Theoretical Insights into Proton-Coupled Electron Transfer from a Photoreduced ZnO Nanocrystal to an Organic Radical

Soumya Ghosh, Janelle Castillo-Lora, Alexander V. Soudackov, James M. Mayer, Sharon Hammes-Schiffer

Research output: Contribution to journalArticlepeer-review

27 Scopus citations

Abstract

Proton-coupled electron transfer (PCET) at metal-oxide nanoparticle interfaces plays a critical role in many photocatalytic reactions and energy conversion processes. Recent experimental studies have shown that photoreduced ZnO nanocrystals react by PCET with organic hydrogen atom acceptors such as the nitroxyl radical TEMPO. Herein, the interfacial PCET rate constant is calculated in the framework of vibronically nonadiabatic PCET theory, which treats the electrons and transferring proton quantum mechanically. The input quantities to the PCET rate constant, including the electronic couplings, are calculated with density functional theory. The computed interfacial PCET rate constant is consistent with the experimentally measured value for this system, providing validation for this PCET theory. In this model, the electron transfers from the conduction band of the ZnO nanocrystal to TEMPO concertedly with proton transfer from a surface oxygen of the ZnO nanocrystal to the oxygen of TEMPO. Moreover, the proton tunneling at the interface is gated by the relatively low-frequency proton donor-acceptor motion between the TEMPO radical and the ZnO nanocrystal. The ZnO nanocrystal and TEMPO are found to contribute similar amounts to the inner-sphere reorganization energy, implicating structural reorganization at the nanocrystal surface. These fundamental mechanistic insights may guide the design of metal-oxide nanocatalysts for a wide range of energy conversion processes.

Original languageEnglish (US)
Pages (from-to)5762-5767
Number of pages6
JournalNano Letters
Volume17
Issue number9
DOIs
StatePublished - Sep 13 2017
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Bioengineering
  • General Chemistry
  • General Materials Science
  • Condensed Matter Physics
  • Mechanical Engineering

Keywords

  • density functional theory
  • nanocrystal
  • nanoparticle
  • proton tunneling
  • Proton-coupled electron transfer
  • zinc oxide

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