Essential explanation of the strong mineralization performance of boron-doped diamond electrodes.
Essential explanation of the strong mineralization performance of boron-doped diamond electrodes.
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DOI：
10.1021/es800298p
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发表时间：
2008-07
影响因子：
11.4
通讯作者：
Xiuping Zhu;Meiping Tong;Shaoyuan Shi;Huazhang Zhao;J. Ni
中科院分区：
文献类型：
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作者：
Xiuping Zhu;Meiping Tong;Shaoyuan Shi;Huazhang Zhao;J. Ni
采用T/硼掺杂金刚石（BDD）、Ti/SnO2-Sb/PbO2和Ti/SnO2-Sb阳极对硝基苯酚的电化学氧化进行了研究。结果表明，Ti/BDD阳极的矿化性能明显强于其他两种阳极。羟基自由基主要以游离羟基形式存在于BDD阳极上，能与有机化合物有效反应。这意味着BDD阳极具有更高的矿化能力的主要机制是BDD阳极电池中存在游离羟基自由基，而不是吸附在BDD阳极上的羟基自由基。为了进一步证实这一假设，我们分别在Ti/BDD、Ti/SnO2-Sb/ PbO2和Ti/SnO2-Sb阳极上研究了对取代酚（对硝基酚、对羟基苯甲醛、苯酚、对甲酚和对甲氧基酚）的电化学氧化。研究发现，对于Ti/BDD电极，对取代酚的降解速率(k)随着Hammett常数（sigma）的增加而增加，这证实了游离羟基自由基在BDD阳极上的优势及其与其中有机物的有效反应。对于Ti/SnO2-Sb/PbO2电极，p取代酚的降解率(k)随着初始表面浓度γ（表征苯酚在电极表面的吸附量）的增加而增加，表明有机化合物主要与吸附在PbO2阳极上的羟基自由基发生反应。然而，对于Ti/SnO2- sb电极，k随着积分参数S的增加而增加（代表sigma和gamma的影响），这意味着有机化合物在SnO2阳极上与吸附的羟基自由基和游离的羟基自由基都发生了反应。
Electrochemical oxidation of p-nitrophenol was examined using differentanodic materials, including T/boron-doped diamond (BDD), Ti/SnO2-Sb/PbO2, and Ti/SnO2-Sb anodes. The results demonstrated that Ti/BDD anodes had a much stronger mineralization performance than the other two anodes. Furthermore, it was found that hydroxyl radicals could mainly exist as free hydroxyl radicals at BDD anodes, which could react with organic compounds effectively. This implied that the dominant mechanism for a much higher mineralization capacity of BDD anodes would be attributed to the existence of free hydroxyl radicals in the BDD anode cell rather than adsorbed hydroxyl radicals on the BDD anode. To further corroborate this hypothesis, electrochemical oxidation of p-substituted phenols (p-nitrophenol, p-hydroxybenzaldehyde, phenol, p-cresol, and p-methoxyphenol) was examined at the Ti/BDD, Ti/SnO2-Sb/ PbO2, and Ti/SnO2-Sb anodes, respectively. The study revealed that for Ti/BDD electrodes, the degradation rate of p-substituted phenols (k) increased with the increase of Hammett's constant (sigma), which confirmed the dominance of free hydroxyl radicals at BDD anodes and its effective reaction with organics therein. For Ti/SnO2-Sb/PbO2 electrodes, the degradation rate of p-substituted phenols (k) increased with the increase of initial surface concentration gamma (representing the adsorption capacity of phenols to electrode surface), which indicated that organic compounds mainly reacted with adsorbed hydroxyl radicals at PbO2 anodes. For Ti/SnO2-Sb electrodes, however, k increased with the increase of the integrated parameter S (representing the effects of both sigma and gamma), which implied that organic compounds reacted with both adsorbed hydroxyl radicals and free hydroxyl radicals at SnO2 anodes.