In Situ Fourier Transform Infrared Spectroscopic Studies on a Metal Complex‐Immobilized Polyaniline/Prussian Blue‐Modified Electrode and the Application to the Electroreduction of CO 2

In situ Fourier transform infrared spectroscopic studies have been carried out on the nature of a metal complex‐immobilized polyaniline (PAn)/Prussian blue‐modified electrode and on the application of this electrode to the electroreduction of in an aqueous solution. On cathodic polarization, the ring structures of PAn transformed from quinoid to benzenoid states. It was confirmed that the metal complex [1,8‐dihydroxynaphthalene‐3,6‐disulfonato iron (II)] once doped onto the conducting polymer is not undoped in cathodic processes, and the charge balance of the polymer is kept by taking an electrolyte cation in or out. The onset potential where was accumulated with the modified electrode was 0 V vs. Ag/AgCl, and the amount of on the electrode became largest at −0.2 V. The accumulation of with the electrode mediator was caused by the bonding between the mediated PAn and through a linkage of the electrophilic carbon atom of with the nitrogen atom of the benzenoid ring. The prolonged electrolysis of at potentials more negative than −0.3 V led to the generation of species involving lactic and formic acids, and the scheme of the initial reduction process was disclosed.