Electrochemistry at Back-Gated, Ultrathin ZnO Electrodes: Field-Effect Modulation of Heterogeneous Electron Transfer Rate Constants by 30× with Enhanced Gate Capacitance

Yuxin Wang, Yan Wang, C. Daniel Frisbie

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

We report steady-state voltammetry of outer-sphere redox species at back-gated ultrathin ZnO working electrodes in order to determine electron transfer rate constants kET as a function of independently controlled gate bias, VG. We demonstrate that kET can be modulated as much as 30-fold by application of VG ≤ 8 V. The key to this demonstration was integrating the ultrathin (5 nm) ZnO on a high dielectric constant (k) insulator, HfO2 (30 nm), which was grown on a Pd metal gate. The high-k HfO2 dramatically decreased the required VG values and increased the gate-induced charge in ZnO compared to previous studies. Importantly, the enhanced gating power of the Pd/HfO2/ZnO stack meant it was possible to observe a nonmonotonic dependence of kET on VG, which reflects the inherent density of redox acceptor states in solution. This work adds to the growing body of literature demonstrating that electrochemical kinetics (i.e., rate constants and overpotentials) at ultrathin working electrodes can be tuned by VG, independent of the conventional electrochemical working electrode potential.

Original languageEnglish (US)
JournalACS Applied Materials and Interfaces
DOIs
StatePublished - 2023

Bibliographical note

Funding Information:
This work was primarily supported by the Department of Energy, Basic Energy Sciences Catalysis Program (DE-SC0021163). Parts of the work were carried out in the Characterization Facility at University of Minnesota, which is partially supported by the NSF through the MRSEC program (DMR-2011401). Other portions of this work were conducted in the Minnesota Nano Center, which is supported by the NSF through the National Nano Coordinated Infra-structure Network (NNCI) under Award Number ECCS-2025124. The authors thank Jiazhen Xu for help with AFM measurements.

Publisher Copyright:
© 2023 American Chemical Society.

Keywords

  • atomic layer deposition
  • electrochemical kinetics
  • field effect
  • heterogeneous charge transfer
  • high-k dielectric
  • semiconductor electrode
  • voltammogram

MRSEC Support

  • Shared

PubMed: MeSH publication types

  • Journal Article

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