Ag/C cathode catalyst fabricated via an ultrasonic reduction method for the electrolysis of gaseous carbon dioxide

Highly selective carbon monoxide production can be achieved during the electrolysis of carbon dioxide using a cathode catalyst composed of silver nanoparticles loaded onto a carbon support (Ag/C). Although generating abundant Ag species is desirable for efficient CO2 electrolysis, conventional methods tend to produce relatively large Ag particles at high loading levels. In this paper, an advanced Ag/C electrocatalyst is produced via ultrasonic reduction (Ag(USR)/C). Importantly, the activity of this electrocatalyst was demonstrated to be superior to those of Ag/C cathodes prepared via conventional methods. This activity was retained under various conditions. In particular, CO was formed during electrolysis when 10 vol.% CO2 was supplied to the Ag(USR)/C cathode, while only H2 was evolved on the other Ag/C cathodes. Abundant Ag nanoparticles measuring a few nanometres in diameter were detected on the Ag(USR)/C electrocatalyst surface, whereas significantly larger Ag species were observed on the other Ag/C catalysts. Additionally, electrochemical impedance spectroscopy suggested that electrons were injected into CO2 more efficiently when the Ag(USR)/C was employed. Accordingly, these small Ag nanoparticles exhibited superior activity in the efficient low-concentration CO2 electrolysis and 100% CO2 electrolysis processes. These results confirm the high CO2 electrolysis activity of the Ag(USR)/C cathode.