Symposium : F
Solid proton conductors (In honor of Prof. G. Alberti)
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| 09:00 | Welcome | |
| Solid proton conductors 1 : ML Di Vona | ||
| 09:15 | The Matrix Counter-Osmotic Pressure Index (MCPI) method for understanding the behaviour of proton conducting ionomer membranes and its application to long life medium temperature Fuel Cells. Authors : Giulio Alberti, M. Luisa Di Vona and Riccardo Narducci Affiliations : Chemical Department, University of Perugia, via Elce di Sotto 8, Perugia, Italy; Tor Vergata University, Rome, Italy Resume : Although it was well known that a good ionomer hydration is essential for obtaining high proton conductivity; the relations among water-uptake, temperature and relative humidity (RH) were only known on a qualitative basis. The mechanical properties of ionomer membranes are also strongly dependent on water-uptake; however, the most part of previous experimental determinations have been performed at room temperature and the history of the ionomer was generally not well accounted.
Some years ago we decided to revise the role of ionomer hydration in a quantitative manner. An osmotic model was used for deriving simple equations relating the osmotic pressure of inner proton solution to external RH and temperature. An index proportional to the counter pressure of the ionomer matrix balancing the inner osmotic pressure was used for understanding ionomer matrix properties.
Other than from a fundamental point of view, MCPI method has been found to be very useful for understanding the mechanical degradation and proton conductivity decay in medium temperature Fuel Cells and reinforcement of mechanical properties by annealing procedures.
A brief description of the MCPI method together with some significant examples of possible applications for long life medium temperature Fuel Cells are discussed.
[1] Alberti, G., Narducci, R., Sganappa, M. J. Power Sources 2008, 178, 575.
[2 ] Alberti, G., Narducci, R.Fuel Cells 2009, 9, 410.
[3] Alberti G., Casciola M., Chapter in Comprehensive Membrane Science, Elsevier 2010
[4] Alberti, G., Narducci, R. and Di Vona ML., Int. J. Hydrogen Energy, in press | 1 1 |
| 09:45 | The Kinetics of Water Sorption in Perfluorinated Membranes : a subsecond-to-years story. Authors : Sandrine Lyonnard;Q. Berrod;G.Gebel;A. Guillermo Affiliations : Structures et Propriétés d'Architectures Moléculaires, UMR 5819 (CEA-CNRS-UJF). Laboratoire des Polymères Conducteurs Ioniques, INAC/SPrAM, CEA-Grenoble, 38054 Grenoble Cedex 9, France. Resume : Optimizing the water management in a proton exchange membrane fuel cell is a major issue. In addition to the operating conditions, it is controlled by the membrane water sorption and transport processes, which are not clearly understood yet. We have conducted a systematic study by small-angle neutron and X-rays scattering techniques to shed light on the sorption mechanisms. The morphological changes in different types of membranes (perfluorinated/hydrocarbonated) have been measured as a function of hydration time. Two different methods were used: A) membranes were equilibrated with vapour and liquid water [1], B) a stopped-flow device was used to inject water and record the spectra after injection at subsecond timescales. The novelty of the approach is thus to obtain the kinetics of water sorption on extended times-scale: from tenths of milliseconds to few years (some samples were immersed in water for 6 years).
The firs important result is that water diffusion within the membrane appears not to be the limiting process in case of membranes A. The sorption kinetics are dominated by the transfer at the membrane interface. This result provides new insight into the numerous data published on these properties.
Secondly, the swelling kinetics of a Nafion membrane immersed in liquid water have been studied for the first time. Two regimes have been evidenced: a very fast purely Fickian process due to water diffusion, followed by a slower process (logarithmic dependence) due to membrane reorganization. Both regimes are affected by membrane chemical composition, charge density and temperature.
[1] G. Gebel, S. Lyonnard, H.Mendil-Jakani, Arnaud Morin; Water sorption kinetics in Nafion® membranes: a small-angle neutron scattering study. Journal of Phys. Cond. Matt. 23 (2011), 234107.
[2] Gebel G., Diat O., Escribano S., Mosdale R. Water profile determination in a running PEMFC by small-angle neutron scattering. Journal of Power Sources, 2008, 179, 132-139. | 1 2 |
| 10:00 | Coffee break | |
| Solid proton conductors: theory and concepts : T. Norby | ||
| 10:30 | Defects, Ion Transport and Surface Structures of Proton-Conducting Oxides Authors : Saiful Islam Affiliations : University of Bath UK Resume : It is clear that fundamental materials research is a crucial component in the discovery and characterisation of ion conduction materials for solid oxide fuel cells and related applications. In this context, advanced computational techniques are now powerful tools for probing the properties of energy materials on the atomic- and nano-scale. This presentation will highlight recent studies on solid-state proton conductors [1,2] focusing on perovskite-type materials (such as doped BaZrO3) and novel oxide structures containing tetrahedral units (such as LaBaGaO4, doped LaNbO4, and Ge-based apatites). Key properties investigated include local protonic sites, defect-dopant association and surface structures. Our results are closely correlated with the available experimental studies (e.g. diffraction, conductivity, NMR).
[1] L. Malavasi et al., Chem. Soc. Rev. 39, 4370 (2010); S.J. Stokes, M.S. Islam, J. Mater. Chem. 20, 6258 (2010).
