Ampere-Level CO2-to-Ethanol Conversion via Boron-Incorporated Copper Electrodes

Partial positive valence Cu (Cuδ+) sites on Cu-based electrocatalysts are important for C–C coupling to form C2+ products; however, maintaining the stability of Cuδ+ remains a challenge. Herein, an ultrastable Cuδ+ (0 < δ < 1) site over the copper penetration electrode was constructed using boron to tailor the *CO adsorption strength and configuration for facilitating C–C coupling, which achieves a C2+ Faradaic efficiency (FE) of 78.9% at −0.91 V (vs reversible hydrogen electrode), of which the ethanol FE reaches 52.4% with an ultrahigh partial current density of 1.25 A cm–2, far outperforming state-of-the-art electrocatalysts, corresponding to the ethanol cathodic energy efficiency (CEE) of 27.7%. Spectroscopy and computation results show that introducing boron to optimize the coordination numbers and oxidation states of surface Cu atoms enables enrichment of locally asymmetric *COatop and *CHO intermediates to trigger asymmetric C–C coupling to form ethanol.