Understanding anodic wear at boron doped diamond film electrodes

Brian P. Chaplin, David K. Hubler, James Farrell

Research output: Contribution to journalArticle

64 Scopus citations

Abstract

This research investigated the mechanisms associated with anodic wear of boron-doped diamond (BDD) film electrodes. Cyclic voltammetry (CV), x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS) were used to measure changes in electrode response and surface chemistry as a function of the charge passed and applied current density. Density functional theory (DFT) modeling was used to evaluate possible reaction mechanisms. The initial hydrogen-terminated surface was electrochemically oxidized at lower potentials than water oxidation (≤ 1.83 V/SHE), and was not catalyzed by the hydrogen-terminated surface. In the region where water oxidation produces hydroxyl radicals (OH), the hydrogen-terminated surface may also be oxidized by chemical reaction with OH. Oxygen atoms became incorporated into the surface via reaction of carbon atoms with OH, forming both C O and C-OH functional groups, that were also detected by XPS measurements. Experimental and DFT modeling results indicate that the oxygenated diamond surface lowers the potential for activationless water oxidation from 2.74 V/SHE for the hydrogen terminated surface to 2.29 V/SHE for the oxygenated surface. Electrode wear was accelerated at high current densities (i.e., 500 mA cm-2), where SEM results indicated oxidation of the BDD film resulted in significant surface roughening. These results are supported by EIS measurements that document an increase in the double-layer capacitance as a function of the charge passed. DFT simulations provide a possible mechanism that explains the observed diamond oxidation. DFT simulation results indicate that BDD edge sites (=CH2) can be converted to COOH functional groups, which are further oxidized via reactions with OH to form H 2CO3(aq.) with an activation energy of 58.9 kJ mol -1.

Original languageEnglish (US)
Pages (from-to)122-131
Number of pages10
JournalElectrochimica Acta
Volume89
DOIs
StatePublished - Feb 1 2013

Keywords

  • Anodic corrosion
  • Boron-doped diamond
  • Density functional theory
  • Ultrananocrystalline

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Electrochemistry

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