Hydrothermal preparation and photocatalytic water splitting properties of ZrW₂O₈

Abstract

ZrW₂O₈ was prepared by adjusting Zr:W mole ratio and HCl concentration in hydrothermal reaction processes. The obtained sample was crystallized in α-ZrW₂O₈ phase (cubic, P2₁3), with band gap energy of 4.0 eV. The properties of photocatalytic water splitting were examined under UV light irradiation. The average rate of H₂ evolution over 0.3wt% Pt/ZrW₂O₈ in the presence of CH₃OH as electron donor (ED) was 23.4 μmol/h, while the average rate of O₂ evolution over ZrW₂O₈ in the presence of AgNO₃ as electron scavenger (ES) was 9.8 μ mol/h. Moreover, H₂ was evolved over 0.3wt% Pt/ZrW₂O₈ from pure water splitting at a rate of 5.2 μ mol/h. The study indicated that the band structure of ZrW₂O₈ was suitable for reducing H⁺ to H₂ and oxidizing H₂O to O₂. The band structure and photocatalytic water splitting properties of ZrW₂O₈, different from either ZrO₂ (5.0 eV) or WO₃ (2.7 eV), were attributed to the hybridization of W5d and Zr4d in conduction band (CB) as well as the change in crystal structure.

Keywords

photocatalyst / hydrogen / zirconium tungsten oxide / hydrothermal preparation

References

[1] Fujishima A., Honda K. Electrochemical Photolysis of Water at a Semiconductor Electrode[J]. Nature, 1972, 238(5358): 37-38.

[2] Kudo A. Development of Photocatalyst Materials for Water Splitting[J]. Int. J. Hydrog. Energy, 2006, 31(2): 197-202.

[3] Maeda K., Domen K. New Non-oxide Photocatalysts Designed for Overall Water Splitting Under Visible Light[J]. J. Phys. Chem. C, 2007, 111(22): 7 851-7 861.

[4] Osterloh F. E. Inorganic Materials as Catalysts for Photochemical Splitting of Water[J]. Chem. Mat., 2008, 20(1): 35-54.

[5] Kudo A., Miseki Y. Heterogeneous Photocatalyst Materials for water Splitting[J]. Chem. Soc. Rev., 2009, 38(1): 253-278.

[6] Kato H., Asakura K., Kudo A. Highly Efficient Water Splitting into H₂ and O₂ over Lanthanum-doped NaTaO₃ Photocatalysts with High Crystallinity and Surface Nanostructure[ J]. J. Am. Chem. Soc., 2003, 125(10): 3 082-3 089.

[7] Kato H., Matsudo N., Kudo A. Photophysical and Photocatalytic Properties of Molybdates and Tungstates with a Scheelite Structure[J]. Chem. Lett., 2004, 33(9): 1 216-1 217.

[8] Tang J. W., Zou Z. G., Ye J. H. Photophysical and Photocatalytic Properties of AgInW₂O₈[J]. J. Phys. Chem. B, 2003, 107(51): 14 265-14 269.

[9] Tang J. W., Ye J. H. Correlation of Crystal Structures and Electronic Structures and Photocatalytic Properties of the W-containing Oxides[J]. J. Mat. Chem., 2005, 15(39): 4 246-4 251.

[10] Saito N., Kadowaki H., Kobayashi H., . A New Photocatalyst of RuO₂-loaded PbWO₄ for Overall Splitting of Water[J]. Chem. Lett., 2004, 33(11): 1 452-1 453.

[11] Liu H., Yuan J., Shangguan W. F., . Visible-light-responding BiYWO₆ Solid Solution for Stoichiometric Photocatalytic Water Splitting[J]. J. Phys. Chem. C, 2008, 112(23): 8 521-8 523.

[12] Sayama K., Arakawa H. Photocatalytic Decomposition of Water and Photocatalytic Reduction of Carbon Dioxide over ZrO₂ Catalyst[J]. J. Phys. Chem., 1993, 97(3): 531-533.

[13] Uno M., Kosuga A., Okui M., . Photoelectrochemical Study of Landthanide Zirconium Oxides, Ln₂Zr₂O₇ (Ln=La, Ce, Nd and Sm)[J]. J. Alloy Comp., 2006, 420(1–2): 291-297.

[14] Sutton M. S., Talghader J. Zirconium Tungstate (ZrW₂O₈)-based Micromachined Negative Thermal-expansion Thin Films[J]. J. Microelectromechanical Systems, 2004, 13(4): 688-695.

[15] Xing Q. F., Xing X. R., Yu R. B., . Single Crystal Growth of ZrW₂O₈ by Hydrothermal Route[J]. J. Cryst. Growth, 2005, 283(1–2): 208-214.

[16] Kameswari U., Sleight A. W., Evans J. S. O. Rapid Synthesis of ZrW₂O₈ and Related Phases, and Structure Refinement of ZrWMoO₈[J]. Int. J. Inorg. Mater., 2000, 2(4): 333-337.

[17] Finlayson A. P., Tsaneva V. N., Lyons L. L., . Evaluation of Bi-W-oxides for Visible Light Photocatalysis[J]. Phys. Stat. Sol. (a), 2006, 203(2): 327-335.

[18] Shangguan W. F., Yoshida Y. Influence of Catalyst Structure and Modification on the Photocatalytic Production of Hydrogen from water on Mixed Metal Oxides[J]. Int. J. Hydrog. Energy, 1999, 24: 425-431.

[19] Liu H., Yuan J., Shangguan W. F. Photochemical Reduction and Oxidation of Water Including Sacrificial Reagents and Pt/TiO₂ Catalyst[J]. Energy Fuels, 2006, 20(6): 2 289-2 292.

[20] Ouyang L. H., Xu Y. N., Ching W. Y. Electronic Structure of Cubic and Orthorhombic Phases of ZrW₂O₈[J]. Phys. Rev. B, 2002, 65(11): 113-110.