| Electropolymerization of aniline was conducted on carbon cloth in a solution of0.1mol/L aniline and0.5mol/L HCl through cyclic voltammetric scans to afford polyaniline (PANI). The electrochemical activities of PANI in acidic, neutral and alkaline solutions were studied by cyclic voltammetry, infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) to reveal the doping and undoping of counter anion in PANI.Electrochemical behaviors of PANI in0.5mol/L HCl,0.5mol/L HNO3,0.5mol/L p-toluenesulfonic acid (PTSA) and0.5mol/L dodecylbenzenesulfonic acid (DBSA) were studied by cyclic voltammetry and FT-IR. It was found that the counter anion in the corresponding solutions can enter the polymer as counter anion to replace Cl-which doped in PANI during the electropolymerization of aniline. The size of the counter anion doped in PANI influenced both the onset and the peak of the oxidation potential. The doping and undoping of NO3-in PANI were studied in0.5mol/L NaNO3solution by cyclic voltammetry and FT-IR. The holding at-0.4V vs. SCE facilitated the undoping of NO3-from the polymer and so enhanced the following oxidation of PANI which accompanied with NO3-doping. Electrochemical behevors of PANI in0.5mol/L NaOH solution were studied by cyclic voltammetry and XPS. A redox pair appeared at-0.13and-0.54V on the cyclic voltammogram, corresponding to the oxidation and reduction of PANI which accompanied with the doping and undoping of OH-, respectively.The exchanges of different doping anions in PANI were studied by cyclic voltammetry and FT-IR. The results showed that at least part of Cl-or OH-originally doped in PANI can be replaced by NO3-through cyclic voltammetric scans in0.5NaNO3solution. The originally doped NO3-can also be replaced by OH-through cyclic voltammetric scans in0.5mol/L NaOH solution. PTS-and NO3-can be replaced completely by OH-in a solution of0.5mol/L PTSA or0.5mol/L HNO3containing1.26×10-7and1.12×10-5mol/L OH-, respectively through cyclic voltammetric scans. |
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