Titre :	Single atoms supported on carbon materials for hydrogenation reactions
Type de document :	texte imprimé
Auteurs :	Camila Rivera?cárcamo, Auteur ; Philippe Serp, Directeur de thèse
Langues :	Anglais (eng)
Tags :	SINGLE ATOMS CATALYSTS  CARBON MATERIALS  CATALYSTS PREPARATION  HETEROGENEOUS CATALYSIS  HYDROGENATION REACTIONS
Résumé :	"This research work focuses on the preparation of carbon-based single atom (SA) catalysts and their applicability on hydrogenation reactions. Chapter 1 correspond to a comprehensive review over experimental and computational studies aiming at: i) preparing SAC on carbon materials, ii) understanding the metal-support interactions in SAC, and iii) studying how this relates to catalytic performances. In Chapter 2 we were able to understand the possibility of producing different Ru@fullerene nanostructures that can be nanometrically modulated by varying the conditions during their synthesis, solvent and Ru/C60 ratio, through well-defined nanoparticles (NP) to very small clusters and even single atoms (SA) with a high metallic loading (~ 6-20wt%). We applied these nanostructures as catalysts in the hydrogenation of nitrobenzene, finding that Ru SA is less efficient than Ru NP, performance that was also studied by DFT calculations. Chapter 3, details a new and straightforward protocol for the creation of vacancies over carbonaceous supports. We propose that is possible to create defects/vacancies over the supports by a controlled subsequent two-steps process, which comprises the subsequent creation and composition of surface oxygen groups. Magnetic characterization reflexed the presence of this reactive species with a paramagnetic behavior raising form possible radicals species on the surface. Afterwards, we showed that was possible to use such defects as anchoring point to successfully stabilize single metallic atoms (Ru, Pd, Pt, Ni, Cu, Co, Ir) with a loading up to ~ 1.6wt%. Also, by improving this method, we arrived to be capable to control the ratio SA/NP for a given metallic loading ranging from 10 to 200. Chapter 4, through a combined experimental-theoretical study, we provide an explanation of the influence of structural characteristics of Pd/C catalysts for alkene hydrogenation. Highly dispersed Pd nanoparticles (PdNP) are necessary to activate dihydrogen. A high concentration of surface defects on the carbon support is necessary to stabilize Pd single atoms (PdSA), which coexist with PdNP on Pd/C catalysts. A high concentration of oxygenated surface groups is also necessary on the carbon support to allow hydrogen spillover. We demonstrate that such combination allows a cooperative catalysis to operate between PdNP and PdSA that involve the formation of PdSA-H species, which are much more active than PdNP-H for alkene hydrogenation but also isomerization. Indeed, for myrcene hydrogenation activity variations of several orders of magnitude were measured as a function of the value of this ratio SA/NP. We show that the control of this ratio allows the development of a new generation of highly active catalysts integrating the ultra-rational use of precious metals in short supply. Finally, Chapter 5, focuses on the catalytic performance of SA catalysts in carbon dioxide hydrogenation. The results show highest activity for Pt as well as 99% selectivity to CO. On the other hand, Ru catalysts had highest selectivity to CH4."
Document :	Thèse de Doctorat
Etablissement_delivrance :	Université Toulouse 3
Date_soutenance :	30/10/2020
Ecole_doctorale :	Sciences de la matière (SdM) (Toulouse)
Domaine :	Chimie Organométallique et de Coordination
En ligne :	https://theses.hal.science/tel-03170789

Single atoms supported on carbon materials for hydrogenation reactions [texte imprimé] / Camila Rivera?cárcamo, Auteur ; Philippe Serp, Directeur de thèse . - [s.d.].
Langues : Anglais (eng)

Tags :	SINGLE ATOMS CATALYSTS  CARBON MATERIALS  CATALYSTS PREPARATION  HETEROGENEOUS CATALYSIS  HYDROGENATION REACTIONS
Résumé :	"This research work focuses on the preparation of carbon-based single atom (SA) catalysts and their applicability on hydrogenation reactions. Chapter 1 correspond to a comprehensive review over experimental and computational studies aiming at: i) preparing SAC on carbon materials, ii) understanding the metal-support interactions in SAC, and iii) studying how this relates to catalytic performances. In Chapter 2 we were able to understand the possibility of producing different Ru@fullerene nanostructures that can be nanometrically modulated by varying the conditions during their synthesis, solvent and Ru/C60 ratio, through well-defined nanoparticles (NP) to very small clusters and even single atoms (SA) with a high metallic loading (~ 6-20wt%). We applied these nanostructures as catalysts in the hydrogenation of nitrobenzene, finding that Ru SA is less efficient than Ru NP, performance that was also studied by DFT calculations. Chapter 3, details a new and straightforward protocol for the creation of vacancies over carbonaceous supports. We propose that is possible to create defects/vacancies over the supports by a controlled subsequent two-steps process, which comprises the subsequent creation and composition of surface oxygen groups. Magnetic characterization reflexed the presence of this reactive species with a paramagnetic behavior raising form possible radicals species on the surface. Afterwards, we showed that was possible to use such defects as anchoring point to successfully stabilize single metallic atoms (Ru, Pd, Pt, Ni, Cu, Co, Ir) with a loading up to ~ 1.6wt%. Also, by improving this method, we arrived to be capable to control the ratio SA/NP for a given metallic loading ranging from 10 to 200. Chapter 4, through a combined experimental-theoretical study, we provide an explanation of the influence of structural characteristics of Pd/C catalysts for alkene hydrogenation. Highly dispersed Pd nanoparticles (PdNP) are necessary to activate dihydrogen. A high concentration of surface defects on the carbon support is necessary to stabilize Pd single atoms (PdSA), which coexist with PdNP on Pd/C catalysts. A high concentration of oxygenated surface groups is also necessary on the carbon support to allow hydrogen spillover. We demonstrate that such combination allows a cooperative catalysis to operate between PdNP and PdSA that involve the formation of PdSA-H species, which are much more active than PdNP-H for alkene hydrogenation but also isomerization. Indeed, for myrcene hydrogenation activity variations of several orders of magnitude were measured as a function of the value of this ratio SA/NP. We show that the control of this ratio allows the development of a new generation of highly active catalysts integrating the ultra-rational use of precious metals in short supply. Finally, Chapter 5, focuses on the catalytic performance of SA catalysts in carbon dioxide hydrogenation. The results show highest activity for Pt as well as 99% selectivity to CO. On the other hand, Ru catalysts had highest selectivity to CH4."
Document :	Thèse de Doctorat
Etablissement_delivrance :	Université Toulouse 3
Date_soutenance :	30/10/2020
Ecole_doctorale :	Sciences de la matière (SdM) (Toulouse)
Domaine :	Chimie Organométallique et de Coordination
En ligne :	https://theses.hal.science/tel-03170789