Carbon Nanotube and Porphyrins:Materials for Optics and Energy Applications

International audienceThe fabrication of functional hybrid materials that preserves and combines the properties of their building blocks is a central issue of nanosciences. Among the different classes of nanomaterials, carbon nanotubes are promising for electronics, opto-electronics, catalysis and composite applications. In this context the combination of nanotubes with porphyrins has been widely explored for catalytic or electron transfer purposes. Here I present two results obtained recently on the nanotube/porphyrincomposites, the first deals with the supramolecular organization in micelles of porphyrins around the nanotubes. In this work we were able to explain the Davidoff splitting observed on the absorption bands of the porphyrins by their organization around the nanotubes. The second deals with the synergic effect on catalytic activity of carbon nanotubes and strapped iron porphyrin hybrids for Oxygen Reduction Reaction (ORR). In particular, we demonstrated that the combination of both components - MWNTs and porphyrin - leads to a better catalytic activity than those of the nanotubes or the porphyrins taken separately.This study highlights the importance of the carbon support for the catalysis. The nanotubes ensure the availability of electrons to the porphyrin catalysts and allow the ORR to occur via the 4-electron pathway, avoiding the production of hydrogen peroxide

Fonctionnalisation de nanotubes de carbone par une approche non covalente pour l'électrocatalyse et l'optoélectronique

The production of hybrid materials, combining the properties of their different building blocks without altering them, is a central issue of nanoscience. Among the different classes of nanomaterials being considered for this purpose, carbon nanotubes are an outstanding class of materials due to their optical, conductivity and their functionalization properties, that can be used for various applications in catalysis, electronics and optoelectronics. In the first part of this thesis, supramolecular hybrid structures based on multi-walled carbon nanotubes and macrocycles (porphyrins, phthalocyanine or corrole) containing cobalt and/or iron ions have been performed and tested as catalysts for oxygen reduction reaction (ORR). The non-covalent functionalization methods (based on either Hay-coupling or click chemistry) preserve the electronic properties of the nanotubes and enhances the stability of the resulting hybrids. Thanks to their emission properties in the near infrared region, single-walled carbon nanotubes are of peculiar interest in optoelectronics. However, their extreme sensitivity to the surrounding environment hinders their application. The production of hybrid materials that preserve their optical properties and facilitate their handling is therefore a key challenge. The second part of this PhD is dedicated to the functionalization of single-walled carbon nanotubes for optoelectronics. To this end, it is necessary to carry the synthesis of a core-shell structures, composed of amphiphilic copolymers protecting the carbon nanotubes from their environment and facilitating their solubility in aqueous medium.La fabrication de matériaux hybrides, combinant sans les altérer les propriétés de leurs différents constituants, est au cœur de la recherche en nanosciences. Parmi les différents types de nanomatériaux envisagés à cette fin, les nanotubes de carbone sont des objets prometteurs en raison de leurs propriétés optiques, de conductivité et de leur fonctionnalisation, pour la catalyse, l’électronique et l’optoélectronique. Dans la première partie de cette thèse, des structures hybrides supramoléculaires à base de nanotubes de carbone multi-parois et de macrocycles (porphyrines, phtalocyanine ou corrole) de cobalt et/ou de fer ont été formées et testées comme catalyseurs pour la réduction du dioxygène. La méthode de fonctionnalisation non covalente employée (couplage de Hay et click-chemistry) préserve au mieux les propriétés électroniques des nanotubes et assure la stabilité de l’assemblage obtenu. Grâce à leurs propriétés d’émission dans la région proche infrarouge, les nanotubes de carbone mono-paroi présentent un intérêt en optique et en optoélectronique. Cependant, leur extrême sensibilité au milieu les environnant entrave leur utilisation. La fabrication de matériaux hybrides, préservant leur propriété optique et facilitant leur manipulation est alors primordiale. La deuxième partie de cette thèse est consacrée à la fonctionnalisation de nanotubes de carbone mono-paroi en vue de leur utilisation en optoélectronique. A cet effet, une synthèse de coquille, composée de polymères amphiphiles, protégeant les nanotubes de carbone de leur environnement et facilitant leur solubilité en milieu aqueux, sera réalisée

