title: Exploring the interparticle electron transfer process in the photocatalytic oxidation of 4-chlorophenol.
abstract: This work aimed to investigate the interparticle electron transfer (IPET) process within the coupled-photocatalyst systems on the basis of the degradation of 4-chlorophenol (4-CP). TiO(2), ZnO and SnO(2) are used as the model photocatalysts owing to their increasing energy levels which correspond to the IPET concept. In the single-photocatalyst tests, ZnO tests are associated with the highest degradation rate constants (0.347+/-0.083 h(-1) at pH 7 and 0.453+/-0.011 h(-1) at pH 11) and a better DOC reduction than in other single catalyst tests under given conditions. ZnO/SnO(2) coupled tests have constants of 0.612+/-0.068 and 0.948+/-0.069 h(-1) at pH 7 and 11, respectively. Additionally, the 4-CP prefers the breakdown of chloride group in TiO(2) system while proceeding hydroxylation reaction in ZnO systems. Meanwhile, a phenomenonlogical model coupled with the IPET effect was developed to explore the separation of photo-electrons and photo-holes within catalysts. Based on the model parameters, the recombination rate of photo-electrons and photo-holes in TiO(2)/SnO(2) and ZnO/SnO(2) systems is 20-45% lower than that obtained by a respective single catalyst. Thus, coupled-photocatalyst tests, TiO(2)/SnO(2) and ZnO/SnO(2) efficiently suppress the recombination, particularly for ZnO/SnO(2) tests at pH 11.
authors.affiliation: Research Center for Environmental Pollution Prevention and Control Technology, Graduate Institute of Environmental Engineering, National Taiwan University, 71 Chou-Shan Rd., Taipei 106, Taiwan, ROC.
authors.forename: Hsin-Hung
authors.initials: HH
authors.lastname: Ou
authors.forename: Shang-Lien
authors.initials: SL
authors.lastname: Lo
authors.forename: Chung-Hsin
authors.initials: CH
authors.lastname: Wu
mesh_terms: D002384:Catalysis; D002712:Chlorides / Q000737:chemistry; D002733:Chlorophenols / Q000737:chemistry*; D004583:Electrons; D006863:Hydrogen-Ion Concentration; D007477:Ions / Q000737:chemistry; D007700:Kinetics; D008903:Minerals / Q000737:chemistry; D010084:Oxidation-Reduction; D010777:Photochemistry
chemical_list: D002712:Chlorides; D002733:Chlorophenols; D007477:Ions; D008903:Minerals; C029107:4-chlorophenol