Induced Aqueous Synthesis of Metastable β-Bi₂O₃ Microcrystals for Visible-Light Photocatalyst Study

Metastable β-Bi 2 O 3 microcrystals were fast prepared from Bi(NO 3 ) 3 by an aqueous crystallization strategy without further calcination or other complex treatment. Powder X-ray diffraction, field emission scanning electron microscopy, and optical microscopy were used to characterize the obtained samples and reveal the evolution process of β-Bi 2 O 3 crystals. It was found in the experiments that the introduction of cetyltrimethylammonium bromide (actually Br – ions) facilitated the formation of β-Bi 2 O 3 crystals. Photocatalytic activities of metastable β-Bi 2 O 3 samples under visible-light irradiation were investigated by taking the degradation of rhodamine B (RhB) as a probe reaction. The as-prepared β-Bi 2 O 3 crystals showed excellent photocatalytic efficiency of up to 77.9% (total removal 97.2%) in 2 h of irradiation under visible light; the efficiency underwent no noticeable reduction for four cycles of degradation. A minor amount of BiOCl crystallites appearing at the surface of β-Bi 2 O 3 crystals during degradation process facilitated the photocatalytic properties of the catalysts. A combined photocatalytic mechanism of direct photoexcitation and indirect dye photosensitization was proposed in our work for RhB degradation under visible light.