Selective CO2 electroreduction to multicarbon products exceeding 2 A cm−2 in strong acids via a hollow-fiber Cu penetration electrode†


CO2 electroreduction in acidic media is highly attractive to avoid carbonation loss, but remains a challenge for selective reduction of CO2 due to overwhelming hydrogen evolution reaction (HER) in a proton-rich environment. Herein, we report a hollow-fiber Cu penetration electrode that can effectively inhibit the HER while promoting CO2 reduction kinetics and even C–C coupling to form multicarbon (C2+) products in strong acids. A faradaic efficiency of 73.4%, a partial current density of 2.2 A cm−2, and a single pass carbon efficiency of 51.8% were achieved for C2+ production, sustaining 100 h electrolysis in a pH = 0.71 solution of H2SO4 and KCl. Sufficient CO2 feeding induced by the hollow-fiber penetration configuration greatly improved CO2 coverage on Cu active sites in strong acids, favoring CO2 activation, *CHO and *CO formation, and their couplings to C2+ products.