Thermodynamic Study On TiO₂ Photocatalytic Activity And Synthesis Of TiO₂(SrTiO₃)-CuBi₂O₄ Composite Photocatalyst

Researchers have studied semi-conductor materials in the field of photocatalytic degradation of organic pollution and broadened their application in environmental pollution control for many years since Fujishima and Honda reported the photoelectrochemical water-splitting by TiO₂ electrodes in 1972. During the past few years, nearly all semi-conductor materials such as metal oxides and sulfides have been studied deeply for their potential use in photocatalysis and some of them have been proved to have photocatalytic activity. Among these semi-conductor photocatalysts, TiO₂ and SrTiO₃, as cheap, nontoxic, efficient photocatalysts for the detoxification of air and water pollutants have received much research attention. However, how to improve their photocatalytic efficiency through broadening its scope of solar light response and reducing its recombination rate of the electron-hole pair is still a problem. Main contents in this paper are as follows:1). Temperature effect on the photocatalytic degradation of Methyl Orange under UV-vis light irradiation with TiO₂ hydrosol as the photocatalyst.2). Hydrothermal synthesis of CuBi₂O₄ and the effect of heat-treatment temperature on its crystallization and morphology.3). Hydrothermal synthesis of SrTiO₃(x%)-CuBi₂O₄, TiO₂(x%)-CuBi₂O₄ and SrTiO₃ composite powers.Results obtained in the paper are as follows:1). The rate constant of photo-degradation of Methyl Orange under UV-vis light irradiation with TiO₂ hydrosol as the photocatalyst increased by about 5 times from 3.52×10^-4 to 2.17×10^-3 min^-1 as the experimental temperature increased from 34 to 100℃. The Arrhenius activation energy, entropy and enthalpy of activation are 27.7 kj/mol,-265.5j/K·mol and 24.9kj/mol.2). SrTiO₃ particles were successfully prepared through hydrothermal reaction method using Sr(OH)₂ and PTA sol as raw materials in a autoclave at 180℃. SrTiO₃ sample consists of spherical aggregates with an average size of about 100-200 run and these aggregates compose of many tiny grains. The band gap energy of SrTiO₃ is about 3.2 eV. This synthesized SrTiO₃ sample has low photocatalytic activity.3). CuBi₂O₄ particles were successfully synthesized through hydrothermal synthesis at 70°C under atmospheric pressure. The crystalline products are poorly crystallized with band gap of about 1.5 eV. Well-crystallized CuBi₂O₄ was formed through heat-treatment at 580℃.4). Synthesized TiO₂(x%)-CuBi₂O₄ and SrTiO₃(x%)-CuBi₂O₄ composite powders have no photocatalytic activity. On the contrary, they restrain the self-degradation of Methylene Blue under UV-vis light irradiation.