Synthesise Of The Novel BiOI-based And G-C₃N₄-based Heterojunction Photocatalysts And Their Photocatalytic Degradation Performances Of The Typical Organic Pollutants

With the development of chemical industry, a number of dyes and endocrine disrupting chemicals are extensively used in all walks of life. They are very difficult to be completely degraded in the traditional wastewater treatment processes. Semiconductor photocatalytic technology, which can degrade organic pollutants in wastewater efficiently and completely under a mild condition, has a good application prospect. As classic photocatalyst, TiO2 has a low quantum yield, poor solar energy utilization and deactivation easily, which greatly limits its practical application. Therefore the environmental friendly non-TiO2 photocatalyst with high efficiency has become the focus and hot spot of photocatalysis reasearch.Especially, BiOI and g-C3N4 photocatalysts exhibit excellent photocatalytic properties due to their special layered crystal structure and suitble band gap,so it has important significance to carry out research on modification of BiOI and g-C3N4. In this work, the scanning electron microscopy(SEM), X-ray photoelectron spectroscopy(XPS), transmission electron microscopy(TEM), X-ray diffraction(XRD) and other related instruments are used to investigate the bulk phase, surface structure and morphology of the catalyst detailedly. Subsequently, the optical response of the catalysts, catalytic degradation rate of dye, endocrine disrupting chemicals reduction rate and band structure are characterized by ultraviolet-visible diffuse reflection spectrum(UV-vis DRS), photoluminescence spectra(PL and TA-PL), ultraviolet-visible spectrophotometer, photocurrent(PC) and electrochemical impedance spectroscopy(EIS). The main results and conclusion obtained from these studies are as follows:The results show that:(1) The BiOI/Zn2SnO4 photocatalyst is prepared using a solvothermal-chemical bath method, the irradiation of UV and visible light can result in the obvious degradation of MB. The BiOI/ZSO-35 composite showed the best activity among all these composites,nearly 100% of MB can be decomposed within 100 minutes and 90 minutes under UV and visible light irradiation, respectively. In addition, the BiOI/Zn2SnO4 photocatalyst also possesses a significantly enhanced visible light activity in decomposing RhB and BPA:After 180 and 150 minutes of visible light irradiation, the decomposition ratio of BPA and RhB over BiOI/ZSO-35 are up to 99% and 97%, respectively;under UV irradiation,the decomposition ratio of BPA and RhB over BiOI/ZSO-35 are up to 97% and 100% after 100 and 60 min,respectively.(2) The BiOI/Zn2GeO4 photocatalyst is prepared using a solvothermal-chemical bath method,the photocatalytic performance is performed towards the degradation of BPA in an aqueous solution under visible light illumination. The sample of BiOI/ZGO-30 presents the highest photocatalytic activity,after 70 min of visible light irradiation, the decomposition ratio of BPA over BiOI/ZGO-30 is up to 97% ?(3) The g-C3N4/Zn0.25Cd0.75 S photocatalyst is prepared using a high temperature solid phase polymerization-hydrothermal method,under the irradiation of visible light can result in the obvious degradation of MO ? RhB. The highest degradation efficiency is observed for the CNZS-20 sample. After 75 minutes of visible light irradiation, the decomposition ratio of MO over CNZS-20 is up to 99%, after 45 minutes of visible light irradiation, the decomposition ratio of RhB over CNZS-20 is up to 100%?The original results of this study are as follows:(1) This work is the first time to introduced the BiOI/Zn2SnO4?BiOI/Zn2GeO4?g-C3N4/Zn0.25Cd0.75 S photocatalysts, which shows high efficiency and stability photocatalytic activity.(2) The photocatalysts of the BiOI/Zn2SnO4 ? BiOI/Zn2GeO4 not only show excellent photocatalytic activity in decomposing dyes,but also result in the obvious degradation of BPA.(3) The BiOI/Zn2SnO4 heterojunction is shown good photocatalytic performance under UV and visible light irradiation. The designed development could provide a new idea which could greatly improve the sunlight utilization ratio of the heterogeneous composite nanometer material as well.