title: Mechanism of TiO2-assisted photocatalytic degradation of dyes under visible irradiation: photoelectrocatalytic study by TiO2-film electrodes.
abstract: Photoelectrocatalytic degradation of various dyes under visible light irradiation with a TiO(2) nanoparticles electrode has been investigated to reveal the mechanism for TiO(2)-assisted photocatalytic degradation of dyes. The degradation of both cationic and anionic dyes at different biases, including the change in the degradation rate of the dyes and the photocurrent change with the bias potential, the degraded intermediates, the voltage-induced adsorption of dyes, the accumulation of electrons in the TiO(2) electrode, the effect of various additives such as benzoquinone (BQ) and N,N-dimethyl aniline (DMA), and the formation of active oxygen species such as O(2)(*-) and H(2)O(2) were examined by UV-visible spectroscopy, HPLC, TOC, and spin-trap ESR spectrometry. It was found that the dyes could controllably interact with the TiO(2) surface by external bias changes and charging of dyes. The cationic dyes such as RhB and MG underwent efficient mineralization at negative bias, but the N-dealkylation process predominated at positive bias under visible light irradiation. The discolorations of the anionic dyes SRB and AR could not be accelerated significantly at either negative or positive bias. At a negative bias of -0.6 V vs SCE, O(2)(*-) and dye(*+) were formed simultaneously at the electrode/electrolyte interface during degradation of cationic RhB. In the case of anionic dyes, however, it is impossible for the O(2)(*-) and dye cationic radical to coexist at the electrode/electrolyte surface. Experimental results imply both the superoxide anionic radical and the dye cationic radical are essential to the mineralization of the dyes under visible light-induced photocatalytic conditions.
authors.affiliation: Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Yang
authors.forename: Chuncheng
authors.initials: C
authors.lastname: Chen
authors.forename: Hongwei
authors.initials: H
authors.lastname: Ji
authors.forename: Wanhong
authors.initials: W
authors.lastname: Ma
authors.forename: Jincai
authors.initials: J
authors.lastname: Zhao
mesh_terms: D000327:Adsorption; D000814:Aniline Compounds / Q000737:chemistry; D000880:Anthraquinones / Q000737:chemistry / Q000528:radiation effects; D016227:Benzoquinones / Q000737:chemistry; D002384:Catalysis; D004396:Coloring Agents / Q000737:chemistry* / Q000528:radiation effects*; D004563:Electrochemistry; D004566:Electrodes; D005609:Free Radicals / Q000737:chemistry / Q000528:radiation effects; D008027:Light; D015394:Molecular Structure; D053758:Nanoparticles / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry; D010777:Photochemistry; D017382:Reactive Oxygen Species / Q000138:chemical synthesis / Q000528:radiation effects; D012235:Rhodamines / Q000737:chemistry / Q000528:radiation effects; D012394:Rosaniline Dyes / Q000737:chemistry / Q000528:radiation effects; D013499:Surface Properties; D013997:Time Factors; D014025:Titanium / Q000737:chemistry*
chemical_list: D000814:Aniline Compounds; D000880:Anthraquinones; D016227:Benzoquinones; D004396:Coloring Agents; D005609:Free Radicals; D017382:Reactive Oxygen Species; D012235:Rhodamines; D012394:Rosaniline Dyes; C005095:malachite green; C009495:titanium dioxide; C022027:lissamine rhodamine B; C004532:quinone; C010078:alizarin; C015157:N,N-dimethylaniline; D014025:Titanium; C029773:rhodamine B; D010100:Oxygen