References of "Job, Nathalie"
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See detailDevelopment of novel SOlid Materials for high power Li polymer BATteries (SOMABAT). Recyclability of components.
Zubizarreta, Leire; Gil-Agusti, Mayte; Garcia. et al

in Lecture notes on Mobility (in press)

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See detailResorcinol-Formaldehyde Carbon Xerogels as Lithium-Ion Battery Anodes: Synthesis, Grinding, Coating on current collector and Electrochemical characterization
Piedboeuf, Marie-Laure ULg; Léonard, Alexandre ULg; Pirard, Jean-Paul ULg et al

Poster (2014, July 17)

Rechargeable lithium-ion batteries show great advantages over traditional batteries and are extensively used for consumer electronic devices due to their high energy density and long cycle life. However ... [more ▼]

Rechargeable lithium-ion batteries show great advantages over traditional batteries and are extensively used for consumer electronic devices due to their high energy density and long cycle life. However, the improvement of performance of current lithium-ion batteries requires the optimization of the materials used (electrolyte and electrodes). Therefore, tremendous efforts have been dedicated to exploring new materials with high capacity, excellent cycling performance, low cost and high safety features [1-4]. As an example, carbon xerogels are promising candidates in the development of new high performance C-based anode materials for Li-ion batteries, since such carbonaceous materials show very small changes of volume during the charge/discharge process, providing an improved cycle life. Nevertheless, hard carbons also exhibit quite high irreversible capacity losses due to their intrinsic high microporosity and, compared to graphite, a poor rate performance related to slow diffusion of Li in the internal structure [5-6]. To reduce these disadvantages, the structural and textural characteristics need to be carefully controlled. Also, due to the different morphology of these materials compared to graphite, the deposition of carbon xerogels on current collectors needs to be studied in detail. In this work, porous carbon xerogels were synthetized from Resorcinol-Formaldehyde mixtures by adjusting the pH of the solution in order to obtain different mesopore sizes. Monoliths of carbon xerogels were obtained after drying of the polymer gel and pyrolysis [7]. Mercury intrusion porosimetry and nitrogen adsorption techniques (BET) was used to characterize the pore texture of the carbon xerogels. These monoliths were ground to particles around 10 µm for all the samples. The resulting powders were then mixed with a binder and a solvent to form slurries and then cast on copper foil using a bar coater. After evaporation of the solvent, the resulting coatings were analyzed using scanning electron microscopy (SEM) for the morphology and their thickness was monitored by profilometry. The resulting electrodes were subjected to electrochemical characterization. Since the particle sizes and the method of coating was the same for all the samples, it was possible to evaluate selectively the influence of the textural and structural parameters of the different carbon materials on their performances. Electrochemical characterizations were performed using charge-discharge galvanostatic curves and cyclic voltammetry in Li/C half cells between 0.005 and 1.5 V vs. Li+/Li. References 1) Goodenough J.B., Kim Y. J. Power Sources 2011; 196(16): 6688-6694. 2) Bruce P.G. Solid State Ionics 2008; 179: 752-760. 3) Armand M., Tarascon J.-M., Nature 2008; 451: 652-657. 4) Scrosati B., Garche J., J. Power Sources 2010 ; 195 : 2419-2430. 5) Yuan X., Chao Y.-J., Ma Z.-F., Deng X., Electrochemistry Communications 2007 ; 9 : 2591-2595. 6) Zanto E.J., Ritter J.A., Popov B.N., Proceedings - Electrochemical Society 1999; 98-16: 71-8. 7) Job N., Théry A., Pirard R., Marien J., Kocon L., Rouzaud J., Béguin F., Pirard J. Carbon 2005; 43: 2481-2494. [less ▲]

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See detailSynthesis of Pt/Carbon Xerogel Electrocatalysts for Proton Exchange Membrane Fuel Cells (PEMFC): Effect of the Reduction Procedure
Zubiaur, Anthony ULg; Chatenet, Marian; Maillard, Frédéric et al

Conference (2014, July)

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See detailDesign of Pt/carbon xerogel catalysts for PEM fuel cells
Job, Nathalie ULg; Lambert, Stéphanie ULg; Zubiaur, Anthony ULg et al

Conference (2014, July)

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See detailInfluence du broyage mécanique sur la taille et les paramètres texturaux de particules de xérogels de carbone
Piedboeuf, Marie-Laure ULg; Léonard, Alexandre ULg; Traina, Karl et al

Conference (2014, May 15)

