Hydrothermal Synthesis On Biocl.BiOI Compound Semiconductor And Its Photocatalytic Properties

BiOX (Cl, Br, I) photocatalyst working at visible light because of their uniquestructures and electronic band structures shows the better photocatalytic performancethan that of other types of compound on the photocatalytic degradation of dyes. But thesingle BiOX (Cl, Br, I) shows less photocatalytic performance on the degradation ofdyes, while the activity of different BiOX (Cl, Br, I) is also different on the degradationof the same organic dyes. Therefore, in this paper, BiOI/Bi₅O₇I, BiOCl/BiOI andBiOI/BiOBr compound semiconductor photocatalysts were synthesized by hydrothermalmethod, using XRD, BET, UV-Vis, SEM, TEM, PL and other means to analyzephase structure, specific surface area, the energy band structure, surface morphology ofprepared samples. And the performance of photocatalyst of degradation of dyes wasstudied. BiOI/BiO7I5 catalyst was synthesized via one-step hydrothermal method withBi(NO₃)₃, KI and ammonia. XRD results show that when pH=7, sample of synthesis ispure phase of BiOI, but when pH=9, the diffraction peaks of BiO7I5 are occurred, whenpH=11, BiO7I5 has generated the new phase. So we can control the pH of mixtures toget the two substances. Secondly, through the control the ratio of Bi:I , the proportion ofBiO7I5 in the mixture can be controlled. Photocatalytic test results show thatphotocatalyst of containing two types in the products shows the higher performancethan that of single catalyst. With Bi(NO₃)₃, KI, and NaCl as the starting material,BiOCl/BiOI were synthesized by using hydrothermal method. BiOI was synthesized bythe first step of hydrothermal method, and the second step of hydrothermal methodsynthesized the compound semiconductor of BiOCl/BiOI. XRD results show that thesamples include the diffraction peak of BiOI and BiOCl, that is to say, two phasecoexistence. For BiOCl/BiOI compound semiconductor, SEM results show that BiOIsynthesized by the first hydrothermal method is wafer-like structure with betterdispersibility, while BiOCl is flower globular structure. BiOCl/BiOI compoundsemiconductor has hybrid structures of flake and flower. Finally, photocatalyticactivities of compound semiconductors were studied. Results show that 20%BiOCl/BiOI on the degradation of methyl orange (MO) shows the best activity, but 70%BiOCl/BiOI on the degradation of rhodamineB (RhB) shows the best activity. Becausethe two photocatalyst show the different behaviors on the degradation of dyes, thedifferent mechanism of photocatalytic degradation was proposed based on a series ofexperiments. At last, BiOI/BiOBr photocatalysts prepared by a water shower method. For BiOI/BiOBr, SEM results show that samples of the water bath method are bendingof irregular flower-like structure, while BiOCl and BiOBr of synthesis under the sameconditions are plate-like structure.