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 CO 2 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 CO 2 -to-CO catalysts in MEA because their intrinsic and extrinsic properties can be properly controlled.