CNT as a Reducing Agent

Choi et al. reported the spontaneous reduction of metal ions to metallic form on the sidewalls of the CNTs in aqueous solutions of noble metal ions. They reported that Au and Pt could be deposited spontaneously on the sidewall of the CNTs by a direct redox reaction between the CNTs and metal ions via the immersion of the CNTs in HAuCU (Au +3 and Na2PtCU (Pt +) solutions, respectively. They explained that the principle for the spontaneous reduction of the metal ions on the sidewalls of the CNTs is the difference in the reduction potential between the CNTs and the metal ions. Similarly, the spontaneous formation of Mn02 from MnOJ ions on the CNT sidewall may also be explained by the difference in the reduction potential between the CNT and MnOJ ions. The work function of the CNTs was determined to be nearly 5 eV. The Fermi level of the CNTs is approximately +0.5 V above the potential of the standard hydrogen electrode (SHE), which is well above the reduction potential of Mn04 ions, which is +1.692 V (vs. SHE). The relative potential levels may explain the spontaneous electron transfer from the CNTs to the Mn04 ions. 

Mn04 ions to Mn02 by CNT with decreasing initial pH ofthe solution 

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