Fabrication of Large Area Ag Gas Diffusion Electrode via Electrodeposition for Electrochemical CO2 Reduction.

For the improvement for the commercialization of electrochemical carbon dioxide (CO₂) conversion technology, it is important to develop a large area Ag gas diffusion electrode (GDE), that exhibits a high electrochemical CO₂ conversion efficiency and high cell performance in a membrane electrode assembly (MEA)-type CO₂ electrolyzer. In this study, the electrodeposition of Ag on a carbon-paper gas diffusion layer was performed to fabricate a large area (25.5 and 136 cm²) Ag GDE for application to an MEA-type CO₂ electrolyzer. To achieve uniformity throughout this large area, an optimization of the electrodeposition variables, such as the electrodes system, electrodes arrangement, deposition current and deposition time was performed with respect to the total electrolysis current, CO production current, Faradaic efficiency (FE), and deposition morphology. The optimal conditions, that is, galvanostatic deposition at 0.83 mA/cm² for 50 min in a horizontal, two-electrode system with a working-counter electrode distance of 4 cm, did ensure a uniform performance throughout the electrode. The position-averaged CO current densities of 2.72 and 2.76 mA/cm² and FEs of 83.78% (with a variation of 3.25%) and 82.78% (with a variation of 8.68%) were obtained for 25.5 and 136 cm² Ag GDEs, respectively. The fabricated 136 cm² Ag GDE was further used in MEA-type CO₂ electrolyzers having an active geometric area of 107.44 cm², giving potential-dependent CO conversion efficiencies of 41.99%–57.75% at V_cell = 2.2–2.6 V. [ABSTRACT FROM AUTHOR]