Development of composite sPEEK membranes containing zeolite imidazole frameworks as ionic cross-linkers for energy applications.

Nowadays, electrochemical energy-conversion devices using green hydrogen, such as polymer electrolyte membrane fuel cells (PEMFCs) play a key role due to their high energy conversion efficiency. Perfluorinated-based polymer membranes are still considered as a benchmark but, recently, fluorine was inserted by EU in the Critical Raw Materials list, so significant efforts have been focused on alternative polymers. In this context, sulfonated polyetheretherketone (sPEEK) membranes can be considered as an alternative to conventional PFSA membranes due to high proton conductivity at high sulfonation degree, good mechanical properties and reduced hydrogen crossover and costs [1]. Properties of sPEEK membranes can be tailored controlling the sulfonation degree, even if at high sulfonation level the mechanical strength and membrane stability decrease due to the high swelling. In this work, the development of composite membranes with fillers able to interact with SO3H groups of the polymer with reduced swelling, maintaining the proton conductivity and performance are studied