Surface Oxidation of Carbon Nanofibers Prior to Functionalization

Surface Oxidation of Carbon Nanofibers Prior to Functionalization 

The first studies on CNFs oxidation discussed the impact of the surface treatments on bulk ordering [91]. Investigations for catalytic purposes came later with extensive contributions by the groups in Utrecht, Geus, and de Jong. For an optimal use of CNFs as catalyst supports, their surface has to be modified. 

One way is by introducing oxygen-containing groups. Protocols employ oxidations with concentrated HNO3 or a mixture with H2SO4 under reflux [92-94]. 

The graphitic layers remain unchanged while the pore volume increases [93, 94]. Toebes et at. showed that the most predominant effect is the opening of the inner tubes of the fibers [93]. The oxidation did not only occur at the surface but also developed 2-3 run into the subsurface [93]. Carbonyl groups are formed, which are subsequently converted into carboxyls and carboxylic anhydrides [92]. 

Successful applications of the oxygen-modified CNFs are reported on immobilization of metal complexes ]95], incorporation of small Rh particles [96], supported Pt and Ru CNFs by adsorption and homogeneous deposition precipitation ]97, 98], Co CNFs for Fischer-Tropsch synthesis ]99], and Pt CNFs for PEM fuel cells [100]. 

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