Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
Anal Chem. 2010 Mar 1;82(5):2020-8. doi: 10.1021/ac902753x.
Electrode fouling decreases sensitivity and can be a substantial limitation in electrochemical experiments. In this work we describe an electrochemical procedure that constantly renews the surface of a carbon microelectrode using periodic triangle voltage excursions to an extended anodic potential at a scan rate of 400 V s(-1). This methodology allows for the regeneration of an electrochemically active surface and restores electrode sensitivity degraded by irreversible adsorption of chemical species. We show that repeated voltammetric sweeps to moderate potentials in aqueous solution causes oxidative etching of carbon thereby constantly renewing the electrochemically active surface. Oxidative etching was established by tracking surface-localized fluorine atoms with XPS, by monitoring changes in carbon surface morphology with AFM on pyrolyzed photoresist films, and also by optical and electron microscopy. The use of waveforms with extended anodic potentials showed substantial increases in sensitivity toward the detection of catechols. This enhancement arose from the adsorption of the catechol moiety that could be maintained with a constant regeneration of the electrode surface. We also demonstrate that application of the extended waveform could restore the sensitivity of carbon microelectrodes diminished by irreversible adsorption (electrode fouling) of byproducts resulting from the electrooxidation and polymerization of tyramine. Overall, this work brings new insight into the factors that affect electrochemical processes at carbon electrodes and provides a simple method to remove or reduce fouling problems associated with many electrochemical experiments.
电极污垢会降低灵敏度，在电化学实验中会成为一个很大的限制。在这项工作中，我们描述了一种电化学方法，该方法使用周期性的三角电压脉冲将扫描速率提高到 400 V s(-1)，将碳微电极的表面不断更新到扩展的阳极电势。这种方法允许再生电化学活性表面，并恢复因化学物质不可逆吸附而降低的电极灵敏度。我们表明，在水溶液中反复进行中等电位的伏安扫描会导致碳的氧化刻蚀，从而不断更新电化学活性表面。通过 XPS 跟踪表面定位的氟原子、通过监测热解光致抗蚀剂薄膜的碳表面形貌变化的 AFM、以及通过光学和电子显微镜，证明了氧化刻蚀的存在。使用具有扩展阳极电势的波形显示出对儿茶酚检测的灵敏度有显著提高。这种增强来自于儿茶酚部分的吸附，通过电极表面的不断再生可以维持这种吸附。我们还证明，扩展波形的应用可以恢复由于电氧化和酪胺聚合产生的副产物不可逆吸附（电极污垢）而降低的碳微电极的灵敏度。总的来说，这项工作深入了解了影响碳电极电化学过程的因素，并提供了一种简单的方法来去除或减少许多电化学实验中与污垢相关的问题。
