Papers by Jean-Louis Hazemann
American Mineralogist, 2022
Gold mobilization, transfer, and concentration in the Earth’s crust are controlled by hydrotherma... more Gold mobilization, transfer, and concentration in the Earth’s crust are controlled by hydrothermal sulfur- and chloride-bearing fluids. Yet the exact chemical identity, structure, and stability of Au-bearing species and, in particular, the respective contributions of the sulfide (HS−) and trisulfur ion (S3⋅−) ligands to Au transport lack direct in situ evidence. Here we employed high energy resolution fluorescence detection X-ray absorption spectroscopy (HERFD-XAS) on aqueous sulfate/sulfide/S3⋅−-bearing solutions at typical hydrothermal temperatures and pressures (T = 350 °C, P = 600 bar) to reveal differences in dissolved Au spectral signatures indicative of contrasting fluid-phase Au speciation as a function of acidity and redox conditions. Combined with in situ Au solubility measurements and quantum-chemical and thermodynamic modeling, our spectroscopic data provide direct evidence for the Au(HS)S3− and Au(HS)2− complexes predominant at acidic-to-neutral and alkaline conditions,...
Goldschmidt2021 abstracts, 2021
The production of carbon-neutral fuels from CO 2 presents an avenue for causing an appreciable ef... more The production of carbon-neutral fuels from CO 2 presents an avenue for causing an appreciable effect in terms of volume toward the mitigation of global carbon emissions. To that end, the production of isoparaffin-rich fuels is highly desirable. Here, we demonstrate the potential of a multifunctional catalyst combination, consisting of a methanol producer (InCo) and a Znmodified zeolite beta, which produces a mostly isoparaffinic hydrocarbon mixture from CO 2 (up to ∼85% isoparaffin selectivity among hydrocarbons) at a CO 2 conversion of >15%. The catalyst combination was thoroughly characterized via an extensive complement of techniques. Specifically, operando X-ray absorption spectroscopy (XAS) reveals that Zn (which plays a crucial role of providing a hydrogenating function, improving the stability of the overall catalyst combination and isomerization performance) is likely present in the form of Zn 6 O 6 clusters within the zeolite component, in contrast to previously reported estimations.
ACS Catalysis, 2021
The nonoxidative catalytic dehydrogenation of ethane allows the production of ethylene at lower t... more The nonoxidative catalytic dehydrogenation of ethane allows the production of ethylene at lower temperatures than those applied in steam crackers. This, however, requires stable catalysts that minimize coke production. Here, we report a singlecomponent, promoter-free, low-loading, Cr-based catalyst exhibiting high activity, long-term stability, and improved regeneration properties for the direct dehydrogenation of ethane to ethylene. According to our detailed operando X-ray absorption spectroscopic analysis, the use of all-silica MFI zeolite as support promotes the stabilization of Cr II (−O−Si) 2 species with high coke resistance, even when the dehydrogenation is carried out under high ethane partial pressures (1.5 bar).
EPJ Nuclear Sciences & Technologies, 2020
The objective of this work is to experimentally investigate the effect of the oxygen potential on... more The objective of this work is to experimentally investigate the effect of the oxygen potential on the fuel and FP chemical behaviour in conditions representative of a severe accident. More specifically, the speciation of Cs, Mo and Ba is investigated. These three highly reactive FP are among the most abundant elements produced through 235U and 239Pu thermal fission and may have a significant impact on human health and environmental contamination in case of a light water reactor severe accident. This work has set out to contribute to the following three fields: providing experimental data on Pressurized Water Reactor (PWR) MOX fuel behaviour submitted to severe accident conditions and related FP speciation; going further in the understanding of FP speciation mechanisms at different stages of a severe accident; developing a method to study volatile FP behaviour, involving the investigation of SIMFuel samples manufactured at low temperature through SPS. In this paper, a focus is made o...
Geochimica et Cosmochimica Acta, 2019
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
ACS Catalysis, 2019
The direct hydrogenation of CO2 to methanol using hydrogen is regarded as a potential technology ... more The direct hydrogenation of CO2 to methanol using hydrogen is regarded as a potential technology to reduce greenhouse gas emissions and the dependence on fossil fuels. For this technology to become feasible, highly selective and productive catalysts that can operate under a wide range of reaction conditions near thermodynamic conversion are required. Here we combine a CO-producing In oxide catalyst with a methane-producing Co catalyst to obtain In/Co catalyst for CO2 reduction to methanol. Density functional (DFT) simulations demonstrate that the charge transfer between Co support and In oxide film leads to enrichment of the surface of indium oxide with O vacancies, which serve as active sites for selective conversion of CO2 to methanol. Moreover, our simulations suggest that CO2 reduction on Co-supported In2O3-x films will 2 preferentially yield methanol, rather than CO and methane. As a result, the prepared In@Co catalysts produce methanol from CO2 with high selectivity (>80%) and productivity (0.86 gCH3OH.gcatalyst-1 .h-1) at conversion levels close to thermodynamic equilibrium, even at temperatures as high as 300 C and at moderate pressures (50 bar).