[2] E. Kendrick et al., Nature Mater., 6, 871 (2007). | 2 1 |
| 11:00 | Structural Characteristics and Dynamics of Ba2In2O5 and Ba2In2O4(OH)2 via Experimental and Computational 17O and 1H Solid State NMR Authors : Riza Dervisoglu, Lesley A. Holmes, Derek S. Middlemiss, Frédéric Blanc, Eric E. Hellstrom, Dane Morgan, Ivo Heinmaa, Clare P. Grey Affiliations : University of Cambridge, UK; University of Wisconsin, Madison, WI, USA; National Institute of Chemical Physics and Biophysics, Tallinn, Estonia Resume : Ba2In2O5 is known to be a good oxygen ion conductor at high temperatures as well as a good hydrogen ion conductor at temperatures below 300oC under humid atmosphere. In the present study, structural characterization and dynamics of Ba2In2O5 and the hydrated form, Ba2In2O4(OH)2 were investigated by x-ray diffraction and 17O and 1H solid state NMR measurements. While, in a previous study by Adler et al., the 17O NMR spectra have been interpreted as manifesting three resonances representative of the three crystallographically unique O sites, the present 17O NMR measurements of Ba2In2O5 performed at higher field strengths manifested only two resonances at 185 and 137 ppm, with an intensity ratio of 3:2, respectively. The resonance at 185 ppm is attributed to the combination of the two oxygen ions in In3+O4 coordination and the four equatorial sites in In3+O6 coordination, while the resonance at 137 ppm is attributed to the axial oxygens linking four– and six–fold coordinated In3+ ions. The assignments are confirmed by first principles solid–state DFT NMR calculations within the GIPAW formalism, which provide further insights in relation to the chemical shift– and quadrupole interaction tensors. | 2 2 |
| 11:15 | Plots Counter Pressure Index Vs Temperature: another point of view to explain ionomer annealing Authors : Riccardo Narducci, Giulio Alberti, M. Luisa Di Vona Affiliations : Department of Chemical Science and Technologies, University of Rome Tor Vergata, Via della Ricerca Scientifica 1, Roma, Italy; Chemical Department, University of Perugia, via Elce di Sotto 8, Perugia, Italy Resume : Alberti et al. recently introduced the matrix counter-osmotic pressure Index (nc) 1for obtaining useful information on ionomer characteristics under various conditions of temperature and relative humidity. The nc index, is particularly useful for understanding the ionomer behavior under the various temperature and relative humidity values used in medium temperature polymer electrolyte membrane fuel cells. The nc index is equal to % of proton molar fraction and it is directly related to the osmotic pressure of the inner proton solution, to the relative humidity and to the total water uptake. The nc index is also proportional to the memory of previous treatments; to the irreversible deformation provoked by ionomer swelling; and to the annealing degree.
Annealing procedures are well known in the technology of polymers, and they are commonly used to increase crystallization degree and to decrease the free volume between polymer chains. Quantify the annealing effect is a difficult task. In fact, in many papers, annealing procedures have been used only as empirical treatments. Some attempts to correlate annealing effects and crystallization by small and wide X-ray diffraction have been reported. In our studies, the nc changes in Nafion 1100 provoked by annealing procedures with thermal treatments (e.g. 120 °C for15h)1 or with special annealing agents (e.g. DMSO)2, will be related to changes of the ionomer crystallinity. In our opinion this method is simple, inexpensive and small changes of nc values are detectable in a quantitative manner.
1) Alberti, G., Narducci, R., and Di Vona, Perfluorinated Sulfonic Acids as Proton Conductor Membranes in Solid State Proton Conductors, Eds P. Knauth, M.L. Di Vona, Wiley 2012.
2) Alberti, G., Narducci, R., Di Vona, M.L., Unpublished data | 2 3 |
| 11:30 | First-principles study of proton migration in Gd-doped BaCeO3 Authors : Jessica Hermet, François Bottin, Guilhem Dezanneau, Grégory Geneste Affiliations : CEA, DAM, DIF, F-91297 Arpajon, France ; CEA, DAM, DIF, F-91297 Arpajon, France ; Laboratoire Structures, Propriétés et Modélisation des Solides, Ecole Centrale Paris, CNRS-UMR 8580, Grande voie des vignes 92295, Châtenay-Malabry Cedex, France; CEA, DAM, DIF, F-91297 Arpajon, France Resume : Acceptor-doped BaCeO3 is known to be a very good candidate as electrolyte for Protonic Ceramic Fuel Cell (PCFC) application due to its high protonic conductivity, especially when doped with a trivalent element on the B-site.
We studied by means of density-functional calculations, using the ABINIT code, the three different chemical states of this compound (doped with 12.5% or 6.25% of Gadolinium) : outgassed (with oxygen vacancies and no hydrogen), fully hydrated and fully oxidized. The stable positions for the oxygen vacancy or the proton have been computed in an exhaustive way: we obtain values for hydration and oxidation enthalpies of -1.33 eV/H2O and -0.70 eV/O respectively. Energy barriers of proton hopping and reorientation have been calculated using the String Method to get transition probabilities between two different stable positions of the proton.
These transition rates are then inputted into a Kinetic Monte-Carlo algorithm to get proton trajectories in our material.
