不同吸附类型有机物在TiO_2纳米管阵列电极表面的光电催化性能和反应机制

Photoelectrocatalytic Performance and Reaction Mechanism of Different Organics upon Adsorption on a TiO_2 Nanotube Array Electrode

利用有机物在薄层反应器中发生的耗竭氧化反应,研究了弱吸附型的葡萄糖和强吸附型的邻苯二甲酸氢钾在TiO2纳米管阵列(TNA)电极表面的光电催化反应性能和反应机制.研究表明,光电催化反应电流-时间(I-t)曲线的变化趋势能够很好地反映有机物在TNA电极表面的反应性能.对于弱吸附型的葡萄糖,由于其在TNA电极表面吸附能力弱,从溶液本体被吸附至电极表面较慢,致使葡萄糖在高浓度光催化反应时出现I-t曲线瞬时升高然后迅速下降,再呈现缓慢下降的变化趋势.对于强吸附型的邻苯二甲酸氢钾,其吸附性强且难降解,因而在电极表面总是存在着大量的邻苯二甲酸氢钾,导致溶液中邻苯二甲酸氢钾浓度升高时,光电催化反应的I-t曲线在瞬时升高,然后依然持续升高,之后才呈缓慢下降的变化趋势.本文还对有机物的吸附类型、吸附系数、反应机制等进行了分析.研究表明,利用薄层反应器的耗竭氧化反应,有助于深入了解有机物在电极表面的反应过程及其微观机制.

The kinetics and mechanism of the photoelectrocatalytic degradation of glucose with weak adsorption and potassium hydrogen phthalate with strong adsorption on a self-organized and highly ordered TiO2 nanotube array （TNA） were investigated using a thin layer reactor in which the organic compounds were completely and quickly oxidized. The photogenerated current-time （I-t） profiles were used to analyze the microprocesses of the photoelectrochemical catalytic degradation on the TNA electrode. For glucose the I-t curve increased sharply initially and then decreased rapidly followed by a slow decrease. This is due to the weak adsorbability of glucose and it adsorbed slowly onto the surface of the TNA electrode from the bulk solution. However, the I-t curve for potassium hydrogen phthalate had quite a different trend as it increased sharply initially and then continued to increase and then decreased slowly and this was due to the strong adsorbability and mass existence of potassium hydrogen phthalate on the electrode and, in addition, the low degradability of phthalic acid. The adsorption properties and adsorption coefficient of the organic compounds and the reaction mechanism were also analyzed. We conclude that the obtained photoelectrocatalytic oxidation rate of the organic compounds in the thin-layer cell assisted in determining the surface reaction process and the micro-mechanism of organic compound degradation on the TNA electrode.