Incorporation and expulsion of electrolyte species by tungsten trioxide-, WO3∣ Polyaniline-, and WO3∣ PAn ∣ polyvinylsulfate-confined electrodes during potential cycling

Abstract The ion-transport properties of the tungsten trioxide (WO 3 )-, WO 3  ∣ polyaniline (PAn)-, and WO 3  ∣ PAn ∣ polyvinylsulfate (PVS)-confined electrodes have been studied by means of the in situ Fourier transform infrared (FTIR) spectroscopic method. In highly acidic solution (pH=0), W VI O 3 was reduced to H x W V O 3 by the reaction with H 3 O + and the generated H 2 O molecules were incorporated in the film, but in solutions of pH≧2, the reduction of W VI O 3 was attained by the reaction with H 2 O and the concentration of H 2 O decreased in the film. The charge-compensating reaction for the reduction of WO 3  ∣ PAn films in solutions of pH≧2 depended on the electrode potential. In the potential range between +0.2 and −0.2 V versus Ag ∣ AgCl, the reduction of the positively charged PAn was achieved by expelling anions without the accompanying injection of cations into WO 3 . In the potential range between −0.3 and −0.8 V, however, WO 3 and the charged PAn were simultaneously reduced by protons. PVS remained doped at the WO 3  ∣ PAn ∣ PVS-confined electrode during potential cycling, and the charge-compensation was accomplished by involving cations.