Electrochemical reduction (ECR) of CO2 to value-added chemicals suffers from high overpotential and poor product selectivity. Copper-based catalysts can produce hydrocarbons and oxygenate from CO2 ECR at an applied potential of -1.44 V. To produce the highly desirable C2 products, C–C coupling is the essential step. Previous studies show that the activation barriers for the C–C coupling steps on Cu(100) are 1.38 eV through the dimerization of *CO and 0.60 eV via coupling of *CO and *HCO. Clearly, C–C formation via coupling of *CO and *HCO has a low free energy barrier but the formation of *HCO species on Cu(100) requires a limiting potential of -0.65 V. Lowering the limiting potential for *HCO formation is expected to increase the overall reactivity, and therefore, the reactivity towards C–C coupling. Herein, using density functional theory calculation, we demonstrate that the metal-oxide/Cu(100) interfacial sites ((MO)4/Cu(100, M = Fe, Co and Ni) can lower the limiting potential for *HCO formation. Our results show that limiting potentials for *HCO formation are -0.18 V, -0.48 V and -0.28 V on (FeO)4/Cu(100), (CoO)4/Cu(100) and ((NiO)4/Cu(100), respectively. Combining with *CO on the Cu surface, the metal-oxide/Cu catalysts are expected to offer a lower limiting potential path for C2 products via *HCO and *CO coupling than Cu.

Electrochemical reduction of CO2 to C2 products at the earth-abundant transition metal-oxides/copper interfaces: A DFT study

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