ABSTRACT

Environmental pollution, arising from the release of toxic organic pollutants in air or water, has long been one of the major threats impacting on the well-being of humans and living organisms. Therefore, research to nd a solution to clean up environmental contaminants is of utmost importance. Since the discovery of photoelectrochemical splitting of water on TiO2 electrodes by Fujishima and Honda in 1972,1 TiO2-based semiconductor materials have been widely studied for environmental cleanup applications, due to the nontoxicity, availability, stability, low cost, and efcacy of titania. Titania has three main crystalline structures: anatase, brookite, and rutile.2 Both anatase and rutile phases are commonly used in photocatalysis, with anatase generally

7.1 Introduction .................................................................................................. 201 7.2 Sol-Gel Chemistry Method ..........................................................................205 7.3 Hydrothermal Method .................................................................................. 210 7.4 Solvothermal Method ................................................................................... 216 7.5 Sonochemical Method .................................................................................. 219 7.6 Aerosol-Based or Spray-Drying Method ...................................................... 222 7.7 Anodization Method .....................................................................................224 7.8 Deposition Method ....................................................................................... 227 7.9 Synthesis of Zeolite-Based Semiconductors ................................................230 7.10 Closing Remarks ........................................................................................... 231 References .............................................................................................................. 232

showing greater photocatalytic activity.3 Anatase TiO2 has a wide band gap of 3.2 eV, meaning that the anatase crystal can only absorb light with a wavelength threshold of less than 387 nm, that is, UV light, which makes up only 5% of solar light.4