title: Activation of Ultrathin Films of Hematite for Photoelectrochemical Water Splitting via H2 Treatment.
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.
authors: Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6 (Canada).
authors: Jonathon
authors: J
authors: Moir
authors: Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6 (Canada).
authors: Navid
authors: N
authors: Soheilnia
authors: Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6 (Canada).
authors: Kristine
authors: K
authors: Liao
authors: Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6 (Canada).
authors: Paul
authors: P
authors: O'Brien
authors: Department of Physics, University of Toronto, 60 St. George Street, Toronto, Ontario M5S 1A7 (Canada).
authors: Yao
authors: Y
authors: Tian
authors: Department of Physics, Boston College, 140 Commonwealth Avenue, Chestnut Hill, MA 02467-3804 (USA).
authors: Kenneth S
authors: KS
authors: Burch
authors: Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6 (Canada). gozin@chem.utoronto.ca.
authors: Geoffrey A
authors: GA
authors: Ozin
mesh_terms: D004563:Electrochemistry; D005290:Ferric Compounds / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D007700:Kinetics; D010087:Oxides / Q000737:chemistry; D055668:Photochemical Processes; D017785:Photons; D014867:Water / Q000737:chemistry*
chemical_list: D005290:Ferric Compounds; D010087:Oxides; D014867:Water; C000499:ferric oxide; D006859:Hydrogen
keywords: hematite; oxygen vacancies; photoelectrochemistry; surface states; water splitting