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This work reports the synthesis of nitrogen-doped carbon nanotubes (N-CNTs) using a Chemical Vapor Deposition (CVD) process at temperature ranging from 600 °C to 850 °C and ethane/ammonia concentration (defined as a volume percentage of C 2 H 6 /(C 2 H 6 + NH 3 )) of 20–100%. Several characterizations, i.e. XPS, SEM and TEM were done on the as-synthesized nitrogen-doped carbon nanotubes in order to get more insight about the influence of the synthesis conditions on the characteristics and properties of these N-CNTs. Depending on the synthesis conditions, the atomic percentage of nitrogen in carbon nanotubes varied from 0 at.% to about 5.5 at.%. The undoped carbon nanotubes (N-free CNTs) and two kinds of N-CNTs with different types of nitrogen incorporated species have been used as the supports for palladium in the liquid-phase hydrogenation of cinnamaldehyde. The introduction of nitrogen atoms into the carbon matrix significantly modified the chemical properties of the support compared to the N-free carbon nanotube resulting in a higher metal dispersion. N-CNTs exhibit much higher activity in the hydrogenation reaction compare to the undoped ones. Nitrogen incorporation also strongly improved the selectivity towards the C C bond hydrogenation. The results show that the type of nitrogen species incorporated in CNTs structure can also influence the catalytic activity. Recycling test confirms the high stability of the catalyst as neither palladium leaching nor deactivation has been observed.

The arrays of vertically aligned carbon nano-filaments (VACNF) were synthesized by catalytic chemical vapor deposition on TiOx substrates, obtained via oxidative treatment of polycrystalline Ti and Ti thin films on Si(1 0 0). VACNF were studied using scanning and transmission electron microscopies. The Pt deposition on VACNF was utilized to prepare a set of model catalysts, which were investigated in two fuel cell related reactions: the oxygen reduction (ORR) and the hydrogen oxidation (HOR) reactions. The experimental data were compared with the results of mathematical modeling performed for a fast (quasi)reversible and a slow irreversible electrochemical reaction. The approach made it possible to study electrochemical reactions (HOR, ORR) on nano-materials under well defined mass transport conditions. The influence of the catalytic layer thickness and the Pt coverage on the penetration depth of the reactive species inside the layer and consequently on the performance and on the Pt effectiveness factor were analyzed.

The introduction of foreign elements inside the channel of carbon nanotubes could lead to a significant modification of the intrinsic properties of these nanomaterials. Nitrogen atoms entering in the graphene sheets as substitute of carbon could modify in a large extend the acido-basic properties and also adsorption of the nanotube itself. Depending on the synthesis conditions, i.e. nature of the N-source, temperature and C-to-N atomic ratio, various N-doped carbon nanotubes can be synthesized with different surface properties. The aim of the present work is to report the synthesis of N-doped CNTs using a common nitrogen source precursor namely ammonia (NH 3 ) with C 2 H 6 as carbon source. The as-synthesized N-CNTs were subsequently employed as catalyst support in the liquid-phase hydrogenation of cinnamaldehyde using palladium as an active phase.

Silicon carbide is a ceramic material that has been widely studied because of its potential applications, ranging from electronics to heterogeneous catalysis. Recently, a new type of SiC materials with a medium specific surface area and thermal conductivity, called β-SiC, has attracted overgrowing interest as a new class of catalyst support in several catalytic reactions. A primary electron tomography study, performed in usual mode, has revealed a dual surface structure defined by two types of porosities made of networks of connected channels with sizes larger than 50 nm and ink-bottled pores with sizes spanning from 4 to 50 nm. Depending on the solvent nature, metal nanoparticles could be selectively deposited inside one of the two porosities, a fact that illustrates a selective wetting titration of the two types of surfaces by different liquids. The explaining hypothesis that has been put forward was that this selectivity against solvents is related to the pore surface oxidation degree of the two types of pores. A new technique of analytical electron tomography, where the series of projections used to reconstruct the volume of an object is recorded in energy filtered mode (EFTEM), has been implemented to map the pore oxidation state and to correlate it with the morphology and the accessibility of the porous network. Applied, for the first time, at a nanoscale resolution, this technique allowed us to obtain 3D elemental maps of different elements present in the analysed porous grains, in particular oxygen; we found thus that the interconnected channel pores are more rapidly oxidized than the ink-bottled ones. Alternatively, our study highlights the great interest of this method that opens the way for obtaining precise information on the chemical composition of a 3D surface at a nanometer scale.