Functionalized ORMOSIL-Based Hybrid Membranes for Polymer Electrolyte Membrane Fuel Cells
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0885-A02-04.1
Functionalized ORMOSIL-Based Hybrid Membranes for Polymer Electrolyte Membrane Fuel Cells Silvia Licoccia1, Alessandra D’Epifanio1, M. Luisa Di Vona1, Zakarya Ahhmed1, Serafina Belitto1, Debora Marani1, Cadia D’Ottavi1, Emiliano Moroni1, Marcella Trombetta2, Enrico Traversa1 1
Dipartimento di Scienze e Tecnologie Chimiche, Università di Roma “Tor Vergata”, Via della Ricerca Scientifica 1, 00133 Roma, Italy 2 Interdisciplinary Center for Biomedical Research (CIR), Laboratory of Biomaterials, Università “Campus Bio-Medico”, via E. Longoni 83, 00155 Rome, Italy ABSTRACT Sulfonated poly ether ether ketone (SPEEK) with a high degree of sulfonation (DS = 0.9) was mixed with a modified silane bearing a sulfonic acid function (sulfonated diphenylsilanediole, SDPDO). Homogeneous composite membranes with several SPEEK:SDPDO ratios, were obtained. The addition of the ormosil significantly improved the water uptake and solubility properties of pure SPEEK. The structural and electrochemical characteristics of the composite membranes were investigated by means of thermogravimetric analysis (TG), field emission scanning electron microscopy (FE-SEM), and electrochemical impedance spectroscopy (EIS). The conductivity values of the composites SPEEK/SDPDO demonstrated that they possess good proton transport characteristics, thus being suitable for application in Polymer Electrolyte Fuel Cells operating at intermediate temperature.
INTRODUCTION Proton exchange membrane (PEM) fuel cells have received a great deal of attention due to their promising application as clean and efficient energy conversion systems. The requirements for the electrolytic polymeric membranes are good chemical and electrochemical stability, high proton conductivity (σ ≥ 10-2 Scm-1), low methanol permeation and low price. The most popular proton membranes are based on perfluorosulfonic acid polymers, e.g. NAFION. This polymer has an high conductivity but high methanol permeability and high cost [1,2]. Several non fluorinated polymers have been studied as possible alternatives [3]. We focused our attention on poly ether ether ketone (PEEK), which possesses good thermal stability, appropriate mechanical properties, and interesting conductivity when sulfonated (SPEEK). Unfortunately, at high values of sulfonation degree (DS > 0.8), corresponding at high conductivity, the mechanical properties of SPEEK severely deteriorate [3]. Recently, Class II hybrids with direct links between the sulfonated PEEK (SPEEK) polymeric backbone and –Si(OH)3 moieties were investigated to improve the performance of pure SPEEK [5]. In this case encouraging results were obtained: despite the high DS (0.9), the hybrid material resulted to be insoluble in water and exhibited high and stable conductivity values.
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In this work we chose to use an organosilane derivative, sulfonated diphenylsilanediole (SDPDO), as a filler in SPEEK based membranes. The presence in the filler structure of phenyl rings, highly stable chemical structures which play a prominent role i
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