Synthesis of Bi3NbO7 nanoparticles with a hollow structure and their photocatalytic activity under visible light

Bi3NbO7 nanoparticles with a hollow structure can be easily prepared by a facile molten-salt technique, where an active precursor is firstly synthesized, and then calcined in KNO3. The crystallization and development of Bi3NbO7 nanoparticles can be effectively controlled by adjusting such processing parameters as calcining temperature, holding time, and incorporated salt quantity. Without adding KNO3, only large-sized and irregular particles can be obtained, having lower crystallinity. Introduction of KNO3 will densify their microstructure and reduce their particle size, enhancing their crystallinity. At a low temperature (400 °C), Bi3NbO7 nanoparticles with a hollow structure can be obtained, exhibiting much better photocatalytic activity under visible light than its normal ones, but the hollow structure is sensitive to calcining temperature; at 500 °C, it completely disappears.

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► Molten salt route to Bi3NbO7 nanoparticles.
► Their hollow structure exhibits better visible-light photocatalytic ability.
► A possible forming mechanism was proposed.