At the same time, Path Integral Molecular Dynamics simulations are conducted to take into account the quantum nature of proton. Indeed, hydrogen is known to exhibit quantum effects at high temperature (up to thousands of kelvins), so that considering these effects is expected to lower significantly energy barriers, and thus may change the results of Kinetic Monte-Carlo. | 2 4 |
| 11:45 | Oxygen vacancy segregation and space-charge effects in grain boundaries of dry and hydrated barium zirconate Authors : B. Joakim Nyman, Edit E. Helgee, Göran Wahnström Affiliations : Chalmers University of Technology Resume : Acceptor-doped barium zirconate is an intermediate temperature proton conductor with good chemical stability and therefore it has potential as an electrolyte. However, the grain boundaries (GB:s) in sintered materials display a low proton conductivity which limits the total proton conductivity of the material. A possible explanation for this phenomenon is the segregation of oxygen vacancies to the GB:s, which would lead to depletion of mobile positive defects such as protons in the region close to the boundary. We have therefore performed density functional theory (DFT) calculations of segregation energies of +2 charged oxygen vacancies at the mirror-symmetric (112)[-110] tilt GB. It is found that vacancies segregate to the boundary with a segregation energy of about -1.25 eV. Under wet conditions oxygen vacancies in barium zirconate are filled by hydroxide ions, and the question arises whether the GB vacancies will also be filled. To investigate this we have used a space charge model to calculate the vacancy concentration in the GB under equilibrium conditions. We find that the vacancies in the GB will not be completely filled even at low temperatures, meaning that the GB retains a positive charge also under wet conditions. This result gives strong support to the space charge model as an explanation for the low grain boundary conductivity in barium zirconate. | 2 5 |
| 12:00 | Lunch break | |
| Instrumental analysis of solid proton conductors : P. Knauth | ||
| 14:00 | Solid State Proton Diffusion and Quasielastic Neutron Scattering Authors : Rolf Hempelmann Affiliations : Physical Chemistry, Saarland University, D-66123 Saarbruecken, Germany Resume : Proton diffusion in proton conducting polymer membranes represents a liquid-like diffusion of the proton carrier molecules; this vehicle-type diffusion takes place in geometric confinements, and confinement effects make this type of diffusion more complex than bulk liquid diffusion.
Aliovalently doped perovskites are non-hydrogen-bonded solid oxide proton conductors, which contain protons as defects and thus in non-stoichiometric (low) quantities. QENS data taken on Yb-doped SrCeO3, e.g., have quantitatively been described in terms of a two-state-model: the protons alternate between being trapped state near the dopants and free diffusion in the undisturbed part of the lattice.
In sulfates, selenates and phosphates proton diffusion consists of proton motion along the hydrogen bond, bond breaking and reorientation.
It will briefly be outlined how hydrogen single particle motion in these material systems are investigated on atomistic scales of time and space using QENS.
[1] R. Hempelmann, Quasielastic Neutron Scattering and Solid State Diffusion, Oxford Series on Neutron Scattering in Condensed Matter, Clarendon Press, Oxford 2000
[2] R. Hempelmann, Structure and Diffusivity in Proton Conducting Membranes studied by Quasielastic Neutron Scattering, in Ph. Knauth and M.L. Di Vona (Eds.), Solid Proton Conductors, John Wiley & Sons, Chichester 2012 | 3 1 |
| 14:30 | A BaIn0.6Yb0.2O2.6-s(OH)2s structural investigation upon dehydration process by means of thermal X-ray, neutron and electron diffraction as well as QENS Authors : Angélique Jarry (1), Eric Quarez (1), Maria-teresa Caldès (1), Philipe Leone (1), Jean Marc Zanotti (2), Olivier Joubert (1) Affiliations : (1)Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, CNRS, 2, rue de la Houssinière, BP 32229, 44322 Nantes, FRANCE/ (2)Laboratoire Léon-Brillouin (CEA-CNRS), CEA Saclay, 91191 Gif-sur-Yvette, FRANCE Resume : A major limitation to the perovskite type PCFC electrolyte performance is the actual competition between a high conductivity and a good stability. A suitable basicity and a high crystallographic symmetry are essential to avoid decomposition by reaction with CO2 while allowing protonic defects stabilization by hydration. With an optimization of those key features, we expect the best couple conductivity/stability.
Such strategies were carried out on BaIn0.8Ti0.2O2.6 by Ln→In substitution, leading to BaIn0.6Ln0.2Ti0.2O2.6 (Ln = Dy, Yb, Lu) with promising protonic conductivities, close to 1.5 mS.cm-1 at 400°C, and good chemical stability under 3% CO2 atmosphere. Even though the strong correlations between perovskite crystal phase and transport properties are well known, a better fundamental understanding of conduction mechanisms is still necessary to tailor electrolyte performance. I will present here a BaIn0.6Ln0.2O2.6-s(OH)2s structural investigation upon dehydration processes.
We combined thermal X-ray, electron and neutron diffraction as well as neutron time-of-flight scattering data to follow the structural evolution in temperature with an emphasis on proton location and behaviour. A reversible phase transformation occurs at 250°C. Fully hydrated phase crystallize in a tetragonal supercell structure while at higher temperature a cubic structure is observed. Oxygen ordering, proton preferential site occupation and relative mean square displacement values are also discussed. | 3 2 |
| 14:45 | What we understand about the structure of radiation-grafted block copolymers synthesized for fuel cells Authors : Sandor Balog 1, Urs Gasser 1, Kell Mortensen 2, Hicham Ben youcef 3, Lorenz Gubler 3, and Guenther G. Scherer 3 Affiliations : 1 Laboratory for Neutron Scattering, Paul Scherrer Institut, Switzerland; 2 Department of Natural Sciences, University of Copenhagen, Denmark; 3 Electrochemistry Laboratory, Paul Scherrer Institut, Switzerland Resume : The current focus regarding polymeric proton-exchange materials is (a) to improve the chemical stability of partially fluorinated or hydrocarbon polymers, (b2) to obtain mechanical integrity at high ionic content, and (c) to moderate the loss in proton conductivity at low water content. Therefore, to comprehend the aspects of structure-property relationships is of paramount importance for identifying fundamental challenges for the development of novel cost-effective polymeric materials having improved functionality. Small-angle neutron scattering (SANS) and small-angle X-ray scattering (SAXS) are excellent tools to investigate the structure of these polymer electrolytes, and thus, provide insight into the correlations between fuel-cell-relevant properties, monomer composition, copolymer topology, and electrolyte structure. The objective of the talk is to review the findings of small-angle scattering studies dedicated to radiation-grafted block copolymers developed at Paul Scherrer Institut.
