Vito Di Noto

Structure-Relaxation Interplay of a New Nanostructured Membrane Based on Tetraethylammonium Trifluoromethanesulfonate Ionic Liquid and Neutralized Nafion 117 for High-Temperature Fuel Cells

In this report, the electrical performance at T > 100 degrees C and low relative humidity of proton-conducting Nafion-based membranes was improved by preparing new materials based on Nafion 117 (N117) neutralized with triethylammonium (TEA(+)) and doped with the ionic liquid (IL) trifluoromethanesulfonate of triethylammonium (TEA-TF). In particular, a new two-step protocol for the preparation of [N117(x-)(TEA(+))(x)/(TEA-TF)(y)] is proposed. [N117(x-)(TEA(+))(x)/(TEA-TF)(y)] membrane is composed of ca. 30 wt % of TEA-TF. The structure of the different nanophases composing the materials and their interactions were investigated by FT-IR ATR and micro-Raman spectroscopy. The thermal stability, water uptake, and mechanical properties of the membranes were studied by thermogravimetric analysis and dynamic mechanical analysis measurements. With respect to pristine N117, the thermal and mechanical properties of the proposed materials were improved. The electric response of [N117(x-)(TEA(+))(x)/(TEA-TF)(y)] was studied by broad band dielectric spectroscopy in the frequency range from 10(-2) Hz to 10 MHz and for temperatures between 5 and 155 degrees C. In comparison to the N117 reference, the following was observed: (a) the stability range of conductivity (SRC) of the [N117(x-)(TEA(+))(x)] membrane increases up to 155 degrees C, while its sigma(DC) at T = 100 degrees C is lowered by ca. 2 orders of magnitude; (b) the SRC of [N117(x-)(TEA(+))(x)/(TEA-TF)(y)] is similar to that of [N117(x-)(TEA(+))(x)], while the sigma(DC) at 145 degrees C decreases in the order 7.3 x 10(-3) > 6.1 x 10(-3) > 9.7 x 10(-4) S x cm(-1) for [N117(x-)(TEA(+))(x)/(TEA-TF)(y)], N117, and [N117(x-)(TEA(+))(x)] membranes, respectively. In conclusion, the lower water uptake, the improved thermal and mechanical stability, and the good conductivity make [N117(x-)(TEA(+))(x)/(TEA-TF)(y)] a promising membrane to improve for application in proton exchange membrane fuel cells operating under anhydrous conditions at T > 100 degrees C.

Interplay between Structure and Relaxations in Perfluorosulfonic Acid Proton Conducting Membranes

This study focuses on changes in the structure of ionomer membranes, provided by the 3M Fuel Cells Component Group, as a function of the equivalent weight (EW) and the relationship between the structure and the properties of the membrane. Wide-angle X-ray diffraction results showed evidence of both non-crystalline and crystalline ordered hydrophobic regions in all the EW membranes except the 700 EW membrane. The spectral changes evident in the vibrational spectra of the 3M membranes can be associated with two major phenomena: (1) dissociation of the proton from the sulfonic acid groups even in the presence of small amounts of water; and (2) changes in the conformation or the degree of crystallinity of the poly(tetrafluoroethylene) hydrophobic domains both as a function of EW and membrane water content. All the membranes, regardless of EW, are thermally stable up to 360 °C. The wet membranes have conductivities between 7 and 20 mS/cm at 125 °C. In this condition, the conductivity values follow VTF behavior, which suggests that the proton migration occurs via proton exchange processes between delocalization bodies (DBs) that are facilitated by the dynamics of the host polymer. The conductivity along the interface between the hydrophobic and hydrophilic domains makes a larger contribution in the smaller EW membranes likely due to the existence of a greater number of interfaces in the membrane. The larger crystalline domains present in the higher EW membranes provide percolation pathways for charge migration between DBs, which reduces the probability of charge transfer along the interface. Therefore, at higher EWs although there is charge migration along the interface within the hydrophobic-hydrophilic domains, the exchange of protons between different DBs is likely the rate-limiting step of the overall conduction process.