Functionalization of carbon nanotubes by non covalent approach for electrocatalysis and optoelectronic

La fabrication de matériaux hybrides, combinant sans les altérer les propriétés de leurs différents constituants, est au cœur de la recherche en nanosciences. Parmi les différents types de nanomatériaux envisagés à cette fin, les nanotubes de carbone sont des objets prometteurs en raison de leurs propriétés optiques, de conductivité et de leur fonctionnalisation, pour la catalyse, l’électronique et l’optoélectronique. Dans la première partie de cette thèse, des structures hybrides supramoléculaires à base de nanotubes de carbone multi-parois et de macrocycles (porphyrines, phtalocyanine ou corrole) de cobalt et/ou de fer ont été formées et testées comme catalyseurs pour la réduction du dioxygène. La méthode de fonctionnalisation non covalente employée (couplage de Hay et click-chemistry) préserve au mieux les propriétés électroniques des nanotubes et assure la stabilité de l’assemblage obtenu. Grâce à leurs propriétés d’émission dans la région proche infrarouge, les nanotubes de carbone mono-paroi présentent un intérêt en optique et en optoélectronique. Cependant, leur extrême sensibilité au milieu les environnant entrave leur utilisation. La fabrication de matériaux hybrides, préservant leur propriété optique et facilitant leur manipulation est alors primordiale. La deuxième partie de cette thèse est consacrée à la fonctionnalisation de nanotubes de carbone mono-paroi en vue de leur utilisation en optoélectronique. A cet effet, une synthèse de coquille, composée de polymères amphiphiles, protégeant les nanotubes de carbone de leur environnement et facilitant leur solubilité en milieu aqueux, sera réalisée.The production of hybrid materials, combining the properties of their different building blocks without altering them, is a central issue of nanoscience. Among the different classes of nanomaterials being considered for this purpose, carbon nanotubes are an outstanding class of materials due to their optical, conductivity and their functionalization properties, that can be used for various applications in catalysis, electronics and optoelectronics. In the first part of this thesis, supramolecular hybrid structures based on multi-walled carbon nanotubes and macrocycles (porphyrins, phthalocyanine or corrole) containing cobalt and/or iron ions have been performed and tested as catalysts for oxygen reduction reaction (ORR). The non-covalent functionalization methods (based on either Hay-coupling or click chemistry) preserve the electronic properties of the nanotubes and enhances the stability of the resulting hybrids. Thanks to their emission properties in the near infrared region, single-walled carbon nanotubes are of peculiar interest in optoelectronics. However, their extreme sensitivity to the surrounding environment hinders their application. The production of hybrid materials that preserve their optical properties and facilitate their handling is therefore a key challenge. The second part of this PhD is dedicated to the functionalization of single-walled carbon nanotubes for optoelectronics. To this end, it is necessary to carry the synthesis of a core-shell structures, composed of amphiphilic copolymers protecting the carbon nanotubes from their environment and facilitating their solubility in aqueous medium

Iron Strapped Porphyrins on Carbon Nanotubes As Hybrid Materials for the ORR Reaction

