Preparation of Supported Catalysts on CNTs and CNFs

Besides the classical nitric acid treatments, other oxidative agents have been used to prepare functionalized CNTs. Rao et al. [170] have compared the effects of concentrated nitric acid, aqua regia, HF-BF3, aqueous OSO4, and KMn04 (acid/alkali) solutions on MWCNT structures [170]. Indeed, all these oxidants 

System Preparation Method 5bet (m /g) Loading (%w/w) Mean Particle Size (nm) Ref. 

PtRu/MWCNT Impregnation on oxidized MWCNTs — 25Pt-25Ru -3 203 

Chemical vapor deposition is a recognized method for the preparation of well-dispersed catalysts [183], and it has been explored for CNT- and CNF-based catalyst preparation [184-186], However, this method has two important limitations (1) if it is condncted by two successive steps, it only affords low loadings [184,185] and (2) it is difficnlt to scale-up since deposition mnst be carried out in a linidized bed, and CNTs and CNFs are difficnlt to linidize without external activation snch as vibration. 

Electrodeposition is a process by which metal particles are prodnced by the redaction of a metal salt solntion at a cathode. The electrodeposition method has limitations dne to difficnlties in controlling the metal loading because of the concurrent rednction of protons and in reaching small particle sizes [125,187], 

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