pH effect on the electrochemical redox reaction of disulfide with polyaniline film electrode in organic solution

2,5-Dimercapto-1,3,4-thiadiazole/polyaniline (DMcT/PAn) composite electrode is prepared by DMcT electrochemical oxidation on PAn film electrode in DMcT solution with a different pH. The electroactivity, DMcT concentration profile in the PAn film and the in situ resistivity of the composite are investigated in the electrolyte solution with or without DMcT. The composite film prepared in acidic condition shows higher current density and better electroactivity than those prepared under neutral and basic conditions because the protons may contribute to the protonation of PAn film. When DMcT/PAn composite is transferred into the solution without DMcT, it has enhanced electroactivity such as an anodic peak shift to a lower potential and increased cathodic current. The enhancement of electroactivity is considered to be caused by the increase of ion diffusion coefficient and the decrease of electrical resistivity. The ion diffusivity increases due to the detachment of excess DMcT from the film and the resistivity decreases by the dissociation of DMcT from the imine group of PAn.