Symposium : F
|Solid proton conductors 5 : M. Casciola|
|09:00||Materials for low and high temperature PEM fuel cells|
Authors : Deborah J. Jones
Affiliations : ICGM-Aggregates, Interfaces and Energy Materials, University Montpellier 2, 34095 Montpellier cedex 5, France
Resume : A broad array of polymers and ionomers have been developed and evaluated in recent years as possible components of membrane materials for proton exchange membrane fuel cells (PEMFC), with particular efforts dedicated to satisfying the exacting set of properties required for automotive use, and the extended durability requirements of stationary applications. While leading to a vast number of novel sulfonic acid functionalised non-fluorinated polyaromatics, as well as polymer materials comprising protogenic functions other than sulfonic acid, these endeavours have also notably advanced perfluorosulfonic acid technologies that have thence produced a new generation of benchmark fuel cell membranes. This presentation will point out general directions and current trends in the research for new membrane materials for low and high temperature fuel cells, with emphasis on strategies for improving the mechanical properties of highly functionalised proton exchange membranes.
|09:30||Cathode-electrolyte matching in PCFCs: electrochemical investigation and chemical compatibility between Pr2NiO4 cathodes and BaCe0.65Zr0.20Y0.15O3 electrolyte materials|
Authors : S. Fasolin1, S. Barison1, S. Boldrini1, L. Doubova1, M. Fabrizio1, S. Fourcade2, A. Grimaud2, F. Mauvy2, E. Mercadelli3,C. Mortalò1, A. Sanson3
Affiliations : 1 CNR-IENI 4, Corso Stati Uniti, 35127 PADOVA (Italy); 2 ICMCB-CNRS 87,Avenue du Dr A.Schweitzer, 33608 PESSAC CEDEX (France); 3 CNR-ISTEC 64, Via Granarolo, 48018 FAENZA (Italy)
Resume : Protonic Ceramic Fuel Cells (PCFCs) have recently gained interest due to their advantages on decreasing solid oxide fuel cell operating temperatures. Proton conducting electrolyte materials based on Y-doped BaCe1-xZrxO3 have been investigated, because of their high proton conductivity and chemical stability at 500 to 800°C. The development of proper cathode materials for PCFCs remains a challenge, since the high polarization at the cathode side is still a hindrance to PCFC development. To this end, recent studies have highlighted the potential of layered materials based on Ruddlesden-Popper series (An+1BnO3n+1) for cathode applications. In particular n=1 members, notably those based on Ln2NiO4+δ, have to be underlined. In this work, aiming to investigate the possible use of Pr2NiO4+δ cathode materials with BaCe0.65Zr0.20Y0.15O3 (BCZY) electrolyte, anode-supported PCFCs based on Ni-BCZY/ BCZY/Pr2NiO4+δ were prepared. A colloidal spray deposition technique was developed for the preparation of BCZY dense electrolyte films on Ni-BCZY porous cermets. The cathode layer was deposited by screen-printing. The cell has been characterized in single cell configuration in the temperature range 550-750°C. The cell, fed with wet H2 and air, exhibited a 1V open circuit voltage and a maximum power density of 40 mW/cm-2 at 600°C. With the view of understanding the cell performance, chemical compatibility between Pr2NiO4+δ and BCZY was checked at high temperatures and under operating conditions.
|09:45||High Temperature PBI Membranes for Fuel Cells and Sustainable Energy Devices|
Authors : Brian C. Benicewicz
Affiliations : Department of Chemistry and Biochemistry USC NanoCenter University of South Carolina Columbia, SC, USA 29208
Resume : Polybenzimidazole (PBI) polymers are excellent candidates for PEM fuel cell membranes capable of operating at temperatures up to 200˚C. The ability to operate at high temperatures may provide benefits such as faster electrode kinetics and greater tolerance to impurities in the fuel stream. In addition, PBI membranes doped with phosphoric acid can operate efficiently without the need for external humidification and the related engineering hardware to monitor and control the hydration levels in the membrane. PBI membranes are currently being investigated as candidates for portable, stationary, and transportation PEM fuel cell applications. The development of the PBI membranes has also led to major advances in hydrogen separation, purification, pumping, and compression technologies. The basic properties of these membranes as high temperature (>100˚C) proton conductors, combined with the well-known chemical stability, high tolerance to gas impurities, and potential for low cost, provide the significant advancement in this enabling technology for hydrogen purification. In this presentation, we will describe the polymer membrane technology associated with these devices and some new chemistry, as well as their applications in both the future hydrogen economy and current industrial hydrogen gas user markets.
