Interrogating the Surface Intermediates and Water Oxidation Products of Boron-Doped Diamond Electrodes with Scanning Electrochemical Microscopy

Michael J. Counihan, Worapol Setwipatanachai, Joaquín Rodríguez-López

Research output: Contribution to journalArticle

Abstract

Boron-doped diamond (BDD) electrodes are widely used in electrochemical sensing and water purification owing to their chemical and structural stability under harsh reaction conditions. Water oxidation at BDD electrodes is known to produce reactive oxygen species, but the discharged and surface chemistries involved in these processes have not been studied in depth. Here, we present scanning electrochemical microscopy (SECM) studies of electrogenerated intermediates and products formed on sp2 carbon-containing BDD electrodes that display stark differences in their reactivity as a function of electrolyte type and pH during water oxidation. The most reactive and abundant species discharged from the electrode were observed at pH 11 in sulfate electrolyte. With the surface interrogation mode of SECM, two kinetically distinct surface intermediates were clearly distinguished, with one forming two orders of magnitude faster than the other but displaying a slower desorption rate. The surface coverage of these species was estimated in the range of 4–7×10−5 mol/cm2 for the first, and 3–4.4×10−5 mol/cm2 for the second one. SECM imaging suggested that regions of increased product evolution have decreased electron transfer kinetics and limited surface sites for intermediate binding. This work establishes methods for studying highly reactive intermediates found in BDD and paves the way for the inspection of other interfaces where solvolysis impacts their reactivity and evolution.

Original languageEnglish (US)
Pages (from-to)3507-3515
Number of pages9
JournalChemElectroChem
Volume6
Issue number13
DOIs
StatePublished - Jul 1 2019

Keywords

  • boron-doped diamond
  • reactive intermediates
  • scanning electrochemical microscopy
  • surface chemistry
  • water splitting

ASJC Scopus subject areas

  • Catalysis
  • Electrochemistry

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