Conduction and Valence Band Positions of Ta<sub>2</sub>O<sub>5</sub>, TaON, and Ta<sub>3</sub>N<sub>5</sub> by UPS and Electrochemical Methods
Wang‐Jae ChunChemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan, Catalysis Research Center Hokkaido University Sapporo 060-0811, Japan, Surface Chemistry Laboratory, Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako 351-0198, Japan, Department of Applied Chemistry, Faculty of Engineering, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-0862, Japan, and Core Research for Evolutional Science and Technology (CREST), Japan Science andAkio IshikawaChemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan, Catalysis Research Center Hokkaido University Sapporo 060-0811, Japan, Surface Chemistry Laboratory, Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako 351-0198, Japan, Department of Applied Chemistry, Faculty of Engineering, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-0862, Japan, and Core Research for Evolutional Science and Technology (CREST), Japan Science andH. FujisawaChemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan, Catalysis Research Center Hokkaido University Sapporo 060-0811, Japan, Surface Chemistry Laboratory, Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako 351-0198, Japan, Department of Applied Chemistry, Faculty of Engineering, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-0862, Japan, and Core Research for Evolutional Science and Technology (CREST), Japan Science andTsuyoshi TakataChemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan, Catalysis Research Center Hokkaido University Sapporo 060-0811, Japan, Surface Chemistry Laboratory, Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako 351-0198, Japan, Department of Applied Chemistry, Faculty of Engineering, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-0862, Japan, and Core Research for Evolutional Science and Technology (CREST), Japan Science andJunko N. KondoChemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan, Catalysis Research Center Hokkaido University Sapporo 060-0811, Japan, Surface Chemistry Laboratory, Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako 351-0198, Japan, Department of Applied Chemistry, Faculty of Engineering, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-0862, Japan, and Core Research for Evolutional Science and Technology (CREST), Japan Science andMasahiko HaraChemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan, Catalysis Research Center Hokkaido University Sapporo 060-0811, Japan, Surface Chemistry Laboratory, Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako 351-0198, Japan, Department of Applied Chemistry, Faculty of Engineering, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-0862, Japan, and Core Research for Evolutional Science and Technology (CREST), Japan Science andMaki KawaiChemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan, Catalysis Research Center Hokkaido University Sapporo 060-0811, Japan, Surface Chemistry Laboratory, Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako 351-0198, Japan, Department of Applied Chemistry, Faculty of Engineering, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-0862, Japan, and Core Research for Evolutional Science and Technology (CREST), Japan Science andYasumichi MatsumotoChemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan, Catalysis Research Center Hokkaido University Sapporo 060-0811, Japan, Surface Chemistry Laboratory, Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako 351-0198, Japan, Department of Applied Chemistry, Faculty of Engineering, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-0862, Japan, and Core Research for Evolutional Science and Technology (CREST), Japan Science andKazunari DomenChemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan, Catalysis Research Center Hokkaido University Sapporo 060-0811, Japan, Surface Chemistry Laboratory, Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako 351-0198, Japan, Department of Applied Chemistry, Faculty of Engineering, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-0862, Japan, and Core Research for Evolutional Science and Technology (CREST), Japan Science and
2003en
ABI
Аннотация
The conduction and valence band edges for electronic band gaps and Fermi levels are determined for Ta2O5, TaON, and Ta3N5 by ultraviolet photoelectron spectroscopy (UPS) and electrochemical analyses. Reasonable agreement between the results of the two methods is obtained at the pH at which the ζ potentials of the particles are zero. The tops of the valence bands are found to be shifted to higher potential energies on the order Ta2O5 < TaON < Ta3N5, whereas the bottoms of the conduction bands are very similar in the range −0.3 to −0.5 V (vs NHE at pH = 0). From the results, it is concluded that TaON and Ta3N5 are promixing catalysts for the reduction and oxidation of water using visible light in the ranges λ < 520 nm and λ < 600 nm, respectively. It is also demonstrated that the proposed UPS technique is a reliable alternative to electrochemical analyses for determining the absolute band gap positions for materials in aqueous solutions that would otherwise be difficult to measure using electrochemical methods.
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