[1] K. Mortensen, U. Gasser, S. Alkan-G?l, G. G. Scherer, Journal of Polymer Science Part B: Polymer Physics 46 (2008), 1660
[2] S. Balog, U. Gasser, K. Mortensen, L. Gubler, H. Ben youcef, G. G. Scherer, Macromolecular Chemistry and Physics 211 (2010), 635
[3] S. Balog, U. Gasser, K. Mortensen, L. Gubler, H. Ben youcef, G. G. Scherer, Journal of Membrane Science 383 (2011) 50
[4] S. Balog, U. Gasser, K. Mortensen, L. Gubler, H. Ben youcef, G. G. Scherer, Polymer 53 (2012) 175 | 3 3 |
| 15:00 | Experimental and Theoretical NMR Spectroscopic Studies of Protonic Conductors Authors : Frédéric Blanc,1 Luke Sperrin,1 Lucienne Buannic,1 Riza Dervisoglu,1 Derek S. Middlemiss,1 and Clare P. Grey1,2 Affiliations : 1Department of Chemistry, University of Cambridge Lensfield Road, CB2 1EW, UK; 2Department of Chemistry, State University of New York, Stony Brook, NY 11794-3400, USA Resume : The application of solid state Nuclear Magnetic Resonance (NMR) approaches to correlate structure and dynamics with function in protonic conductors materials for solid oxide fuel cells will be described. A particular focus is the development of methodology to examine the local structure and the locations of both the vacancies and the proton mobile ions. An approach combining experimental multinuclear NMR spectroscopy with density functional theory total energy and GIPAW NMR calculations yields a comprehensive understanding of the structural and protonic defect chemistries of a series of protonic conductors including Y/Sc doped BaMO3 (M = Zr, Sn)[1,2] and Ba2In2O5, and how this affects the protonic ion motion in these systems. Insight into both the oxygens, vacancies and protons dynamics will also be discussed from in situ high temperature NMR data, where we measured the dynamics at the very different timescale accessible by NMR (ranging from kHz to MHz) and accessed the activation energy of the motional processes.
[1] Buannic, L.; Blanc, F.; Hung, I.; Gan, Z.; Grey, C. P. J. Mat. Chem. 2010, 20, 6322.
[2] Buannic, L.; Blanc, F.; Middlemiss, D. S.; Grey, C. P. J. Am. Chem. Soc. 2011, submitted. | 3 4 |
| 15:15 | Some aspects of the microstructure of Nafion: Temperature dependent deuteron NMR measurements of residual quadrupolar interactions in D2O swollen membranes Authors : J.-P. Melchior, K. D. Kreuer Affiliations : Max Planck Institut für Festkörperforschung, Heisenbergstraße 1, D-70569 Stuttgart, Germany Resume : The microstructure of Nafion is still a matter of debate[1,2,3] although a recent article claims to provide the first quantitative picture of Nafions’s microstructure from simulating a small-angle x-ray scattering (SAXS) spectrum using a new algorithm[1]. The suggested “parallel cylinder water nanochannel” morphology seems to naturally explain the high diffusion coefficient of water and protonic charge carriers especially at low degrees of hydration which is a common feature of perfluoro-sulfonic-acid (PFSA) membranes. Apparently, the microstructural model is experimentally supported by a recent NMR study using the residual quadrupolar interaction of deuterons in D2O imbibed into stretched Nafion in order to screen the anisotropy of the polymer matrix (pseudo nematic effect)[4]. In the present work, we have extended this type of experiments to higher temperatures for the whole angular range of sample orientations. The results are presented together with a critical discussion of Nafion’s microstructure.
Additionally, the data are contrasted to the same type of data obtained on sulfonated poly(p-phenylensulfone)s [5] allowing for a quantitative comparison of the microstuctures of these two families of ionomers.
