Anodized ZnO nanostructures for photoelectrochemical water splitting

Mao Chia Huang, Tsinghai Wang, Bin Jui Wu, Jing Chie Lin, Ching Chen Wu

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25 Scopus citations

Abstract

Zinc oxide (ZnO) nanostructures were fabricated on the polished zinc foil by anodic deposition in an alkaline solution containing 1.0 M NaOH and 0.25 M Zn(NO 3 ) 2 . Potentiostatic anodization was conducted at two potentials (-0.7 V in the passive region and -1.0 V in the active region vs. SCE) which are higher than the open circuit potential (-1.03 V vs. SCE) and as-obtained ZnO nanostrcutures were investigated focusing on their structural, optical, electrical and photoelectrochemical (PEC) characteristics. All samples were confirmed ZnO by X-ray photoelectron spectroscopy and Raman spectra. Observations in the SEM images clearly showed that ZnO nanostructures prepared at -0.7 V vs. SCE were composed of nanowires at while those obtained at -1.0 V vs. SCE possessed nanosheets morphology. Result from transmission electron microscope and X-ray diffraction patterns suggested that the ZnO nanowires belonged to single crystalline with a preferred orientation of (0 0 2) whereas the ZnO nanosheets were polycrystalline. Following PEC experiments indicated that ZnO nanowires had higher photocurrent density of 0.32 mA/cm 2 at 0.5 V vs. SCE under 100 mW/cm 2 illumination. This value was about 1.9 times higher than that of ZnO nanosheets. Observed higher photocurrent was likely due to the single crystalline, preferred (0 0 2) orientation, higher carrier concentration and lower charge transfer resistance.

Original languageEnglish
Pages (from-to)442-450
Number of pages9
JournalApplied Surface Science
Volume360
DOIs
StatePublished - 1 Jan 2016

Keywords

  • Electrochemical anodic deposition
  • Photoelectrochemical water splitting
  • ZnO

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