Les xérogels de carbone sont des candidats prometteurs pour une utilisation dans de nombreux domaines tels que le stockage de l’énergie électrochimique (anodes pour batteries Li-ion ou supercondensateurs ... [more ▼]

Les xérogels de carbone sont des candidats prometteurs pour une utilisation dans de nombreux domaines tels que le stockage de l’énergie électrochimique (anodes pour batteries Li-ion ou supercondensateurs), l’adsorption ou en tant que supports de catalyseurs (dont les électrocatalyseurs de pile à combustible PEM, par exemple) [1]. En plus de leur grande pureté, un des avantages principaux des xérogels de carbone est de pouvoir contrôler leur texture poreuse notamment via les conditions de synthèse [2, 3]. Ce sont les étapes de séchage et de pyrolyse qui permettent de moduler la texture finale des matériaux obtenus. Après vieillissement, les mélanges aqueux résorcinol-formaldéhyde mènent à des gels polymères susceptibles d’être convertis en polymères secs après séchage sous vide et, in fine, en xérogels de carbone après pyrolyse sous atmosphère inerte. Au cours de ces étapes, les produits obtenus restent cependant sous forme monolithique. Dans le cadre des applications pré-citées (catalyse, stockage électrochimique ou adsorption), il est néanmoins nécessaire de réduire les pièces monolithiques en particules de dimensions appropriées pour l’application cible. Dans ce cas, une étape clé est de pouvoir contrôler leur taille finale. Le comportement à l’attrition de matériaux présentant différentes textures poreuses a été étudié en détail. Les broyages ont été effectués dans un broyeur planétaire en conditions sèche ou humide sur des gels polymères secs ainsi que sur des xérogels de carbone obtenus après pyrolyse à 800°C. La granulométrie laser à diffraction lumineuse ainsi que la microscopie électronique à balayage ont été utilisées afin d’évaluer la distribution des tailles particulaires de la poudre broyée. Les résultats indiquent que la texture poreuse des matériaux, leur nature (polymère ou carbone) et leur dureté sont des facteurs significatifs qui influencent fortement les mécanismes de comminution/fragmentation lors du broyage, en particulier si l’on considère les xérogels de carbone. En effet, il apparait que le broyage par voie sèche de polymères secs (avant pyrolyse) semble être la manière la plus efficace pour obtenir une distribution de taille de particules homogène pour toutes les textures poreuses étudiées. Dans les conditions de broyage employées, il est possible d’obtenir des particules carbonées présentant une distribution de taille de particules centrée sur 10 µm, avec rétention de la texture mésoporeuse. Les résultats de cette recherche montrent également la possibilité d’utiliser la porosimétrie à intrusion de mercure en tant qu’outil pour évaluer simultanément la taille des mésopores ainsi que la taille des particules de matériaux broyés. 1. Yuan, X., Y.-J. Chao, Z.-F. Ma and X. Deng, Electrochemistry Communications, 9(10), 2591-2595 (2007). 2. Job, N., R. Pirard, J. Marien and J.-P. Pirard, Carbon, 42(3): p. 619-628 (2004). 3. Scherdel, C., R. Gayer and G. Reichenauer, J Porous Mater, 19(3): p. 351-360 (2012).  [less ▲]

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See detailUsing the Multiple SEA Method to Synthesize Pt/Carbon Xerogel Electrocatalysts for PEMFC Applications
Zubiaur, Anthony ULg; Chatenet, Marian; Maillard, Frédéric et al

in Fuel Cells - From Fundamentals to Systems (2014), 14(3), 343-349

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See detailRapid aqueous synthesis of ordered mesoporous carbons: Investigation of synthesis variables and application as anode materials for Li-ion batteries
Léonard, Alexandre ULg; Gommes, Cédric ULg; Piedboeuf, Marie-Laure ULg et al

in Microporous & Mesoporous Materials (2014), 195

Ordered mesoporous carbons (OMC) were synthesized via a direct templating pathway by a synthesis route that features short duration, moderate temperature and aqueous media. Resorcinol was used as carbon ... [more ▼]

