High-Pressure Electrocatalytic Reduction of CO₂ to CO Under Realistic Conditions

We study the key factors governing the high-pressure electrochemical reduction of CO₂ to CO using commercial silver electrodes. Voltammetry and electrolysis results, combined with X-ray diffraction and microscopy analyses, show that the applied current density is the most important parameter. When this is doubled from 150 to 300 mA/cm²_geo, the CO yield goes down drastically, and more hydrogen is produced at the cathode. At the lower current density (150), the hydrogen production is independent of the type of electrode (roughness factor). Conversely, the CO yield does depend on the type of electrode. At the high current density, both H₂ and CO production depend on the electrode parameters. The highest CO yield (> 80%) is obtained using a commercially available etched silver foam at 150 mA/cm²_geo.