Improving the CO₂ electrochemical reduction to formic acid using iridium-oxide-modified boron-doped diamond electrodes

Modification of iridium on the surface of boron-doped diamond (BDD) electrode has been performed to decrease the overpotential reduction of carbon dioxide (CO₂) and produce value-added carbon compounds. The modification was performed using the cyclic voltammetry (CV) technique that successfully deposited iridium oxide on the surface of the BDD electrode with an Ir-to-C ratio of approximately 1:100. When the modified BDD electrode was utilized for CV of a dissolved-CO₂-saturated solution, hydrogen evolution occurred at a potential of approximately −1.2 V (vs. Ag/AgCl), which was lower than that when an unmodified BDD was used. Furthermore, when this electrode was utilized for amperometry of the same solution at −1.7 V for 1 h, formic acid (HCOOH) was produced with a Faradaic efficiency of approximately 50%. Results indicated that the modified electrode has considerable potential for application to CO₂ electrochemical reduction.