Photoelectrochemical Properties of Anodic TiO2 Layers Prepared by Various Current Densities

Abstract

Photoelectrochemical studies were performed using passivated titanium electrodes. The passive films were formed by anodization of Ti in galvanostatically with current densities between 2 and 100 mA/cm², with a constant passed charge of 4 A · s/cm². Photocurrent spectra in , short‐circuit photocorrosion in and changes of refractive index suggest the dependence of oxide properties on the anodization rate. With increasing current density of anodization, the bandgap for indirect transitions becomes smaller, the refractive index increases, and the photocorrosion increases at . The time dependence of photocorrosion indicates that the quality of the oxide is not the same along the cross section. X‐ray diffraction confirms that the film is composed of anatase and rutile phases of polycrystalline with very fine grains. The fraction of rutile increases at large current densities and the layer is more porous, especially after the anodization breakdown had occurred.