Highly-performing and low-cost nanostructured membranes based on Polysulfone and layered doubled hydroxide for high-temperature proton exchange membrane fuel cells

Abstract

The low cost, reduced fuel crossover and ease of preparation make sulfonated Polysulfone (sPSU) a potential candidate to replace Nafion electrolyte in proton exchange membrane fuel cells (PEMFCs). To reach a satisfactory proton conductivity the general strategy involves the preparation of macromolecules with high ion exchange capacity (IEC), even at the cost of sacrificing their mechanical properties. In this study, sPSU with relatively low IEC was used as polymer matrix for the preparation of nanocomposite electrolytes by dispersing Mg/Al–NO3- Layered Double Hydroxides (LDH). sPSU-LDH membranes were prepared by solution intercalation method and characterized by XRD, TGA and DMA, whereas water dynamics and proton conductivity were investigated by NMR (PFG and T1) and EIS spectroscopies, respectively. The complete exfoliation and nanodispersion of the LDH platelets into the polymer enhance the thermo-mechanical resistance, the dimensional stability and the water retention capacity of the electrolytes. The formation of highly connected ion channels promotes an effective Ghrotthus-type mechanism for the proton transport also under dehydrating environment. Such features allowed proton conductivity values and electrochemical performances in single cell PEMFC distinctly higher than the Nafion recast, demonstrating the possibility to prepare cost-effective and high performing sPSU-based membranes able to operate under low-humidification and high temperatures conditions.