Date on Master's Thesis/Doctoral Dissertation

8-2011

Document Type

Master's Thesis

Degree Name

M. Eng.

Department

Chemical Engineering

Committee Chair

Sunkara, Mahendra K.

Author's Keywords

Hematite; Water splitting; Photoelectrochemistry; Nanowire; Solar cell; Iron oxide

Subject

Photoelectrochemistry; Hematite; Nanowires

Abstract

Hematite synthesized by low pressure oxygen plasma has been shown previously to exhibit promising characteristics as a photo-anode for a photoelectrochemical water splitting cell. It is cheap, stable and has a 2.1 eV bandgap and exhibits a significant photoactivity due to the presence of a thin interfacial layer and oxygen vacancy planes throughout the sample. Unfortunately, due to the nature of vacuum systems, this process would be difficult to scale-up and as such atmospheric plasma synthesis was explored. Photoactive hematite nanowire arrays were synthesized using an atmospheric microwave plasma jet reactor. They exhibited all of the characteristics of those synthesized under low pressure except for poor photoactivity due to a thin amorphous oxide layer on the surface layer. This oxide layer was removed by hydrofluoric acid etching and subsequently produced a significant photoactivity. Further synthesis improvements have yielded hematite nanowire arrays with no amorphous oxide layer present. Removal of nanowires from the nanowire array decreased the subsequent photoactivity of the electrode, indicating that photoactivity is due to the nanowires present on the sample and not due to the thin interfacial layer. Testing at different light intensities under constant voltage shows that photoactivity of hematite nanowire arrays is linearly dependent on light intensity.

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