CO₂ reduction by single copper atom supported on g-C₃N₄ with asymmetrical active sites

Abstract

Electrochemical reduction of CO2 requires catalysts beyond Cu with high activity and selectivity to produce C2 products. Different from many single-atom catalysts that show high performance in obtaining C1 products, Cu supported on carbon nitride (Cu-C3N4) has shown a unique capability to generate C2 products by providing asymmetrical active sites. Herein, we study 17 possible pathways and reaction mechanisms of CO2 reduction toward ethylene – a featured C2 product, on Cu-C3N4. The possible reaction intermediates along with different reaction pathways on three active sites of Cu-C3N4 (Cu, C, and N) were obtained by density functional theory (DFT) computations. The most probable reaction pathway toward C2H4 production is 1.08 eV at open circuit conditions, which is benefited by the synergistic effect of both Cu and C active sites. Comparing with other pathways utilizing Cu/N and C/N active sites, the carbon atom provides a perfect settling centre for the first CO2 after reduction by Cu and leaves Cu vacant for the second CO2 reduction. Our study provides reaction mechanism insights for C2 production on Cu-C3N4 and sheds light on designing electrocatalysts with dual active sites.