1 K. Schmidt-Rohr and Q. Chen Nat Mater 7 (2008) 75
2 H.G. Haubold et al. Elect. Acta 46 (2001) 1559
3 K.D. Kreuer, S. Mascotto and G. Portale to be submitted
4 J. Li, J.K. Park, R.B. Moore and L.A. Madsen Nat Mater 10 (2010) 507
5 C.C. de Araujo et al. PCCP 11 (2009) 3305 | 3 5 |
| 15:30 | Coffee Break | |
| Poster session 1 : M.L. Di Vona, P. Knauth, T. Norby, J. Roziere, J. Thomas | ||
| 16:00 | Proton-conducting hybrid materials based on Polyvinylidene fluoride/Heteropolyacid/SiO2 Authors : Uma Thanganathan* Affiliations : Research Core for Interdisciplinary Sciences (RCIS), Okayama University Resume : In recent years, significant progress has been made in the development of hybrid electrolyte membranes for PEMFCs in terms of cost reduction and improvement of functionality, together with other associated technology advancements. In this research, a class of nanocomposite hybrid membranes was prepared by sol-gel method using polymer polyvinylidene fluoride (PVdF) and phosphosilicate with heteropolyacid (phosphotungstic acid, PWA) as proton conductor. The thermal and structural properties of the membranes were studied. The conductivity of the membranes was analyzed as a function of temperature and humidity conditions, and the maximum value of conductivity was found in the order of 10-2 S cm-1. Polyanion PWA clusters have been incorporated with inorganic phosphosilicate framework and they never dissociate from the hybrid matrix. PWA and polymer concentration on the thermal stability and protonic conductivity was discussed. | 4 1 |
| 16:00 | Polybenzimidazole/1H-imidazole-4-sulfonic acid hybrid membranes for high-temperature proton exchange membranes fuel cells Authors : Chung-Hsun Shen1, Steve Lien-chung Hsu1*, Elena Bulycheva2, Natalya Belomoina2 Affiliations : 1Department of Materials Science & Engineering, Research Center for Energy Technology and Strategy, National Cheng-Kung University, Tainan, 701-01, Taiwan, R.O.C.;2A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow, Russia Resume : A new sulfonated organic compound, 1H-imidazole-4-sulfonic acid (ImSA), was successfully synthesized. A series of the polybenzimidazole (PBI) /1H-imidazole-4-sulfonic acid hybrid membranes were prepared from an organosoluble, fluorine-containing PBI with ImSA to improve the conductivity of PBI membranes. The introduction of ImSA rendered the plasticizing effect of the PBI membranes with the increase of elongation at break. The conductivity of the phosphoric acid doped PBI/ImSA hybrid membranes increased with both the temperature and the ImSA content. The conductivity of acid doped PBI/ImSA could reach 7 ?10-2 (S/cm) at 160 oC. The addition of ImSA could significantly improve the conductivity, but it slightly reduces the mechanical properties of the pristine PBI membranes. | 4 2 |
| 16:00 | Composite Membrane Based on SPEEK and Functionalized Titania for Polymer Electrolyte Membranes Fuel Cell Authors : M. Luisa Di Vona,1 E. Sgreccia,1 P. Knauth,2 G. Auer 3 Affiliations : 1 Università di Roma Tor Vergata, Dip. Scienze e Tecnologie Chimiche, Rome, Italy; 2 Aix-Marseille Univ - CNRS, Laboratoire Chimie Provence (UMR 6264), Centre St Jérôme, 13397 Marseille, France; 3 Crenox Pigments GmbH, Krefeld, Germany Resume : Polyaromatic polymers, such as polyetherketones (PEEK), show a chemical, mechanical and thermal stability like that of fluorinated polymers, but at low cost. Another interesting aspect of polyaromatic polymers is the possibility of functionalization reactions, such as sulfonation. SPEEK shows rather large conductivity when sulfonated, but its mechanical, solubility and morphological properties progressively deteriorate with the degree of sulfonation (DS), because acid groups directly linked to the aromatic hydrophobic backbones cannot assemble in phase separated domains.
The introduction of an inorganic filler into the ionic conductor may stabilize the polymeric phase, overcome the temperature barrier limit, reduce fuel crossover, and improve the mechanical strength of the material without sacrificing important polymer properties necessary to operate in FCs. | 4 3 |
| 16:00 | Proton-conducting polymers: relations between macromolecular structure, water activity and proton mobility Authors : Philippe Knauth 1 and Maria Luisa Di Vona 2 Affiliations : 1 Aix-Marseille University-CNRS, LCP, Centre St Jerome, F-13397 Marseille, France 2 University of Roma Tor Vergata, Dip. Scienze Tecnologie Chimiche, I-00133 Roma, Italy Resume : Sulfonated Aromatic Polymers (SAPs) are credible alternative polymer electrolytes for Proton Exchange Membrane Fuel Cells. Objective of the development is to obtain a suitable proton-conducting polymer for use at intermediate temperatures (typically 120°C) and under low relative humidity and to improve long-term durability.
In our recent work, we focus on the study of physico-chemical properties of various SAP, including Sulfonated Poly-Ether-Ether-Ketone (SPEEK) with various Degree of Sulfonation, but also Sulfonated PolyPhenylSulfone (SPPSU) and cross-linked derivatives, obtained by innovative synthesis procedures or by optimized thermal annealing. [1-4]
In this presentation, we will discuss the water activity and proton mobility in the acid solutions present inside the polymer matrix. [5] These data are obtained from water uptake isotherms and proton conductivity measurements by impedance spectroscopy. The presence of the polymer matrix is observed in several aspects.
The effect on water activity can be taken into account by the visco-elastic properties of the polymer, introducing their yield stress. The water activity of various SAP and Nafion tends to be very similar at intermediate humidification levels.
The effect on proton mobility can be discussed taking into account the tortuosity of the membranes and the percolation threshold of the nanometric aqueous channels inside the matrix.
