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Effect of phosphoric acid concentration on the oxygen reduction and hydrogen oxidation reactions at a gas diffusion electrode

1992; Elsevier BV; Volume: 37; Issue: 10 Linguagem: Inglês

10.1016/0013-4686(92)85090-8

1873-3859

Denise Rocco de Sena, Ernesto R. González, Edson A. Ticianelli,

Electrochemical Analysis and Applications

In this work a study was conducted in order to examine the effect of the H3PO4 concentration on the oxygen reduction reaction (ORR) using platinum catalysed gas diffusion electrodes. The main objective was to show to what extent the characteristics of the reaction on smooth electrodes can be applied to dispersed platinum supported on carbon. In spite of not being kinetically limiting in fuel cells, the study was also extended to the hydrogen oxidation reaction (HOR). The behaviour of electrode potential vs current density curves and Tafel plots obtained experimentally for ORR as a function of H3PO4 concentration was analysed in terms of the following parameters: (i) gas solubility; (ii) proton activity; (iii) anion adsorption; (iv) double layer structure; (v) oxygen coverage and (vi) active area of the electrodes. When the first five parameters are considered, the conclusion is that the behaviour of a gas diffusion electrode is similar to that of the smooth Pt surface. However, for the gas diffusion electrode, a particular effect of variation of the Pt active area as a function of H3PO4 concentration, is brought out by the experimental results.