Characterization of titanium oxide thin films obtained by galvanostatic anodization in black acacia pyroligny liqueur

Abstract

The condensation of smoke from the pyrolysis of black wattle for the production of charcoal generates a by-product known as pyroligneous liquor. It is widely used in the agricultural area as a fertilizer and phytosanitiser, and its chemical composition presents compounds rich in hydrogen and oxygen, which makes it a potential electrolyte for anodizing. Thus, black wattle pyroligneous liquor was used as anodizing electrolyte for commercially pure titanium. The anodized surfaces were characterized in terms of topography by scanning electron microscopy (SEM); regarding the crystalline structure by X-ray diffraction (DRX); to electrochemical behavior by open-circuit potential (OCP) and electrochemical impedance spectroscopy (EIS); regarding wettability by the sessile drop method; and for semiconductor behavior by UV–visible spectrophotometry. The results showed that the anodized TiO2 film obtained forms interfering colors, with an estimated thickness between 18.4 and 52 nm, being basically amorphous with crystalline concretions that appear with the anodization time. In addition, they exhibit hydrophilic behavior in water and maintain the electrochemical passivity of native titanium oxide, as well as showing semiconductor characteristics with a band gap between 1.75 and 2.9 eV.