Nitrogen-doped CNTs

Fig. 14.19 Polarization curves of oxygen reduction on nitrogen-doped CNTs with different nitrogen content. Operating conditions 0.1 M KOH, 5 mVs-1 scan rate, 1600 rpm rotation speed,...

CNTs, such as nitrogen-doped CNT, have been reported having high catalytic activity for PEMFC cathode reaction [163-165]. 

Preformed gold NPs deposited on several kinds of CNTs were tested as catalysts for the CO-PROX. No significant confinement effects were detected in these catalysts however, promising results were obtained with Au NPs deposited over nitrogen-doped CNTs [143]. Confinement effects on Ru based nanocatalysts were also investigated [48,119]. Both studies reveal that Ru NPs confined in the inner cavity of the CNTs show better activities in the CO-PROX. The authors conclude that the channels of CNTs can selectively increase the density of reactants, and the encapsulation of Ru NPs in the channels of CNTs can provide a microenvironment to reinforce the reactivity of catalytic sites. 

Nitrogen-Doped CNTs by In Situ Method 279 High-temperature synthesis method 279 Low-temperature synthesis method 280... 

The aim of this chapter is to summarize the results obtained in different fields related to research on nitrogen-doped CNTs including synthesis, characterization, and catalytic applications. The catalytic results will be discussed and compared with those reported for conventional supported catalysts in order to highlight some critical aspects that require... 

Nitrogen-doped CNT synthesis can be carried out in two different ways, either directly during synthesis of CNTs in situ method) or by post-treatment of the as-synthesized CNTs ex situ method). For both approaches, various synthetic techniques such as arc discharge, laser ablation, chemical vapor decomposition (CVD), and organometallic functionalization have been employed. Among them the CVD method, or low-temperature synthesis, is the most commonly employed due to its versatility and the facility for scale-up process. 

In heterogeneous catalysis, medium- to large-pore carbons with a high total pore volume are preferred in order to increase the contact surface between the reactants and the active sites. Nitrogen-doped CNTs lead to the more active support for gas adsorption. Peng and Cho reported that N-CNTs could be used as gas sensors for CO and water while CNTs are not sensitive to these molecules [99]. 

Nitrogen-doped CNTs have also been reported recently by Pham-Huu and coworkers as an efficient metal-free catalyst in the partial oxidation of H2S into elemental sulfur [139]. Such reaction is mostly catalyzed by iron-based catalysts supported on different carriers such as silica, alumina, or silicon carbide [140,141]. The optimization process was further conducted... 

The following part of this work will be devoted to the use of these macroscopically shaped nitrogen-doped CNTs and mesoporous carbon for catalysis applications. It is worthy to note that reports that deal with the use of these macroscopic N-CNTs remain scarce nowadays despite their high potenhal. However, results obtained indicate that this new family of metal-free catalysts will play a key role in the relentless development race of future catalysts with better catalytic performance alongside with low carbon footprint. 

CNTs and graphene can also be doped with heteroatoms as a substitute for carbon in the hexagonal lattice, known as substitutional doping. The most common heteroatoms are boron, a p-type dopant in carbon, and nitrogen, a n-type dopant in carbon. " Dopants significantly effect the electronic properties like the DOS near Ep and the band structure. Nitrogen-doped CNTs (N-CNTs) exhibit strong electron donor states on the conduction band near Likewise, boron-doped... 

SI-NMP [70, 71]. For instance, heating of nitrogen-doped CNTs in the presence of both dibenzoyl peroxide and TEMPO afforded the corresponding alkoxyamine-modified CNTs. The SI-NMP of styrene then provided PS brushes [70]. 

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