Three dimensional BiOX (X=Cl, Br and I) hierarchical architectures: facile ionic liquid-assisted solvothermal synthesis and photocatalysis towards organic dye degradation

•High-crystalline hierarchical BiOX (X=Cl, Br and I) microspheres were prepared.•The BiOX (X=Cl, Br and I) microspheres are assembled by numerous interlaced nanosheets.•Choice of solvent plays an important role in determining the BiOI morphologies.•BiOI hierarchical microspheres with smallest band gap exhibited superior photocatalytic efficiency.

High-crystalline hierarchical BiOX (X=Cl, Br and I) microspheres were prepared by a generalized ionic liquid-assisted solvothermal method. The as-prepared BiOX (X=Cl, Br and I) microspheres were uniform in size and the average diameters ranged from one to several micrometers, which were assembled by numerous interlaced nanosheets. According to the UV–Vis diffuse reflectance spectra, the band gaps were calculated to be 3.20, 2.72 and 1.76 eV for the BiOCl, BiOBr and BiOI samples, respectively. Evaluated by the decomposition of methyl orange (MO) solution, the BiOI product exhibited much better photocatalytic efficiency to BiOCl and BiOBr samples, which could respond to more visible light as well as facilitate the spatial transfer of the photoexcited carriers.

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