Browsing by Author "Nicotera, Isabella"

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Hybrid nanostructured fillers for polymer electrolytes in the PEM Fuel Cells
(2012-11-30) Angjeli, Kristina; Versace, Carlo; Nicotera, Isabella; Bartolino, Roberto
The present thesis is focused on the development of novel nancomposite membranes, prepared by the incorporation of two-dimensional inorganic layered structures such as (i) smectite clays (synthetic and natural), (ii) graphene oxide (GO), and (iii) layered double hydroxides (LDHs) with different compositions into the polymer matrix of Nafion, for use as electrolytes in Proton Exchange Membrane fuel cells. The characteristics of the membranes were studied mainly, in terms of transport properties by NMR spectroscopy, in order to study the water dynamics inside the electrolyte membranes. For this purpose the Pulse-Field-Gradient Spin-Echo NMR (PFGSENMR) method was employed to obtain a direct measurement of water self-diffusion coefficients on the water-swelled membranes in a wide temperature range (25-140 °C). This technique together with the 1H-NMR spectral analysis and NMR spin-lattice relaxation times (T1) conducted under variable temperature. Furthermore, both pristine materials (fillers and Nafion) as well as the resulted nanocomposite membranes were characterized by a combination of X-ray diffraction, FTIR spectroscopy, thermal analysis (DTA/TGA), Raman spectroscopies and scanning electronic microscopy (SEM).
Probing membrane and interface properties inconcentrated electrolyte solutions
(2014-04-14) Fontananova, Enrica; Zhang,Wenjuan; Nicotera, Isabella; Simari,Cataldo; van Baak,Willem; Di Profio,Gianluca; Curcio,Efrem; Drioli, Enrico
This study deals with the membrane and interface electrical properties investigation by electrochemical impedance spectroscopy (EIS). The EIS is a powerful technique for characterizing electrical behavior of systems in which coupled electrical processes occur at different rates.A systematics tudy on the effect of solution concentration,temperature and velocity, on the electrical resistance of anion-and cation- exchange membranes (AEMs and CEMs) and their interfaces (electrical double layer and diffusion boundary layer), was carried out. At the best of our knowledge, for t he first time electrolyte concentrations up to 4 M were used for the study of membranes and interface by EIS. Moreover, Pulsed Gradient Spin Echo Nuclear Magnetic Resonance (PGSE-NMR)technique was used to measure the water self-diffusion coefficients in swelled membrane as a function of the solution concentration and temperature.These measurements gave additional important insights about the effect of the electrolyte solution and fixed charges concentration in membrane,on membrane microstructure and its transport and electrical properties. & 2014TheAuthors.PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBY
Solid-state-electrolytes for advanced power devices
(Università della Calabria, 2021-04-06) Lufrano, Ernestino; Cipparrone, Gabriella; Nicotera, Isabella; Simari, Cataldo; Baglio, Vincenzo
Il problema della produzione e immagazzinamento dell’energia, risulta essere ad oggi, un problema di fondamentale importanza, considerando la continua crescita demografica e le problematiche legate all’elevato inquinamento ambientale. Per tali motivi, la ricerca di nuovi metodi di produzione e immagazzinamento, acquista un’importanza sempre più rilevante. Oggi, uno dei sistemi di accumulo di energia più utilizzati nei vari settori è quello delle batterie agli ioni di litio, grazie alla loro elevata capacità di accumulo e all'elevata efficienza energetica. Tali dispositivi, sono utilizzati per apparecchiature mobili quali computer portatili, telefoni cellulari, e per l'alimentazione di veicoli elettrici. In riferimento a questi ultimi, nello specifico, lo scopo è quello di raggiungere una maggiore competitività rispetto al motore a combustione interna, in termini di autonomia, costi e potenza. Un sistema di propulsione ibrido, il cui compito è quello di garantire un'elevata efficienza ma allo stesso tempo un basso impatto ambientale, è generalmente costituito da un gruppo motore-generatore e da un serbatoio di accumulo elettrico. Attualmente tale sistema risulta essere la soluzione più praticata, ma da alcuni anni la ricerca è stata indirizzata verso proposte