CO2 electroreduction to multicarbon products in strongly acidic electrolyte via synergistically modulating the local microenvironment

Electrochemical CO2 reduction to multicarbon products faces challenges of unsatisfactory selectivity, productivity, and long-term stability. Herein, we demonstrate CO2 electroreduction in strongly acidic electrolyte (pH <= 1) on electrochemically reduced porous Cu nanosheets by combining the confinement effect and cation effect to synergistically modulate the local microenvironment. A Faradaic efficiency of 83.7 +/- 1.4% and partial current density of 0.56 +/- 0.02 A cm(-2), single-pass carbon efficiency of 54.4%, and stable electrolysis of 30h in a flow cell are demonstrated for multicarbon products in a strongly acidic aqueous electrolyte consisting of sulfuric acid and KCl with pH <= 1. Mechanistically, the accumulated species (e.g., K+ and OH-) on the Helmholtz plane account for the selectivity and activity toward multicarbon products by kinetically reducing the proton coverage and thermodynamically favoring the CO2 conversion. We find that the K+ cations facilitate C-C coupling through local interaction between K+ and the key intermediate *OCCO.

Automated summary

This study demonstrates the successful electrochemical reduction of CO2 to multicarbon products in strongly acidic electrolyte by combining the confinement effect and cation effect, showing high Faradaic efficiency, partial current density, and stability. The cation effect is found to play a crucial role in C-C coupling.