Preparation And Photocatalytic Properties Of Bismuth Oxides Composite Photocatalyst

The development of global industrialization has caused a serious energy crisis and environmental pollution.The search for new clean energy sources and the strategy to achieve sustainable development is the common goal of the Party and the people.Xi Jinping proposed on the road of developing socialism with Chinese characteristics:we should deeply fight the battle of pollution prevention and control and build a sound environmental governance system.The issue of pollution control is extremely important,and solar energy has been widely paid attention to due to its advantages of easy access,sufficient reserves,and high renewability.Solar photocatalytic technology is also widely used in the field of treating wastewater.In this paper,we aim to find new green,efficient and low-energy photocatalysts for the photocatalytic degradation of wastewater.In this paper,three new binary bismuth-based composite photocatalysts were prepared by compounding and constructing heterojunctions with a bismuth-based oxide core,and different types of wastewater materials were simulated for photocatalytic degradation performance testing.In addition,the microscopic morphology,optoelectronic properties,photocatalytic mechanism and degradation pathways of some wastewater materials of the composites were also investigated by using relevant characterization techniques.The details are as follows:（1）The g-C₃N₄/BiO_2-X composites with different doping ratios were prepared by a two-step hybrid calcination method.XRD,SEM,XPS,and UV-Vis characterization observed the crystalline structure and morphological changes of the composites,which verified the formation of heterojunctions and the enhancement of optical properties.PL,EIS and photocurrent demonstrated the enhancement of electrochemical properties of the composites.Compared with the monomer,g-C₃N₄/BiO_2-Xsignificantly improved the photocatalytic degradation of methyl orange（MO）under visible light,and the optimal ratio 0.2CNB had the most excellent degradation activity.In addition,the cycling stability test and active species capture experiments of the composites were carried out,and the possible photocatalytic degradation mechanism of the g-C₃N₄/BiO_2-Xcomposite photocatalyst was proposed in combination with the energy band structure analysis.g-C₃N₄/BiO_2-X heterojunction composites broadened the visible light absorption range and promoted the electron-hole separation and transfer rate,thus realizing the photocatalytic performance enhancement.（2）A novel Z-scheme Bi₂O₃/Ag₃PO₄ composite photocatalyst was prepared by a simple in situ precipitation method.The microscopic morphology,optical properties,and electrochemical properties of the photocatalyst were investigated using a series of characterization tools.To further explore the photocatalytic performance of the composite,visible light degradation experiments were performed on the antibiotic tetracycline（TC）and the organic dyes methylene blue（MB）and methyl orange（MO）.The photocatalytic performance of the 0.025BA composite was better than that of the other samples,and the degradation rate decreased slightly after five cycles of the experiment.The main reason for the decrease in the photocatalytic degradation rate was speculated by comparing the XRD and XPS of the materials before and after the cycles.The active species capture experiments and ESR showed that h⁺,·O₂^-were the main active species affecting the photocatalytic degradation,and·OH played a secondary role.The intermediate products and possible degradation pathways of tetracycline were analyzed by LC-MS.TOC verified the final photocatalytic degradation products.Finally,the possible photocatalytic reaction mechanism was speculated in conjunction with the energy band structure analysis.The high photocatalytic activity of the 0.025BA composite may be the result of its Z-scheme heterojunction formation,which allows rapid transfer and high separation of photogenerated carriers at the heterojunction interface,and also accelerates the redox reaction rate of electron-hole pairs.（3）A novel Z-scheme BiO_2-X/Ag₃PO₄ composite photocatalyst with defective structure was prepared by hydrothermal post-in situ precipitation.The optimal ratio1.5BOA showed excellent photocatalytic degradation of methyl orange（MO）,tetracycline（TC）,and ciprofloxacin（CIP）under visible light irradiation,and maintained good structural stability and cycling efficiency after five cycles.XPS and EPR tests confirmed the presence of oxygen-deficient structures in the complexes.PL,EIS and photocurrent confirmed the high electron-hole transfer rates.The active species capture experiments and ESR confirmed the active species playing a role in the degradation process.LC-MS speculated the possible degradation pathway of CIP.TOC confirmed the final photocatalytic degradation products.Finally,the reaction mechanism of the Z-scheme BiO_2-X/Ag₃PO₄ composite photocatalyst was speculated.the oxygen-deficient structure of BiO_2-X formed a Z-scheme heterostructure with Ag₃PO₄,the oxygen vacancies served as electron capture centers and active sites,which not only improved the photogenerated electron transfer rate,but also avoided the photocorrosion of Ag₃PO₄ to a certain extent.Thus,the structural stability and photocatalytic performance of the complexes were achieved.