Anion-incorporation model proposed for interpreting the interfacial physical origin of the faradaic pseudocapacitance observed on anodized valve metals--with anodized titanium in fluoride-containing perchloric acid as an example.
Anion-incorporation model proposed for interpreting the interfacial physical origin of the faradaic pseudocapacitance observed on anodized valve metals--with anodized titanium in fluoride-containing perchloric acid as an example.
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DOI：
10.1021/la9036869
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发表时间：
2010-01
期刊：
影响因子：
--
通讯作者：
Desheng Kong
中科院分区：
文献类型：
--
作者：
Desheng Kong
本文以含氟高氯酸溶液中的阳极化钛为例，首次解释了低频电化学阻抗谱（EIS）中常见的法拉第赝电容C（0）的物理来源，即某些电解质阴离子（即，F（-）-离子）在薄膜生长过程中在电场作用下进入氧化膜。结果表明，法拉第赝电容行为的出现，不仅表明了显着的纳入到氧化物膜的阴离子，但也反映了他们在金属/氧化物界面的到来。阴离子的掺入/转移过程用改进的点缺陷模型描述，并通过阻塞、受限有限长度扩散阻抗模型（已广泛用于研究离子插入电极）来模拟。掺入的电解质物质的快速向内迁移，沿着它们在金属/膜界面处的积累（由于该界面的阻挡效应），是负责由在阀金属上阳极生长的氧化膜的低频下的EIS谱中的垂直电容线揭示的低频电容行为。阳极氧化阀金属（如Ti、Bi、Ta、Al等）的许多相关已发表结果与模型预测一致。本工作还表明，电化学方法制备F（-）掺杂的TiO（2）薄膜材料应该是一种简单，低成本，甚至更有效的一种使用。
With anodized titanium in fluoride-containing perchloric acid solution as an example in the present Article, the physical origin of the faradaic pseudocapacitance C(0) frequently observed in electrochemical impedance spectroscopy (EIS) spectra at low frequencies was interpreted for the first time by the incorporation/insertion of some electrolyte anions (i.e., F(-)-ions in this work) into the oxide film under the electric field during film growth. It was shown that the emergence of the faradaic pseudocapacitive behavior not only indicates a significant incorporation of anions into the oxide films but also reflects the arrival of them at the metal/oxide interface. The anion incorporation/transfer process was depicted with a modified point-defect model and simulated by a blocking, restricted finite-length diffusion impedance model (which has been widely used for studying the ion-insertion electrodes). The fast inward migration of the incorporated electrolyte species, along with the accumulation of them at the metal/film interface (due to the blocking effect of this interface), is responsible for the low-frequency capacitance behavior revealed by a vertical capacitive line in EIS spectra at low frequencies for anodically growing oxide films on valve metals. Many related published results for anodized valve metals (such as Ti, Bi, Ta, Al, etc.) are in good accordance with the model predictions. This work also suggests that the electrochemical method for the preparation of F(-)-doped TiO(2) thin film materials should be an easy, low-cost, and even more effective one to be used.