Hydrothermal synthesis and photocatalytic properties of bismuth molybdate materials

The three kinds of well-known bismuth molybdates α-Bi2Mo3O12, β-Bi2Mo2O9, and γ-Bi2MoO6 have been prepared employing mild hydrothermal methods. By tuning the Bi/Mo ratio and pH values, controlling formation of bismuth molybdates can be achieved. Low pH and high concentration of molybdenum lead to the formation of α-Bi2Mo3O12. High pH and high concentration of bismuth lead to the formation of γ-Bi2MoO6. The pure form of the β-phase can be prepared by calcining the hydrothermal product at 560 °C. Photophysical and photocatalytic studies show that Aurivillius structure γ-Bi2MoO6 shows an intense absorption band in the visible light region and better photocatalytic activity than α-Bi2Mo3O12 and β-Bi2Mo2O9 under visible light irradiation. The factors that result in different photocatalytic activities for three kinds of photocatalysts are discussed.