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The dielectric and conductivity study of two series of five three-dimensional hybrid inorganic–organic networks as polymer electrolytes (3D-HION-APEs), with formula {Al[O(CH2CH2O)8.7]ρ/(LiClO4)z}n (1.86 ≤ ρ ≤ 2.24, 0 ≤ z ≤ 1.06) and {Zr[O(CH2CH2O)8.7]ρ/(LiClO4)z}n (1.81 ≤ ρ ≤ 1.99, 0 ≤ z ≤ 0.91) is presented. The real and imaginary components of the complex dielectric permittivity spectra ɛ* and conductivity spectra σ* are measured between −60 °C and 80 °C. Spectral analysis points out that the conductivity mechanism is determined by two dielectric relaxation events, α and β. The relaxation β occurs at higher frequencies than α, and is attributed to the segmental motion with characteristic frequency fseg. The relaxation α is attributed to the ionic motion with characteristic frequency fion. The profiles of the direct conductivity σdc and the frequencies fion and fseg vs. the reciprocal temperature exhibit a Vogel–Tamman–Fulcher (VTF) behavior. The study of the activation energies of the dielectric relaxations α and β allows to determine their relative contribution to the direct conductivity σdc at lower and higher temperatures. The dependence of the VTF parameters vs. the mole-to-mole ratios nLi/nO and nLi/nM (M = Zr, Al) in combination with previous equivalent conductivity studies, allows to identify the role of the ionic species and the metal nodes present in the polymer structure at various salt concentrations. The correlation between the diffusion coefficient D and the relaxation frequencies fseg and fion of the 3D-HION-APEs is investigated.

In this report are presented the preparation and the characterization of six nanocomposite membranes of formula { Nafion / [ ( Ti O 2 ) ⋅ ( W O 3 ) 0.148 ] ψ Ti O 2 } with ψ Ti O 2 in the range 0–2.988. These materials are based on Nafion and [(TiO2)·(WO3)0.148] nanofiller. The effect of [(TiO2)·(WO3)0.148] nanopowders on the structural, thermal, mechanical and electrical properties of { Nafion / [ ( Ti O 2 ) ⋅ ( W O 3 ) 0.148 ] ψ Ti O 2 } membranes was studied. The water uptake (WU) value of materials was lower than that of pristine Nafion and was correlated with ψ Ti O 2 . The thermal transitions were investigated by modulated differential scanning calorimetry (MDSC). The mechanical parameters and relaxation processes on temperature were studied by dynamical mechanical analyses (DMA). The FT-IR ATR and μ-Raman vibrational investigations allowed to determine the structure of the hydrophobic polytetrafluoroethylene (PTFE) domains of Nafion and the interactions Nafion–[(TiO2)·(WO3)0.148] and Nafion–[H2O] in bulk materials. The analysis of complex conductivity plots were evaluated in the 10−2 Hz–10 MHz and 5–155 °C regions. Results indicated that the conductivity of { Nafion / [ ( Ti O 2 ) ⋅ ( W O 3 ) 0.148 ] ψ Ti O 2 } nanocomposite membrane, with ψ Ti O 2 = 1.616 , at 135 °C, is 5.0 × 10−2 S cm−1, while its stability range of conductivity (SRC) extends up to 135 °C.

In this paper is described the preparation of new platinum-free Pd-Co carbon-nitride electrocatalysts (Pd-Co-CNs) for application in lowtemperature fuel cells. Two groups of materials with formula Kn[PdxCoyCzNlHm] were synthesized, which are grouped in two ensembles: the first is characterized by a molar ratio y/x > 1 (I), and the second by y/x < 1 (II). Kn[PdxCoyCzNlHm] materials were prepared through a two-step synthesis protocol. The effect of the Pd/Co molar ratio and of the temperature of the thermal treatments on the structure and properties of the products were studied extensively by thermogravimetry, scanning electron microscopy, and vibrational (FT-IR and micro-Raman) and XPS spectroscopy. Vibrational studies revealed that I and II systems consist of two polymorphs of - and graphitic-like carbon-nitride nanomaterials. The electrochemical activity towards the oxygen reduction reaction (ORR) and the hydrogen oxidation reaction (HOR) was measured by cyclic voltammetry measurements with thin-film rotating disk electrode (CV-TF-RDE). The electrochemical performance of Pd-Co-CNs of group I obtained at tf >=700 oC resulted higher than that measured for a platinum-based commercial electrocatalyst in terms of both the activity towards the ORR and the HOR and of the resistance towards the poisoning effect of methanol towards the ORR. © 2007 Elsevier Ltd. All rights reserved.

This paper reports the synthesis of a new Z-IOPE material based on poly(ethylene glycol) 600, (CH3)2SnCl2 and K4Fe(CN)6. This material was synthesized via a sol-gel transition. FIR and MIR spectroscopy studies together with detailed compositional data allowed us to propose a final structure for this Z-IOPE material. It was concluded that this compound is a mixed inorganic-organic network in which clusters formed by tin and iron complexes are bonded together by PEG 600 bridges. The conformation of polyethereal chains in the bulk material is of the TGT (T=trans, G=gauche) type. Impedance spectroscopy measurements revealed that the material has a conductivity of 4.77.10−5 S cm−1 at 21.3°C.

A δ -MgCl 2 was synthesized by reacting metallic magnesium with 1-chlorobutane. This salt is extremely anhydrous and shows a high crystallographic disorder and reactivity toward Lewis bases. By using this δ -MgCl 2 , eight poly(ethylene glycol)/( δ -MgCl 2 ) x complexes, with 3.29×10 −3 ≤ x ≤ 7.00×10 −1 , were synthetized. The interaction between Mg 2+ ion and poly(ethylene glycol) (PEG) ligands was investigated by mid and far FT-IR spectroscopy. It was concluded that in these polymer electrolytes: (a) Mg 2+ ions could be accommodated in two distinct distributions of coordination sites and (b) PEG chains present a TGT conformation. Conductivity data of PEG 400/( δ -MgCl 2 ) x was determined by impedance spectroscopy. The room temperature conductivities of these polymer electrolytes are ca . 1.9×10 −5 S cm −1 .

Dipartimento di Scienze Chimiche, Universita di Padova, Via Marzolo 1, 35131 Padova (PD), Italy Istituto di Scienze e Tecnologie Molecolari del CNR, ISTM-CNR c/o Dipartimento di Scienze Chimiche, Via Marzolo 1, 35131 Padova, Italy Department of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany Max-Planck-Institut fur Festkorperforschung, Heisenbergstrase 1, D-70569 Stuttgart, Germany Dipartimento di Ingegneria dei Materiali e Tecnologie Industriali, Universita degli Studi di Trento, via Mesiano 77, I-38100, Trento, Italy INSTM, UdR Trento, Italy