Oxygen reduction on oxide/polypyrrole composite electrodes: effect of doping anions

Multilayered composite electrodes on glassy carbon, GC, having the structure GC/PPy/PPy(Ox)/PPy, with PPy the polypyrrole and Ox a mixed valence oxide of transition metals, exhibit high reactivity and stability towards the oxygen reduction reaction (orr), when the orr proceeds electrocatalytically on the oxide particles dispersed throughout the inner layer, PPy(Ox). However the nature and concentration of the doping anions, A, of PPy have a profound effect on the resulting orr currents, due to their effects on the conductivity and morphology of the PPy layers. The paper shows and discusses these effects in the case of the composite electrode with Ox = Cu_1.4Mn_1.6O₄ and A = Cl⁻, ClO₄⁻, NO₃⁻, PF₆⁻ and SO₄²⁻, in acid solution (pH 2.2). Optimal conditions were encountered with Cl⁻.