Synthesis And Photocatalytic Properties Of Spherical Iodine Oxide Nanostructures

Bismuth based oxyhalides is a novel semiconductor photocatalytic materials, which have been extensively investigated because of their unique layered structure with atoms arranged and therefore exhibit excellent photocatalytic activity. Among them, bismuth oxyiodide ?BiOI? is regarded as a promising visible light photocatalytic materials and become a hotspot in the research of photocatalysis for the smallest band gap ?Eg=1.8 eV? and great photocatalytic performance under visible irradiation. In this paper, pure spherical BiOI nanostructure were prepared by the EG-assisted solvothermal method using Bi?NO₃?₃·5H₂O and KI as raw materials, Er³⁺ -doped BiOI powders were synthesized using Er?NO₃?₃·6H₂O as an erbium source, porous Bi₅O₇I spherical structure were obtained by phase transition with the heat treatment of pure BiOI. The phase structure, morphology, and optical property of the samples were characterized by XRD, XPS, SEM, TEM, BET, UV-vis spectroscopy, respectively. The photocatalytic performances of the samples were evaluated by the degradation of Rhodamine B ?RhB?, methyl orange ?MO?, the heavy metal ion ?Cr???? and methylene blue ?MB? solution under visible light irradiation. In this paper, the main contents as follows:?1? Pure spherical BiOI nano-powders were synthesised by EG-assisted solvothermal method. From the analysis combining SEM and TEM results, it can be seen that the BiOI possesses porous microspheres structure with an average diameter about 2 ?m, which were composed of lots of self-assembled ultrathin nanosheets with the thickness about 4 nm. The HRTEM indicated that the BiOI nanostructures are well exposed with highly reactive dominant {001} facets. It was found that BiOI displayed a strong adsorption over Rhodamine B ?RhB? and the heavy metal ion ?Cr???? solution in the dark environment. Under visible light irradiation, it can be observed that the RhB solution was completely degraded by BiOI within 90 minutes for the initial concentration of 50 mg/L. Moreover, it can show an extraordinary photocatalytic reduction performance under a certain degree of acidic conditions over Cr ???, and the degradation rate can be up to 99% for the initial concentration of 0.2 mmol/L?2? In order to further improve the photocatalytic activity of BiOI, Er³⁺ -doped BiOI powders were synthesized using Er?NO3?3 · 6H2O as an erbium source, the doping content of erbium was 1 mol%,2 mol%,3 mol%,4 mol% and 5 mol%, respectively. The phase structure and morphology of the samples were carried by XRD, XPS, SEM, TEM, BET spectroscopy, respectively. Rhodamine B ?RhB?, methyl orange ?MO? and methylene blue ?MB? dyes were used as probe organic pollutants, and the photocatalytic performance of Er³⁺ -doped BiOI were evaluated under the irradiation with visible light. From the results, when the doping content of erbium was 2 mol%, the Er³⁺ -doped BiOI exhibited a remarkable photocatalytic activity toward the degradation of single and binary organic dye systems.?3? Bi₅O₇I powders were fabricated by a thermal conversion of BiOI microspheres according to the phase transition principles. The influence of different heat treatment temperature about phase structure, surface morphology, and photocatalytic performance of all the Bi₅O₇I powders were characterized by XRD, XPS, SEM, TEM and another tests. It turned out that the sample heat treated at 450 ? demonstrated a higher photocatalytic activity for the degradation of RhB and MO in aqueous solution under visible-light irradiation. In addition, the Bi₅O₇I powders ?450 ?? can retain their relatively excellent photocatalytic activity even after ten cycles, and the degradation efficient of RhB solution can still reach 83.5%.