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

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 opencircuit 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.(C) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

Various electrocatalysts developed for the cathode of PEMFC show better performance on a rotating disk electrode (RDE) compared to being assembled in the membrane electrode assembly (MEA), but this phenomenon has not been quantitatively explained yet. In this study, the Butler-Volmer equation is further developed based on the detailed disassembly of the elemental reaction processes on the cathodic catalyst surface and in the MEA. These analytical equations quantitatively indicate how the catalyst's structural parameters and the electrode's microstructural parameters influence the catalyst's performance. Further analysis reveals that optimizing the structure of the catalytic layer can potentially improve the PEMFC's current density by more than one order of magnitude when using traditional catalysts like Pt/C. However, increasing hydrogen permeation not only reduces the open-circuit voltage but also decreases the PEMFC's lifetime. The established equations in this work, derived from strict mathematical and physical deductions, provide new guidance for evaluating and improving the performance of electrocatalysts in MEA assembly.