Contrôle de la chimie de surface et mise en forme du nanodiamant pour la production de carburants solaires

Among the many allotropes of carbon, nanodiamond (ND) has unique properties that enable its use in a wide variety of applications. The synthetic ND used here come from two distinct sources: detonation nanodiamonds (DND) and milled nanodiamonds (MND). This PhD thesis proposes a detailed analysis of DND and MND with oxidized and hydrogenated surface chemistries. Their physicochemical properties and behavior in aqueous suspension will be discussed at length. Its unique electronic structure sets nanodiamond as an excellent candidate for solar fuel generation. Hence, ND will be used as photocatalysts to photogenerate H2 and photoreduce CO2. Finally, an innovative shaping process will be used to synthesize porous nanocomposite structures of nanodiamonds and amorphous carbon for photoelectrocatalysis applications.Parmi les nombreux allotropes du carbone, le nanodiamant (ND) présente des propriétés singulières permettant son utilisation dans des domaines très variés. Les ND synthétiques utilisés ici proviennent de deux sources distinctes: les nanodiamants de détonation (DND) et ceux issus de broyage (MND). Cette thèse propose une analyse fine des DND et des MND avec des chimies de surfaces oxydées et hydrogénées. Les propriétés physico-chimiques ainsi que leurs comportements en suspension aqueuse seront longuement discutés. La structure électronique exceptionnelle du nanodiamant le place en excellent candidat pour la génération de carburants solaires. Les ND seront donc utilisés comme photocatalyseurs pour photogénérer du H2 ainsi que pour la photoréduction du CO2. Enfin, un procédé innovant de mise en forme sera utilisé pour synthétiser des structures poreuses nanocomposites de nanodiamants et de carbone amorphe pour des applications en photoélectrocatalyse

Stabilité colloïdale des nanodiamants de synthèse hydrogénés dans l'eau

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Caractérisation en spectroscopie de photoémission de nanodiamants produits par différents modes de synthèse présentant différentes chimies de surface

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Oxidized detonation nanodiamonds act as an efficient metal‐free photocatalyst to produce hydrogen under solar irradiation

International audienceHerein, it is revealed for the first time that oxidized detonation nanodiamonds (Ox‐DND) can produce hydrogen under solar irradiation without addition of cocatalyst or formation of heterojunction with another semiconductor. This hydrogen production is investigated using two sacrificial reagents and compared to the one of hydrogenated detonation nanodiamonds (H‐DND). The effect of the Ox‐DND and sacrificial reagent concentrations on the hydrogen production is also studied. At its maximum, a H$_2$ production yield of 32 μmol h$^{−1}$ is obtained for a Ox‐DND concentration of 12.5 μg mL$^{−1}$ (using only 1 vol% of triethanolamine as sacrificial reagent), similar to the one of TiO$_2$ nanoparticles tested at the same concentration in the same illumination conditions

Oxidized Detonation Nanodiamonds Act as an Efficient Metal‐Free Photocatalyst to Produce Hydrogen Under Solar Irradiation

Herein, it is revealed for the first time that oxidized detonation nanodiamonds (Ox‐DND) can produce hydrogen under solar irradiation without addition of cocatalyst or formation of heterojunction with another semiconductor. This hydrogen production is investigated using two sacrificial reagents and compared to the one of hydrogenated detonation nanodiamonds (H‐DND). The effect of the Ox‐DND and sacrificial reagent concentrations on the hydrogen production is also studied. At its maximum, a H2 production yield of 32 μmol h−1 is obtained for a Ox‐DND concentration of 12.5 μg mL−1 (using only 1 vol% of triethanolamine as sacrificial reagent), similar to the one of TiO2 nanoparticles tested at the same concentration in the same illumination conditions

Colloidal stability over months of highly crystalline high-pressure high-temperature hydrogenated nanodiamonds in water

International audienceIn this study, milled nanodiamonds synthesized from HPHT diamond (MND) were successfully hydrogenated and stabilized in colloidal suspension in water over months. The optimal hydrogenation conditions correspond to a minimization of carbon/oxygen bonds and sp$^2$ /amorphous carbon at MND surface as shown by FTIR and XPS. Clean crystalline particles were observed by HR-TEM. The colloidal stability is discussed in terms of sp$^2$ carbon and role of facets. The signature of a surface conductivity was identified by FTIR. A particular arrangement in colloidal suspension of H-MND was observed by Cryo-EM for H-MND with the formation of chain like structures extending over micron range