Ordered mesoporous carbons (OMC) were synthesized via a direct templating pathway by a synthesis route that features short duration, moderate temperature and aqueous media. Resorcinol was used as carbon precursor and hexamethylenetetramine as a source of formaldehyde and ammonia to respectively cross-link the framework and regulate the pH. The temperature of the heat treatment leading to the formation of the solid polymer was shown to have a strong influence on the structural and textural parameters. In particular, moderate temperatures led to the coexistence of differently-sized entangled hexagonal mesostructures, whereas the higher temperatures led to a sharp decrease in the mesopore volume. The performance of these materials as anode materials for Li-ion batteries has been investigated in detail. Although these OMC show reversible capacities similar to those reported for hard carbons, their long-term cycling remains very stable for over 100 cycles of charge/discharge. The optimization of the reported short preparation pathway offers new possibilities regarding the application of ordered mesoporous carbons in various fields, such as energy storage, sorption and heterogeneous catalysis [less ▲]

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See detailPt/C catalyst for PEM fuel cells: low pressure and low temperature plasma synthesis of Pt nanoparticles
Devant, Ludovic; Laurent-Brocq, Mathilde; Job, Nathalie ULg et al

Conference (2014)

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See detailEfficient method for a controlled deposition of Pd nanoparticles on a glassy carbon electrode
Olu, Pierre-Yves; Chatenet, Marian; Job, Nathalie ULg

Poster (2014)

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See detailCharacterization of multi-walled carbon nanotube dispersion in resorcinol-formaldehyde aerogel
Haghgoo, Majid; Yousefi, Ali Akbar; Zohouriaan Mehr, Mohammad Jalal et al

in Microporous & Mesoporous Materials (2014), 184

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See detailInfluence of the surface morphology of smooth platinum electrodes for the sodium borohydride oxidation reaction
Olu, Pierre-Yves; Gilles, Bruno; Job, Nathalie ULg et al

in Electrochemistry Communications (2014), 43

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See detailHighly dispersed Pt/C catalysts prepared by the Charge Enhanced DryImpregnation method
Cao Chongjiang; Yang Guang; Dubau Laetitia et al

in Applied Catalysis B : Environmental (2014), 150-151

tAn efficient method to synthesize highly dispersed Pt/carbon xerogel catalysts for Proton ExchangeMembrane fuel cell applications is described. The synthesis proceeds via the Charge Enhanced ... [more ▼]

tAn efficient method to synthesize highly dispersed Pt/carbon xerogel catalysts for Proton ExchangeMembrane fuel cell applications is described. The synthesis proceeds via the Charge Enhanced DryImpregnation method (CEDI), which combines dry impregnation with the Strong Electrostatic Adsorp-tion technique (SEA). The samples prepared via CEDI or SEA techniques were dried and reduced underhydrogen to obtain supported Pt nanoparticles. In order to increase the Pt mass fraction up to 10 wt.%,two successive impregnation-drying-reduction cycles were performed. The synthesized Pt nanoparticlesare homogeneously distributed on the carbon support and highly dispersed (mean Pt nanoparticle sizeof ca. 2 nm). The CEDI method is ideally suited to avoid Pt losses during the catalyst preparation. [less ▲]

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See detailFunctionalization of carbon xerogels for the preparation of palladium supported catalysts applied in sugar transformations
Mager, Nathalie; Meyer, Nathalie; Léonard, Alexandre ULg et al

in Applied Catalysis B : Environmental (2014), 148-149

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See detailPt/C catalyst for PEM fuel cells: Control of Pt nanoparticles characteristics through a novel plasma deposition method
Laurent-Brocq, Mathilde; Job, Nathalie ULg; Eskenazi, David ULg et al

in Applied Catalysis B : Environmental (2014), 147

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See detailSynthesis of Pt/Carbon Xerogel Electrocatalysts for PEM Fuel Cells by the Multiple SEA Method
Zubiaur, Anthony ULg; Chatenet, Marian; Maillard, Frédéric et al

Poster (2013, November 15)

1. Introduction Proton exchange membrane fuel cell (PEMFC) catalysts are generally made of carbon black-supported Pt-based nanoparticles. However, carbon blacks do not display optimal properties for ... [more ▼]

