Yang Juan, Chen Chuncheng, Ji Hongwei, Ma Wanhong, Zhao Jincai
Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China.
J Phys Chem B. 2005 Nov 24;109(46):21900-7. doi: 10.1021/jp0540914.
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.
采用TiO₂纳米颗粒电极，研究了可见光照射下各种染料的光电催化降解过程，以揭示TiO₂辅助光催化降解染料的机理。通过紫外可见光谱、高效液相色谱、总有机碳和自旋捕获电子顺磁共振光谱等方法，考察了不同偏压下阳离子和阴离子染料的降解情况，包括染料降解速率的变化、光电流随偏压的变化、降解中间体、电压诱导的染料吸附、TiO₂电极中电子的积累、各种添加剂（如苯醌（BQ）和N,N-二甲基苯胺（DMA））的影响以及活性氧物种（如O₂⁻*和H₂O₂）的形成。结果发现，通过外部偏压变化和染料充电，染料可以可控地与TiO₂表面相互作用。阳离子染料如罗丹明B（RhB）和亚甲基蓝（MG）在负偏压下能有效矿化，但在可见光照射下，正偏压时N-脱烷基过程占主导。阴离子染料酸性红B（SRB）和酸性铬蓝K（AR）在负偏压或正偏压下，褪色均未显著加速。在相对于饱和甘汞电极（SCE）为 -0.6 V的负偏压下，阳离子RhB降解过程中，电极/电解质界面同时形成O₂⁻和染料阳离子自由基（dye⁺）。然而，对于阴离子染料，O₂⁻*和染料阳离子自由基不可能在电极/电解质表面共存。实验结果表明，超氧阴离子自由基和染料阳离子自由基对于可见光诱导光催化条件下染料的矿化至关重要。
