Electrochemical properties of assembled polypyrrole/V2O5 xerogel films

Mixed vanadium pentoxide xerogel (VXG)/polypyrrole (PPy) films were assembl ed onto fluorine doped thin oxide glass electrodes (FTO), according to thre e different sequential coating procedures, as represented by A = FTO/VXG/PP y, B=FTO/(VXG+PPy) and C=FTO/PPy/VXG. Type A films exhibited maximum conduc tivity in the 500-1000 mV range and relatively fast electrochemical respons e. No memory effect was observed by chronoamperometry, after alternating th eir 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 electrochemica l response in this case was intermediary fast, and the conduction window wa s 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 VX G deposited onto an electropolymerized film of PPy. The conductivity proper ties in this case exhibited a narrow window around 500 mV and a much slower electrochemical response, with little memory effect. In this case the char ging of the external VXG layer is controlled by the intermediate PPy film. (C) 2000 Elsevier Science Ltd. All rights reserved.