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Abstract: In this report, three hybrid inorganic-organic proton-conducting membranes based on a novel fluorinated titania labeled TiO2F dispersed in Nafion were prepared. The mass fraction of TiO2F nanofiller ranged between 0.05 and 0.15. The water uptake and the proton exchange capacity of the membranes were determined; the membranes were further characterized by TG, DMA and FT-IR ATR investigations. Finally, the hybrid membranes were used in the fabrication of membrane-electrode assemblies (MEAs), which were tested in operating conditions as a function of the back pressure and of the hydration degree of the reagents streams. It was demonstrated that, with respect to pristine recast Nafion, at 25%RH the MEA fabricated with the membrane including a mass fraction of TiO2F equal to 0.10 yielded a higher maximum power density (0.206 W cm−2 vs. 0.121 W cm−2). Finally, it was proposed a coherent structural model of this family of hybrid membranes accounting for both the properties determined from “ex-situ” characterizations and for the performance obtained from measurements in a single fuel cell in operating conditions. [Copyright &y& Elsevier]

This paper describes the synthesis and characterization of three-dimensional hybrid inorganic–organic networks prepared by a polycondensation reaction between Zr(O(CH2)3CH3)4 and polyethylene glycol 400 (PEG400). Eleven hybrid networks doped with varying concentrations of LiClO4 salt were prepared. On the basis of analytical data and FT-Raman studies it was concluded that these polymer electrolytes consist of inorganic–organic networks with zirconium atoms bonded together by PEG400 bridges. These polymers are transparent with a solid rubber consistency and are very stable under inert atmosphere. Scanning electron microscopy revealed a smooth glassy surface. X-ray fluorescence microanalysis with energy dispersive spectroscopy demonstrated that all the constituent elements are homogeneously distributed in the materials. Thermogravimetric measurements revealed that these materials are thermally stable up to 262 °C. Differential Scanning Calorimetry measurements indicated that the glass transition temperature Tg of these inorganic–organic hybrids varies from −43 to −15 °C with increasing LiClO4 concentration. FT-Raman investigations revealed the TGT (T=trans, G=gauche) conformation of polyether chains and allowed characterization of the types of ion-ion and ion–polymer host interactions in the bulk materials. The conductivity of the materials at different temperatures was determined by impedance spectroscopy over the 20 Hz–1 MHz frequency range. Results indicated that the materials conduct ionically and that their ionic conductivity is strongly influenced by the segmental motion of the polymer network and the type of ionic species distributed in the bulk material. Finally, it is to be highlighted that the hybrid network with a nLi/nO molar ratio of 0.0223 shows a conductivity of ca. 1×10−5 S cm−1 at 40 °C. [Copyright &y& Elsevier]

Abstract: This report presents detailed studies on the elemental analysis, vibrational spectroscopy, thermal stability and electrical spectroscopy of two new hybrid inorganic–organic polymers which have been synthesised by a sol–gel method using glycerol and zirconium(IV)butoxide as precursors. These materials have been doped by means of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIm-TFSI) ionic liquid (IL), which is insoluble in water. The elemental composition of the obtained polymers [Zr(C6O5H11)] (1) and [Zr(C11O4H31)] (2) has been determined by CHN analysis and by ICP-AES measurements. FT-IR and FT-Raman spectroscopy investigations have been performed to study the molecular structure of the polymers and the interactions of EMIm-TFSI with the host networks. Differential scanning calorimetry measurements show the presence of at least one glass transition temperature (T g) in both 1 and 2 materials. The broadband dielectric spectroscopic measurements have been carried out between 10−2 Hz to 10MHz from −100°C to 100°C with a 5°C step. The conductivities of the polymers 1 and 2 have been found to be in the order of 10−8 to 10−11 Scm−1 at 25°C, so they can be defined as dielectric materials. After doping 2 with EMIm-TFSI, the conductivity at 25°C of the obtained complex [Zr(C11O4H31)]15/(EMIm-TFSI) (2′) increased three orders of magnitude resulting ca. 10−5 Scm−1. The permittivity spectra revealed two relaxation bands which were attributed to the α relaxation modes of the polymer networks. [Copyright &y& Elsevier]