Journal of Materials Chemistry A, 2019
Dissolved MoO42− from NiMo electrodes during hydrogen evolution redeposits during high energy spe... more Dissolved MoO42− from NiMo electrodes during hydrogen evolution redeposits during high energy spectroscopy, providing misleading but important insights into Mo behavior.
Ore Geology Reviews, 2019
Cabri et al., 2000 for review); such large variations make it difficult to attribute to Au an exa... more Cabri et al., 2000 for review); such large variations make it difficult to attribute to Au an exact structural position in pyrite and to identify the nature of coordinating atoms (e.g., Au, Fe, S). The situation is further complicated by the presence of other minor and trace elements (Cu, Sb, Ni, Co, Ag, Bi, Se, Te) and, in particular, of arsenic with which gold is systematically correlated in arsenian pyrite (e.g., Reich et al., 2005). These elements, often present in far greater concentrations (>0.1-1.0 wt%) than Au (typically <0.01-0.1wt%), greatly complicate the assessment, using inter-element correlations, of the Au oxidation state and atomic substitutions in pyrite. The use of direct redox-sensitive spectroscopic methods such as X-ray photoelectron, Xray absorption or Mössbauer spectroscopy is often limited by low concentrations, poor selectivity for Au in the presence of As and other elements, and a lack of adequate standards.
Environmental science & technology, Jan 18, 2017
The ISO-standardized RHIZOtest is used here for the first time to decipher how plant species, soi... more The ISO-standardized RHIZOtest is used here for the first time to decipher how plant species, soil properties, and physical-chemical properties of the nanoparticles and their transformation regulate the phytoavailability of nanoparticles. Two plants, tomato and fescue, were exposed to two soils with contrasted properties: a sandy soil poor in organic matter and a clay soil rich in organic matter, both contaminated with 1, 15, and 50 mg·kg(-1) of dissolved Ce2(SO4)3, bare and citrate-coated CeO2 nanoparticles. All the results demonstrate that two antagonistic soil properties controlled Ce uptake. The clay fraction enhanced the retention of the CeO2 nanoparticles and hence reduced Ce uptake, whereas the organic matter content enhanced Ce uptake. Moreover, in the soil poor in organic matter, the organic citrate coating significantly enhanced the phytoavailability of the cerium by forming smaller aggregates thereby facilitating the transport of nanoparticles to the roots. By getting rid...
Chemistry of Materials, 2015
Establishing efficient cobalt based catalytic sites for oxygen evolution on a Ta3N5 photocatalyst... more Establishing efficient cobalt based catalytic sites for oxygen evolution on a Ta3N5 photocatalyst 2015:150805135245001 Chemistry of Materials Eprint version Post-print
American Mineralogist, 2014
The partition of Zr between high P-T aqueous fluids and melts has been investigated in situ in th... more The partition of Zr between high P-T aqueous fluids and melts has been investigated in situ in the haplogranite-H 2 O and haplogranite-(F)-H 2 O systems to assess the mobilization of High Field Strength Elements (HFSE) in magmatic-hydrothermal processes in subduction zones. The partition coefficients were determined from Zr concentrations measured in situ by Synchrotron X-ray Fluorescence (SXRF) in both aqueous fluids and F-free or F-bearing hydrous haplogranite melts equilibrated in diamond-anvil cells at 575 to 800 °C and 0.3 to 2.4 GPa. This experimental approach eliminates the need for internal or external calibrations of the SXRF signal and/or post-mortem analysis of the melt phase, hence decreasing the total uncertainties on below 16%. Above 0.6 GPa, Zr partitions favorably into the hydrous silicate melt in both F-free and F-bearing systems, with that range between 0.19 ± 0.02 and 0.38 ± 0.03. However, the relatively high values indicate that alkali-silica rich aqueous fluids generated by metamorphic devolatilization may contribute significantly to the recycling of HFSE in subduction zones. The efficient uptake of Zr (and likely other HFSE) by subduction zone fluids, regardless of their nature (aqueous fluid, m f Zr D / m f Zr D / m f Zr D / m f Zr D / This is a preprint, the final version is subject to change, of the American Mineralogist (MSA) Cite as Authors (Year) Title. American Mineralogist, in press. (DOI will not work until issue is live.
