Simultaneous electrochemical and mössbauer measurements on polymeric iron phthalocyanine oxygen electrodes

Abstract

Mössbauer spectra have been obtained on porous, hydrophobic electrodes in situ when used as oxygen reduction electrodes in sulphuric acid electrolyte. The electrodes consisted of polymeric iron phthalocyanine precipitated on activated carbon. Mössbauer spectra were also obtained on the same kind of electrodes which had been used for different amounts of time. The polymeric iron phthalocyanine was prepared using iron enriched in ⁵⁷Fe to get resolvable spectra.

The Ms̈sbauer spectra are characterized by the increase of a signal corresponding to oxidized iron as the catalytic activity decreases. A correlation between the amount of iron dissolved into the electrolyte and the electrode potential is seen during the first 100 h of operation.

It is suggested that Fe(II) is oxidized to Fe(III) which is dissolved into the electrolyte.