Electrodeposited Ag catalysts for the electrochemical reduction of CO₂ to CO

For the electrochemical reduction of CO₂to CO, a dendrite-type Ag catalyst was fabricated via an electrodeposition method in an ammonia-based Ag deposition solution containing ethylenediamine (EN) as an additive. The influence of electrodeposition parameters on the properties of this catalyst was examined and further correlated with CO production efficiency. The addition of EN changed the intensity ratio of (220) vs. (111) planes in the Ag catalyst, which was shown to be proportional to the CO production activity. Furthermore, EN modified the chemical shift of Ag3d_5/2in the negative direction, increasing the CO production efficiency. Under optimized deposition conditions (–0.45 V vs. Ag/AgCl, 40 mM EN), which were a compromise between intensity ratio and chemical shift, the fabricated Ag catalysts exhibited the highest Faradaic efficiency and mass activity for CO during CO₂electrolysis in 0.5 M KHCO₃. The experimental correlation between CO production efficiency and the crystalline/electronic structures of the catalyst suggested guidelines for further improving the Ag catalyst activity.