Propriedades fotoeletroquimicas do polipirrol-dodecilsulfato

AUTOR(ES)
DATA DE PUBLICAÇÃO

1998

RESUMO

The photoelectrochemical properties of polypyrrole, PPy, doped with a surfactant are systematically examined in this work. Dodecylsulfate, DS, makes possible the synthesis in an aqueous medium yielding flexible films with good electrochemical, mechanical and electrochromic stabilities. The interaction of light with the surface of a reduced PPy-DS film (p-type semiconductor) in a cell is observed as cathodic photocurrents. Models developed for solid and microporous inorganic semiconductors were used to discuss the results. Films obtained by galvanostatic synthesis (Q = 10-190 mC cm) on Pt electrodes generate superficially homogeneous photocurrents of ca. 2.5 mA cm when they are irradiated with polychromatic light of 152 mW cm in a cell, in contact with an aqueous electrolyte. Action spectra measured between 350 and 600 nm show two indirect electronic transitions at 1.7 and 2.8 eV, assigned to intermediate transitions in the gap, and a flat band potential EBP = -0.37 V vs Ag/AgCl. The depletion layer thickness of a 0.75 mm thick film is 23 nm. Effects of morphology, thickness, oxidation degree and illumination of the films were observed by Electrochemical Impedance Spectroscopy and the results were analysed using equivalent circuits. An increase of 40% of the charge carriers was observed in a film under illumination. The Scanning Microscope for Semiconductor Characterisation (SMSC) was used to measure photocurrents with spatial resolution and to make a photoelectrosynthesis of PPy-DS on specific regions of a microporous TiO2 electrode with good results.

ASSUNTO(S)

polimeros condutores impedancia (eletricidade)

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