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Charge‐Transfer Mechanism in Pt/KTa(Zr)O 3 Photocatalysts Modified with Porphyrinoids for Water Splitting
Author(s) -
Hagiwara Hidehisa,
Inoue Takanori,
Kaneko Kenji,
Ishihara Tatsumi
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200901772
Subject(s) - catalysis , photocatalysis , x ray photoelectron spectroscopy , photoluminescence , water splitting , chemistry , photochemistry , materials science , analytical chemistry (journal) , inorganic chemistry , chemical engineering , organic chemistry , optoelectronics , engineering
The mechanism of photocatalytic splitting of H 2 O into H 2 and O 2 on Pt/KTa(Zr)O 3 modified with various porphyrinoids was investigated. The photocatalytic activity of KTaO 3 catalysts is improved by dye modification. Cyanocobalamin (vitamin B 12 ) is the most effective for improving water‐splitting activity, and the formation rates of H 2 and O 2 achieved values of 575 and 280 μmol g cat. −1 h −1 , respectively. X‐ray photoelectron spectroscopy spectra of KTa(Zr)O 3 photocatalysts showed that Pt loaded onto dye‐modified KTaO 3 was slightly oxidized and had low catalytic activity for the H 2 oxidation reaction. Photoluminescence (PL) spectra of KTaO 3 catalysts suggested that excitation energy was transferred between KTaO 3 , tetraphenylporphyrinatochromium(III) (Cr–TPP), and the Pt cocatalyst. The wavelength dependence of the activity of dye‐modified KTa(Zr)O 3 photocatalysts indicated that excitation of both KTa(Zr)O 3 and the dye was essential for achieving increased photocatalytic activity. This result suggests that two‐step excitation occurred in the dye‐modified KTa(Zr)O 3 photocatalysts. Because the lifetime of the charge‐separated state increased, this study reveals that modification with porphyrinoids is effective for increasing water‐splitting activity.