Chuong 5 ung dung xuc tac quang

Chƣơng ỨNG DỤNG XÚC TÁC QUANG TRONG XỬ LÝ MÔI TRƢỜNG Introduction Bases of photocatalytic enhancement Improvement of Absorption of photons to create electron–hole pairs photon absorption Separation and migration of the photogenerated electrons and holes; either migration to surface reaction sites (ii)a, or recombination (ii)b Reduction of recombination Surface chemical reactions, for which surface character (active sites) and quantity (surface area) are important Main processes in semiconductor heterocatalysis Activation of surface CARBON 49 (2011) 741 Improvement of photon absorption Metal or Nonmetal doping Schematic band structures of a metal oxide (NaTaO3) and metal (oxy)nitride (BaTaO2N) J Phys Chem C 2007, 111, 7851-7861 Sensitization Mechanism of dye-sensitized photocatalytic hydrogen production under visible light irradiation Renewable and Sustainable Energy Rev 11 (2007) 401 Structural model for the CdTi nanohybrid Seong-Ju Hwang, et al Adv Funct Mater 2011, 21, 3111 Reduction of recombination Reducing of particle size Decreasing particle size reduces the probability of electron–hole recombination due to reduced migration distances and fewer defects CARBON 49 (2011) 741 Metal deposition Metal deposition particles can act as electron trapping to reduce the recombination rate of photogenerated electron-hole pairs Applied Catalysis A: General 325 (2007) Activation of surface Increase of active sites Co-catalyst Schematic illustration of overall water splitting on a heterogeneous photocatalyst Chem Mater 2010, 22, 612–623 Increase of surface area Reducing particle size or using porous materials TEM micrograph of TiO2 nanoparticles in a microporous region of activated carbon CARBON 49 (2011) 741 CƠ CHẾ PHẢN ỨNG XÚC TÁC QUANG TRONG XỬ LÝ CÁC HỢP CHẤT HỮU CƠ Effect of operating parameters on the degradation of pesticides and phenols Types and composition of photocatalyst Influence of substituent group Light intensity and wavelength Pollutant type and concentration Catalyst loading Medium pH Synthesis technique and calcination temperature Doping and mixed semiconductor Interfering substances 10 Oxidants/electron acceptor 11 Mode of application: suspended vs immobilized system