International audienceOne of the most important challenge of nanosciences is the fabrication of functional hybrid materials, preserving and combining the properties of their building blocks. Among the different classes of nanomaterials, carbon nanotubes are promising for electronics, opto-electronics, catalysis and composite applications. Within the context of sustainable development and renewable energy, we and others have been envisioning the use of functionalized or doped carbon nanotubes in electrocatalytic systems.1,2 In such systems, catalytic sites need to be supported on conducting materials. Carbon nanotubes, thanks to their electrical conductivity and their high surface, area appear to be the ideal material for that purpose.In actual Proton Exchange Membrane Fuel Cell Devices (PEMFC), the reactions at the electrodes and in particular the reduction of oxygen are performed by platinum nanoparticles. The cost of platinum is an incentive to developing new catalysts-based on non-noble metals. Thus, whereas in nature oxygen reduction is performed by iron porphyrins in the active center of enzymes, bio-inspired catalysts based on cobalt or iron macrocycles have been extensively studied for Oxygen Reduction Reaction (ORR).3,4Here, we describe the synergic effect on catalytic activity of carbon nanotubes and strapped iron porphyrin hybrids for ORR. In particular, we demonstrate that combining both MWNTs and porphyrins leads to better catalytic activity compared to isolated nanotubes or porphyrins on their own. This study hence highlights the importance of carbon support for the catalysis: nanotubes ensure the availability of electrons to porphyrin catalysts and allow ORR to occur via the 4-electron pathway, avoiding the production of hydrogen peroxide.For this study, two series of iron-strapped porphyrins have been explored.5-6 In the first one, the porphyrins were adsorbed at the surface on nanotubes whereas, for the second one, porphyrins were synthesized with propargylic ether groups at their periphery, allowing covalent linkage by Hay coupling at the surface of the nanotubes. Each of the nanotube hybrids was characterized and tested for ORR in a series of electrochemical measurements

ORR activity of metalated phenanthroline-strapped porphyrin adsorbed on carbon nanotubes

International audienceDeveloping efficient noble metal-free systems for electrocatalysis and the reduction of oxygen (ORR) is crucial for hydrogen economy. Bioinspired hybrids combining iron or copper/iron porphyrins with multiwalled carbon nanotubes were tested for ORR using a rotating ring-disk electrode at pH 13 to 8. The porphyrin-nanotube hybrids exhibited better electrocatalytic properties than their constituents alone due to the electrical network formed by the nanotubes, and they reduced oxygen via a four-electron pathway to produce water. Whereas the presence of Cu was not mandatory to reduce oxygen, its presence improved ORR activity and decreased the overpotential compared to monometalic (iron porphyrin) hybrids.La conception de matériaux sans métaux nobles pour la réaction de réduction de l'oxygène (ORR) est cruciale pour le développement d'une économie basée sur l'hydrogène. Ici, des matériaux hybrides bioinspirés à base de porphyrines métallées et de nanotubes de carbone multi-parois ont été testés pour l'ORR avec un système d'électrode disque-anneau entre pH 8 et 13. Les matériaux hybrides présentent systématiquement de meilleures propriétés électrocatalytiques que celles de leurs constituants pris individuellement et permettent de réduire l'oxygène par un processus à quatre électrons. La présence du cuivre dans les hybrides n'est pas obligatoire mais elle améliore légèrement les propriétés électrocatalytiques

Catalytic Activity of Carbon Nanotubes and Strapped Iron Porphyrin Hybrids for Oxygen Reduction Reaction

International audienceFor the last decade, the development of non-noble metal or metal-free catalysts for hydrogen economy has been a field of growing interest. Among others, Hydrogen Evolving Reaction (HER), water splitting and Oxygen Reduction Reaction (ORR) are crucial reactions that must be well controlled to improve the production of hydrogen or to optimize the efficiency of fuel cells. The reduction of oxygen is the reaction that takes place at the cathode of a fuel cell, its slow kinetics, its multistep process and the competition between the two-electron and four-electron pathway make ORR the limiting reaction in fuel cells. In nature, the reactions involving oxygen, like oxygen reduction, oxidation reaction, oxygen transport are often performed by iron porphyrins located in protein complexes. Cytochrome $c$ Oxidase is a famous example of protein performing the reduction of oxygen; thus, bioinspired catalysts based on porphyrin and phthalocyanine derivatives, mimicking the structure of active center of the protein have been developed and extensively investigated for ORR. Here, we focus on the ORR activity of MWNT functionalized with iron (III) strapped-porphyrins. The porphyrins contain a bridge bearing one or two carboxylic functions between the phenyl groups in 5 and 15 $meso$ positions. The overhanging bridge prevents the aggregation of the porphyrins and we assume that only one face is available to interact with the nanotubes by $\pi$-stacking. The electrocatalytic activity of several catalysts prepared with different mass ratio of MWNT/FeP was tested at different pH. The goal of this study is first to measure the ORR properties of strapped porphyrins bearing proton relay and second to evaluate the influence of the communication between the nanotube and the catalytic centers

