This paper describes how one-pot preparation of polypyrrole (PPy) on Al2O3 layer in an aluminum solid capacitor could be achieved by electropolymerization of pyrrole (Py) in acetonitrile with small amounts of water, using ammonium borodisalicylate (ABS) as a new electrolyte. The effects of monomer and electrolyte concentrations, current density, and polymerization temperature on the PPy formation on Al2O3 layer in aluminum solid are also discussed. Polymerization occurred smoothly to give PPy on the Al2O3 layer under the following conditions: [ammonium borodisalicylate] = 0.02 M, [Py] = 0.1 M, and polymerization temperature = -42 degrees C, current density = 10mA cm(-2). The normalized capacitance, the C-p/C-0 value of capacitor fabricated, reached more than 0.9, indicating that the porosity and surface of the All 03 layer are filled up and covered with PPy. The Raman spectra of the PPy film showed that the peak assignable to C=C backbone stretching shifted to a lower wave number of 1585 cm(-1). This indicates formation of the film with well-conjugated C=C backbone. The SEM micrograph of PPy on Al2O3 layer showed a closely packed globular morphology. These results indicate that the new electrolyte, ABS, has an excellent ability to form PPy film directly on Al2O3 surface by electropolymerization. (c) 2006 Elsevier B.V. All rights reserved.