alternative, quali ad esempio la tecnologia delle celle a combustibile (FC), le quali sono in grado di generare elettricità in modo pulito ed efficiente utilizzando l'idrogeno come combustibile. Tra i vari tipi di celle, quelle basate su un elettrolita polimerico, sono particolarmente rilevanti per il settore automobilistico. In particolare le Proton- Exchange Membrane Fuel Cells (PEMFCs) offrono interessanti vantaggi nelle applicazioni veicolari o portatili, come la rapidità di avviamento, l'elevata efficienza di conversione energetica (~ 50%), il ridotto impatto ambientale per le basse emissioni di CO2 (zero nel caso in cui l'idrogeno sia il carburante) e temperature di funzionamento relativamente basse (tra 60 e 130 °C). Le celle a combustibile e le batterie agli ioni di litio sono state oggetto della presente tesi di dottorato sviluppata nel Laboratorio di Chimica Fisica e Materiali Applicati (PCAM LAB) presso il Dipartimento di Chimica e Tecnologie Chimiche dell'Università della Calabria. La sezione dedicata alle celle a combustibile, comprende aspetti generali su questa tecnologia, la descrizione delle membrane a scambio protonico e a scambio anionico, la preparazione di membrane composite, e infine i risultati della mia ricerca. L'obiettivo generale del lavoro è stato quello di progettare, sintetizzare e valutare elettroliti compositi innovativi con proprietà specifiche per le celle a combustibile a membrana polimerica. Mentre, la sezione dedicata alle batterie agli ioni di litio riguarda lo studio degli elettroliti polimerici compositi in gel (GPE) a base di argille organo-modificate disperse in miscele di polimeri PEO-PAN e liquidi ionici (IL). Le principali tecniche impiegate per lo studio degli elettroliti sintetizzati vanno dalla spettroscopia NMR alla spettroscopia di impedenza elettrochimica, dall'analisi meccanica (DMA) fino alle misure di polarizzazione elettrochimica nelle celle a combustibile DHFC e DMFC.
Transport Properties in Polymer Nanocomposite Membranes Cataldo Simari
(2015-12-15) Simari, Cataldo; Versace, Carlo; Nicotera, Isabella
The aim of this thesis has been to prepare and characterize innovative composite membranes for polymer electrolyte fuel cells (PEMFCs) applications. Among the different energy conversion devices based on polymer electrolytes, PEMFCs, both hydrogen (DHFC) and direct methanol (DMFC), seems to be one of the most promising clean energy technologies. As electrochemical devices able to directly convert the chemical energy of a fuel into electrical energy, PEMFCs offer interesting advantages in vehicular or portable applications , as the quick start, the high energy conversion efficiency (~ 50%), the reduced environmental impact for the low CO2 emissions (zero in the case where the primary fuel is hydrogen) and the flexibility respect to the fuel, in fact, besides hydrogen (DHFC), they can be fed for example with methanol (DMFC). However, considerable efforts are still needed to be able to achieve satisfactory performance in terms of efficiency, durability and cost for mass deployment of such technology. It is necessary to deal with some problems that concern the electrolyte membrane, such as the degradation of the materials, the low proton conductivity at low relative humidity (RH) and poor mechanical properties at temperature higher than 130 °C. Therefore, the development of high-performance proton conducting polymer electrolyte membranes is critical for the optimal power density and efficiency a PEMFC can achieve because membrane ohmic loss is the major cause of overpotential in the operational current range of the fuel cell. In recent years, increasing interest has been devoted to the development of high temperature proton conducting polymer electrolyte fuel cell systems. In fact, most of the shortcomings associated with the lowtemperature PEMFC technology based on perfluorosulfonic acid (PFSA) membranes can be solved or avoided by developing alternative membranes with suitable ionic conductivity and stability up to 150 °C. The increasing the operational temperature would result in increased performance of the cell because of easier and more efficient water management, higher reaction rates to the electrodes, improved CO tolerance by the anode electro-catalysts, faster heat rejection rates and better systems integration. It has been mentioned the possibility to feed PEMFCs