STABILITY OF THICK POLYPYRROLE FILMS ELECTROGENERATED ON STAINLESS-STEEL

Thick polypyrrole films (> 10 mum) were electrogenerated on steel electrodes, and their stability was checked through the variation of electrical charge stored in the film under different anodic potential limits and in different solvents. 0.1 M LiClO4 acetonitrile, water and propylene carbonate solutions were used. Consecutive potential waves (square and triangular) were employed in the cycling. Water and acetonitrile solutions give higher charge storage efficacies (25-30 A h kg-1) than propylene carbonate solutions (0.7 A h kg-1). The stability is lower when the anodic potential is higher: polypyrrole films lose half of their charge storage efficacy after 250 cycles between -500 and 1000 mV versus SCE, after 1100 cycles between -600 and 700 mV and after 1800 cycles between -600 and 400 Mv.