1. E. Sgreccia et al., J. Power Sources, 192, 353-359 (2009).
2. M. L. Di Vona et al. J. Phys. Chem. B, 113, 7505–7512 (2009).
3. M.L. Di Vona et al., J. Membrane Sci., 354, 134-141 (2010).
4. E. Sgreccia, M. L. Di Vona, P. Knauth, Int. J. Hydrogen Energy, 36, 8063-8069 (2011).
5. P. Knauth et al., J. Electrochem. Soc., 158, B159-165 (2011). | 4 4 |
| 16:00 | Isotopic exchange of hydrogen in proton-conducting oxides Authors : L.P. Putilov, V.I. Tsidilkovski Affiliations : Inst. of High-Temperature Electrochemistry, Russian Academy of Sciences, 620990 Ekaterinburg, Russia Resume : Investigations of H/D isotope effects in the interface exchange and the transfer of hydrogen in proton-conducting oxides can provide essential information about these processes. Studies of the H/D isotopic exchange allow determination of the exchange rate and the diffusivity of hydrogen from experimental data. However, to the best of our knowledge, there is no theoretical description of hydrogen isotopic exchange in oxides that takes into account H/D isotope effects.
We present here a phenomenological theory of hydrogen isotope exchange between proton-conducting oxides and gas phase including H/D isotope effects in the interface exchange rate and the bulk diffusivity. The kinetics of isotopic exchange is studied for the oxide powders and the effect of granule size distribution is analyzed. The derived equations allow analysis and fitting of the experimental data on exchange kinetics and determination of the exchange rate and the diffusivity of protons. The solutions of these equations for different limiting stages (surface-limited and diffusion-limited) and for different time asymptotes are presented. It is shown that the analysis of isotopic exchange data using the found solutions makes it possible to determine the H/D isotope effects for the rates of exchange and diffusion.
The work was supported by the Russian Foundation for Basic Research (grants 10-03-00707 and 12-03-00457) and by the Research Program of the Ural Branch of RAS (project "Hydrogen isotopes in oxides") | 4 5 |
| 16:00 | Thermal, structural and conductivity studies on polyvinyl alcohol ammonium chloride composites as electrolytes for fuel cells Authors : Arbi Fattoum, Mourad Arous Affiliations : Unit of Research: Materials Environment and Energy (06/UR/12-01), Faculty of Sciences Gafsa,Tunisia; Laboratory of composite materials composites and polymers, faculty of sciences Sfax, Tunisia. Resume : The effects of ammonium chloride amount on thermal, structural and electrical conductivity properties of polyvinyl alcohol ammonium chloride composites are studied. Thermo gravimetric analysis (TGA) showed water Wt% content between 4.2% and 5.8%. Differential scanning calorimetric (DSC) analysis showed decreased glass transition Tg temperature for hydrated samples, but the Tg increases by both introducing ammonium chloride salt or eliminating water content. Infrared absorption showed a little shift of characteristic absorption bands of PVA matrix due to interactions with salt inclusions. The dc conductivity showed a maximum value in the vicinity of 4% of salt mol%. The electrical conductivity is attributed to hopping processes of H+ protons between localization states situated around hydroxyl groups, water molecules and ammonium complexes. We found that dc conductivity is thermally activated and obeys the Arrhenius law only in two regions, low temperature and high temperature, separated by an intermediate region where the conductivity decreases located around the evaporation temperature of water. The dc conductivity is enhanced by many orders of magnitude by increasing the water content. The ac conductivity studied in the frequency range from 10-1Hz to 1MHz and the temperature range from 10°C to 150°C is well described by the universal law of Jonsher characteristic of disordered materials. | 4 6 |
| 16:00 | 1H NMR study of the hydrogen dynamics in the (NaS)xGe(OH)4-x ∙ yH2O ceramic proton conductors Authors : A. Shastri, D. Shane, J. Nordstroem, A. Matic, S. W. Martin Affiliations : A. Shastri; Department of Physics and Astronomy, Minnesota State University Moorhead, Moorhead, MN, 56563, USA D. Shane; Department of Physics, Washington University, Saint Louis, MO, 63130, USA J. Nordstroem, A. Matic; Department of Applied Physics, Chalmers University of Technology, SE-412 96, Gothenburg, Sweden S. W. Martin; Department of Materials Science and Engineering, Iowa State University, Ames, IA, 50011, USA Resume : 1H NMR was performed on the ceramic proton conductor (NaS)xGe(OH)4-x ∙ yH2O for x=2, 3 and y~1- 4 over the temperature range -100 °C to 400 °C. NMR spectra, nuclear spin-lattice relaxation rates (R1), spin-spin relaxation rates (R2), and rotating frame relaxation rates (R1ρ) were obtained for both hydrated and dehydrated samples. The data are consistent with proton conduction via a Grotthuss mechanism occurring simultaneously with water diffusion. Molecular rotations of the Grotthuss mechanism occur via H2O molecules, and the participation of H3O was not detected within the experimental uncertainty. | 4 7 |
| 16:00 | Hydrogenated barium titanate films and their potential for integrated supercapacitors Authors : Fadhel El Kamel, Patrice Gonon Affiliations : 1. Laboratory for Materials, Organisation and Properties, Tunis, Tunisie. 2. Microelectronics Technology Laboratory, Grenoble, France. Resume : According to the advances in thin film processes and materials engineering, electronic chips now integrate a lot of electronic functions on the same area. As a result, micro-energy sources need to be developed in order to drive such integrated electronic devices, or to provide power during the temporary failure of the primary power sources. Supercapacitors have been widely regarded as energy storage devices for several electronic systems. Hence, they can ensure this power request since they have high power density, which can be supplied in a very short time.
