One step growth Of WO3-loaded Al2O3 micro/nano-porous films by micro arc oxidation

Micro arc oxidation process was employed to synthesize WO3-Al2O3 porous composite films for the first time. Surface morphology and topography of the layers were investigated by scanning electron microscopy (SEM) and atomic force microscope (AFM). X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques were also used to study phase structure and chemical composition of the composite layers. It was found that the composite layers had a porous structure with a rough surface. The layers consisted of gamma-alumina, gamma-alumina, and tungsten trioxide phases fractions of which varied with the applied voltage. The band gap of the composite layers was calculated as 3.42 eV using a UV-vis spectrophotorneter. Furthermore, photocatalytic performance of the synthesized composite layers was determined by measuring the decomposition rate of methylene blue solution on the surface of the layers. It was found that more than 88% of the methylene blue was degraded after 120 min UV-irradiation with a rate constant of k = 0.0175 min(-1). In addition, a growth mechanism was put forward with emphasis on electrochemical foundations. (C) 2009 Elsevier B.V. All rights reserved.