Characterization of mucilage aggregates in Adriatic and Tyrrhenian Sea: structure similarities between mucilage samples and the insoluble fractions of marine humic substance

The appearance of gelatinous aggregates called mucilages causes serious damages to tourism and fishery industries of the Adriatic Sea. So, many studies have been planned and some of them are still in progress to clarify the origin and causes of the phenomenon. The scientific research has showed that mucilages are produced by several marine organisms when peculiar climatic and trophic conditions occur. Moreover, as far as the mucilage composition is concerned, although it is well known that polysaccharides give a high contribution, knowledge of the structural characteristics of mucilages and their relationship with the natural organic matter of the marine environment has not been clarified yet. In this paper a study on the characterization of the marine mucilage samples collected in the Adriatic and Tyrrhenian Seas is described. The study was performed by spectroscopic (infrared and colorimetric) techniques, and elemental analysis. The results showed that mucilage samples have chemical and structural similarities with the insoluble fraction of the marine humic substance (humin). According to experimental evidences it is possible to establish the relationship between mucilages and the dissolved organic matter (DOM) in the marine environment in order to identify the most likely pathways of mucilage formation.

Dielectric investigation of inorganic–organic hybrid film based on zirconium oxocluster-crosslinked PMMA

Abstract Through photocopolymerisation of the cluster Zr4O2(OMc)12 bearing 12 polymerisable groups with methylmethacrylate in a monomer:cluster molar ratio of 50, a novel inorganic–organic hybrid thin film was obtained. The prepared thin film, having a thickness of about 70 μm, was characterised through dielectric spectroscopy. The dielectric spectra of the film were measured at different temperatures (20–73.4 °C) and in the frequency range 20 Hz–1 MHz. The α and β relaxations typical of polyalkylmethacrylate polymers were detected and the electric response mechanisms were investigated by analysing the dielectric spectra in terms of the Davidson–Cole phenomenological equation. Finally, a dielectric constant of 1.93 at 25 °C and 1 kHz was determined. This value classifies this system as a promising dielectric material for the development of electronic devices, such as polymer based field effect transistors.

Mechanism of ionic conductivity in poly(ethylene glycol 400)/(MgCl2)x polymer electrolytes: studies based on electrical spectroscopy

Abstract In this paper, eight solvent-free polymer electrolytes PEG400/(MgCl 2 ) x (0.00329≤ x ≤0.7000) were prepared in order to investigate the mechanism of ionic motion and the interactions existing in these systems. The study was carried out by impedance spectroscopy in the 20-Hz to 1-MHz range at different temperatures. Real and imaginary components of conductivity spectra in terms of equivalent circuit analysis (EC) and correlated ionic motion analysis based on a generalized universal power law (UPL) were investigated. Results revealed that in the PEG400/(MgCl 2 ) x , the ionic species formed in the bulk materials are crucial for the overall conductivity. Indeed, in PEG400/(MgCl 2 ) x , conductivity is ionic and takes place through hopping of the cationic species Mg 2+ and [MgCl] + between the coordination sites present along the polyethereal chains.

Graphene-based technologies for energy applications, challenges and perspectives

Here we report on technology developments implemented into the Graphene Flagship European project for the integration of graphene and graphene-related materials (GRMs) into energy application devices. Many of the technologies investigated so far aim at producing composite materials associating graphene or GRMs with either metal or semiconducting nanocrystals or other carbon nanostructures (e.g., CNT, graphite). These composites can be used favourably as hydrogen storage materials or solar cell absorbers. They can also provide better performing electrodes for fuel cells, batteries, or supercapacitors. For photovoltaic (PV) electrodes, where thin layers and interface engineering are required, surface technologies are preferred. We are using conventional vacuum processes to integrate graphene as well as radically new approaches based on laser irradiation strategies. For each application, the potential of implemented technologies is then presented on the basis of selected experimental and modelling results. It is shown in particular how some of these technologies can maximize the benefit taken from GRM integration. The technical challenges still to be addressed are highlighted and perspectives derived from the running works emphasized.

