Author
Jean Claude Lavalley
Bio: Jean Claude Lavalley is an academic researcher from University of Caen Lower Normandy. The author has contributed to research in topics: Adsorption & Infrared spectroscopy. The author has an hindex of 29, co-authored 69 publications receiving 3752 citations.
Papers published on a yearly basis
Papers
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TL;DR: In this paper, the reduction of CeO2 by hydrogen has been studied from 300-1200 K by several complementary techniques: temperature-programmed reduction (TPR), magnetic susceptibility measurements, Fourier transform infrared (FTIR), UV-VIS diffuse reflectance and X-ray photoelectron (XP) spectroscopy.
Abstract: The reduction of CeO2 by hydrogen has been studied from 300–1200 K by several complementary techniques: temperature-programmed reduction (TPR) and magnetic susceptibility measurements, Fourier-transform infrared (FTIR), UV–VIS diffuse reflectance and X-ray photoelectron (XP) spectroscopy. Two CeO2 samples were used with B.E.T. surface areas of 115 and 5 m2 g–1, respectively. The concentration of Ce3+ was determined in situ by measuring the magnetic susceptibility and the CeIII photoemission line. The reduction began at 473 K, irrespective of the initial surface area of the ceria. In the case of the low-surface-area sample, an intermediate reduction step was observed between 573 and 623 K, corresponding to the reduction of the surface. This intermediate step was less easily observed in the case of the high-surface-area ceria. In both cases, the reduction led to a stabilised state with the formal composition CeO1.83. Temperatures higher than 923 K were required to reduce the ceria further. The surface CeIII content determined by XPS was close to that determined by magnetic susceptibility measurements. The intensity of the 17 000 cm–1 band in the UV–VIS reflectance spectrum also varied with the degree of reduction. Finally, the evolution of the surface species observed by IR spectroscopy was in good agreement with the results from the other techniques. The IR results indicated large changes in the concentration and nature of both the hydroxyl and the polydentate carbonate species during the reduction process. The adsorption of oxygen on samples previously reduced to the composition CeO1.83 led to almost complete reoxidation at room temperature. The state of the initial B.E.T. surface did not influence the oxidation process. A slight excess adsorption of oxygen was evident on the surface. This was thermodesorbed at 380 K under vacuum.
577 citations
TL;DR: In this article, the surface chemistry of anatase, in particular acidity, greatly depends on the preparation of the sample, both through the resulting morphology and the presence of surface impurities.
364 citations
TL;DR: In this article, it was shown that in the presence of H2O or excess surface OH groups this is converted to type groups, thus accounting for the increased Bronsted acidity.
359 citations
TL;DR: In this paper, two surface sulfate species were formed after oxidation of between 10 and about 250 μmol g−1, and although the extent of formation of each was dependent on the quantity oxidized, the total band area between 1400-1350 cm−1 was a linear function of the quantity of H2S or SO2 introduced into the infrared cell.
221 citations
TL;DR: In this article, the authors evaluated the adsorption and release of biologically active NO over a series of highly flexible iron(III) dicarboxylate MOFs of the MIL-88 structure type, bearing fumaric or terephthalic spacer functionalized or not by polar groups.
Abstract: Adsorption and release of the biologically active nitric oxide (NO) was evaluated over a series of highly flexible iron(III) dicarboxylate MOFs of the MIL-88 structure type, bearing fumaric or terephthalic spacer functionalized or not by polar groups (NO2, 2OH). As evidenced by ex situ X-ray powder diffraction and in situ IR spectroscopy, it appears that if the contracted dried forms of MIL-88 do not expand their structures in the presence of NO, the combination of very narrow pores and trimers of iron polyhedra leads to the adsorption of significant amounts of NO either physisorbed (very narrow pores) and/or chemisorbed [iron(II) or iron(III) coordinatively unsaturated metal sites (CUS)]. The delivery of NO under vapor of water or in simulated body fluid does not exceed 20% range of the total adsorbed amount probably due to a partial release that occurs between the adsorption/desorption setup and the chemiluminescence release tests. Some of these solids nevertheless exhibit a significant release at the b...
219 citations
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TL;DR: A survey of the use of cerium oxide and CeO2-containing materials as oxidation and reduction catalysts is presented in this paper, with a special focus on catalytic interaction with small molecules such as hydrogen, carbon monoxide, oxygen, and nitric oxide.
Abstract: Over the past several years, cerium oxide and CeO2-containing materials have come under intense scrutiny as catalysts and as structural and electronic promoters of heterogeneous catalytic reactions. Recent developments regarding the characterization of ceria and CeO2-containing catalysts are critically reviewed with a special focus towards catalyst interaction with small molecules such as hydrogen, carbon monoxide, oxygen, and nitric oxide. Relevant catalytic and technological applications such as the use of ceria in automotive exhaust emission control and in the formulation of SO x reduction catalysts is described. A survey of the use of CeO2-containing materials as oxidation and reduction catalysts is also presented.
3,077 citations
1,800 citations
TL;DR: Advances in flexible and functional metal-organic frameworks (MOFs), also called soft porous crystals, are reviewed by covering the literature of the five years period 2009-2013 with reference to the early pertinent work since the late 1990s.
Abstract: Advances in flexible and functional metal–organic frameworks (MOFs), also called soft porous crystals, are reviewed by covering the literature of the five years period 2009–2013 with reference to the early pertinent work since the late 1990s. Flexible MOFs combine the crystalline order of the underlying coordination network with cooperative structural transformability. These materials can respond to physical and chemical stimuli of various kinds in a tunable fashion by molecular design, which does not exist for other known solid-state materials. Among the fascinating properties are so-called breathing and swelling phenomena as a function of host–guest interactions. Phase transitions are triggered by guest adsorption/desorption, photochemical, thermal, and mechanical stimuli. Other important flexible properties of MOFs, such as linker rotation and sub-net sliding, which are not necessarily accompanied by crystallographic phase transitions, are briefly mentioned as well. Emphasis is given on reviewing the recent progress in application of in situ characterization techniques and the results of theoretical approaches to characterize and understand the breathing mechanisms and phase transitions. The flexible MOF systems, which are discussed, are categorized by the type of metal-nodes involved and how their coordination chemistry with the linker molecules controls the framework dynamics. Aspects of tailoring the flexible and responsive properties by the mixed component solid-solution concept are included, and as well examples of possible applications of flexible metal–organic frameworks for separation, catalysis, sensing, and biomedicine.
1,560 citations
1,156 citations
TL;DR: In this paper, a review of the development of water gas shift (WGS) catalysis, especially during the last decade, is reviewed. And a critical review of WGS reaction mechanism is also presented.
Abstract: Developments in water gas shift (WGS) catalysis, especially during the last decade, are reviewed. Recent developments include the development of 1 chromium‐free catalysts that can operate at lower steam to gas ratios and 2 more active catalysts that can operate at gas hourly space velocities above 40,000 h−1. A current challenge is to develop catalysts for use in fuel cell applications. Precious metal catalysts supported on partially reducible oxide supports (Pt‐ceria, Pt‐titania, Au‐ceria, etc.) are the current front runners. A critical review of the mechanism of the WGS reaction is also presented.
895 citations