Modified equations for the performance of oxygen reduction reaction catalyst from rotating disk electrode to membrane electrode assembly

Abstract

Kinds of electrocatalysts developed for the cathode of Polymer electrolyte membrane fuel cell (PEMFC) show more outstanding performance when loading on rotating disk electrode (RDE) than assembling in the membrane electrode assembly (MEA), and this phenomenon has not be explained quantitatively yet. Here we developed the Butler-Volmer equation further on the base of the detailed disassembly of the elemental reaction processes that occurring on the surface of the cathodic catalyst and in the MEA. These analytical equations quantifiably indicate how the catalyst's structural parameters and electrode's microstructural parameters to influence the performance of catalyst. Further analysis shows there may be more than one order of magnitude for the PEMFC's current density improvement when using the traditional catalyst like Pt/C, after optimizing the structure of catalytic layer. Meanwhile, the increasing hydrogen permeation not only lower the open-circuit voltage but also cause the whole polarization curve moving down, which means an attenuation of PEMFC's lifetime. These equations shown in this work are established on the strict deduction of mathematics and physics and will give the new guidance for evaluating and improving the performance of electrocatalysts when assembling in MEA.