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 sulfuric acid solutions on platinum dispersed on carbon with 10, 20, 30, and 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 the rotating disk electrode technique were employed to study the oxygen reduction reaction. Cyclic voltammetry showed that the activity of the Pt particles with respect to the hydrogen adsorption/desorption process is dependent on the particle size. From the combination of the polarization data with the thin film-flooded agglomerate model it was possible to obtain the kinetic and mechanistic parameters for the oxygen reduction reaction, which resulted only dependent on the catalyst nature. It was observed that the mechanism and the kinetic behavior of the reaction were the same as those on gas diffusion electrodes or on smooth polycrystalline platinum. The only difference was found in the Tafel slopes of the polarization diagrams which double as a consequence of the porous nature of the dispersed catalyst electrodes.