Recent developments in electrochemical and photoelectrochemical CO2 reduction: involvement of the (CO2)2. ? dimer radical anion

Abstract

Electrochemical CO2 reduction was examined on high-area transition metal catalysts supported on nanoporous activated carbon fiber (ACF) supports, in the form of gas diffusion electrodes, in aqueous KHCO3 solution. The most active catalyst was ACF/Ni, on which up to ca 65 mA cm−2 current density for CO production was observed, with simultaneous production of hydrogen of ca 15 mA cm−2 at −1.6 V vs SCE. At more negative potentials, higher H2/CO ratios can be obtained. The reaction mechanism for CO production probably involves a chemical reaction between CO2 and the radical anion CO2. − to produce the CO2 dimer radical anion (CO2)2. −. The results are compared with those for photoelectrochemical CO2 reduction on p-InP, on which the mechanism is thought to involve the one-electron reduction of two adsorbed CO2 molecules to produce the CO2 dimer radical anion. Copyright © 2001 John Wiley & Sons, Ltd.