Boron-Doped Diamond as a Quasi-Reference Electrode

• Published in: Analytical chemistry (Washington) Vol. 94; no. 48; pp. 16831 - 16837
• Main Authors: Peng, Zhen, Fiorani, Andrea, Akai, Kazumi, Murata, Michio, Otake, Atsushi, Einaga, Yasuaki
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 06.12.2022
• Subjects: Analytical chemistry; Anions; Biomonitoring; Boron; Boron - chemistry; Capacitance; Chemistry; Chlorine; Diamond - chemistry; Diamonds; Dopamine; Electrochemical analysis; Electrochemical Techniques; Electrochemistry; Electrodes; Harsh environments; Hydrogen; Hydrogen - chemistry; In vivo methods and tests; Open circuit voltage; Potassium chloride; Potassium ferricyanide; Redox properties; Reproducibility; Surface stability
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/acs.analchem.2c03923

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 (E 1/2) of 0.0037 V in 0.1 mM K3[Fe­(CN)6]/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 K3[Fe­(CN)6]/1 M KCl, showing a maximum E 1/2 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 (R 2 > 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 in vivo biological monitoring.