Electrocatalytic CO2 reduction reaction over group 15 bismuth and antimony film electrodes: What makes difference?

Electrocatalytic CO2 reduction reaction (EC CO2 RR) activities and products are known to be highly dependent on the nature of electrode materials. Herein, Bi and Sb (in group 15 with n-1d10ns2np3) electrodes were chosen and evaluated for EC CO2 RR under various conditions of different applied potentials, electrolytes, concentration, and UV light. Major products were observed to be formate and H2, and minor products included CO. Bi film electrode showed high Faradaic efficiency (FE) of ~94% and the selectivity of 95% for formate. Overlayer vanadium on Bi further enhanced the FE of formate. However, Sb film exhibited much higher FE of H2 than that of formate. UV light was observed to promote formate and CO productions. The FEs of formate and H2 were discussed with exposed crystal facets and density of states near the Fermi level. The very unique detailed study provides valuable information on the development of Bi and Sb-based electrodes for EC CO2 RR of producing value-added carbon products.