APPLICATION OF THE FLOODED-AGGLOMERATE MODEL TO STUDY OXYGEN REDUCTION ON THIN POROUS COATING ROTATING-DISK ELECTRODE

In this work, the thin-film /flooded-agglomerate model of gas diffusio n electrodes was used to study the oxygen reduction reaction (ORR) on rotating disk electrodes with thin porous coating in alkaline solution s. Vulcan XC-72 carbon and 10, 20, and 30% w/w Pt/C catalysts were use d as electrode materials. Fitting of the theoretical equations to the experimental data was employed to simulate the polarization characteri stics of the ORR on the catalysts and to obtain the oxygen concentrati on profiles along the thickness of the flooded agglomerate as a functi on of the electrode potential and the structural parameters of the ele ctrodes. The method was found to be a simple and adequate way to evalu ate the performance of the supported catalysts. The predicted effect o f doubling of the Tafel slope of the ORR due to diffusion of the react ant in the flooded agglomerate was confirmed experimentally. The kinet ic parameters obtained for the ORR in alkaline media indicated that, f or the lower Pt/C ratios, there is a strong participation of the carbo n substrate in the catalysis of the reaction.