Bi _<b>2</b> O _<b>3</b> -Modified Cu Catalysts for Enhanced Ethanol Selectivity in CO _<b>2</b> Electroreduction

Electrochemical CO2 reduction reaction (CO2RR) offers a sustainable route to convert CO2 into value-added chemicals. Among the available catalysts, Cu-based systems are unique in producing C2+ products efficiently. However, selectively steering product distribution remains a major challenge. Herein, we report a Bi2O3-decorated Cu catalyst (Cu/Bi2O3) that enables the selective CO2RR to ethanol (EtOH). Under CO2RR conditions, the catalyst undergoes spontaneous reconstruction, resulting in a uniform dispersion of Bi2O3 across the Cu surface. In a membrane electrode assembly (MEA)-type cell, the Cu/Bi2O3 catalyst achieves a C2+ selectivity exceeding 50% and an ethanol Faradaic efficiency (FEEtOH) of 25%. The ethanol-to-ethylene ratio reaches 1.4, more than 2-fold that of pristine Cu. The catalyst exhibits a high ethanol current density (jEtOH) of 125 mA cm–2 and an ethanol energy efficiency (EEEtOH) of 16% at 2.6 V. In situ Raman spectroscopy reveals that the Cu/Bi2O3 catalyst stabilizes Cu+ active sites enhancing the adsorption of *CO2– and *CO intermediates and promoting C–C coupling. Moreover, Bi2O3 decoration enhances the stability and hydrogenation of key intermediates (*OCHCH3) in ethanol formation, thereby steering the reaction pathway toward ethanol rather than ethylene.