Preparation And Performance Of Photocatalysts Derived From Zn-Fe Prussian Blue Analogue

In recent years,with the development of industrialization,a large number of organic pollutants have been discharged into the water environment,among which the industrial textile dye Rhodamine B（RhB）and the antibiotic tetracycline hydrochloride（TC）are the representative pollutants,therefore,there is an urgent need for an efficient,green and low-cost treatment method to solve water pollution issues.Photocatalysis technology is a green and sustainable treatment technology driven by solar energy,which has the advantages of non-toxicity,low-cost,and environmental friendliness.However,traditional photocatalysts have the disadvantages of low light absorption efficiency,the low separation efficiency of photogenerated carriers,and difficult recovery and reuse.Based on this,investigating the preparation of high-efficiency photocatalysts with both visible light response characteristics and rapid separation of photogenerated carriers that are easy to recover has high theoretical significance and practical application value.The specific research contents are as follows.1.Cubic Zn-FePrussian blue analogue（Zn-FePBA）was successfully synthesized by a facile coprecipitation method.Micro/nano hierarchical flower-like ZnS/FeS₂ direct Z-scheme heterojunction visible-light catalyst was in-situ derived from Zn-FePBA by a facile one-pot hydrothermal sulfidation strategy.The as-prepared ZnS/FeS₂ catalyst shows extraordinarily boosted visible-light photocatalytic degradability for Rhodamine B（Rh B）with the synergism of peroxydisulfate（PDS）.The degradation efficiency can achieve 98.5%within 15 min and100%within 20min of visible-light illumination with excellent structural stability.The degradation kinetic constant of ZnS/FeS₂+PDS is 9.33 times that of ZnS/FeS₂,23.02 times that of p-ZnS/FeS₂（physical mixture）,24.05 times that of FeS₂,and 28.25 times that of ZnS,respectively.The ZnS/FeS₂ heterojunction shows significant synergistic benefits in the photocatalytic degradation reaction.More advantageously,ZnS/FeS₂+PDS shows excellent photocatalytic degradation performance in a wide p H range（1-10）.The ZnS/FeS2heterojunction photocatalyst derived from Zn-FePBA in situ can effectively expand the light absorption range and accelerate the separation of photogenerated carriers under the synergistic effect with PDS.The crucial active species in the ZnS/FeS₂+PDS composite catalytic system are·OH,·SO₄^-,h⁺,and·O₂^-.Based on this,a reasonable direct Z-scheme charge transfer mechanism was proposed.The micro/nano hierarchical flower-like structure of ZnS/FeS₂simultaneously combines the high activity of nano-materials with the advantages of easy recycling of micro-sized materials.2.Microsphere-shaped Zn-FePBA was successfully synthesized by co-precipitation by changing Fesource.Then,a segmented heating process was utilized to prepare ZnFe₂O₄@ZnO（ZFO@ZO）with a core-shell structure that retained the microsphere morphology.Lastly,Cd S particles were deposited on the surface of the microsphere to fabricate a magnetic and recoverable ZnFe₂O₄@ZnO/Cd S（ZFO@ZO/Cd S）stepped heterojunction visible-light catalyst.The ZFO@ZO/Cd S photocatalyst shows excellent visible-light photodegradation performance towards tetracycline hydrochloride（TC）.With visible light irradiation for 60 min,ZFO@ZO/Cd S degrades TC with an efficiency of 100%,and the reaction rate constant is 8.61times that of ZnO,7.09 times that of ZnFe₂O₄,3.45 times that of ZFO@ZO,and 2.96 times that of Cd S.Characterization results show that the ZFO@ZO/Cd S composite photocatalyst has an enlarged light absorption range and improved efficiency of photogenerated carrier separation.The main reason for the above performance improvement is that the constructed stepped heterojunction is conducive to the efficient separation of photogenerated carriers.Moreover,the core-shell structure of the composite catalyst is conducive to enhancing the visible light absorption efficiency of the catalyst.Due to the strong magnetism of ZnFe₂O₄ and the stability of the core-shell structure,the composite photocatalyst exhibits excellent cycling stability and recoverability.3.In the preparation process of Zn-FePBA,In³⁺was doped and the In element was successfully introduced without changing the original morphology of Zn-FePBA,resulting in the preparation of Zn-In-FePBA.Then,a one-step pyrolysis process was used to achieve a microsphere-shaped core-shell structure ZnFe₂O₄/ZnO/In₂O₃（ZFO/ZO/IO）stepped heterojunction visible-light catalyst from Zn-In-FePBA.The chemically bonded heterojunction photocatalyst ZFO/ZO/IO obtained by a facile one-step pyrolysis reaction has excellent visible light TC degradation performance.After visible light irradiation for 60 min,the TC degradation efficiency can reach 91.6%.The reaction rate constant is 6.04,4.99,7.66,and 3.47 times those of ZnO,ZnFe₂O₄,In₂O₃,and ZnFe₂O₄/ZnO,respectively.Through band structure analysis,quenching experiments of active species and electron spin resonance（ESR）tests,there is a favorable stepped potential gradient between the three components of the composite photocatalyst,which can greatly improve the separation efficiency of photogenerated electrons and holes.The core-shell structure obtained by pyrolysis can guide the light to the core site to enhance the light absorption capacity of the catalyst,and the stability of the core-shell structure is also conducive to the recycling of the photocatalyst.The strong magnetism of ZnFe₂O₄contributes to the excellent recoverability of the composite photocatalyst.