Effect of Ce-Based Scavengers on Properties and Stability of Recast Aquivion® Membranes as Mitigating Agents of Degradation for PEMFC Application

Polymeric electrolyte membranes based on a low equivalent-weight Aquivion^® commercial dispersion (D72-25BS; EW = 720 g eq^-1, Syensqo) were fabricated using a standardized in-house doctor-blade casting technique for application in proton exchange membrane fuel cells (PEMFCs). The low equivalent-weight (EW) Aquivion^® dispersion is a copolymer of tetrafluoroethylene (TFE) and sulfonyl fluoride vinyl ether (SFVE), commonly referred to as a short-side-chain (SSC) ionomer, which exhibits higher ion-exchange capacity (IEC) and proton conductivity than long-side-chain (LSC) perfluorosulfonic membranes. A home-made 30 wt.% Pt/CeO₂ radical scavenger (denoted syn-scavenger) was synthesized via a colloidal method and incorporated into the Aquivion^® membranes to investigate its mitigating effect on chemical degradation induced by peroxide radicals, a role typically associated with Ce-based scavengers. Particularly, the unique aspects of the Pt/CeO₂ scavenger synthesis could be summarized in the following points: (i) the mild aqueous deposition approach enabling highly dispersed Pt species on CeO₂ without the use of organic ligands; and (ii) the tailored redox interaction between Pt and ceria that enhances radical scavenging activity. Two Aquivion^® membranes (denoted Aqu) containing different syn-scavenger loadings (1.0 and 1.5 wt.%) were prepared and compared with a pristine Aquivion^® membrane and a membrane containing commercial CeO₂ (1.0 wt.%). Physicochemical characterization of the scavenger was performed using transmission electron microscopy (TEM), BET surface area analysis, and X-ray diffraction (XRD). The membranes were characterized by micro-Raman spectroscopy, water uptake and hydration number (λ), IEC, and proton conductivity measurements. To assess membrane stability, exsitu chemical oxidative degradation tests were conducted using Fenton's reagent. Overall, the membrane containing 1.0 wt.% syn-scavenger emerged as the most promising candidate, exhibiting favourable chemical-physical properties and the lowest reductions in IEC and proton conductivity following the degradation test.