1. Introduction Proton exchange membrane fuel cell (PEMFC) catalysts are generally made of carbon black-supported Pt-based nanoparticles. However, carbon blacks do not display optimal properties for electrocatalysis: they may contain high amount of chemical impurities, are essentially microporous, and the final structure of the electrodes is hardly tunable, which may cause diffusional limitations within the catalytic layer [1]. A possible solution to these drawbacks is the use of synthetic nanostructured materials with a controllable and reproducible texture and with a pure, known and constant chemical composition; carbon xerogels (CX) exhibit such properties [2]. In addition, high Pt weight percentages are necessary to achieve high electrical performance with thin electrodes. Highly dispersed CX-supported Pt nanoparticles catalysts (Pt/CX) can be prepared by the strong electrostatic adsorption (SEA) method [3,4]. This method consists in impregnating the CX support by a solution of metal precursor at an optimum pH measured beforehand (2.4-2.5 for the impregnation of CX with H2PtCl6 [5]). If the conditions of synthesis are well controlled, the coulombic interactions between the support and the metal precursor are maximized. Metal nanoparticles are obtained after filtration, drying and reduction under hydrogen. However, achieving high Pt weight percentages requires multiple “impregnation-drying-reduction” cycles [4]. The use of large volumes of fresh 1 gPt L-1 solution for each impregnation step induces inacceptable Pt losses. In order to improve the synthesis efficiency, efforts were targeted so as to re-use the same, highly loaded Pt solution for several impregnation steps. The present study is focused on the synthesis and the characterization of Pt/CX nanoparticles by the “multiple SEA method” in view of testing and using them as PEMFC electrocatalysts. 2. Experimental The support used in this work was a CX prepared by drying and pyrolysis of a resorcinol-formaldehyde aqueous gel [6]. The pore size distribution of this CX was centred at 80 nm. After pyrolysis, the CX was crushed and sieved between 75 and 250 μm. To synthesize Pt/CX catalysts, 1 g of CX powder was first mixed with 567 mL of an H2PtCl6 solution at 8.97 mmol L-1 (i.e. 1.75 gPt L-1) with an initial pH of 2.5. The surface loading (SL), i.e. the total area of CX surface in solution, was equal to 1000 m² L-1 and the concentration of H2PtCl6 was chosen high enough to re-use the solution five times. After 1 h of stirring, the mixture was filtered and the filtrate was kept for re-use in another impregnation step. The solid was dried in an oven at 333 K during 12 h. Then, the dried material was reduced at 473 K under H2 flow (0.04 mmol s-1) during 1 h to obtain carbon-supported Pt nanoparticles. In order to synthesize several catalysts with various Pt weight percentages, the complete procedure was repeated one to five times on the same support. After the last impregnation, each catalyst was reduced at 723 K under H2 (0.04 mmol s-1) during 5 h to clean the surface of the Pt particles from chlorine residues [4]. The five catalysts are labelled according to the number of “impregnation-drying-reduction” cycles (e.g. Pt-2 for the catalyst obtained after two cycles). The Pt weight percentage of the catalysts was measured by inductively coupled plasma-atomic emission spectrometry (ICP-AES). The Pt particles were observed by transmission electron microscopy (TEM) and analysed by X-ray diffraction (XRD). The electro-active surface area of the Pt nanoparticles was measured by CO stripping voltammetry performed in 1 M sulphuric acid aqueous solution [7-9]. The specific activity of Pt particles for the Oxygen Reduction Reaction (ORR) was measured on a rotating disk electrode (RDE) in the same liquid electrolyte. 3. Results and discussion Table 1 summarizes some characteristics of the synthesized catalysts. The multiple SEA method leads to the synthesis of well dispersed Pt/CX catalysts with high Pt weight percentage, PtICP, which can be adjusted via the number of “impregnation-drying-reduction” cycles, and reaches 25 wt.% after five cycles. It is worth noting that the quantity of Pt deposited on the CX in one cycle, mPt, decreases after the first two cycles. This might be due to the successive impregnations in the acidic solution, the pH of which equals 2.4 - 2.5, and to the successive reduction steps: both procedures probably modify the surface chemistry of the CX, and leads to a shift of the optimal adsorption pH. This pH shift would induce a decrease in the amount of Pt deposited during the next cycles. This hypothesis remains under investigation. The analysis of TEM micrographs indicates that the five catalysts display the same mean Pt particle size, dTEM. This is corroborated by the comparison between the surface-averaged mean particle size, dS, and the CO equivalent diameter, dCO, or between the volume-averaged mean particle size, dV, and the average crystallite size calculated from XRD, dXRD. The values of the electroactive specific surface area of the Pt particles calculated from CO Journée scientifique GEPROC 2013 Procédés et Matériaux durables Université de Liège 15 novembre 2013 stripping, SCO, are the same for all the catalysts (ca. 95 m² gPt -1). The specific activity, SA, of the catalysts for the ORR is derived from the value of the Tafel plots and intercept. Fig. 1 shows that the Tafel plots are superimposed; as a result, the values of the specific activity at a given electrode potential are nearly identical for the five catalysts, and the Tafel slope, which is characteristic of the reaction mechanism, is almost constant as well (ca. -74 mV dec- 1). Since the specific activity depends on the average size of the Pt nanoparticles (the ORR is a structure-sensitive reaction), this result indicates that the number of impregnation sequences has no impact on the Pt nanoparticle size, and degree of agglomeration. 4. Conclusions The multiple SEA method allows obtaining well dispersed Pt/CX catalysts with high weight percentage up to 25 wt.%, and particle size close to ca. 2.5 nm. Studies are in progress to determine the maximum weight percentage that can be achieved without alteration of the metal dispersion. The multiple SEA method requires the use of less Pt than the SEA method from which it is inspired. Considering the synthesis of a 25 wt.% Pt/CX, the two methods require five “impregnation-drying-reduction” cycles but, for the SEA method, five solutions of 1gPt L-1 are used instead of only one solution of 1.75 gPt L-1, the latter being re-used in the case of multiple SEA. This difference leads to a nearly threefold decrease in the consumption of Pt. Further analyses will be performed so as to determine the optimal Pt weight percentage and the optimal thickness of the catalytic layer by modifying these two variables in a series of membrane-electrodes assemblies. [less ▲]

