Preparation Of Visible-light-driven Bi₅O₇I Photocatalysts And Composites With Their Photocatalytic Performance Study

In the past decades,environmental pollution and energy shortages which are very harmful to human beings have become a global issue.Photocatalytic technology is receiving increasing attention and concern for environment remediation and new energy development due to the wide applications of photocatalysts in the field of photodegradation,CO₂ reduction,water splitting,etc.But the use of photocatalytic technology in modern industry is seriously restricted due to the technical challenges.Therefore,synthesis of new photocatalysts capable of utilizing the visible light has become more practically importance.Recently,bismuth oxyhalides semiconductor photocatalysts have attracted much attention due to their efficient visible-light-driven ability.In this paper,pure Bi₅O₇I with different morphologies were synthesized by different methods,and a kind of composite photocatalyst materials with microsphere structure was prepared based on Bi₅O₇I.The main researches are listed as follows:Firstly,various morphologies of pure Bi₅O₇I were synthesized by hydrothermal alkalization,calcination and molecular precursor method,respectively.The structure,morphology and photoeletrochemical properties of materials prepared in this study were characterized by XRD,SEM,Uv-vis diffuse reflectance spectroscopy and BET method,and methyl orange and rhodamine B were used as the representative organic pollutants to evaluate the photocatalytic activities of the as-prepared samples.The results indicated that Bi₅O₇I microsphere showed the best performance.The above experiment research provided a foundation to build composite photocatalyst.Based on the above results,novel g-C₃N₄/Bi₅O₇I heterojunction microspheres with different amount of g-C₃N₄ were successfully prepared by a one-pot ethylene glycol?EG?-assisted hydrothermal method followed by calcination in air.The structure,morphology,composite and optical performance of materials prepared in this study were characterized by a series of methods.Bi₅O₇I microspheres grafted with g-C₃N₄ nano-sheets were formed and studied by electron microscopy.The morphological effects on g-C₃N₄/Bi₅O₇I photocatalytic capability with varied g-C₃N₄ contents were investigated and discussed.The g-C₃N₄/Bi₅O₇I microspheres exhibited much improved photocatalytic degradation performance under visible light irradiation compared with bare Bi₅O₇I and g-C₃N₄.The photocatalytic performance is optimal when the ratio of g-C₃N₄ is 10 wt%.The effects of catalyst dosage,the initial concentration and pH of solution on the degradation of MO under visible light irradiation.We found that the optimum dosage of g-C₃N₄/Bi₅O₇I-10 is 1.0 g/L.The best photocatalytic performance of g-C₃N₄/Bi₅O₇I-10 occurred at low initial concentration and pH of MO.Analyses by both photoluminescence?PL?and photocurrent independently confirmed that photo-induced electron-hole pairs in the g-C₃N₄/Bi₅O₇I composite have been effectively created which was responsible for the observed photocatalysis.The capture experinment for active species and ESR test verified that that h⁺and·O₂^-are the primary active species to take part in the photodegradation reaction.Based on the analysis of the experiment results,a Z-Scheme heterojunction photocatalytic mechanism was proposed.