Lightly Fluorinated Graphene as a Protective Layer for n-Type Si(111) Photoanodes in Aqueous Electrolytes

Adam C. Nielander, Annelise C. Thompson, Christopher W. Roske, Jacqueline A. Maslyn, Yufeng Hao, Noah T. Plymale, James Hone, Nathan S Lewis

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Abstract

The behavior of n-Si(111) photoanodes covered by monolayer sheets of fluorinated graphene (F-Gr) was investigated under a range of chemical and electrochemical conditions. The electrochemical behavior of n-Si/F-Gr and np+-Si/F-Gr photoanodes was compared to hydride-terminated n-Si (n-Si-H) and np+-Si-H electrodes in contact with aqueous Fe(CN)6 3-/4- and Br2/HBr electrolytes as well as in contact with a series of outer-sphere, one-electron redox couples in nonaqueous electrolytes. Illuminated n-Si/F-Gr and np+-Si/F-Gr electrodes in contact with an aqueous K3(Fe(CN)6/K4(Fe(CN)6 solutions exhibited stable short-circuit photocurrent densities of ∼10 mA cm-2 for 100,000 s (>24 h), in comparison to bare Si electrodes, which yielded nearly a complete photocurrent decay over ∼100 s. X-ray photoelectron spectra collected before and after exposure to aqueous anodic conditions showed that oxide formation at the Si surface was significantly inhibited for Si electrodes coated with F-Gr relative to bare Si electrodes exposed to the same conditions. The variation of the open-circuit potential for n-Si/F-Gr in contact with a series of nonaqueous electrolytes of varying reduction potential indicated that the n-Si/F-Gr did not form a buried junction with respect to the solution contact. Further, illuminated n-Si/F-Gr electrodes in contact with Br2/HBr(aq) were significantly more electrochemically stable than n-Si-H electrodes, and n-Si/F-Gr electrodes coupled to a Pt catalyst exhibited ideal regenerative cell efficiencies of up to 5% for the oxidation of Br- to Br2.

Original languageEnglish
Pages (from-to)4082-4086
Number of pages5
JournalNano Letters
Volume16
Issue number7
DOIs
Publication statusPublished - Jul 13 2016

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Keywords

  • 2D materials
  • anticorrosion
  • graphene
  • Photoelectrochemistry
  • solar energy conversion

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Mechanical Engineering

Cite this

Nielander, A. C., Thompson, A. C., Roske, C. W., Maslyn, J. A., Hao, Y., Plymale, N. T., Hone, J., & Lewis, N. S. (2016). Lightly Fluorinated Graphene as a Protective Layer for n-Type Si(111) Photoanodes in Aqueous Electrolytes. Nano Letters, 16(7), 4082-4086. https://doi.org/10.1021/acs.nanolett.6b00773