Department of Chemistry, Keio University, 3-14-1 Hiyoshi, Yokohama223-8522, Japan.
Anal Chem. 2022 Dec 6;94(48):16831-16837. doi: 10.1021/acs.analchem.2c03923. Epub 2022 Nov 21.
As a working electrode, boron-doped diamond (BDD) has been studied in detail in electrochemical processes because of its superior electrochemical properties. However, these characteristics have rarely been mentioned when BDD is used as a quasi-reference electrode (QRE). Herein, we conducted a systematic investigation on BDD electrodes, with different boron-doping levels (1 and 0.1%) and different surface terminations (hydrogen and oxygen) for their application as a QRE. A BDD electrode with 1% boron and a hydrogen-terminated surface achieved the best stability. Its open-circuit potential (OCP) exhibited less than 100 mV of potential drift over 6000 s and showed a minuscule half-wave potential difference () of 0.0037 V in 0.1 mM K[Fe(CN)]/1 M KCl solution before and after the OCP measurement. Based on these observations, anions are found to contribute to the potential, which we preliminarily speculate as related to the capacitance caused by electrostatic adsorption on the positively charged hydrogen-terminated surface. The repeatability of measurement was verified through continuous cyclic voltammetry tests in 0.1 mM K[Fe(CN)]/1 M KCl, showing a maximum difference of 0.042 V. The contribution of the redox couples was excluded, and the repeatability was considered to originate from its surface stability. Finally, a linear response of the optimized BDD as a QRE was validated ( > 0.99) by determination of free chlorine and dopamine concentrations, respectively. These results consolidate the existing fundamental research on BDD electrodes and promote the possibility of its application as a QRE in harsh environments or biological monitoring.
作为工作电极，由于硼掺杂金刚石（BDD）具有优异的电化学性能，因此在电化学过程中对其进行了详细研究。然而，当 BDD 用作准参比电极（QRE）时，很少提及这些特性。在此，我们对具有不同硼掺杂水平（1%和 0.1%）和不同表面终止（氢和氧）的 BDD 电极进行了系统研究，以将其用作 QRE。具有 1%硼和氢终止表面的 BDD 电极具有最佳的稳定性。其开路电位（OCP）在 6000 秒内漂移小于 100 mV，并且在 OCP 测量前后在 0.1 mM K[Fe(CN)]/1 M KCl 溶液中显示出微小的半波电位差（）为 0.0037 V。基于这些观察结果，发现阴离子对电位有贡献，我们初步推测这与带正电荷的氢终止表面上静电吸附引起的电容有关。通过在 0.1 mM K[Fe(CN)]/1 M KCl 中连续循环伏安测试验证了测量的重复性，最大差异为 0.042 V。排除了氧化还原对的贡献，并且认为重复性源自其表面稳定性。最后，通过确定游离氯和多巴胺的浓度，验证了优化后的 BDD 作为 QRE 的线性响应（> 0.99）。这些结果巩固了 BDD 电极的现有基础研究，并促进了其在恶劣环境或生物监测中作为 QRE 的应用可能性。
