Electrochemical reduction of CO2 at an activated silver electrode

Abstract The electrochemical reduction of CO2 to CO in aqueous NaClO4 solution saturated with CO2, at polycrystalline Ag cathodes was investigated as a function of the potential, temperature and electrolysis duration. A poisoning process has been found to occur in parallel with the CO formation. Building‐up of the surface species closely similar to the detected poison has been observed at a Ag electrode immersed (at open‐circuit) in a solution containing small amounts (10−4mol dm−3) of formaldehyde. A periodic anodic stripping of these inhibiting species was shown to produce stable current densities and faradaic efficiencies of CO over 4 – 5 h electrolysis runs. A tentative reaction pathway for CO2 reduction to CO, taking into account the experimentally determined onset potential, is proposed.