|Solid proton conductors: mechanisms : G. Alberti|
|10:30||The mechanisms of proton conduction in phosphorous oxoacids|
Authors : Klaus-Dieter Kreuer
Affiliations : Max-Planck-Institut für Festkörperforschung Heisenbergstr. 1, 70560 Stuttgart, Germany
Resume : From a fundamental point of view, the family of compounds known as phosphorus oxoacids are among the most intriguing proton conducting systems. Neat liquid phosphoric acid (H3PO4) has the highest intrinsic proton conductivity of any known substance, systems containing phosphates play a central role in the structure and function of biological systems and are attracting increasing interest as electrolytes for emerging fuel cell applications. The number of potential proton donors and acceptors vary systematically in the order phosphoric (H3PO4), phosphonic (H3PO3) and phosphinic acid (H3PO2), and this is also reflected in the observed proton conductivities and proton diffusion coefficients. Here, we describe our current understanding of proton conduction in bulk phosphorous acids and compares this to the proton conduction mechanism in water and hydrated systems (such as Nafion). Most of our notion is based on recent ab initio molecular dynamics simulations indicating the formation of polarized chains by correlated proton transfers along chains of hydrogen bonds in a close sense to the original notion of Grotthuss mechanism for proton conduction in water. It is the particular interplay between these chains and configurational H-bond network ‘frustration’ which is suggested to lead to the very high intrinsic proton conductivity. 1 T Dippel et al Solid State Ionics 61 41 (1993). 2 L Vilciauskas et al J Phys Chem A 113 9193 (2009) 3 K D Kreuer et al Chem Rev 104 4637 (20
|11:00||New sulfonated PBIs for PEMFC application|
Authors : Angioni Simone, Garlaschelli Luigi, Mustarelli Piercarlo, Quartarone Eliana, Righetti Pierpaolo, Villa Davide Carlo
Affiliations : Department of Chemistry, University of Pavia
Resume : Solid polymer electrolytes for fuel cell application have gained much attention recently as a promising technology. In the last decade, acid-doped polybenzimidazole (PBI) membranes have been studied for PEMFC use, showing good properties that allow them to be used in PEMFC at temperatures as high as 200 °C without humidification. We have synthesized new arylether-polybenzimidazoles incorporating diaminobenzoic acid subunits to improve performances of the commercial PBI. Membranes thereof have shown, among other interesting properties, good proton conductivity, a fundamental prerequisite for the preparation of PEMFC operating above 120°C, under very low humidity conditions. The arylether spacers in our monomers can be easily mono- or even poly-sulfonated and the appended sulfonic groups should grant an increased proton conductivity. Indeed, the conductivity of some sulfonated polybenzimidazoles (copolymers or blends) is reported to be about two orders of magnitude higher than that of the corresponding non-sulfonated subunit at the same doping level. Electrochemical properties of our monosulfonated polymers has been studied and show an excellent proton conductivity. Other developments should allow us to introduce new spacers, such as fluorinated subunits, to improve the chemical stability, or/and to insert more sulfonic groups to increase the proton donor properties and decrease (or even eliminate) the needed amount of dopants.
|11:15||Cathode Materials for Low Temperature Solid Oxide Protonic Fuel Cells|
Authors : M.D. Sharp and J.A. Kilner
Affiliations : .
