Carbon Shell Drives Interfacial Electron and Cu Oxidation State Stabilization for Highly Selective CO2 Electroreduction to Ethanol

Abstract

The electrocatalytic reduction of CO2 into value-added products, including ethanol, represents a promising strategy for carbon utilization; however, achieving high selectivity toward ethanol remains a significant challenge. Here, we report the synthesis of copper-based catalysts (CuOx@C-400, CuOx@C-600, and CuOx-800) with carbon shells of varying thicknesses, derived via the pyrolysis of copper-based metal-organic frameworks (Cu-MOFs) as precursors. The CuOx@C-400 electrode with a complete carbon shell coating exhibits the best electrochemical performance. At a potential of 1.33 V vs. RHE (reversible hydrogen electrode), the Faradaic efficiency (FE) of ethanol reaches 70.43%, and during the 100 h stability test, the FE of ethanol remains above 60%. Mechanistic studies reveal that the carbon shell coating effectively suppresses the over-reduction of Cu2+ to metallic Cu0 under reductive conditions. This stabilization facilitates C–C coupling, thereby enabling high ethanol selectivity and sustaining the long-term catalytic stability of the electrode. This work offers an effective strategy for designing catalysts that maintain long-term stability and high ethanol selectivity in practical applications.