In-Plane Catalyst Loading Gradient Improves Electrochemical CO₂ to C₂₊ Product Conversion

The structure of the catalyst layer (CL) is a prominent factor in determining the activity and selectivity of copper gas diffusion electrodes for electrochemical carbon dioxide reduction reaction. Here, we demonstrate that tailoring a gradient in catalyst loading in the CL significantly enhances the selectivity and productivity for C2+ products, particularly C2H4, in both flow cell and membrane electrode assembly (MEA) cell. Specifically, the gradient CL promotes the Faradaic efficiency of C2H4 by 13% compared to conventional homogeneous CL under identical cell voltage of the MEA cell, while achieving a maximum increase of 29% in the partial current density of C2H4. This enhancement is attributed to the extended residence time of reactants facilitated by the gradient geometry, which promotes higher conversion down the electrode for both the CO2-to-CO and CO-to-C2+ reaction steps. Multiphysics simulations further reveal that the gradient structure increases the average surface coverage of *CO intermediates compared with a homogeneous CL, thereby accelerating C–C coupling kinetics and driving the formation of C2+ products. Moreover, the gradient CL design can be scaled up through periodic incorporation of the gradient structure across larger electrodes, offering a viable pathway for industrial-scale applications.