Resume : A large quantity of current research on protonic ceramic membrane fuel cells (PCMFCs) is directed towards the reduction of operating temperatures, in an analogous fashion to solid oxide fuel cells (SOFCs) based on oxygen ion conducting electrolytes. In order to realise such a temperature reduction, several areas require further understanding: the cathode processes, the transport numbers of cell components, and the mechanism of proton conduction in both existing and new potential materials. The cathode processes of the protonic cell are regarded to be more complex compared with cells based on oxygen ion conducting electrolytes, and there appears to be some dispute in the literature as to the exact requirements of the cathode, and if these requirements can be met with single phase materials. In a purely proton conducting electrolyte, it would appear that the optimum cathode should be a mixed proton/electron conductor. However, as the splitting of O2 at the cathode may be a rate limiting step, there are reports of comparable performance with the more traditional mixed hole-oxide ion conductors. Double perovskites, substituted with rare earth elements, such as those in the LnBaCo2O5 δ series, may exhibit protonic, oxygen ion and p-type conductivity, depending on how the acceptor is compensated. Generally, one element of conductivity is dominant e.g. p-type in GdBaCo2O5 δ (GBCO). In analogy to previous work done in determining oxygen surface exchange (k*) and oxygen tracer exchange (D*) coefficients in the LnBaCo2O5 δ series, using the isotope (18O/16O) exchange depth profile (IEDP) method, we present our method for determining k* and D* values for proton exchange. Initial results using this method with GBCO have shown D* values in the region of 4.5 x 10-15 cm2/S at 300 ˚C, a value approximately three orders of magnitude lower than the D* value obtained for oxygen exchange, suggesting that GBCO is a relatively slow proton conductor, though this may still be important for the cathode processes. We also report D* values over a range of temperatures. Finally, and complimentary to the previously mentioned IEDP work done using secondary ion mass spectrometry, we also present results obtained from experiments performed using low energy ion scattering (LEIS).
|11:30||The conduction mechanisms in Nafion-ionic liquids measured by four-electrodes method|
Authors : Ioan Stamatin, Adriana Balan, Stefan Iordache, A-M Ducu, , C.Ceaus, L. Popovici, A. Cucu , S. Stamatin1,2,
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 : Nafion 112, impregnated with few ionic liquids are designed for improving conductivity and the catalyst coating in the process for MEA technology. A series of membranes were designed by layer-by layer selfassembling respective by impregnation. The catalyst coating (Pt60/X72) has been performed for 0.3mg/cm2. The polarization curves and the proton conductivity are measured with Bank Test- Bekktech at fixed temperature 800C and RH=40-90%. The conductivity show a strongly dependence of type of ionic liquid reaching 150-200mS/cm and maximum current density reaches 800mA/cm2. Thermal degradation and stability still remains in the nafion limits.
|11:45||Cation Transport in Proton Conducting Lanthanum Tungstate|
Authors : Einar Vøllestad, Reidar Haugsrud
Affiliations : Centre for Materials Science and Nanotechnology, Department of Chemistry, University of Oslo
Resume : Lanthanum tungstate, La5.4WO12, is a promising material for both fuel cell and hydrogen gas separation membrane applications due to its high proton conductivity and chemical resistance towards acidic gases. Fast cation transport could be detrimental to the long term durability of the functional components for these applications, as they will be exposed to large potential gradients at elevated temperatures for long durations. Despite the importance of the phenomenon, no reports are available on the cation transport in LWO, and only a few studies regarding cation diffusion are reported for other candidate membranes. In this work, cation transport is studied by interdiffusion between La5.4WO12-Nd5.4WO12 and La5.4WO12-La5.4Mo0.3W0.7O12 as a function of T and pO2, for La- and W-site diffusion respectively. Diffusion profiles determined by Electron Probe Micro Analysis were fitted to the Whipple-LeClaire solution of Fick’s first law from which interdiffusion coefficients were estimated. Interestingly, the bulk diffusivity of La3+ and W6+ was approximately identical at all temperatures, exhibiting Arrhenuis type behavior: Dbulk (La3+, W6+) = (0.6 ± 0.7) ∙ exp [(-400 ± 50 kJmol-1)/RT] Grain boundary diffusion was found to be 3-4 orders of magnitude faster than transport through the grain interior. Furthermore, neither DLa nor DW showed any dependency on pO2, indicating a transport mechanism dominated by intrinsic defects. Recent work has shown that ¼ of the W-cations reside at lantT