In the present study, barium titanate films were grown under H2-rich atmosphere. Therefore, they display high dielectric constant and can be employed as electrolytes in the all-solid-state supercapacitors. This behavior was attributed to the accumulation of protons at the metal-electrolyte interface over a Debye length (capacitive double layer). In such capacitors the double-layer capacitance can reach values up to several µF/cm2 depending on the nature of both dielectric and electrode constituting the device.
Electrical measurements were carried out on hydrogenated layers (BaTiO3:H) and tri-layer stack (BaTiO3/BaTiO3:H/BaTiO3) to study the active defects at the origin of the conduction mechanisms. | 4 8 |
| 16:00 | Improved Durability and Cost-effective Components for New Generation Solid Polymer- DURAMET Project Authors : Antonino S. Aricò Affiliations : CNR-ITAE, Via Salita S. Lucia sopra Contesse 5 – 98126 Messina, Italy, Resume : The aim of the DURAMET project is to develop cost-effective components for direct methanol fuel cells (DMFCs) with enhanced activity and stability in order to reduce stack costs and improve performance and durability. The project concerns with the development of DMFCs for application in auxiliary power units (APU) as well as for portable systems. The efforts will be focused on new cost-effective membranes with better resistance than Nafion to methanol cross-over as well as to the drag of Ru ions. Improved durability electro-catalysts will be developed with the aim to reduce costs, degradation and noble metals content. To validate the new membranes and electro-catalysts materials, specific development of membrane-electrode assembly will be carried out with tailored hydrophobic-hydrophilic electrode characteristics. The new developed components will be thus validated in short stacks to assess their performance and durability under practical operation. Specific attention will be devoted to the exploitation, dissemination and the training of young researchers.
Acknowledgement
The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2011-2014) for the Fuel Cells and Hydrogen Joint Technology Initiative under grant agreement Duramet n°278054).” | 4 9 |
| 16:00 | Permeability and Diffusivity Measurements on Polymer Exchange Membranes Authors : Francesco Arena, Rolf Hempelmann Affiliations : Physical Chemistry, Saarland University, 66123 Saarbrücken, Germany Resume : An essential material property directly influencing the long-life capacity of H2-PEM-FC systems at elevates temperatures (> 80°C) is the permeability of the PEM material towards gases. The membrane permeability regarding hydrogen and oxygen is responsible for a significant drop in OCV, and therefore a loss in fuel cell efficiency. Furthermore permeating oxygen is suspected to form membrane degrading O-radicals species.
Taking into account the importance of gas permeability for further PEM R&D activities we present a test bench for the experimental determination of gas diffusivities and permeabilities for such polymeric material. The advantages of a direct coupling between permeation measurement cell and a gas chromatograph as analyzer are outlined. Diffusivity as well as permeability of hydrogen and oxygen of prospective new materials such as cross-linked SPEEK are determined at different temperatures and are compared to state of the art PFSA materials. A significantly lower permeability regarding hydrogen and oxygen was determined for cross-linked SPEEK materials. In addition the influence of hydro-thermal history of PFSA materials, postulated by Prof. G. Alberti [1], on membrane diffusivity was studied.
[1] G. Alberti, R. Narducci, M. Sganappa, J. Power Sources, 178 (2008) 575 | 4 10 |
| 16:00 | Doping, stoichiometry and proton transport properties of “Gd6WO12” Authors : Wen Xing, Reidar Haugsrud Affiliations : Department of Chemistry, University of Oslo, FERMiO, Centre for Materials Science and Nanotechnology, Gaustadalleen 21, NO-0349 Oslo, Norway Resume : Relatively high proton conductivity and good chemical stability towards acidic gases have been reported for nominally undoped “La6WO12” [1] which makes this material a good candidate for hydrogen technologies. Therefore, it is interesting to investigate the other materials in the series of rare-earth tungstates and in this contribution we focus on gadolinium tungstates. Samples of nominal Gd6WO12, Gd5.94Ca0.06WO12-, Gd5.7Ca0.3WO12 and Gd5.7WO12 were synthesized by wet chemical methods. The structure and phase purity were analyzed by means of XRD and SEM. The Gd/W ratio must be below 5.7 to form single phase materials, which corresponds to the La-W system. The electrical conductivity was measured as a function of temperature, oxygen- and water vapor partial pressure H/D isotope shifts were, moreover, utilized to verify effects of protons on the total conductivity. Below 700 ºC, the conductivity increases with Ca-doping and is higher than that of undoped and Gd deficient samples. This behaviour is different from the La-W system where the conductivity decreases when the materials are acceptor doped. The conductivity increases with increasing levels of water vapour and with the profound isotope effect below 800 °C, one may conclude that protons are the predominating charge carrier at low temperatures under wet conditions. At higher temperatures, electronic conductivity is dominating and the differences in total conductivity among the different compositions vanish. The maximum pro[1] R. Haugsrud, Defects and transport properties in Ln6WO12 (Ln=La, Nd, Gd, Er), Solid State Ionics, 178 (2007) 555-560. | 4 11 |
| 16:00 | Study of new amorcors by ozonization of polyfluoride of vinyliden (P.V.D.F) Authors : A. SERDANI1; A. DJEBAILI2*, J.P. CHOPART3 Affiliations : 1 Laboratoire de chimie Physique. Institut des Sciences Exactes. Université de Skikda-21000- Algérie. 2 Laboratory of chemistry and environmental chemistry L.C.E.C - University of Batna- Algeria 3 Laboratory of Mechanical Stress-Transfer Dynamics at Interfaces – LACMDTI URCA,BP 1039, 51687 University of Reims Cedex2, France Resume : We studied the polymerisation of different monomers enhanced by the ozonised PVDF. For a better understanding of this reaction the decay constant of hydroperoxyds and peroxides was determined at different temperatures together with their half life time. On one hand, we showed that this reaction satisfies the rules of first order reactions and the values of constant Kd obtained are of the same order of magnitude as those found for polyethylene PE and polychlorur vinyl PVC ozonised at the same temperature and that ozonised PVDF can be stored at room temperature for few days to be used later as precursor in a polymerisation reaction. Having established the nature of the precursors and their decomposition speed, we studied the graft of various monomers using the techniques in solid and in solution. From this study we deduce that solid graft technique, besides its easy way of making, leads to better efficiency rates of graft with relatively short time reaction in comparison with those carried out in solution.
