Dendritic Ag Electrocatalyst with High Mass-Specific Activity for Zero-Gap Gas-Fed CO₂ Electroreduction

Electrodeposited silver catalyst is attractive compared to commercially available silver nanoparticles because it allows for the investigation of catalyst morphology and crystallography on the performance of CO 2 electrolyzer for the conversion of CO 2 to CO. In this work, Ag electrodes with different Ag structures varying from polycrystalline to dendrite were fabricated by controlling different electrodeposition parameters: deposition voltage, ethylenediamine additive and ammonium sulfate concentration, and time of deposition. The electrode performance was evaluated in a zero-gap, gas-fed, polymer electrolyte membrane-based cell. The highest mass-specific activity of 362 mA·mg Ag –1 and a CO selectivity of 94% at a cell potential of 3 V were achieved for dendritic Ag catalyst (0.29 mg·cm –2 ) that possessed the maximum (220)/(111) facet ratio, as determined by X-ray diffraction. The long-term durability test on the electrode demonstrated a robust performance after 100 h of CO 2 reduction at a 3 V cell voltage.