|Solid proton conductors 6 : M. L. Di Vona, P. Knauth, T. Norby, J. Roziere|
|14:00||Broadband Electric Spectroscopy for the study of the conduction mechanism of proton-conducting membranes|
Authors : Vito Di Noto, Matteo Piga, Guinevere A. Giffin, Enrico Negro, Keti Vezzù
Affiliations : Vito Di Noto; Matteo Piga; Guinevere A. Giffin; Enrico Negro: Department of Chemical Sciences, University of Padova, Via Marzolo 1, I-35131 Padova (PD), Italy Keti Vezzù: Dipartimento di Chimica, Università Ca’ Foscari di Venezia, Dorsoduro, Calle Larga S. Marta 2137, I-30123 Venezia (VE), Italy
Resume : Proton-conducting membranes are fundamental components of a variety of energy conversion and storage devices such as low-temperature fuel cells and open batteries. A detailed understanding of the charge transfer mechanism in the membrane and its correlation with the composition and structure is of fundamental importance for both fundamental studies and applications. Broadband Electric Spectroscopy (BES) is a powerful tool to obtain this information. The broad frequency range (from 10-5 Hz up to 1010 – 1011 Hz) accessible to BES permits the study of: (a) the relaxations of material substructures, from functional groups to macromolecular chains; (b) the polarizations occurring at the interfaces between the various phases present; and (c) the dependence of phenomena (a) and (b) on temperature, pressure and hydration. This work overviews the BES studies of several families of proton-conducting materials such as perfluorinated systems, sulfonated aromatic hydrocarbon materials and basic aromatic polymers (e.g., polybenzimidazole), both as pristine polymers and doped with suitable solid or liquid additives. The results are interpreted taking into account: (a) the phase separation between domains characterized by different permittivity values; (b) the dynamics of each domain and their correlation with the chemical structure of the different system components; and (c) the relevance of each relaxation and polarization event in the overall long-range charge transfer mechanism.
|14:30||Metallic nanoparticles and proton conductivity: improving proton conductivity of BaCe0.9Y0.1O3-δ and La0.75Sr0.25Cr0.5Mn0.5O3-δ by Ni-doping|
Authors : M.T. Caldes1, K.V. Kravchyk1, M. Benamira1, N. Besnard1, O. Joubert1 O.Bohnke2, V.Gunes2, N. Dupré1
Affiliations : 1Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, CNRS, 2, rue de la Houssinière, BP 32229, 44322 Nantes Cedex 3, France 2 Laboratoire des Oxydes et Fluorures (UMR 6010 CNRS), Institut de Recherche en Ingénierie Moléculaire et Matériaux Fonctionnels (FR CNRS 2575), Université du Maine, Av. O. Messiaen, 72085 LE MANS Cedex 9, France
Resume : Metallic nanoparticles (Ni, Ru) catalyze the hydrogen dissociation and can consequently facilitate the incorporation of protons in ceramic. We used this approach to improve proton conductivity of the ceramic electrolyte BaCe0.9Y0.1O3-δ (BCY) and of the electrode material La0.75Sr0.25Cr0.5Mn0.5O3-δ (LSCM). Therefore, Ni-doped compounds BaCe0.9-xY0.1NixO3-δ (0≤x≤0.2) and La0.75Sr0.25Cr0.5Mn0.5-xNixO3-δ (x=0, 0.06 and 0.2) were prepared and characterised. Under reducing atmosphere an exsolution of Ni was observed . The incorporation of Ni in BCY improves considerably total conductivity. Below 600°C and under reducing atmosphere, BaCe0.9-xY0.1NixO3-δ compounds exhibit higher conductivity than BCY. An increase of one order of magnitude was observed for BaCe0.7Y0.1Ni0.2O3-δ Moreover, the curvature of the plots above 600°C suggests a protonic contribution to the total conductivity. This phenomenon is more pronounced for the compounds containing more nickel in surface (as determined by XPS). The electronic conductivity of Ni doped compounds, negligible below 600°C, was evaluated by using Hebb–Wagner method. For La0.75Sr0.25Cr0.5Mn0.5-xNixO3-δ compounds, Ni doping induces a lowering of the total conductivity under reducing atmosphere. However, considering only substituted compounds, total conductivity seems to increase with the Ni rate. The curvature of the plots below 400°C suggests a protonic contribution to the total conductivity. NMR results confirm that these compounds contain protons. References  T. Jardiel, M.T. Caldes, F. Moser, J. Hamon, G. Gauthier, O. Joubert, New SOFC electrode materials: The Ni-substituted LSCM-based compounds, Solid State Ionics, 181 (2010) 894
