Preparation Of Bi-based Composites And Their Photocatalytic Degradation Properties Of Pollutants

In recent years,with the continuous improvement of the level of industrialization,water pollution has become an increasingly serious problem.The traditional wastewater treatment technology is difficult to effectively remove refractory organic pollutants.Therefore,it is necessary to seek new and efficient technology to solve these problems.Photocatalytic technology has attracted much attention due to its advantages of high efficiency and environmental protection as well as the effective treatment of refractory organic wastewater.Among many photocatalytic materials,bismuth halide oxide and Bi₂O₄ has attracted much attention because of their unique electronic structure and excellent photocatalytic activity.However,both of them have the disadvantage with high photo-generated carrier recombination rate,and the photocatalytic performance still needs further improvement.Therefore,bismuth halide oxide and Bi₂O₄ composite photocatalytic materials were synthesized based on bismuth halide oxide and Bi₂O₄,the degradation performance and mechanism of organic pollutants were studied in detail.The main research contents and conclusions of this paper are as follows:?1?The Z-scheme BiOI/Bi₂O₄ heterojunction with different ration was constructed via ultrasonic-assisted hydrothermal method.The BiOI/Bi2O4heterojunction was characterized by XRD,SEM,TEM,UV-vis DRS and XPS,respectively.The calculation results of UV-vis DRS and DFT showed that the combination of Bi2O4 and BiOI could effectively enhance the absorption ability to visible light.The photocatalytic performance of BiOI/Bi2O4 heterojunction photocatalysts were investigated by degrading rhodanine B?RhB?solution,the results showed that the degradation ratio of RhB solution over BiOI/Bi2O4 heterojunction photocatalyst with BiOI mass ratio of 30%reached approximately 2.8 times and 30times higher than those of Bi₂O₄ and BiOI,respectively.It was proved that the the combination of Bi₂O₄ and BiOI could contribute to the faster separation and transfer of photo-generated carries by photoluminescence and electrochemical impedance spectroscopy.The radical trapping experiments certified that hole and superoxide radical were the main active species.Moreover,the conduction band potentials of BiOI and Bi₂O₄ were calculated by Mott-Schottky measurements,and the mechanism of photocatalytic degradation of RhB by BiOI/Bi2O4 heterojunction using Z-scheme electron transfer path was proposed.In addition,the results of XRD,TEM and XPS revealed that the ultrathin Bi₂O₂CO₃ nanosheets in-situ grew on the surface of BiOI/Bi₂O₄ heterojunction under visible light irradiation.The existent of Bi₂O₂CO₃nanosheets could accelerate the separation and transfer of photo-generated carries and improve the photocatalytic performance of BiOI/Bi₂O₄ photocatalysts.?2?The BiOCl/Bi2O4 heterojunction with different ration was successfullyprepared by controlling the amount of hydrochloric acid added.The results of UV-vis DRS indicated that the combination of Bi₂O₄ and BiOCl could effectively expand the photoresponse range of BiOCl.The photocatalytic performance of BiOCl/Bi2O4photocatalysts was investigated by degradation of tetracycline?TC?solution.The results showed that BiOCl/Bi₂O₄ photocatalysts showed good photocatalytic activity.In addition,the results of photoluminescence spectra,photocurrent response and electrochemical impedance spectroscopy showed that the combination of Bi2O4 and BiOCl could effectively accelerated the separation and migration of photo-generated carries.The conduction band potentials of BiOCl and Bi2O4 were calculated by Mott-Schottky measurements.The valence band and conduction band positions of the two semiconductors indicated that they can form stable heterojunction.The primary active radicals of BiOCl/Bi2O4 heterojunction were determined to be superoxide radical and holes through scavenger experiments.On this basis,the photocatalytic degradation mechanism of BiOCl/Bi₂O₄ heterojunction was proposed.This work can provide practical and theoretical references for the preparation and properties of bismuth halide oxide and Bi₂O₄ composites.