Effect of electrical parameters on morphology, chemical composition, and photoactivity of the nano-porous titania layers synthesized by pulse-microarc oxidation

TiO2 layers were grown via pulse type microarc oxidation process under different applied voltages, frequencies, and duty cycles. Surface chemical composition and phase structure of the synthesized layers were studied utilizing X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Furthermore, scanning electron microscope (SEM) and atomic force microscope (AFM) were employed to investigate surface morphology and topography of the layers. It was revealed that the layers had a porous structure with both anatase and rutile phases. The anatase relative content in the layers increased with the applied frequency; meanwhile, it decreased with duty cycle at low applied voltages, but increased with duty cycle at high applied voltages. The topographical evaluations showed that the surface of the layers is rough with an average roughness of about 1.8-9.9 nm. It was also found that the pore size decreased with the current frequency and increased with duty cycle at a fixed applied voltage. Photocatalytic performance of the layers was also examined by measuring the decomposition rate of methylene blue solution under ultraviolet irradiation of the surface. It was also found that about 94% of methylene blue solution was decomposed on the synthesized catalysts after 160 min UV irradiation of the surface. (C) 2009 Elsevier Ltd. All rights reserved.