|15:00||Nafion-1,2,3-triazole blend membranes for high temperature PEMFC|
Authors : Je-Deok Kim1,2,*, Mun-Suk Jun1, Maria Luisa Di Vona2
Affiliations : 1; National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki, 305-0044 Japan 2; Dipartimento di Scienze e Tecnologie Chimiche, Università di Roma Tor Vergata, via della Ricerca Scientifica 1, 00133 Roma, Italy
Resume : PEMFCs have been attracting attention as a next-generation power generating device. The proton transport properties of these membranes are strongly determined by their water contents, and in practice, they are limited to operating temperatures below 90oC when utilizing near-atmospheric reactant pressures. On the other hand, operating at temperatures higher than 100oC leads to the advantages of improved tolerance of the Pt electrodes to carbon monoxide, and it simplifies system wide heat management while improving the effectiveness of the cogeneration of water, heat, and electricity. Therefore, electrolyte membranes with alternative chemistries that are tolerant to high temperatures (above 100oC) have been investigated. Previously, we reported various acid-base membranes such as Nafion- benzimidazole, Nafion-1,2,4-triazole, and Nafion-1,2,3-triazole blends [1-4]. The blend membranes showed high proton conductivity at temperatures over 100oC under a nonhumidified condition. Moreover, Nafion-1,2,3-triazole blend membranes were showed more homogeneity and flexibility than Nafion-benzimidazole and Nafion-1,2,4-triazole. In this paper, various properties and single cell performance of Nafion-1,2,3-triazole blend membranes will be discussed. 1. J.-D. Kim, Y. Oba, M. Ohnuma, M.-S. Jun, Y. Tanaka, T. Mori, Y.-W. Choi, and Y.-G. Yoon, J. Electrochem. Soc., 157, B1872 (2010). 2. J.-D. Kim, Y. Oba, M. Ohnuma, T. Mori, C. Nishimura, and I. Honma, Solid State Ionics, 181, 1098 (2010). 3. J
|15:15||Optimization of the La6WO12 (electrolyte) / Pr2NiO4 (cathode) half cell for application in proton conducting solid oxide fuel cells|
Authors : E. Quarez, Y. Oumellal, O. Joubert
Affiliations : Institut des Matériaux Jean Rouxel (IMN), CNRS UMR 6502, Université de Nantes, 2, rue de la Houssinière, BP 32229, 44322 Nantes Cedex 3, France
Resume : Nowadays, the most studied electrolytes for use in proton conducting SOFC are materials derived from the perovskite BaCeO3 doped with cations such as Y, Zr etc. La6WO12 is a good challenger with proton conductivity higher than 3x10-3 S cm-1 in wet H2 at 750°C . We have already studied the mechanical and chemical compatibility of La6WO12 with standard cathode materials LSM, LSCM and BSCF but the ASR values obtained from the symmetrical cells cathode / electrolyte / cathode were too high to consider these cathode materials suitable for the electrolyte La6WO12 for use in PC-SOFC. Indeed, the best result was obtained for LSM with ASR = 4.3 Ω cm2 in humidified air at 750°C . We present here the latest results showing improvements of the ASR by a factor superior to 10 by using the cathode material Pr2NiO4. To optimize the ASR value, different parameters are modified such as the Pr2NiO4 synthesis temperature, the thickness of the Pr2NiO4 layer, the annealing temperature of the half cell and the composition of the composite cathode. Presented results show that La6WO12 electrolyte associated with Pr2NiO4 cathode is a promising half cell for application in PC-SOFC. This work has been performed in the frame of the FP7 Project EFFIPRO “Efficient and robust fuel cell with novel ceramic proton conducting electrolyte” (Grant Agreement 227560).  R. Haugsrud, C. Kjølseth, J. Phys. Chem. Solids 69 (2008) 1758  E. Quarez, K. V. Kravchyk, O. Joubert, doi.org/10.1016/j.ssi.2011.11.003
|15:30||Protic Ionic liquid-based proton-conducting membranes for anhydrous proton exchange membrane application|
Authors : Bencai Lin, Lihua Qiu, Feng Yan*
Affiliations : Department of Polymer Science and Engineering, School of Chemistry and Chemical Engineering, Soochow University, Suzhou 215123, P.R. China.
