Abstract
Electrocatalytic CO2 reduction to multi-carbon products is a promising approach for achieving carbon-neutral economies. However, the energy efficiency of these processes remains low, particularly at high current densities. Herein, we demonstrate that the low energy efficiencies are, in part, sometimes significantly, attributed to the high concentration overpotential resulting from the instability (i.e., flooding) of catalyst-layer during electrolysis. To tackle this challenge, we develop copper/gallium bimetallic catalysts with reduced activation energies for the formation of multi-carbon products. Consequently, the reduced activation overpotential allows us to achieve practical-relevant current densities for CO2 reduction at low cathodic potentials, ensuring good stability of the catalyst-layer and thereby minimizing the undesired concentration overpotential. The optimized bimetallic catalyst achieves over 50% cathodic energy efficiency for multi-carbon production at a high current density of over 1.0Acm−21.0Acm-2<math><mn>1.0</mn> <mspace></mspace> <mi>A</mi> <mspace></mspace> <msup><mrow><mi>cm</mi></mrow> <mrow><mo>-</mo> <mn>2</mn></mrow> </msup> </math> . Furthermore, we achieve current densities exceeding 2.0Acm−22.0Acm-2<math><mn>2.0</mn> <mspace></mspace> <mi>A</mi> <mspace></mspace> <msup><mrow><mi>cm</mi></mrow> <mrow><mo>-</mo> <mn>2</mn></mrow> </msup> </math> in a zero-gap membrane-electrode-assembly reactor, with a full-cell energy efficiency surpassing 30%.