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Reference : UMR5026-FREBON0-036
Workplace : PESSAC
Date of publication : Wednesday, October 02, 2019
Scientific Responsible name : Etienne GAUDIN
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 6 January 2020
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
The improvement of sustainable ammonia catalytic synthesis represents a major worldwide challenge since ammonia is one of the most synthesized chemicals in the world. Indeed, ammonia is employed in many industrial sectors, mainly as nitrogen source in fertilizers for agricultural crops. The Haber-Bosch process remains currently the main industrial technology for ammonia production thanks to the use of Fe-based catalysts. However, this process requires high temperatures (400-600°C) and high pressures (200 bars) to be efficient, resulting in high energy and thus in emission of greenhouse gas.
The PhD work aims to explore in details novel supported catalysts based on electride-like intermetallics RTX (R = rare earth; T = transition metal; X = Si, Ge) of CeScSi-type structure to enhance the catalytic synthesis of ammonia in milder conditions and hence reduce its energy consumption. Electrides are crystals that contain excess electrons periodically located in crystallographic sites throughout the lattice. The ability of these RTX materials to transfer these electrons promotes the dissociation of an adsorbed molecule (N2) by weakening its chemical bond. This study is highly motivated by the discovery of the outstanding catalytic activity of some silicides when combined with ruthenium. The excellent catalytic activities of such type of materials are ascribed to their ability to supply electrons to Ru and absorb reversibly hydrogen in the working conditions of NH3 synthesis (N2+H2), preventing notably H poisoning of the Ru surface.
The PhD student work will consist in synthesizing these RTX intermetallics (by melting the elements in an arc furnace or induction furnace) and determining their hydrogen absorption/desorption properties. He/She will also deposit the ruthenium nanometric particles on intermetallic powder. These materials will be characterized by X-ray diffraction, TEM/SEM microscopy and by ICP-OES spectrometry. The objective is to find the optimal chemical compositions to obtain the best yields for the synthesis of NH3. We will play mainly on the nature of the rare earth. DFT calculations will also allow us to explore the electride character of the phases by investigating their electronic structure. These calculations will help us in the choice of catalysts compositions.
The thesis will take place at the “Institut de Chimie de la Matière Condensée de Bordeaux” (ICMCB), a laboratory which is internationally recognized for its expertise in solid state chemistry, materials science and molecular science. The thesis is part of the project INTERMETALYST (“Intermetallic electrides: New promising materials for ammonia catalytic synthesis”) funded by the French ANR research agency. The work will be done in close collaboration with specialists of catalysis of the “Institut de Chimie des Milieux et des Matériaux de Poitiers” (IC2MP) and, therefore, some trips/stays in Poitiers are expected during the thesis.
We are looking for a very motivated student, with a Master2 in solid state chemistry or materials science and with a solid background interests in experimental synthesis and characterization. The candidate should have a solid background in solid state chemistry and X-ray diffraction (powder and/or single crystal). Skills in intermetallic synthesis would be an asset but is not necessary. The candidate is expected to be proficient in English and/or French and in oral communication.
Founded in 1995, the lnstitute for Condensed Matter Chemistry of Bordeaux activities include both fundamental and applied research and focus on 3 domains: Solid State Chemistry, Materials Science and Molecular Science.
ICMCB has extensive expertise in design, synthesis, shaping and characterisation of materials, with the goal to explore and optimise their functionalities. This wide scope and a large, complementary spectrum of methods available, generate fruitful synergies among our faculty (researchers,
engineers and technical staff) - contribuing to teh outstanding reputation of the ICMCB
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