Resume : The polymer electrolyte membranes (PEM), which acts as an electrolyte to transport protons from the anode to the cathode, is one of the key components of polymer electrolyte membrane fuel cells (PEMFCs). However, the most commonly used humidified perfluorosulfonic acid (PFSA)-based membranes, represented by Nafion, cannot be used at high temperature above 100 °C because of the evaporation of water, which results in a rapid loss of conductivity. Protic ionic liquids (PILs) have been considered as effective proton transferring carriers for high temperature PEMFCs because of their non-volatility, high proton conductivity, excellent chemical and thermal and stability properties. We recently prepared PIL-based PEMs via polymerization of a bicontinuous microemulsion in which PILs were dispersed in a monomer oil-continuous phase stabilized by suitable surfactants. PIL nanostructures formed in the precursor microemulsions could be preserved in the resultant polymeric matrix, without macroscopic phase separation even if the produced vinyl polymers are incompatible with PIL cores. The preserved PIL networks in the composite membranes, therefore, will enhance the proton conductivity of membranes. The concept provided in this work combines the advantages of both the polymerization of microemulsions and the properties of PILs.
|15:45||Synthesis and properties of chemically modified membranes by radiation co-grafting of styrene and methacrylonitrile|
Authors : K. Jetsrisuparb, Z. Zhang, H. Ben youcef, G.G. Scherer, A. Wokaun, L. Gubler
Affiliations : Electrochemistry Laboratory, Paul Scherer Institut, CH-5232 PSI, Switzerland
Resume : The polymer electrolyte fuel cell (PEFC) has proven its technical readiness for a wide range of applications. However, the commercialization of PEFC is still limited owing to its shortcomings in durability and cost. The emphasis of this work is on membrane synthesis and understanding the effects of membrane materials on the degradation and properties of proton conducting membranes. Among potential membrane synthesis methods, radiation grafting has been chosen, since it allows a wide selection of base films and monomers to design the properties of the membrane. Earlier work in our group has shown that an appropriate co-monomer, namely methacrylonitrile (MAN), may be introduced to stabilize membranes containing poly(styrene sulfonic acid) (PSSA). Styrene / MAN co-grafted into an ETFE membrane reduces gas permeation and thereby increase the durability in the fuel cell at 80°C, compared to that of a pure styrene grafted membrane. In the present work, we explored the influence of MAN on radiation grafting and the fuel cell relevant properties. An increase in MAN molar fraction enhanced the hydrophilicity of the membrane, resulting in a higher water uptake. Comparison of the fuel cell performance and durability of co-grafted membranes with different ratios of styrene and MAN and fixed ion exchange capacity (IEC) will be presented.
|16:30||Membranes for fuel cells: from structural studies to new concepts.|
Authors : Gérard Gebel
Affiliations : Laboratoire SPrAM UMR 5819, CEA-CNRS-UJF, INAC, CEA Grenoble, 17 rue des martyrs, 38054 Grenoble cedex 9 France
Resume : The development of new and efficient alternative membranes requires a complete understanding of the membrane structure and transport properties, its behaviour in fuel cell conditions, and the degradation mechanisms. Nafion® membranes (a perfluorosulfonated ionomer) are the reference material as proton exchange membrane for many year but their structure and properties are still non fully elucidated. In the recent years, significant advances in terms of experiments, models and simulations have allowed new insights in the membrane structure and transport properties. These results will be discussed and some conclusions will be extracted for the design of alternative membranes. Extensive research was devoted to the development of sulfonated polyaromatic membranes without being able to reach the required targets in terms of performance and stability (mechanical and chemical). Similarly, polymer blends and organic-inorganic hybrid materials have only lead to incremental progresses. We will then discuss of some new concepts of membranes that have recently appeared (ionic liquid doped membranes to increase the operating temperature, swift heavy ions irradiated and grafted membranes, hybrid membranes based on a non ionic polymer and functionalized sol-gel inorganic materials or interpenetrated polymer networks to separate the mechanical and conducting properties.
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