Core–Shell Multiwalled Carbon Nanotube/Cobalt Corrole Hybrids for the Oxygen Reduction Reaction

International audienceThe development of hybrid nanomaterials that preserve and combine the properties of their constituents is a central issue of nanosciences. Herein, we describe the polymerization via CuAAC (copper-catalyzed azide-alkyne cycloaddition) of cobalt(III) corroles around conductive carbon nanotubes to produce chemically robust hybrid catalysts for Oxygen Reduction Reaction (ORR). A combination of techniques including UV-Vis-NIR absorption, Raman and X-ray Photoelectron Spectroscopy (XPS) as well as Scanning Electron Microscopy (SEM) were used to characterize the assembly of the two parts of the functional hybrid system for which the activity and the selectivity toward the ORR process in acidic media are enlightened by a combination of Rotating Disk Electrode (RDE) and Rotating Ring Disk Electrode (RRDE) measurements. The polymerized hybrid (click MWNT-CoCorr) exhibits an overpotential of ca. 230 mV compared to a reference platinum ink; the number of electrons involved in the reduction of oxygen is close to 3 in acidic media demonstrating that the corrole cobalt centers in the hybrids reduce oxygen via a mix of 2 and 4 electrons pathways

Carbon Nanotube and Porphyrins:Materials for Optics and Energy Applications

International audienceThe fabrication of functional hybrid materials that preserves and combines the properties of their building blocks is a central issue of nanosciences. Among the different classes of nanomaterials, carbon nanotubes are promising for electronics, opto-electronics, catalysis and composite applications. In this context the combination of nanotubes with porphyrins has been widely explored for catalytic or electron transfer purposes. Here I present two results obtained recently on the nanotube/porphyrincomposites, the first deals with the supramolecular organization in micelles of porphyrins around the nanotubes. In this work we were able to explain the Davidoff splitting observed on the absorption bands of the porphyrins by their organization around the nanotubes. The second deals with the synergic effect on catalytic activity of carbon nanotubes and strapped iron porphyrin hybrids for Oxygen Reduction Reaction (ORR). In particular, we demonstrated that the combination of both components - MWNTs and porphyrin - leads to a better catalytic activity than those of the nanotubes or the porphyrins taken separately.This study highlights the importance of the carbon support for the catalysis. The nanotubes ensure the availability of electrons to the porphyrin catalysts and allow the ORR to occur via the 4-electron pathway, avoiding the production of hydrogen peroxide

Oxygen reduction reaction catalyzed by overhanging carboxylic acid strapped iron porphyrins adsorbed on carbon nanotubes

International audienceA series of hybrid catalysts for the oxygen reduction reaction (ORR) has been investigated. They are composed of multi-wall carbon nanotubes (MWNTs) coated with iron strapped porphyrins. Two porphyrins have been probed; both are strapped with the same skeleton and differ only by the number of overhung carboxylic acid(s), either one or two. In this structure, the carboxylic acid group can act as a proton relay between the medium and the catalyst or as a polar group surrounding the dioxygen binding cavity. While the number of carboxylic acid group(s) does not exhibit a significant influence on the catalytic properties, the combination of both components–MWNTs and porphyrin–leads to a better catalytic activity than those of the nanotubes or the porphyrins taken separately