Nanotubes Oxidation reactions

Carbon nanotubes can act both as electron donor or acceptor and consequently exhibit an abundant redox chemistry. Still oxidizing reactions mainly take place at the tubes ends and at defects. The direct oxidation of carbon atoms in an intact side wall, on the other hand, rarely ever occurs. It would require much... 

Initial attempts to functionalize these compounds were limited to oxidation reactions [85] that resulted in shortened nanotubes with carboxylic acid groups on the open edges. Haddon and coworkers first reported use of these acid groups to attach long alkyl chains by means of amide linkages [86]. Later, Sun and coworkers showed that esterification can also be used to functionalize SWNTs [87]. These procedures afforded solubilized SWNTs, which enabled characterization and further solution-based investigations. 

The reaction of covalent functionalization of carbon nanotubes is always preceded by an oxidation reaction for obtaining of carbonyl and carboxyl groups, which can be created during the oxidation by oxygen, air, concentrated sulfuric or nitric acid, aqueous hydrogen peroxide and acid mixture. The oxidative processes induce the opening of the ends and the formation of holes in the walls of the carbon nanotubes (Sahoo et al. 2010 Tasis et al. 2006). 

Cui, Z., Li, C.M. Jiang, S.P. PtRu catalysts supported on heteropolyacid and chitosan functionalized carbon nanotubes for methanol oxidation reaction of fuel-cells. Phys. Chem. Chem. Phys. 13 (2011), pp. 16,349-16,357. 

So far, the Pt-Ru alloy has shown the most promising performance for the oxidation of methanol and hydrogen oxidation reaction in the presence of CO. Carbon black has been used as support for the metal nanoparticles, particularly Vulcan XC-72 (Cabot), which has a surface area of 240 m g . Methanol oxidation starts at lower potential values for all the Pt-Ru/C catalysts than for Pt/C anodes. Comparison of electrodes prepared with Pt and Pt-Ru as the electrocatalyst supported on nanotubes and those prepared with the most usual support, Vulcan XC-72 showed that multi-wall carbon nanotubes produce catalysts (Pt-Ru/MWNT) with better performance than on other supports, particularly with respect to those prepared with the traditional Vulcan XC-72 carbon powder [18],... 

Machado, G.S., Castro, K, Wypych, F. Nakagaki, S. (2008) Immobilization of metalloporphyrins into nanotubes of natural halloysite toward selective catalysts for oxidation reactions. Journal of Molecular Catalysis a-Chemical, 283, 99-107. 

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