In addition, the solid reaction can be controlled following the variation of the resistive couple as a function of time.
Key Words: Copolymer - PVDF- PE- PVC- monomer - Graft- Kinetics - Synthesis | 4 12 |
| 16:00 | Comparison between experimental and calculated energy barriers for proton migration in bulk yttrium-doped barium cerate Authors : Yong-Chan Jeong1, Dae-Hee Kim1, Byung-Kook Kim2, Yeong-Cheol Kim1 Affiliations : 1School of Energy, Materials & Chemical Engineering, Korea University of Technology and Education, Korea; 2High Temperature Energy Materials Center, Korea Institute of Science and Technology, Korea Resume : Comparison between experimental and calculated energy barriers for proton migration in bulk yttrium-doped barium cerate (Y-doped BaCeO3) was investigated using density functional theory. A proton attached to an O ion can rotate around the O ion or transfer to a neighboring O ion in BaCeO3. The calculated proton migration that is the combination of rotation and transfer in pure BaCeO3 required an overall energy barrier of 0.32 eV, which is lower than the experimentally measured energy barriers in Y-doped BaCeO3 (0.5-0.54 eV). A lower energy barrier of 0.27 eV for proton migration was calculated when an Y dopant was added to BaCeO3. By considering the interaction between two protons in Y-doped BaCeO3, an energy barrier of 0.45 eV was obtained for the proton migration, which is in good agreement with the measured ones (0.5-0.54 eV). | 4 13 |
| 16:00 | The conductivity behavior Nafion-PPY Authors : Adriana Balan, Ioan Stamatin, Stefan Iordache, A-M Ducu, , C.Ceaus, L. Popovici, S. Stamatin1,2, A.Cucu Affiliations : 1University of Bucharest, Faculty of Physics, 3Nano-SAE Research Centre , MG-38, Bucharest-Magurele, Romania 2University of Southern Denmark, Campusvej 55, DK-5230 Odense, Denmark Resume : The aim of this study is to investigate conduction mechanism modifications induced by poly-pyrrol (PPY) when polymerized into perfluorosulfonated membrane pores. PPY concentration was controlled by precursor loading and oxidant exposure time. The in-plane four-point technique was used to measure the proton conductivity as function of relative humidity at different operating temperatures (40-900C). The modified membranes were investigated by Fourier transform infrared spectroscopy for identifying specific structural features. Thermo-gravimetric analysis and differential scanning calorimetry were employed for the study of thermal stability and degradation processes. A general evaluation of the PPY modified PFSA membranes is provided. Fuel cell application potential is determined in terms of thermal stability, ionic conductivity and activation energies. | 4 14 |
| 16:00 | Long-life PEM-FCH &CHP systems at temperatures ≥100°C: LoLiPEM Authors : G. Barbieri, M.L. Di Vona, P. Knauth, R. Hempelmann, D. Beretta, M. Schuster, L. Vega, A. Stachowicz Affiliations : ITM-CNR Univ. Calabria 87030 Rende CS, ITALY; University of Roma Tor Vergata 00133 Rome, Italy; Univ. Aix-Marseille 13397 Marseille, France; Saarland Univ. 66123 Saarbrücken, Germany ; EDISON Spa 10028 Trofarello (TO), Italy; FuMA-Tech GmbH, St. Ingbert 66386, Germany; MATGAS, Campus UAB 08193 Bellaterra, Barcelona, Spain;. Cracow Univ. Technology 31-155 Kraków, Poland Resume : LoLiPEM is an European Project under the EU-FP7 (FCH-JU) framework (GA 245339).
The aim is the development of stationary power generation & combined heat and power (SPG&CHP) systems based on Polymeric Electrolyte Membrane Fuel Cell Hydrogen (PEMFCH). A drawback in the state of the art systems is the too low operating temperatures of PEMFCHs for cogeneration purposes. Operating temperatures above 100°C would have several advantages including easier warm water distribution in buildings, reduced anode poisoning and improved fuel oxidation kinetics. A PEMFCH operating in the temperature range of 100-130°C is highly desirable and could be decisive for the development of SPG&CHP systems. Main research tasks of the project: (1) Develop long life perfluoro sulfonic acid membranes and sulfonated aromatic polymer membranes operating at 100-130°C ; (2) Create new long-life catalytic electrodes and MEAs working in the above temperature range; (3) Perform accelerated ageing tests and long-term single cell tests to understand degradation mechanisms, to make lifetime predictions and to give input to objectives 1 and 2; (4) Develop a prototype of a modular SPG&CHP system based on multi-PEMFCHs realized with the new long-life MEAs; (5) Benchmarking the single-cell and the modular prototype performance at temperatures above 100°C against the best literature results. In this contribute a general presentation of the project and the main results are reported. | 4 15 |
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