Mechanistic studies of CO2 reduction on a mediated electrode with conducting polymer and inorganic conductor films

Electrocatalytic reduction of CO2 on a metal complex-immobilized polyaniline (PAn)/Prussian blue (PB)-laminated electrode has been investigated by means of long-term electrolysis, liquid chromatography/mass spectroscopy (LC/MS) and in situ Fourier transform infrared (FTIR) reflection absorption spectroscopy. The major products were lactic, acetic, and formic acids, methanol, and ethanol. The roles of PAn and the metal complex [1,8-dihydroxynaphthalene-3,6-disulfonatoferrate(II)] are to render CO2 chemically active by combining the electrophilic carbon atom with the amino group of PAn and the basic oxygen atom with the central metal of the complex, and that of PB is to provide catalytically H-ads atoms on its zeolitic lattice. The activated CO2 is hydrogenated and converted to organic acids and alcohols by the reaction with H-ads atoms. It is suggested that formaldehyde is a precursor for the organic acids (except formic acid) and alcohols and the insertion reactions of CO2 into intermediates are essential to the formation of C-2 and C-3 compounds.