Effects of crystal and electronic structures of ANb2O6 (A=Ca, Sr, Ba) metaniobate compounds on their photocatalytic H2 evolution from pure water
✍ Scribed by In-Sun Cho; Shin Tae Bae; Dong Hoe Kim; Kug Sun Hong
- Book ID
- 103832306
- Publisher
- Elsevier Science
- Year
- 2010
- Tongue
- English
- Weight
- 896 KB
- Volume
- 35
- Category
- Article
- ISSN
- 0360-3199
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✦ Synopsis
Hydrogen production a b s t r a c t Alkali-earth metaniobate compounds, ANb 2 O 6 (A ¼ Ca, Sr, Ba), were prepared by the conventional solid-state reaction route and their electronic band structures and photocatalytic activities were investigated. The prepared powders were characterized using X-ray diffraction (XRD), field-emission electron microscopy (FE-SEM), UVevis diffuse reflectance spectroscopy, and fluorescence spectroscopy. It was found that the particle sizes (w1 mm) and BET surface areas (w1 m 2 /g) of the metaniobate compounds were nearly identical. From the electronic band structure calculations, however, the band-gap energies of these metaniobate compounds were found to be in the order of CaNb 2 O 6 > SrNb 2 O 6 > BaNb 2 O 6 . These calculated band-gap energies were consistent with those estimated from the UVevis diffuse reflectance spectra. Moreover, the conductionband edge (reduction potential) of SrNb 2 O 6 calculated from the electronegativity data was higher than those of CaNb 2 O 6 and BaNb 2 O 6 . The photoluminescence spectra revealed that CaNb 2 O 6 exhibited a strong blue luminescence emission (at 300K), while no obvious emissions were observed in either SrNb 2 O 6 or BaNb 2 O 6 . The luminescence behaviors of these metaniobate compounds and their band structure variations originating from their crystal structures play an important role in their photocatalytic activity for the evolution of H 2 from pure water. SrNb 2 O 6 , which has a higher conduction-band edge potential than the other compounds, exhibited higher photocatalytic activity.