Polyaniline as cathode for O2 reduction: kinetics of the reaction with H2O2 and use of the polymer in a model H2/02 fuel cell.

Oxygen reduction at a polyaniline cathode occurs in aqueous sulfuric acid through a chemica-electrochemical route which involves the intermediate oxidation of leucoemeraldine to emetaldine with the formation of H,O,. This paper specifically deals with the conversion of leucoemeraldine to emeraldine by H,O, whose kinetics, apparently second order on the charge exchanged, are similar to those found for the reaction with O,, although they occur at lower rate. The catalytic four electron 0, reduction mediated by the Fe(III)/Fe(II) couple which decomposes H,O, is not fully achieved. However, polyaniline proved to be a reliable cathode for O,, sustaining the working of a model HJO, fuel cell.