Real-Time Detection of Hydroxyl Radical Generated at Operating Electrodes via Redox-Active Adduct Formation Using Scanning Electrochemical Microscopy

Jaxiry S. Barroso-Martínez, Adolfo I.B. Romo, Sanja Pudar, Seth T. Putnam, Erika Bustos, Joaquín Rodríguez-López

Research output: Contribution to journalArticlepeer-review

Abstract

The hydroxyl radical (OH) is one of the most attractive reactive oxygen species due to its high oxidation power and its clean (photo)(electro)generation from water, leaving no residues and creating new prospects for efficient wastewater treatment and electrosynthesis. Unfortunately, in situ detection of OH is challenging due to its short lifetime (few ns). Using lifetime-extending spin traps, such as 5,5-dimethyl-1-pyrroline N-oxide (DMPO) to generate the [DMPO-OH]adduct in combination with electron spin resonance (ESR), allows unambiguous determination of its presence in solution. However, this method is cumbersome and lacks the necessary sensitivity and versatility to explore and quantify OH generation dynamics at electrode surfaces in real time. Here, we identify that [DMPO-OH]is redox-active with E0= 0.85 V vs Ag|AgCl and can be conveniently detected on Au and C ultramicroelectrodes. Using scanning electrochemical microscopy (SECM), a four-electrode technique capable of collecting the freshly generated [DMPO-OH]from near the electrode surface, we detected its generation in real time from operating electrodes. We also generated images of [DMPO-OH]production and estimated and compared its generation efficiency at various electrodes (boron-doped diamond, tin oxide, titanium foil, glassy carbon, platinum, and lead oxide). Density functional calculations, ESR measurements, and bulk calibration using the Fenton reaction helped us unambiguously identify [DMPO-OH]as the source of redox activity. We hope these findings will encourage the rapid, inexpensive, and quantitative detection of OH for conducting informed explorations of its role in mediated oxidation processes at electrode surfaces for energy, environmental, and synthetic applications.

Original languageEnglish (US)
Pages (from-to)18896-18907
Number of pages12
JournalJournal of the American Chemical Society
Volume144
Issue number41
DOIs
StatePublished - Oct 19 2022

ASJC Scopus subject areas

  • General Chemistry
  • Biochemistry
  • Catalysis
  • Colloid and Surface Chemistry

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