ELECTROCHEMICAL REDUCTION OF CO2 AT SB AND BI ELECTRODES IN KHCO3 SOLUTION

Electrochemical reduction of CO2 in KHCO3 solutions was studied using differently prepared Sb and Bi electrodes. With Sb plated electrodes, H-2 was produced mainly with a small amount of HCOOH, i.e., Sb was not effective for CO2 reduction. On the other hand, with Bi electrodes, HCOOH was produced in high current efficiencies with a trace amount of CO. The current efficiency and the rate for HCOOH formation were largely improved by the use of Bi plated electrodes, and dependent on the kind of electrode substrates on which Bi was plated. The utility of a Bi plated glassy carbon electrode gave HCOOH in near 100% current efficiency in the potential region of -1.4 to -1.7 V vs. SCE at the production rate of ca. 1A . dm(-2). The current efficiency seems to be dependent on the purity of the electrode surface and the particle size of Bi plated rather than the roughness factor of the electrode surface.