We have developed a recovery, regeneration, and reapplication process for Nafion, a perfluorinated sulfonic acid (PFSA) ionomer, from end-of-life (EoL) low-temperature proton-exchange membrane (PEM) fuel cells (FCs). Samples of PFSA PEM recovered from EoL membrane-electrode assemblies (MEAs) with a history of close to 19,000 h of operation were recycled by dissolving the polymeric material in ethanol and applying the dissolved PFSA ionomer for producing the ionomer phase of the catalyst layer of new PEMFC cathodes. Structural characterizations show a marginally lower abundance of sulfonic groups for the EoL PEM compared to a fresh sample. Sulfonation of the former was employed to regenerate sulfonic groups to compensate for the lost ones. New gas-diffusion electrodes (GDEs) were prepared with the recycled PFSA ionomer both with and without sulfonation, and MEAs with these GDEs as cathodes were assembled through a state-of-the-art procedure. Electrochemical characterizations of the GDEs and single-cell studies of the MEAs showed that the electrochemical performances of catalyst layers containing recycled PFSA ionomer were at least similar to those containing fresh. Durability studies of the GDEs and MEAs, performed through a three-electrode liquid cell and a single cell, respectively, show the highest durability for the GDE/MEA with PFSA ionomer recycled without applying the sulfonation step. However, the GDE with PFSA ionomer obtained from recycling a re-sulfonated PEM shows a durability comparable to that of the GDE with fresh PFSA ionomer. Hence, PFSA material aged during PEMFC operation may be employed to produce highly functional and durable regenerated PFSA ionomer for PEMFC catalyst layers. The studied process of PFSA ionomer recycling is highly attractive for industrial adoption.
Keywords: PEM dissolution; PEMFC; PFSA ionomer; catalyst ink; recycling; regeneration; sulfonation.