Asymmetric Copper-Sulphur Sites Promote C–C Coupling for Selective CO2 Electroreduction to C2 Products

Abstract

Sustainable multicarbon e-chemicals are of particular interest due to their potential future, high market values, and demand. In the direct electrocatalytic formation of multicarbon e-chemicals from CO2, the elementary C–C coupling by CO dimerization is considered the rate-limiting step. Here, a generalized surface structural design principle of asymmetric metal pair sites is proposed, explored, and experimentally tested in order to promote CO dimerization on surfaces. First a computational model of N-doped Cu2S layers featuring adjacent, electronically asymmetric Cuδ1+-Cuδ2+ (0 < δ1+ < δ2+ < 1) metal atomic pairs evidenced by their non-uniform charge distribution is considered. The electronic asymmetry resulted in distinct CO adsorption energies and the associated self-adjusting structures, which lowered C–C coupling energy barriers significantly. The computational hypotheses are experimentally tested using X-ray photoelectron spectroscopy of Cu-N moieties within N-doped Cu2S layers. In-situ Fourier-transform infrared spectroscopy confirms linear *CO and *CO-CO adsorption configuration by the peaks of ≈2080 and 1920 cm−1, respectively. After N-doping, the catalytically C2 faradaic efficiency can significantly be elevated to 14.72% due to the promotion of C–C coupling.