Synthesis of mesoporous Nb₂O₅ with crystalline walls and investigation of their photocatalytic activity

抄録

We synthesize various kinds of mesoporous Nb₂O₅ samples by changing surfactants (P123 and Brij 56), followed by calcination (from 400 to 500 and 600°C). The effect of these parameters helps to produce a well-defined mesoporous framework with crystallinity. The mesoporous Nb₂O₅ samples are well characterized by using small-angle X-ray scattering (SAXS) measurements, N₂ adsorption–desorption isotherms, and wide-angle XRD measurements. In a P123 system, the frameworks are well crystallized to the TT-phase (pseudo-hexagonal) by calcination at 500°C with retention of the mesoporous structures. In the Brij 56 system, after calcination at 500°C, the framework is well retained in an amorphous state. It is proved that the thick walls prepared with P123 are easily crystallized in comparison to thin walls prepared with Brij 56. Furthermore, we investigate the photocatalytic activity by using several types of mesoporous Nb₂O₅ prepared with P123. All these mesoporous Nb₂O₅ samples show photocatalytic activity with their decomposition reaction of methylene blue (MB) molecules. It is concluded that the reaction rates depend on their crystallinities in the frameworks, surface areas, and average mesopore sizes.