Electrochemical properties of assembled polypyrrole/V2O5 xerogel films

Mixed vanadium pentoxide xerogel (VXG)/polypyrrole (PPy) films were assembled onto fluorine doped thin oxide glass electrodes (FTO), according to three different sequential coating procedures, as represented by A = FTO/VXG/PPy, B=FTO/(VXG+PPy) and C=FTO/PPy/VXG. Type A films exhibited maximum conductivity in the 500-1000 mV range and relatively fast electrochemical response. No memory effect was observed by chronoamperometry, after alternating their exposition to reducing species such as ferrocene, and then to the pure electrolyte solution. Type B films consisted of a composite material where PPy was generated inside the interlamellar space of VXG. The electrochemical response in this case was intermediary fast, and the conduction window was shifted to the 0-500 mV range. This type of film exhibited a good memory, responding to ferrocene ions in open circuit. Type C films consisted of VXG deposited onto an electropolymerized film of PPy. The conductivity properties in this case exhibited a narrow window around 500 mV and a much slower electrochemical response, with little memory effect. In this case the charging of the external VXG layer is controlled by the intermediate PPy film. (C) 2000 Elsevier Science Ltd. All rights reserved.