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See detailResorcinol-Formaldehyde Carbon Xerogels as Anode Material for Lithium-Ion Battery: Synthesis, Grinding and Coating on Current Collector
Piedboeuf, Marie-Laure ULg; Léonard, Alexandre ULg; Pirard, Jean-Paul ULg et al

Poster (2013, September 24)

Rechargeable lithium-ion batteries show great advantages over traditional batteries and are extensively used for consumer electronic devices due to their high energy density and long cycle life. However ... [more ▼]

Rechargeable lithium-ion batteries show great advantages over traditional batteries and are extensively used for consumer electronic devices due to their high energy density and long cycle life. However, the improvement of performance of current lithium-ion batteries requires the optimization of the materials used (electrolyte and electrodes). Therefore, tremendous efforts have been dedicated to exploring new materials with high capacity, excellent cycling performance, low cost and high safety features [1-3]. As an example, carbon xerogels are promising candidates in the development of new high performance C-based anode materials for Li-ion batteries, since such carbonaceous materials show very small changes of volume during the charge/discharge process, providing a long cycle life. Nevertheless, hard carbons also exhibit quite high irreversible capacity losses due to their intrinsic high microporosity [4]. To overcome these disadvantages, the structural and textural characteristics need to be carefully controlled. Also, due to the different morphology of these materials compared to graphite, the deposition of carbon xerogels on current collectors needs to be studied in detail. In this work, porous carbon xerogels have been synthesized from Resorcinol-Formaldehyde mixtures by adjusting the pH of the solution in order to obtain different mesopore sizes. Monoliths of carbon xerogels are obtained after drying of the polymer gel and pyrolysis [5]. These monoliths have been ground by two different methods and particle size distributions were measured by granulometry. Mercury intrusion porosimetry and nitrogen adsorption techniques (BET) have been used to characterize the pore texture of the monolithic and the powder materials. Different conditions have been used for the mixing of carbon xerogels with a binder and a solvent to form slurries. The latter have been cast on a copper foil using bar coating with different openings. After evaporation of the solvent, the resulting coatings were analyzed using scanning electron microscopy (SEM) for the morphology and their thickness was monitored by profilometry. First results indicate that the method of grinding has no influence on the final particle size distribution of the powder. The structural features of the carbon xerogels is well preserved for particles down to one micrometer. Nevertheless, a study of grinding duration shows that additional particles with sizes close to that of the porosity of the carbon appear. As a consequence, the grinding conditions were chosen so as to obtain a compromise between particles small enough to realize a coating on a current collector and particles large enough to maintain the carbon gel structural characteristics. References 1) Goodenough J.B., Kim Y. J. Power Sources 2011; 196(16): 6688-6694. 2) Bruce P.G. Solid State Ionics 2008; 179: 752-760. 3) Cairns A. J., Albertus P. Ann. Rev. Chem. Biomol. Eng. 2010; 1: 299-320. 4) Tran T., Yebka B., Song X., Nazri G., Kinoshita K., Curtis D. J. Power Sources 2000; 85: 269-278. 5) Job N., Théry A., Pirard R., Marien J., Kocon L., Rouzaud J., Béguin F., Pirard J. Carbon 2005; 43: 2481-2494. [less ▲]

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