature of C-C coupling and strategy of tuning the catalytic activity of Cu-N-C catalysts for electro-reduction of CO2 to ethanol

Abstract

With high atomic utilization and remarkable catalytic activity, Cu-N-C type catalysts display great potential for electro-catalysis in CO2 reduction. However, the relationship between the active moiety and catalytic activity of generating high-value C2 products is still unclear, and the explicit screening criteria is scarcity. Herein, based on the first-principle simulation, the structure-performance relationship on Cu-N-C type catalysts has been investigated by modulating the CO2 reduction process as the number of Cu atom (Cu1, Cu2, Cu3) and the ligand environment (B, C, N, O, P, S) changed. We find the adsorption strength of intermediate *CO strongly affect the possibility of C-C coupling, which can be determined by Bader charge on Cu atom, mainly depending on the number of loaded atomic Cu on Cu-N-C catalysts. Furthermore, the Bader charge can be refined by adjusting the coordination atom of Cu, thus optimizing catalytic activity for the CO2 to ethanol. The moderate Bader charge value, between +0.35 and +0.45, enables the catalyst to behave as a potentially excellent activity with low limiting potential for generating ethanol. More importantly, an intrinsic descriptor, composed of the radius, electronegativity, and number of valence electrons of coordination atoms (φ=∑χ∑r⁎∑np), was established to characterize the catalytic activity of Cu-N(X)-C catalysts for producing ethanol. Two excellent catalysts, Cu3-N2O2 (-0.51V) and Cu3-N3S (-0.64V), are screened out for the CO2RR to generate ethanol. This work discloses theoretical basis for catalytic selectivity of C2 products on Cu-N-C catalysts and provides a regulating and screening principle for high performance catalysts to ethanol.