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anbaozhen金虫 (小有名气)
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[求助]
急求四段电化学聚苯胺修饰电极的论文翻译
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The cyclic voltammograms for PANI-Fc/ G.C electrode in 0.3M H2SO4 and CH3OH at different concentrations are shown in Fig. 3.1. The shape of the curves indicates the behavior of polyaniline. Peak1 and peak2 arise from the transformation of leucomeraldine (LM) to emeraldine (EM) whereas peak3 and peak4 arise from the further oxidation of emeraldine to fully oxidezed pernigraniline (P). The peak M can be attributed to the degradation products and the redox of ferrocene. The intensities of PANI-Fc peaks decrease with an increase in methanol concentrations. For example in the presence of 0.5M methanol only two kinds of peaks (anodic and cathodic) remain and the others disappear. This behavior is consistent with the literature . According to K.R. Prasad and coworker , this feature of the cyclic voltammograms may be explained on the basis of adsorption of CH3OH on polyaniline. It is now known that the methanol adsorption on polyaniline occurs at potential below 0.4V . Moreover K.R. Prasad and coworker found that adsorption of CH3OH is likely to hinder doping of ions into polyaniline which results in the disappearence of the LM/EM transformations. We can say that below 0.4V the adsorption of methanol on PANI-Fc is occurring. It is important to note that the anodic peak potentials corresponding to LM shift towards the positive potentials when the concentration of methanol is increased. Moreover Iwasita reported that methanol oxidation cannot begin below 0.45V. Thus the anodic peaks shift towards the potentials where the methanol oxidation can occur. However the cathodic peak potentials shift towards the negative potentials. It is then possible that those shifts are caused by the methanol. This phenomenon was found by J. Kan et al with ethanol when the cathodic peaks are broader and more negative in the presence of ethanol. If we consider only the sharp peaks (at almost 0.22V and at almost 0.6V) the difference between the anodic peak current at 0.2M and the current at 0.5M is about 0.11mA whereas the difference between the cathodic peak currents is 0.31mA. This means that the diminish of the cathodic peak in the presence of methanol is quicker than the anodic peak. This feature has been reported by Jafarian et al with the cobalt hydroxide modified glassy carbon electrode. Also we have found that methanol is electro-inactive on the bare G.C. electrode in the potential window of this study. |
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