Atomic Arrangement of AuAg Alloy on Carbon Support Enhances Electrochemical CO2 Reduction in Membrane Electrode Assembly

Tailoring catalyst performance is especially crucial in a zero-gap membrane-electrode assembly (MEA) electrolyzers for electrochemical CO2 reduction reaction at the industrial scale. However, few studies have directly focused on MEA systems combined with operando techniques when compared to aqueous catholyte-based flow cells or H-cells. Using the MEA system, this study demonstrates improved catalytic performance of the AuAg bimetallic catalyst by adjusting the atomic arrangement of the alloy structure and its extrinsic properties with a carbon support. The AuAg catalyst containing only 10 at. % Au and the AgCl domain underwent atomic arrangement via AgCl reduction. The catalyst with more oxidative Ag species achieved near-unity CO selectivity (97.3%) and three-fold higher CO partial current compared to Ag nanoparticles. Operando X-ray absorption analysis of the active AuAg catalyst in the MEA cell demonstrates that the AuAg active site contained more Ag+ and under-coordinated surfaces. When the carbon support was properly adjusted, high CO production activity is achieved with a CO partial current density and mass activity of 618 mA cm–2 and 0.824 A mg–1, respectively, by effectively alleviating the mass transport restriction. AuAg catalysts are competitive with CO2-to-CO catalysts in MEA because their intrinsic and extrinsic properties can be properly controlled.