systems with other fuel respect to hydrogen. In particular, direct methanol fuel cells (DMFCs) combine the merits of polymer electrolyte fuel cells fueled by H2 with the advantages of a liquid fuel, such as easy handling and high energy density. However, despite these advantages, also regard this devices there are still technical barriers to overcome for their widespread commercialization such as methanol crossover from anode to cathode through the proton exchange membrane. From the above, it is thus highly important to enhance the proton conductivity of the electrolyte membrane under low RH in order to accomplish higher PEMFCs performance. On the other hand, is essential to develop polymer electrolytes with reduced methanol cross-over for DMFC. The work presented in this thesis is the result of a Ph.D. project carried out during a period of about three years from 2012 – 2015, in the Physical Chemistry Soft Matter Laboratory “Mario Terenzi” (PC_SM Mario Terenzi) at the Department of Chemistry and Chemical Technologies in the University of Calabria. The thesis was written as part of the requirements for obtaining the doctor of philosophy degree. The overall objective of this doctoral thesis was to design, synthesize and evaluate innovative composite electrolytes with specific properties suitable for PEM fuel cells that operate at high temperatures (above 100 ° C ) and low RH and/or with low methanol permeability. To this purpose, three main classes of materials have been explored as nanoadditives to create nanocomposite membranes: (i) organo-modified TiO2 nanoparticles, (ii) layered materials based on clays (anionic and cationic) and graphene oxide and (iii) hybrids clays-carbon nanotubes. While, as concern the ionomers, perfluorosulfonic acid (Nafion®) and polyaromatic polymers (sulfonated Polyether Ether Ketone and Polybenzimidazole) have been evaluated. In my doctoral porject an attempt was made to conjugate an intense basic research in order to understand the molecular mechanisms at the basis of ionic conduction in such complex systems, and the design, synthesis and more comprehensive characterization of new nanocomposites with opportune requisites. For this purpose an deep study of the transport properties of the water confined within the electrolyte membranes has been performed by NMR spectrocopy (diffusometry, relaxometry and 1H spectral analysis) together to a wide physico-chemical, mechanical and electrochemical characterization in order to achieve a systematic understanding at a fundamental level of the effects of dimensionality, architecture and organization of these nanofillers on the properties of the ionomers and to exploit this knowledge for the preparation of high performance electrolytes. Some of the electrolytes membranes investigated during my PhD thesis were prepared and studied in the framework of the PRIN Project: NAMED-PEM “Advanced nanocomposite membranes and innovative electrocatalysts for durable polymer electrolyte membrane fuel cells”. The last part of this thesis concerns a research work arisen from a collaboration with ITM-CNR of the University of Calabria, on the Ion Exchange Membranes for Reverse Electrodialysis (RED) process. Here, the NMR techniques were used to study the water dynamics in anion- and cation- exchange membranes (AEMs and CEMs) in order to achieved additional important insights about the effect of the electrolyte solution, on membrane microstructure and its transport and electrical properties. The results of this research have been published in scientific international Journals and reported in appendix to the end of the thesis. During these years I have spent two stages periods abroad: 1) in the “Department of Materials Science and Engineering of the University of Ioannina, Ioannina (Greece)”, where I worked under the supervision of Prof. D. Gournis, my research has been focused on the synthesis of novel carbon-based materials as additives for nanocomposite membranes; 2) in Department of Physics & Astronomy of the Hunter College, New York (USA), where I worked under the supervision of Prof. S. Greenbaumn, I performed the High Pressure NMR investigation of water and methanol transport properties in sPEEK-based nanocomposite electrolytes. Two scientific papers, based on the results obtained during these stages, have been recently submitted and also reported in appendix