Electrochemical surface rehydrogenation of boron-doped diamond electrodes after electrochemical polishing

Author(s)

Brocenschi, Ricardo F. ; Irikura, Kallyni ; Wachter, Naihara ; Swain, Greg M. ; Rocha-Filho, Romeu C.

• Document type: Journal article
• Source: DIAMOND AND RELATED MATERIALS; v. 136, p. 13-pg., 2023-05-16.

Abstract

Non-diamond carbon impurity and surface roughness are features that can affect the response of boron-doped diamond (BDD) electrodes. Herein, we report on the electropolishing of BDD electrodes carried out in the presence of acetic and sulfuric acid for different times (1, 2, and 4 h). The wet electrochemical treatment smooths the polycrystalline diamond surface and reduces the non-diamond sp2 carbon impurity content while increasing the surface oxygen content. Changes in surface texture and microstructure were revealed by atomic force mi-croscopy, Raman spectroscopy, and cyclic voltammetry. Subsequently, the surface oxygen content was reduced by increasingly severe cathodic pretreatments (CPTs). This was revealed by changes in the voltametric response for the [Fe(CN)6]3-/4- and ascorbic acid (AA) redox systems, as both exhibit electron transfer kinetics sensitive to the level of oxidation of the BDD surface. For [Fe(CN)6]3-/4-, greater Delta Ep values were obtained for the elec-tropolished (EP-BDD) electrodes, as compared to the as received (AR-BDD) electrode. However, after CPTs the EP-BDD electrodes exhibited smaller Delta Ep values (-60 mV), which indicate significantly improved electro-chemical reversibility and faster electron-transfer kinetics caused by the decreased level of surface oxidation (greater hydrogenation). The increased surface oxygen content brought on by the electropolishing process had also a significant effect on the AA oxidation peak potential (Eap), making it at least-140 mV more positive than that for the AR-BDD electrode. However, after CPTs the Eap values for the EP-BDD electrodes became at least-0.1 V less positive than that for the AR-BDD electrode, indicating that the surface of the EP-BDD electrodes possesses less surface carbon-oxygen functional groups (i.e., it is more hydrogenated). The combination of electropolishing and cathodic pretreatment is a way to process the BDD electrode surface to create a smoother, low oxygen surface in much the same way as a hydrogen plasma treatment does. (AU)

• FAPESP's process: 14/11769-6 - Effect of electrochemical pretreatments on the superficial terminations of boron-doped diamond electrodes and influence of these terminations on the electrochemical response of different redox species
• Grantee: Ricardo Francisco Brocenschi
• Support Opportunities: Scholarships in Brazil - Post-Doctoral