Activation of Ultrathin Films of Hematite for Photoelectrochemical Water Splitting via H2 Treatment.
ChemSusChem
; 8(9): 1557-67, 2015 May 11.
Article
em En
| MEDLINE
| ID: mdl-25650837
ABSTRACT
Thermal treatment of ultrathin films of hematite (α-Fe2 O3 ) under an atmosphere of 5 % H2 in Ar is presented as a means of activating α-Fe2 O3 towards the photoelectrochemical splitting of water. Spin-coated films annealed in air exhibited no photoactivity, whereas films treated in hydrogen exhibited a photocurrent response. X-ray photoelectron spectroscopy and UV/Vis absorption spectroscopy results showed that the H2 -treated films contain oxygen vacancies, which suggests improved charge transport. However, Tafel slopes, scan-rate dependent measurements, and kinetic analyses performed by using H2 O2 as a hole scavenger suggested that surface modification may also contribute to their induced photoactivity. Electrochemical impedance spectroscopy results revealed the buildup of a surface trap capacitance at the point of photocurrent onset for the hydrogen-treated films under illumination. A decrease in charge trapping resistance was also observed, which suggests improved transport of charges away from the surface.
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MEDLINE
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Água
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Compostos Férricos
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Hidrogênio
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En
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2015
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Article