The voltammetric response of nanometer-sized carbon electrodes
The voltammetric response of nanometer-sized carbon electrodes
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DOI：
10.1021/jp025847r
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发表时间：
2002-09-12
影响因子：
3.3
通讯作者：
Kucernak, A
中科院分区：
文献类型：
--
作者：
Chen, SL;Kucernak, A
采用电化学腐蚀碳纤维和电泳漆沉积的方法制备了纳米碳电极。这些电极的特征在于与稳态伏安法使用一系列的氧化还原探针。选择这些氧化还原探针是因为它们显示出一系列形式电位和动力学速率常数（0），并且带电程度不同。这些电极在支持电解质的存在和不存在下的伏安响应进行了研究。在支持电解质的存在下，明确定义的稳态伏安曲线的S形形状已获得电极上的有效半径小至1纳米。然而，在没有支持电解质的情况下，伏安行为随氧化还原体系而变化。当电极小于20 nm时，观察到与预期的迁移-扩散响应的偏差，用于还原多电荷阳离子物种六金属钌（III）（Ru（NH3）（6）（3+））。偏离理想的迁移耦合扩散行为表现在电极上，即使是微米尺寸的多电荷的六氰基铁（III）的阴离子（Fe（CN）（6）（3-）），它具有一个中等的还原电位和相对较低的k（0）的还原过程中。对于六氰基铁（II）阴离子（Fe（CN）（6）（4-））的氧化也观察到这种效应。相比之下，具有更高k（0）和更正还原电位的六氯铱酸盐（IV）阴离子（IrCl 62-）显示出与六氨合钌（III）所见的偏差类似的偏差;即，直到电极尺寸小于CA，才观察到与预期行为的偏离。20纳米。认为动态扩散双层效应而不是弗鲁姆金效应是观察到的非理想行为的主要来源。结果表明，即使当电极反应是可逆或准可逆的时，动态扩散双层效应也可以起作用，并且在非常小的电极上变得更加明显。讨论了纳米尺寸电极上伏安响应的尺寸效应的性质。
Carbon electrodes of nanometer size have been fabricated by electrochemical etching of carbon fibers followed by deposition of electrophoretic paint. These electrodes have been characterized with steady-state voltammetry using a range of redox probes. These redox probes were chosen because they show a range of formal potentials and kinetic rate constants (0) and are charged to different extents. The voltammetric response of these electrodes in both the presence and absence of supporting electrolyte has been investigated. In the presence of supporting electrolyte, well-defined steady-state voltammograms of sigmoidal shape have been obtained on electrodes with effective radii as small as 1 nm. In the absence of supporting electrolyte, however, the voltammetric behavior varies with the redox system. Deviation from the expected migration-diffusion response is observed when the electrode is smaller than 20 nm for the reduction of the multicharged cationic species hexammineruthenium(III) (Ru(NH3)(6)(3+)). Deviation from the ideal behavior of migration-coupled diffusion is exhibited at electrodes even of micrometer size during the reduction of the multicharged hexacyanoferrate(III) anion (Fe(CN)(6)(3-)), which has a median reduction potential and relatively low k(0). Such an effect is also observed for the oxidation of the hexacyanoferrate(II) anion (Fe(CN)(6)(4-)). In comparison, the hexachloroiridate(IV) anion (IrCl62-), with a higher k(0) and more positive reduction potential, shows deviations similar to those seen for hexaammineruthenium(III); i.e., no deviation from expected behavior is seen until the electrode size is less than ca. 20 nm. It is argued that the dynamic diffuse double-layer effect rather than the Frumkin effect is the major source of the observed nonideal behavior, The results indicate that the dynamic diffuse double-layer effect can function even when the electrode reaction is reversible or quasi-reversible and becomes more pronounced at very small electrodes. The nature of size effects on the voltammetric response at nanometer size electrodes are discussed.