Electrochemical and photoelectrochemical properties of the interface between titania nanotubes covered by conducting polymer in aqueous by conducting polymer in aqueous electrolytes – The effect of various geometry and electrolytes concentration

Abstract

In the present work we show the impact of nanotubes (NTs) geometry of titania utilized as a substrate in organic-inorganic systems acting as a p-n junction on efficient conversion of radiation energy into electrochemical energy. The electrolytic bath composition and electrolysis conditions were controlled in order to obtain TiO2NTs of various geometry as a result of electrochemical oxidation of titanium foil. The electrode material was characterized using scanning electron microscopy, Raman and UV–vis spectroscopies in order to investigate their morphology, crystallinity and absorbance ability, respectively. According to SEM inspection, the electrolyte bath composition (water content) and duration of electrolysis significantly affects TiO2NTs morphology, namely the internal diameter and the layer thickness. The TiO2NTs electrode/electrolyte interface characterized using electrochemical impedance spectroscopy (EIS) exhibits varied impedance parameters depending on the outer K2SO4 electrolyte concentration (in the range of: 0.01–0.2 M) as the electric charge distribution at the interface is concentration dependent. The series of hydrogenated titania substrates were electrochemically modified by the conducting polymer: poly(3,4-ethylenedioxytiophene) doped with polystyrene sulphonate (pEDOT:PSS) thin film. The optimal geometry of titania was determined based on the photocurrent density recorded for the composite material (TiO2NTs/pEDOT:PSS). The most photoactive organic inorganic junction is composed of titania tubes of 2.5 µm length, the outer diameter equal to 205 nm giving the real surface area equal to 49.9 cm2 per 1 cm2.