Dynamic Electrochemical Impedance Spectroscopy (DEIS) as a Tool for Analyzing Surface Oxidation Processes on Boron-Doped Diamond Electrodes

Abstract

Surface oxidation processes play a key role in understanding electrochemical properties of boron-doped diamond (BDD) electrodes. The type of surface termination groups, which create the potential window of electrolytic water stability or hydrophobicity, influences such properties. In this study the kinetics of oxidation process under anodic polarization were studied in situ by means of Dynamic Electrochemical Impedance Spectroscopy (DEIS) technique. This novel approach allows for obtaining the impedance data for nonstationary systems. It has been proven that for [B] dopant level of 10k ppm, polarization to 1.5 V vs. Ag|AgCl is sufficient to initiate transformation of the film terminating BDD electrodes. XPS analysis and wettability measurements confirmed oxidation under given conditions. Boron-doped diamond (BDD) electrodes have been recently studied in-depth because of their outstanding electrochemical features which include a wide electrochemical potential window in aqueous electrolytes, 1 high anodic stability, 2 and particular electrochemical stability in harsh environments. 3,4 These properties make BDD a useful electrode material for applications in wastewater treatment, 5-7 electrochemical sensing 8-11 and electrocatalysis. 12-14 BDD is mostly synthesized by hot-filament CVD (HF CVD) 15,16 or microwave plasma-assisted CVD (MW PA CVD) and in situ doped with boron precursors. 17 The boron dopant density influences not only the electrical properties of electrode, but also its morphology and structure (sp 3 /sp 2 ratio). 6,18,19 Nevertheless, the electrochemical behavior of BDD depends on these properties. 20,21 Boron concentration has impact on the electrochemical and electrical properties of BDD electrodes. The final density of boron dopant, achieved by using microwave plasma-assisted chemical vapor deposition (MW PA CVD), ranges from 10 16 to 10 21 atomsccm −3 , for the dopant density of 2 · 10 20 the p-type semiconducting material transform to semimetal. 5 The processes occurring on the BDD semiconducting electrodes are irreversible. 22 The potential window of electrolytic water stability rises with increasing dopant concentration. Not only the dopant level but also the surface termination type (hydrogen and oxygen 23-25 and other compounds added during plasma etching, i.e. CF 4 , Cl 2 , Ar and CH 4 26 ) of boron-doped diamond electrodes is an important factor in the electrode kinetics 27 and its reversibility. 28 Many kinds of surface treatment can be utilized, including dry and wet processes such as plasma treatment or electrochemical polarization. Recently, many investigators focus on hydrogen terminations (HT-BDD) and oxygen terminations (OT-BDD). BDD films deposited by microwave plasmaassisted chemical vapor deposition mainly present HT-BDD due to using hydrogen plasma. 6,11 Transformation of HT-BDD to OT-BDD is worthy of interest. It can be achieved by oxygen plasma treatments, chemical oxidation or anodic polarization. 29,30 As a result of such transformation, different combinations of bonds can be ...

Melamine‐modified Boron‐doped Diamond towards Enhanced Detection of Adenine, Guanine and Caffeine

“…Finally, the last peak used in deconvolution of the spectra is located at 287.5 eV and corresponds mostly to CN bonds. Such a fitting procedure and is in good agreement with the literature review and earlier studies carried out by authors 37, 42–44. The N1s peak was deconvoluted by using two sub‐peaks originating from different bonds between the carbon and nitrogen atoms, namely, CN and NH 2 , located at 398.1 eV and 400.0 eV, respectively.…”

“…BDD electrodes were deposited in an MW PA CVD system on p‐type Si substrates with (111) orientation. The fabrication process of boron‐doped diamond films can be found elsewhere 37. The multi‐step pre‐treatment of the deposited Si/BDD electrodes was applied to obtain H‐terminated surface and etch sp 2 phase impurities, as reported elsewhere 38–40.…”

Poly-l-lysine-modified boron-doped diamond electrodes for the amperometric detection of nucleic acid bases

“…The interpretation of the peaks has been summarized in Table 1. Additionally, a partial change in the surface termination type of BDD electrode (oxidation) under chemical or electrochemical conditions occurred as a shift by +0.6 eV with respect to the main C1s peak [65], which can also be a part of the peak visible at 284.8 eV. The peak attributed to the C-NH bonds overlaps with the peak assigned to the C-O bonds in poly-L-lysine film.…”

Multifrequency nanoscale impedance microscopy (m-NIM): A novel approach towards detection of selective and subtle modifications on the surface of polycrystalline boron-doped diamond electrodes

“…Hydrogen-terminated (HT-) electrodes are hydrophobic, non-polar and possess high electric conductivity [46][47][48] in contrast to hydrophilic oxygen-terminated (OT-) electrodes whose conductivity is also significantly decreased [46,48,49]. A large difference in conductivity results from the acceptor role of hydrogen atoms [21]. Also, the potential window is much wider for OT-electrodes compared to HT-BDD, shifting the energy bands to lower values [21,50,51].…”