Reduction of redox mediators by CO in the presence of a Co porphyrin: Implication for electrochemical cells powered by CO

We found that a water-soluble cobalt tetraphenylporphyrin tetrasulfonic acid catalyzes the reduction of redox mediators (quinones and indigo carmine) by CO. The reduction was analyzed by constant-potential amperometry, UV-spectroscopy, and gas chromatography. The rate of this reaction was quantitatively determined by monitoring the reduced forms of these compounds by amperometry. The reduction rate significantly depended on the redox potentials of these compounds. Since the reduced forms of indigo carmine and quinones can act as a good fuel for fuel cells, this reaction can be regarded as the conversion of the fuel from CO to other redox active species.

► We demonstrated that a Co porphyrin can catalyze the reduction of quinones by CO.
► The reaction was confirmed by amperometry, UV-spectroscopy, and gas chromatography.
► The rate of this reaction significantly depended on the redox potentials of quinones.
► This reaction can be regarded as the regeneration of fuel for an indirect CO fuel cell system.