Herein, we fabricated hydroxyl groups decorated Bi 4 O 5 I 2 nanosheets, and the contents of hydroxyl groups on the surface could be controlled by changing the reducibility of organic solvents. The stronger reducibility of organic solvents, the more hydroxyl groups on the surface. The hydroxyl groups on the surface of Bi 4 O 5 I 2 nanosheets have significant effects on photocatalytic activity. For degradation of organic pollutants, the surface hydroxyls form hydrogen bonds with organic pollutants, which is conducive to the adsorption of the substrates. For NO removal, the NO adsorbed on the hydroxyl groups is more oxidized into a toxic by-product NO 2 instead of NO 3 - , so less hydroxyl groups are important for photocatalysts towards NO removal. These new discoveries provide new insights to improve photocatalytic activities by modulating surface functional groups of photocatalysts.
Xin Xiao,Chunlan Xing,Guangping He,Xiaoxi Zuo,Junmin Nan,Lishi Wang
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.
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