Abstract
The increase in regulations on per- and polyfluoroalkyl substances (PFAS) due to health and environmental concerns,1 has resulted in an increasing need for alternatives to polyfluoroalkylsulfonic acid (PFSA) based proton exchange membranes (PEMs). An alternate class of polymers are functionalized polyarylenes, such as sulfonated polyphenylenesulfone (sPPS)2, sulfonated phenylated polyphenylenes (sPPP)3, and the co-polymer sulfonated polyphenylene quinquephenylene (SPP-QP)4.Despite good progress made in reaching comparable performance to Nafion, radical induced degradation of phenyl(sulfonate) rings during fuel cell operation remains prevalent. In a recently published study,5 we investigated the potential of using a Cu(II)-porphyrin complex as an antioxidant for aromatic sulfonate compounds. First, γ-radiolysis was used on aqueous solutions containing the model aromatic compound potassium 4-(tert-butyl)-2-methoxyphenylsulfonate with varying amounts of antioxidant. The exposure of water-based solutions to high-energy radiation results in the formation of hydroxyl radicals, which in turn react with the model compound. Resulting degradation of the compounds was analyzed using high performance liquid chromatography (HPLC). In the second part of the study, we incorporated the Cu(II)-porphyrin into PEMs to test membrane stability during fuel cell operation using an accelerated degradation protocol. The measurements combined with post-mortem analysis show that membranes containing antioxidants have a five-fold increased stability compared to reference non-stabilized membranes.
Published Version
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