US EPA

7918240 

Journal Article 

Base-Assisted Nitrate Mediation as the Mechanism of Electrochemical Benzyl Alcohol Oxidation 

Dimeglio, JL; Terry, BD; Breuhaus-Alvarez, AG; Whalen, MJ; Bartlett, BM 

2021 

Yes 

Journal of Physical Chemistry C
ISSN: 1932-7447
EISSN: 1932-7455 

American Chemical Society 

125 

15 

8148-8154 

English 

10.1021/acs.jpcc.0c10476 

WOS:000644438400013 

Nitrate anion (NO3-) oxidation to nitrate radical (NO3-) is chemically irreversible in acetonitrile (MeCN) solvent due to solvent-based hydrogen-atom transfer (HAT). Introducing benzyl alcohol (PhCH2OH) leads to competition with MeCN for electrochemically generated NO3- and affords benzaldehyde (PhCHO) product with ∼80% faradaic efficiency (FE) in 250 mM PhCH2OH. Stoichiometric HNO3 forms during HAT reactions (observed by UV-vis spectroscopy) and exists as an electrochemically inert and weak electrolyte; this off-cycle form of nitrate can be reintroduced to the catalytic cycle upon deprotonation by 2,6-lutidine while maintaining the base-free FE. Oxygen reduction complements nitrate oxidation during catalysis and reduced oxygen species (ROS) generated during proton-coupled oxygen reduction are identified through rotating ring-disk electrochemistry; proton-coupled oxygen reduction indicates ROS are capable of rendering NO3- catalytic when collocal. Directly observing ROS as the stoichiometric base generated during nitrate anion oxidation resolves differences in photocatalytic vs photoelectrochemical reactivity of NO3- in base-free conditions and points toward HAT as the general mode of reactivity for nitrate radical in acetonitrile solutions. © 2021 American Chemical Society.