References of "Lambert, Stéphanie"
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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 (in press)

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See detailNanostructured catalysts by sol-gel process
Lambert, Stéphanie ULg; Heinrichs, Benoît ULg

Conference (2014, April 25)

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See detailPreparation of polyaniline-modified local clay and study of its sorption capacity
Benhebal, Hadj; Chaid, Messaoud; Léonard, Angélique ULg et al

in Journal of Nanostructure in Chemistry (2014), 4(98), 6

Clay minerals are frequently used in adsorption processes with aqueous solution; it was found that the adsorption properties of clays change when the samples are modified. In this context, polyaniline ... [more ▼]

Clay minerals are frequently used in adsorption processes with aqueous solution; it was found that the adsorption properties of clays change when the samples are modified. In this context, polyaniline-modified clay nanocomposite (at 10 %) was prepared by in situ polymerization processes. The structural and morphological characteristics of the synthesized material are systematically examined by X-ray diffraction, scanning electron microscopy, thermo-gravimetry, differential scanning calorimetry and infrared spectroscopy techniques. The adsorption property of the modified clay was evaluated for the removal of a reactive dye (methylene blue) from aqueous solution at room temperature (25 C) via batch adsorption. [less ▲]

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See detailVisible-light photo-activity of alkali metal doped ZnO
Benhebal, Hadj; Chaib, Messaoud; Malengreaux, Charline ULg et al

in Journal of the Taiwan Institute of Chemical Engineers (2014), 45(1), 249-253

In order to utilize visible light more efficiently in the field of photocatalysis, Li, Na and K-doped ZnO nanoparticles were prepared using a sol–gel method. The obtained samples were characterized by BET ... [more ▼]

In order to utilize visible light more efficiently in the field of photocatalysis, Li, Na and K-doped ZnO nanoparticles were prepared using a sol–gel method. The obtained samples were characterized by BET surface area measurements, X-ray diffraction, scanning electron microscopy and UV–vis analysis. The photocatalytic activity of the photocatalysts was evaluated for the degradation of p-nitrophenol (p-NP) under visible light irradiation. It has been observed that these photocatalysts could be a promising photocatalyst for degradation of organic molecules as compared to transition metal doped ZnO under visible light. Li-doped ZnO is the most active photocatalyst and shows high photocatalytic activity for the degradation of p-nitrophenol (p-NP). The enhanced photocatalytic activity of Li-doped ZnO is mainly due to the electron trapping by lithium metal ions, small particle size, large surface area, and high surface roughness of the photocatalysts. [less ▲]

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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 detailEpuration catalytique de biogaz
Claude, Vincent ULg; Lambert, Stéphanie ULg; Heinrichs, Benoît ULg et al

Poster (2013, November 15)

The poster presents the recent observations concerning the of Ni-Al2O3 catalysts synthesized in 2013. Particles size, surface areas and crystallinity of the samples are controlled thanks to the initial ... [more ▼]

The poster presents the recent observations concerning the of Ni-Al2O3 catalysts synthesized in 2013. Particles size, surface areas and crystallinity of the samples are controlled thanks to the initial reactives (surfactants, EDAS). [less ▲]

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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 detailNi/Al2O3 xerogel catalysts for biogas cleaning
Claude, Vincent ULg; Heinrichs, Benoît ULg; Lambert, Stéphanie ULg

Poster (2013, August 29)

This poster summarize the firsts results of the PhD project started on October 2012 about the catalytic purification of biogas. The aim of this project consists in the development of Ni/Al2O3 catalyst in ... [more ▼]

This poster summarize the firsts results of the PhD project started on October 2012 about the catalytic purification of biogas. The aim of this project consists in the development of Ni/Al2O3 catalyst in order to reform the tars present in the outlet gas of biomass gasifier. In order to obtain catalysts with high performance and lifetime, materials need to have optimized specific surface and metal particle dispersion. This poster investigate the effect of different surfactants (Pluronic P123; F127; stéarique acide, EDAS) on the materials properties. [less ▲]

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See detailPhysico-chemical properties and photocatalytic activity of P/Ag-doped TiO2 xerogels
Bodson Céline; Pirard, Sophie ULg; Pirard René et al

Conference (2013, July)

Detailed reference viewed: 12 (2 ULg)