Study On The Effect Of Microstructure On The Performance Of Typical Photocatalytic Materials To Degrade Dyes

With the rapid development of the world,the environmental pollution is increasingly severe,which restricts the sustainable development of the society.Dye is a typical industrial wastewater.Since it is of complex component,strong toxicity and poor biodegradability,it is difficult to do the degradation.Hence,the dye degradation research is the hotpot.Due to the virtue of its greenness and sustainability,photocatalysis has been widely utilized in removing environmental dyes.Unfortunately,the limited light absorption and the low separation efficiency of photoexcited electron-hole pairs have constrained its practical application.In this work,the effect of microstructure(crystal water,layer bond,vacancy and interface structure)on light absorption and electron-hole pair separation has been studied.Our work paves a new way of protecting the environment.(1)Zn₃(PO₄)₂·2H₂O and Zn₃(PO₄)₂ were successfully prepared by a simple hydrothermal method without using any surfactant or template.It is found that although as a weak electron donor,the coordination of H₂O with zinc(II)increases the electron density of zinc(II),and a ligand-to-metal charge transfer(LMCT)occurs from H₂O to zinc(II),obviously increasing the light absorption of Zn₃(PO₄)₂·2H₂O.Under ultraviolet light irradiation(??420 nm),Zn₃(PO₄)₂·2H₂O has a photocatalytic activity 1.25 times higher than that of Zn₃(PO₄)₂ for the degradation of Methylene Blue(MB).We believe that crystal water chemicals could become a new category of photochemical materials,which may greatly enrich the photochemical science.(2)Bi₂SiO₅ and Bi₂O₂CO₃ were successfully prepared by a simple hydrothermal method.For Bi₂SiO₅,the newly-formed Bi-O-Si bonds between anion and cation layers would favor for the electron transfer,thus improving the photocatalytic activity.For Bi₂O₂CO₃,there is no newly-formed bond between the anion layers and cation layers,which does not favor for improving the photocatalytic activity.Under UV light irradiation(??420 nm),the degradation activity of Rhodamine B(Rh B)over Bi₂SiO₅ is as about 1.73 times as high as that over Bi₂O₂CO₃.This work demonstrates that fine layer bond has a significant influence on the photochemical properties.(3)From the surface deposition of low-cost metal,an advanced semimetal-MOF hybrid material is constructed through one-pot hydrothermal reduction of Bi nanoparticles on ZIF-67.Due to the surface plasmon resonance(SPR)property of Bi semimetal,the visible-light-harvesting of Bi/ZIF hybrids have been conspicuously enhanced.Furthermore,the results of EIS and photocurrent spectra show that Bi semimetal serves as an electron trap via Schottky junction formed at the Bi/ZIF interface would improve the charge separation and transfer efficiency of the catalyst.Under visible-light irradiation(??420 nm),Bi/ZIF-5 has a photocatalytic activity 2.30,1.03 and 1.11 times as high as that of ZIF-67,Bi/ZIF-10 and Bi/ZIF-15,respectively(Methylene Blue,MB).This is great significant that low-cost and abundant Bi semimetal can substitute for expensive noble metals to get advanced photocatalysts.(4)ZnCo-ZIFs with and without Zn vacancies(V_zn)were synthesized by a simple method at the room temperature.It is found that the as-synthesized V_zn-ZnCo-ZIF has shown enhanced visible-light photocatalytic activity.This enhanced performance can be ascribed to the improved visible light absorption and the facilitated electron-hole pair separation because of the formation of Zn vacancy.Under visible-light irradiation(??420 nm),V_zn-ZnCo-ZIF has a photocatalytic activity 1.56 times as high as that of ZnCo-ZIF(Methylene Blue,MB).This work paves a new way of utilizing the post-synthesis strategy to enhance the photocatalytic performance of bimetallic zeolite imidazolate frameworks.