Physical Review B, 1997
We report on the experimental investigation of high-pressure Kr clusters in Be and Si single crys... more We report on the experimental investigation of high-pressure Kr clusters in Be and Si single crystals by x-ray absorption near-edge spectroscopy. The samples, obtained by ion implantation, were investigated for several temperatures in the range 83-670 K. We show that the near-edge structure of the absorption spectra is sufficient to obtain valuable quantitative information concerning the contracted lattice parameter of the solid rare gas agglomerates, depending on the overpressure exerted on the clusters by the host matrix. Our data compare to the extended x-ray absorption fine structure ͑EXAFS͒ experimental spectra on solid Kr at 4.2 K, and at 300 K under high pressure. Furthermore, in order to check the consistency of our experimental data with EXAFS results taken from the literature, we performed theoretical simulations using the FEFF6 code. These calculations showed good agreement with both sets of data and confirmed our experimental conclusions, permitting the evaluation of the lattice contraction, average coordination, and size of the cluster ensemble. ͓S0163-1829͑97͒00743-1͔
The Journal of Physical Chemistry B, 2007
This paper presents a comparison between several methods dedicated to the interpretation of V K-e... more This paper presents a comparison between several methods dedicated to the interpretation of V K-edge X-ray absorption near-edge structure (XANES) features. V K-edge XANES spectra of several V-bearing standard compounds were measured in an effort to evaluate advantages and limits of each method. The standard compounds include natural minerals and synthetic compounds containing vanadium at various oxidation state (from +3 to +5) and in different symmetry (octahedral, tetrahedral, and square pyramidal). Correlations between normalized pre-edge peak area and its centroid position have been identified as the most reliable method for determining quantitative and accurate redox and symmetry information for vanadium. This methodology has been previously developed for the Fe K edge. It is also well adapted for the V K edge and is less influenced by the standard choice than other methods. This methodology was applied on an "environmental sample," i.e., a well-crystallized leached steel slag containing vanadium as traces. Micro-XANES measurements allowed elucidating the microdistribution of vanadium speciation in leached steel slag. The vanadium exhibits an important evolution from the unaltered to the altered phases. Its oxidation state increases from +3 to +5 together with the decrease of its symmetry (from octahedral to tetrahedral).
The Journal of Physical Chemistry B, 2003
The reinforcement of regulations concerning environment protection in most countries is a strong ... more The reinforcement of regulations concerning environment protection in most countries is a strong incentive to use "green" cross-linkers for sol-gel processes. Among them, water soluble zirconium complexes seem attractive for various applications in the surface coatings , oil production, sol stabilization, and agriculture industries. Moreover, recent works demonstrated that a zirconium lactate-polyacrylate solution leads to the formation of size controlled microgels under shear flow. The speciation of zirconium, both in aqueous solutions (zirconium lactate) and in polymer gels (a terpolymer of acrylamide), was determined by combining X-ray absorption spectroscopy (XAS) and quantum mechanical calculations using density functional theory. XAS experiments were performed at the Zr-K-edge at the European Synchrotron Radiation Facility by using fluorescence detection in order to get results down to very low concentrations (37 ppm). The X-ray absorption near edge structure (XANES) results show that Zr is mainly surrounded by eight oxygens in the first coordination sphere, forming a dodecahedron. The analysis of extended X-ray absorption fine structure (EXAFS) spectra combined with quantum mechanical calculations results indicates that, in the concentrated zirconium lactate solutions (53300 ppm), which was found to be stable over years, the zirconium complexes are dimers ((Zr) 2 (lactate) 6) surrounded by six bidentate lactate ligands. As zirconium lactate concentration is decreased, the dimers condense first in cyclic tetramers (Zr 4 (lactate) X) and then in larger oligomers by tetramer association. In polyacrylamide microgels ([Zr]) 74 and 148 ppm) the Zr species remains dimers when gelation is completed at pH) 6, whereas tetramers are also observed at pH) 7. The XAS spectra were characterized by a very high signal-to-noise ratio, making possible to observe the gelation, i.e., the exchange of lactate by acrylate ligands.
Philosophical Magazine, 2008
The effects of the addition of small amounts of Zr and Hf (0.5-3 %) on the atomic structure of Al... more The effects of the addition of small amounts of Zr and Hf (0.5-3 %) on the atomic structure of Al 88 Y 7 Fe 5 metallic glass were examined from extended x-ray absorption fine structure (EXAFS) experiments to better understand the influence of these microadditions on the glass forming ability of this alloy. Measurements at the Zr K and Hf LIII absorption edges have allowed the local structures around Zr and Hf atoms to be determined. The same Al environment was found for the different concentrations, consisting of a small cluster extending up to 4.5 Å around the Zr atoms and up to 6 Å around the Hf ones. Although the clustering effect is smaller in the Zr neighbourhood, a drastic shortening of the nearest Zr-Al distance is shown, providing evidence for some covalent character to the bonding, in line with the increased glass-forming ability found in the alloys made with the Zr microaddition.
Uploads
Papers by Jean-Louis Hazemann