A Study of the Oxidation of Phenol at Platinum and Preoxidized Platinum Surfaces
A Study of the Oxidation of Phenol at Platinum and Preoxidized Platinum Surfaces
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DOI：
10.1149/1.2221598
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发表时间：
1993-06
影响因子：
3.9
通讯作者：
M. Gattrell;D. Kirk
中科院分区：
文献类型：
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作者：
M. Gattrell;D. Kirk
用循环伏安法和计时电流法研究了电极表面氧化物对苯酚氧化反应的影响以及反应产物对铂电极钝化的影响。用X射线光电子能谱检测钝化膜性质的变化。在铂金属电极上，苯酚在内外亥姆霍兹层都发生了反应。内层亥姆霍兹层中的苯酚是不可逆吸附的，并且是导电的。它的氧化包括以大于18eq/mol的z[subef]进行环状断裂。外层亥姆霍兹层反应的特点是快速简单的氧化反应，只涉及反应物分子的最小重排。作者假设苯酚氧化过程中的大部分初始电流是由简单快速的外部亥姆霍兹反应引起的。这一初始电流将持续下去，直到未反应产物的积聚阻止了外部亥姆霍兹反应的进一步进行，而较慢的内层反应占主导地位。如果电极被预氧化，产生一层铂氧化物涂层，这种电极行为就会改变。氧化铂涂层电极的内层反应大大减少，从而降低了钝化电极电流。然而，在氧化物涂层电极上，钝化的开始被推迟。这归因于反应产物在电极表面的吸附较弱，需要额外的反应才能产生稳定的钝化膜。根据X射线光电子能谱分析，最终得到的铂和铂氧化物电极上的钝化膜在化学上是相似的，但在厚度上不同，这表明电极钝化不仅仅是由于钝化膜的厚度。
The effects of electrode surface oxide on the oxidation reactions of phenol and on Pt electrode passivation by reaction products were investigated using cyclic voltammetry and chronoamperometry. X-ray photoelectron spectrometry was used to detect changes in the nature of the passive film. Phenol reacted at both the inner and outer Helmholtz layers at platinum metal electrodes. Phenol in the inner Helmholtz layer is adsorbed irreversibly and is conductive. Its oxidation involves ring cleavage with a z[sub eff] greater than 18 eq/mol. The outer Helmholtz layer reactions are characterized by rapid simple oxidations involving minimal rearrangement of the reactant molecule. The authors postulate that the bulk of the initial current flow during phenol oxidation is due to the simple fast outer Helmholtz reactions. This initial current continues until the buildup of unreactive products blocks further outer Helmholtz reactions and the slower inner layer reactions predominate. This electrode behavior changed if the electrode was preoxidized producing a platinum oxide coating. The inner layer reactions were greatly reduced at a platinum oxide coated electrode resulting in lower passivated electrode current flow. The onset of passivation however, was delayed at the oxide coated electrode. This is attributed to a weaker adsorption of reaction productsmore » at the electrode surface requiring additional reaction to produce a stable passive film. The final resulting passive films at Pt and Pt oxide electrodes were chemically similar based on X-ray photoelectron spectrometric analysis but differed in thickness indicating that the electrode passivation is not due simply to the thickness of the passive film.« less