Hybrid Membranes based on Aromatic Polymer Blends for Fuel Cell Applications
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1126-S12-04
Hybrid Membranes based on Aromatic Polymer Blends for Fuel Cell Applications Catia de Bonis1, Alessandra D’Epifanio 1, Barbara Mecheri1, M. Luisa Di Vona1, M. Trombetta2, E. Traversa1 and S. Licoccia1 1
Dipartimento di Scienze e Tecnologie Chimiche, Università di Roma Tor Vergata, Via della Ricerca Scientifica, 00133, Rome, Italy 2 CIR-Centro Interdisciplinare di Ricerca, Università Campus Bio-Medico, Via A. del Portillo, 00128, Rome, Italy ABSTRACT Blend membranes based on sulfonated polyetheretherketone (SPEEK) and containing 5 wt.% of silylated and sulfonated polyphenylsulfone (SiSPPSU) were prepared and characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR/FTIR) and by electrochemical impedance spectroscopy (EIS). Tests in a direct methanol fuel cell station were also performed. The experimental results demonstrated that the presence of hybrid polymer SiSPPSU allowed to increase the proton conductivity of electrolyte and to improve its performance under fuel cell operating conditions. Due to its satisfactory properties, SPEEK/ SiSPPSU blend membrane has a potential use in DMFCs operating at intermediate temperatures. INTRODUCTION Direct methanol fuel cells (DMFCs) are promising energy sources for automotive and stationary applications. They operate at low temperature (less than 120 °C) and offer the advantages of high efficiency, simple design and low polluting emissions. Nowadays, Nafion is the most used electrolyte for DMFCs but its proton conductivity decays at temperatures higher than 80 °C and it suffers from high methanol permeability [1]. Thus, extensive efforts have been devoted to the development of electrolytes alternative to Nafion including aryl polymer ionomer membranes of the polysulfone and polyetherketone families [2]. In particular, polyetheretherketone (PEEK) is a thermoplastic polymer having the operating requirements for fuel cells application, such as excellent chemical inertness, high thermo-oxidative stability and it shows good conductivity if sulfonated. However, it shows unsatisfactory mechanical properties at the sulfonation degree (DS) required to achieve adequate conductivity [3]. In our group several approaches have been followed to obtain SPEEK-based membranes with high hydrolytic stability and good electrochemical properties, including preparation of blends where the microstructure of SPEEK was modified by physical cross-linking with an hybrid organic-inorganic derivative of polyphenylsulfone (PPSU). The introduction of silylated and sulfonated polyphenylsulfone (SiSPPSU) improved the thermal stability and the mechanical properties of SPEEK-based membranes, maintaining adequate proton conductivity [4]. In this work, blend membranes made of SPEEK (95 wt.%) with DS = 0.5 and SiSPPSU (5 wt.%) with degree of silylation DSi = 0.2 and DS = 2 were prepared. The membranes were characterized by attenuated total reflectance Fourier transform infrared spectroscopy
(ATR/FTIR) and their electrochemical behaviour was investigated by proton con
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