Vibrational Studies and Properties of Hybrid Inorganic-Organic Proton Conducting Membranes Based on Nafion and Hafnium Oxide Nanoparticles

In this report, we will describe the effect of different concentrations of HfO2 nanopowders on the structure and properties of [Nafion/(HfO2)n] membranes with n = 0, 3, 5, 9, 11, 13, and 15 wt %, respectively. Films were prepared by a solvent casting procedure using HfO2 oxoclusters and Nafion. Seven new homogeneous membranes were obtained with thicknesses ranging from 200 to 350 microm. Each membrane is characterized by a rough HfO2-rich surface and a smooth Nafion-rich surface, with different physical-chemical properties. Membrane characterization was accomplished by means of thermogravimetric analysis (TGA), morphological measurements (environmental scanning electron microscopy) and vibrational spectroscopy (Fourier transform infrared attenuated total reflectance spectroscopy and Fourier transform Raman spectroscopy). These systems can be described in terms of five types of water domains, Nafion-HfO2 species with well-defined stoichiometry surrounded by Nafion and hydrated hafnia. The highest conductivity at 125 degrees C (3.2 x 10-2 S x cm(-1)) was measured on the [Nafion/(HfO2)5] film by electrical spectroscopy, with a stability range of conductivity between 5 and 115 degrees C.

Synthesis, characterization and ionic conductivity of poly[(oligoethylene oxide) ethoxysilane] and poly[(oligoethylene oxide) ethoxysilane]/(EuCl3)0.67

Poly[(oligoethylene oxide) ethoxysilane)] (I) and poly[(oligoethylene oxide) ethoxysilane)]/(EuCl3)0.67 (II) were synthesized by reacting tetraethoxysilane with oligo(ethylene glycol) of molecular weight 400 and oligo(ethylene glycol)400/(EuCl3)0.317, respectively. The products so obtained are very transparent and rubbery. By Fourier transform infrared and Raman spectroscopy studies and by using analytical results it was concluded that these products are crosslinked macromolecular materials where the Si atom is bonded to one OEt group and to three poly(ethylene oxide) 400 chains. Scanning electronic microscopy studies showed that the presence of EuCl3 in polymer host significantly affects the morphology of the material. Laser luminescence investigations on (II) showed that Eu3+ ion in the polymer host is accommodated in two different types of sites having a distorted C2v symmetry. Moreover, the ionic conductivity of these systems was investigated and the data were satisfactorily fitted by the empirical Vogel Tamman Fulcher equation. At 70°C the conductivities of (I) and (II) were 9 × 10−6 and 14.3 × 10−6 Ω−1 cm−1 respectively.

Polymers: Opening Doors to Future Batteries

Research and development of post lithium ion batteries is attracting considerable attention. While there have been significant advances in understanding the challenges of Li-O2(air) and Li-S batteries, the development of gas separation and ion selective membranes will be crucial in their commercialization due to their potential to separate O2 from air and impede lithium polysulfide dissolution while permitting rapid diffusion of lithium ions. In addition, research leading to novel and highly conductive and selective polymer electrolytes will be essential in overcoming the deficiencies of liquid based electrolytes in both the air and sulfur based battery systems.

Spermine binding to liver mitochondria.

Non-equilibrium binding of spermine to mitochondrial membranes is studied in rat liver mitochondria by applying a new thermodynamic treatment of ligand-receptor interactions (Di Noto, V., Dalla Via, L., Toninello, A. and Vidali, M. (1996) Macromol. Theory Simul. 5, 165-181). The presence on mitochondrial membranes of two spermine binding sites, both with monocoordination, is demonstrated. The calculated binding energy is characteristic for weak interactions. The treatment allows also to evaluate the variations of the molar fraction ratio of spermine bound to sites 1 and 2 as function of total bound spermine. The possible role of the two sites is discussed.