Abstract:

Blue TiO₂ is considered one of the most promising anodes for degradation of organic pollutants due to the excellent electro-catalytic activity. The electro-catalytic activity is subject to morphological structure and interfacial properties of blue TiO₂. The hierarchically nanostructured blue TiO₂ was prepared by anodization in ice-water bath and cathodic reduction, and the corresponding electrochemical oxidation performance was studied. The top of blue TiO₂ was covered with nanoparticles, followed by a porous layer, and nanotube arrays in sequence. The blue TiO₂ prepared with an ice-water bath possessed more Ti³⁺, electrochemical activity surface and better electron transmission ability compared to that without ice-water bath assisting. The methylene blue was 97.68% removed within 120min under the current intensity of 20mA/cm² and the COD of practical wastewater was completely removed within 180min. The free radical quenching results revealed that adding Na₂SO₄ can promote production of hydroxyl radicals and sulfate radicals on blue TiO₂, while the electrochemical degradation performance of blue TiO₂ mainly relied on hydroxyl radicals. Sulfate radicals could contribute a great deal only under the high concentration of Na₂SO₄, low current density and high initial pH. The blue TiO₂ showed a high service life of 990min, 2.4 times as high as that prepared without an ice-water bath, indicating that this special nanostructure was beneficial to improve the stability of blue TiO₂.

Key words: ice-water bath, anodization, blue TiO₂, nanostructure, degradation, stability, electrochemistry

摘要：

蓝色TiO₂具有出色的电催化活性，被认为是降解有机污染物的最有潜力的阳极材料之一。然而蓝色TiO₂的电催化活性受表面形貌和界面性质的影响较大。本文采用冰水浴阳极氧化和阴极还原制备了由纳米颗粒、多孔层、纳米管阵列依次堆叠的多层纳米结构蓝色TiO₂，并探究了其电化学氧化性能。与无冰水浴辅助制备的相比，该方法制备的蓝色TiO₂具有更多的Ti³⁺含量、更大的活性面积和良好的电子传输能力，可有效降解亚甲基蓝（97.7%，120min，20mA/cm²）和实际废水（COD在180min内被完全去除）。自由基淬灭实验结果表明，添加Na₂SO₄能促进蓝色TiO₂产生羟基自由基和硫酸根自由基，而污染物的降解主要依赖于羟基自由基的氧化作用，硫酸根自由基仅在高Na₂SO₄浓度、低电流密度和高初始pH条件下有较大贡献。通过冰水浴阳极氧化制备的蓝色TiO₂的使用寿命是无冰水浴制备的2.4倍，表明这种多层纳米结构有利于提高蓝色TiO₂的稳定性。

关键词: 冰水浴, 阳极氧化, 蓝色二氧化钛, 纳米结构, 降解, 稳定性, 电化学