Methylene blue Photo-degradation on the Hetero-junction system α-Fe2O3 / BaTiO3 under sunlight

Abstract

In recent years, great efforts have been devoted to the development of photocatalysis based on semiconductors for the purification of water and air, on the one hand by the synthesis of these materials by simple, rapid processes and economical and on the other hand by improving their photo-activity essentially by doping process. In this respect, we are interested in improving the photocatalytic activity of Barium Titanate (BaTiO3) under solar irradiation. The perovskite BaTiO3,the hematite α-Fe2O3,and the hetero-junctionα-Fe2O3/BaTiO3synthesized by chemical route were characterized by X-ray diffraction, scanning electron microscopy (SEM), and photo-electrochemistry. These materials have been successfully tested as photocatalysts in the photodegradation of Methylene Blue (MB) under sunlight. The hetero-junctionα-Fe2O 3/ BaTiO3showed enhanced photo-activity compared to end members BaTiO3 orα-Fe2O3.The photo-catalyst nature and its dose, initial MB concentration (Co), and pH were optimized. 20 ppm of MB was completely eliminated after 3 h of exposure to solar irradiation at pH ∼ 11 on α-Fe2O3(15 %)/BaTiO3. A high mineralization degree was confirmed with total organic carbon (TOC) and the results of the quenching test showed that the O2•- radical is the main active specie responsible for the photo-degradation of MB. The kinetic analysis suggested that the MB degradation obeys a pseudo-first-order with a rate constant of1.4 × 10−2min−1 (t1/2 = 50 min). The results were ascribed to the synergistic effect of the hetero-junction α-Fe2O3/BaTiO3, which plays a crucial role in enhancing the electron transfer and thereby in the MB photo-mineralization with elimination rate of 93 %.