HETEROGENEOUS MECHANISMS OF THE OXIDATION OF CATECHOLS AND ASCORBIC-ACID AT CARBON ELECTRODES
HETEROGENEOUS MECHANISMS OF THE OXIDATION OF CATECHOLS AND ASCORBIC-ACID AT CARBON ELECTRODES
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DOI：
10.1021/ac00298a046
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发表时间：
1986-06-01
影响因子：
7.4
通讯作者：
WIGHTMAN, RM
中科院分区：
文献类型：
--
作者：
DEAKIN, MR;KOVACH, PM;WIGHTMAN, RM
对有机物质氧化途径的评估已用于探讨活性炭电极和非活性炭电极之间的差异。一些取代的儿茶酚和抗坏血酸的氧化已被检查在中间pH值的反应的非均相速率常数进行了评估，通过使用半积分。考虑的pKa的中间体和正式的单电子过程的潜力，使微观途径被确定。在pH 7.0时，儿茶酚氧化通过单阴离子的单电子氧化进行，然后是自由基阴离子的氧化。发现抗坏血酸的氧化具有相同的机理行为。在未活化的碳电极上的单电子过程的速率比在金属电极和热处理的碳上观察到的速率慢，或者从均匀的电子转移速率计算得到。因此，可以得出结论，表面活化不会导致电催化，而是消除了存在于未活化电极的电子转移的障碍。
Evaluation of the pathways for the oxidation of organic substances has been used to probe the differences between activated and unactivated carbon electrodes. The oxidation of some substituted catechols and ascorbate has been examined at intermediate pH. The heterogeneous rate constants for the reactions have been evaluated by use of semiintegration. Consideration of the pKa''s of the intermediates and the formal potentials for the one-electron processes has enabled the microscopic pathways to be determined. At pH 7.0, catechol oxidation proceeds through the one-electron oxidation of the monoanion followed by oxidation of the radical anion. Identical mechanistic behavior is found for the oxidation of ascorbate. The rates for the one-electron processes are slower at unactivated carbon electrodes than those observed at metal electrodes and heat-treated carbon, or as calculated from the homogeneous electron transfer rates. Thus, it is concluded that surface activation does not result in electrocatalysis, but rather removes the impediments to electron transfer that exist at unactivated electrodes.