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Rhodium based mono-and bi-metallic nanoparticles : synthesis, characterization and application in catalysis

Abstract : In this thesis, synthesis, characterization and catalytic applications of mono- and bi-metallic rhodium-based nanoparticles are reported. Rhodium has been chosen as a primary metal given its high interest in catalysis, mainly in hydrogenation and hydroformylation reactions. The synthesis of mono-metallic rhodium nanoparticles (NPs) is the core of this work. It was performed by decomposition of the organometallic complex [Rh(C3H5)3] in solution under dihydrogen pressure and in the presence of different stabilizers including ligands and polymers to control the growth of the particles. Selected nanoparticles were deposited on the surface of amino-functionalized magnetic silica as a support for recovery and recycling concerns in catalysis. Diverse bi-metallic nanoparticles have been also prepared in one-pot conditions by co-decomposition of the [Rh(C3H5)3] with other organometallic precursors including [Ni(cod)2], [Ru(cod)(cot)], [Pt(nor)3] and [Pd(dba)2]2. Tuning of the metal ratios between [Rh] and the second metal [M], or of the nature and the amount of the stabilizer used for the synthesis allowed to obtain nanoparticles of different sizes and chemical compositions. The characterization of the obtained nanoparticles was performed by using a combination of state-of-art techniques (TEM, HRTEM, STEM-EDX, ICP, WAXS, EXAFS, Xanes, XPS, NMR...). Surface studies were carried out in some cases, by adsorbing CO on the surface of the particles which was followed by spectroscopic techniques (FT-IR, NMR) to probe their surface state. Some of these nanoparticles were investigated in catalytic reactions, mainly hydrogenation with Rh NPs and hydrogenolysis for RhNiOx NPs. Both colloidal and supported catalytic studies were carried out in the case of hydrogenation catalysis. The originality of this work lies in the development of simple synthesis tools inspired from organometallic chemistry to get well-controlled rhodium-based nanoparticles in terms of size, size distribution, composition and surface state, all these parameters being important whatever the target application. The interest of the obtained nanoparticles in catalysis has been also evidenced in different reactions. This PhD work may open new opportunities of research both in nanochemistry and catalysis.
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Mahmoud Ibrahim. Rhodium based mono-and bi-metallic nanoparticles : synthesis, characterization and application in catalysis. Catalysis. Université Paul Sabatier - Toulouse III, 2016. English. ⟨NNT : 2016TOU30063⟩. ⟨tel-01405805⟩

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