The critical importance of ionomers on the electrochemical activity of platinum and platinum-free catalysts for anion-exchange membrane fuel cells

Abstract

Anion-exchange membrane fuel cells (AEMFCs) show remarkable and rapid progress in performance, significantly increasing the relevance for research on electrocatalysis of the oxygen reduction reaction (ORR) and hydrogen oxidation reaction (HOR) for this technology. Since much of the recent progress in AEMFC performance can be tied to the improved interface between anion-exchange ionomers (AEIs) and catalysts, this topic deserves specific attention. This work reports the ORR and HOR activity measured in rotating disk electrodes for several ionomer–catalyst combinations, involving five different AEIs and Nafion® and four ORR and HOR catalysts selected from the best-in-class PGM-based and PGM-free catalytic materials. The results show little impact of the ionomers on the ORR and HOR activity of Pt/C and PtRu/C catalysts, respectively; however, the choice of the AEI has critical importance on the ORR activity of Fe–N–C and significant effect on the HOR activity of Pd–CeO₂/C.