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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

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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