Interplay of Catalyst and Electrode Design Governs C–C Coupling in Ag-Doped Cu Loaded Gas Diffusion Electrodes

Electrochemical carbon dioxide (CO 2 ) reduction has been intensively studied as a promising route for converting CO 2 into value-added multi-carbon products such as ethylene (C 2 H 4 ). To date, most efforts have focused on the development of highly active electrocatalysts, particularly through alloying and heteroatom doping of Cu, to enhance C–C coupling and C 2 H 4 formation. However, in gas diffusion electrode (GDE) systems operated at industrially relevant current densities, CO 2 reduction proceeds at complex gas–liquid–solid triple-phase interfaces, where the structure of the catalyst layer critically governs the reaction microenvironment and product selectivity. However, how this interfacial structure affect the performance of alloyed catalysts and whether such effects can be generalized across different catalyst compositions remain poorly understood. Here, we demonstrate that CO 2 reduction selectivity in Ag-doped Cu catalyst-loaded GDEs is governed by the cooperative interplay between catalyst and electrode design. Using Ag-doped Cu nanoparticles as a model system, we systematically investigate how Ag doping and catalyst loading collaboratively define the reaction microenvironment and CO 2 reduction selectivity. We demonstrated that moderate catalyst loadings maximize C 2 H 4 selectivity by establishing a balanced reaction environment with appropriate CO accumulation and efficient CO 2 transport, whereas excessively low or high catalyst loadings result in suppressed C 2 H 4 formation also in the alloyed catalysts. These results reveal that alloy catalyst performance is determined not only by inherent electronic and atomic properties but also by the catalyst layer configuration at the triple-phase interface. In GDE systems, optimizing this local environment is essential to fully unlock the catalysts' intrinsic activity.