Enhanced CO2 Activation and Ethylene Electrocarboxylation on Rare-Earth Doped Cu2S: Insights from Electronic and Geometric Modulation

Abstract

M@Cu2S electrocatalysts were theoretically designed by substituting a surface Cu atom on the Cu2S(111) facet with a rare-earth M atom. All M@Cu2S electrocatalysts exhibit favorable structural stability, with negative formation energies and binding energies. On M@Cu2S, the unique bridge-bonded adsorption configuration (both O atoms of *CO2 are bonded to M) enables effective activation of *CO2, with the hydrogenation step, rather than the C–C coupling step, identified as the potential-determining step (PDS) for ethylene electrocarboxylation. Notably, Eu@Cu2S and Yb@Cu2S exhibit limiting potentials (Ulimit) of 0.97 and 0.81 V versus the standard hydrogen electrode (SHE), respectively, which are lower than those of other M@Cu2S electrocatalysts, indicating their superior catalytic performance. Structure–activity relationship analysis reveals that, among all M@Cu2S electrocatalysts, rare-earth dopants M with higher third ionization energies and larger atomic radii deliver lower Ulimit and correspondingly superior electrocatalytic activity toward ethylene electrocarboxylation to succinic acid. This work confirms that rare-earth doping with optimized electronic and geometric characteristics enhances the catalytic performance of M@Cu2S for ethylene electrocarboxylation, laying a reliable theoretical foundation for developing efficient electrocatalysts for CO2 conversion and ethylene valorization.