Electrochemical Formation and Activation of Hydrogen Peroxide from Water on Fluorinated Tin Oxide for Baeyer-Villiger Oxidation Reactions

Adi Herman, Jenny Lee Mathias, Ronny Neumann

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8 Scopus citations

Abstract

The two-electron oxidation of water (2e-WOR) has been studied in the past as a possible method for the alternative preparation of hydrogen peroxide. Often, fluorinated tin oxide (FTO) is used as an anode and FTO itself was found also to be active for 2e-WOR. Because one use of H2O2is as an oxygen donor for Baeyer-Villiger oxidation of ketones catalyzed by tin compounds and materials, presently we were interested in studying the use of in situ formed H2O2for these reactions. First, the formation of H2O2was verified in an acetonitrile/water solvent in a 2e-WOR reaction, which is more efficient than a comparable reaction in water in terms of the H2O2concentration attained and faradaic efficiency at comparable potentials, that is, ∼3 V vs SHE. Second, initial studies on oxygenation of reactive substrates such as sulfides showed normalized reaction rates (NRRs) for two-electron oxidation reactions that were about 3 times higher than the NRR for H2O2formation, indicating the formation of an active oxygen-donating or oxidizing species on the electrode surface prior to the formation and release of H2O2into solution. Third, the Baeyer-Villiger oxygenation of 2-adamantanone at 2.1 V versus SHE in acetonitrile/water showed both the formation of the expected lactone product and hydroxylation at both tertiary and secondary C-H bonds. Hydroxylation is most easily explained by the presence of hydroxyl radical species as supported by the formation of a spin adduct and its identification by electron paramagnetic resonance. However, the potential used, 2.1 V versus SHE, is an underpotential for the formation of a solvated hydroxyl radical in solution, thereby leading to the conclusion that surface-bound hydroxyl species, OH*, are those that are reactive for the apparent one-electron water oxygenation reaction. Fourth, it was shown that although H2O2can be thermally activated on FTO as a catalyst to a minor degree, electrochemical activation is by far more significant, leading to the use of FTO as an electrochemical catalyst for activation of H2O2for the Baeyer-Villiger oxygenation and also alkene epoxidation.

Original languageEnglish
Pages (from-to)4149-4155
Number of pages7
JournalACS Catalysis
Volume12
Issue number7
DOIs
StatePublished - 1 Apr 2022
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2022 American Chemical Society. All rights reserved.

Funding

This research was supported by the Israel Science Foundation grant 1237/18 and the Bernice and Roger Cohn Catalysis Research Fund. Raanan Carmieli is thanked for the EPR measurements. R.N. is the Rebecca and Israel Sieff Professor of Organic Chemistry.

FundersFunder number
Bernice and Roger Cohn Catalysis Research Fund
Israel Science Foundation1237/18

    Keywords

    • Baeyer-Villiger oxidation
    • electrocatalysis
    • fluorinated tin oxide
    • hydrogen peroxide
    • water oxidation

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