Optimizing Reaction Conditions and Gas Diffusion Electrodes Applied in the CO2 Reduction Reaction to Formate to Reach Current Densities up to 1.8 A cm-2

Achieving high current densities in the electrochemical reduction of CO2 is one of the critical issues keeping this technology from commercialization. Although in the past few years, gas diffusion electrode-based electrolyzers have frequently been reported to reach a few hundred milliamperes per square centimeter, higher reaction rates are still endeavored to lower the capital costs and increase the process flexibility necessary for peak-shaving of fluctuating, renewable energies. Here, we report a series of optimizations that allow for the operation of the presented tin oxide nanoparticle-based, homogeneous single-layer gas diffusion electrode at current densities of up to 1.8 A cm(-2). Up to this current density, formate faradic efficiency can be kept above 70%. Individual single parameter optimizations, namely, the type of cation contained in the electrolyte, the catalyst loading of the electrode, and the hydrophobicity of the electrode, are investigated separately and afterward combined to achieve a maximized current density.