Solvothermal synthesis of novel hierarchical Bi4O5I2 nanoflakes with highly visible light photocatalytic performance for the degradation of 4-tert-butylphenol

A facile solvothermal route is successfully developed to synthesize Bi 4 O 5 I 2 , a novel I-poor bismuth oxyiodide, with hierarchical nanoflake structure. The composition, structure, morphology, formation mechanism, photoabsorption, energy band, and photocatalytic properties of this material are systematically investigated. The results reveal that highly pure Bi 4 O 5 I 2 can be easily obtained by reacting Bi 3+ , I − , and OH − at pH values of 6 to 10 under solvothermal conditions, and the formation of such hierarchical structure can be explained by a dissolution–recrystallization mechanism. The as-synthesized Bi 4 O 5 I 2 nanoflakes show a favorable energy band structure (bandgap energy 2.17   eV, conduction band edge potential is more negative than the reduction potential of superoxide radicals), a high specific surface area (38.6   m 2   g −1 ), and a hierarchical micro/nano structures. Thus, they exhibit superior photocatalytic and mineralization efficiency for the degradation of 4- tert -butylphenol (PTBP, a representative alkylphenol) under visible light irradiation, with a reaction rate is 6.8 and 57 times faster than that of BiOI microspheres and N-doped TiO 2 , respectively. The photogenerated reactive species and degradation intermediates are identified, and possible photocatalytic mechanism is proposed. What's more, the as-synthesized Bi 4 O 5 I 2 nanoflakes remain stable during the photocatalytic reaction and can be used repeatedly, revealing their promising applications in the treatment of organic wastewaters.