Impact of catalyst support impurities on chemical degradation in polymer electrolyte membranes

This study investigates the effect of iron and magnesium impurities present in carbon-based catalyst supports on the chemical degradation of polymer electrolyte membranes (PEMs) in polymer electrolyte fuel cells (PEFCs). A strong linear correlation is found between the iron content on the carbon surface and the degree of membrane thinning after 100-h open circuit voltage (OCV) holding tests, while membrane thinning is depressed by acid treatment. In contrast, magnesium impurities have no significant effect on membrane thinning, but Mg 2+ ions cause an increase in ohmic resistance. These findings highlight the critical role of surface Fe impurities in the chemical degradation of PEMs and thereby the durability of PEFCs, as well as the role of Mg in decreasing the ionic conductivity. They also clearly demonstrate that acid treatment of the carbon support is effective in mitigating these modes of degradation, paving the way for the design of more durable PEFCs. • Surface Fe impurities on carbon supports promote PEM degradation. • A strong correlation between Fe content and membrane thinning is found. • Mg impurities do not cause membrane thinning, but do increase the ohmic resistance. • Acid treatment removes ∼90 % of surface Fe, suppressing membrane thinning by ∼50 %. • Control of support impurities is vital for enhanced PEFC performance and durability.