Effect of oxygen terminated surface of boron-doped diamond thin-film electrode on seawater salinity sensing

Tremendous demands for highly sensitive and stable seawater salinometers have motivated intensive research on advanced electrode materials. Boron-doped diamond (BDD) is attractive in terms of its high mechanical stability and chemical inertness, but is usually hindered by its low double-layer capacitance (C-dl) for seawater salinity detection. Here, inspired by the principle of oxygen-terminated BDD electrode endowing higher C-dl than hydrogen-terminated surface, we introduce the oxygen terminated surface by oxygen plasma or reactive ion etch (RIE), and the fabricated oxygen terminated BDD electrodes demonstrate high sensitivity and long-term stability in seawater salinity detection comparing with the hydrogen terminated BDD electrodes. Significantly, the as-fabricated O-BDD-RIE electrodes not only show remarkable enhanced response even better than the commercial platinum black electrodes but also display long-time stability which is weekly verified by continuous monitor for 90 days. The outstanding performance of the oxygen terminated BDD electrodes can be ascribed to the enhancement of C-O surface functional group on C-dl. In addition, a comprehensive analysis of effective electroactive surface area (EASA) and C-dl proves that the surface oxygen is the major factor for the improved C-dl. In summary, the excellent oxygen terminated BDD electrodes promise potential application in seawater salinity detection. (C) 2021 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.