STUDY OF OXYGEN REDUCTION REACTION IN SULFURIC-ACID ON THIN POROUS-ELECTRODES COMPOSED OF CARBON AND PLATINUM

In this work, the oxygen reduction reaction was studied in 0.5 M sulfu ric acid solutions on platinum dispersed on carbon with 10, 20, 30, an d 40% w/w Pt/C ratios, using the thin porous coating technique. Cyclic voltammetry was used to evaluate the Pt electrochemical active areas of the electrodes and steady-state polarization curves obtained with t he rotating disk electrode technique were employed to study the oxygen reduction reaction. Cyclic voltammetry showed that the activity of th e Pt particles with respect to the hydrogen adsorption/desorption proc ess is dependent on the particle size. From the combination of the pol arization data with the thin film-flooded agglomerate model it was pos sible to obtain the kinetic and mechanistic parameters for the oxygen reduction reaction, which resulted only dependent on the catalyst natu re. It was observed that the mechanism and the kinetic behavior of the reaction were the same as those on gas diffusion electrodes or on smo oth polycrystalline platinum. The only difference was found in the Taf el slopes of the polarization diagrams which double as a consequence o f the porous nature of the dispersed catalyst electrodes.