PPO-triazole active nanofiber reinforcement to improve Aquivion® membrane for higher temperature PEMFC operation

Polymeric proton exchange membrane fuel cells offer a feasible solution to decarbonise transportation, especially in heavy duty vehicles. The main factors hindering their commercialisation are identified in the cost, the durability and the performance. To tackle these issues various approaches are being investigated[1]. A great effort has gone into limiting the degradation of the catalyst layer and the membrane[2] during operation. The latter is degraded both mechanically and chemically. Mechanical degradation is caused by the combined effect of the compression the membrane electrode assembly is subjected to in the cell, and the membrane dimensional changes caused by its swelling and shrinking during operation[3]. On the other hand, radical species are known to chemically degrade the polymer[4]. Mitigation strategies for both issues generally revolve around the introduction of active fillers or reinforcement materials[5],[6],[7]. In this work we propose the use of a polymeric fibrous web as reinforcement material: poly(p-phenyleneoxide) functionalised by propyltriazole, obtained by electrospinning, that is embedded within an Aquivion® membrane to improve its mechanical properties and hinder degradation. The functionalisation of PPO allows a strong interaction between the ionomer and triazole groups of the nanofibers, and continuity between fibre and ionomer. The results obtained during accelerated ageing tests show increased mechanical and chemical stability, with a marked reduction in permeability and in fluoride ion emission, suggesting that the functionalisation is also active in reducing the impact of radicals. The use of PPO as active reinforcement also contributes to extending the operation temperature to 95°C. The starting materials and the nanocomposite membranes were characterized for their properties both ex situ and in situ and showed promising results in terms of mechanical improvement and reduced chemical degradation while maintaining performances close to the pristine Aquivion®.