Preparation And Photocatalytic Properties Of ZnFe₂O₄ And ZnFe₂O₄/?-Fe₂O₃?SnS₂?

With the development of industry,the wastewater has become a problem to be urgently solved.The ferrite ZnFe₂O₄ has been widely applied as a magnetic semiconductor catalyst.The ZnFe₂O₄ has many advantages,such as narrow band gap?1.70 eV¹.90 eV?fitting to absorpt visible light,wide absorption of sunlight,stable photochemical properties,low cost,and reusability.However,the defect of ZnFe₂O₄is valence band?VB?potential is too low to generate enough hydroxyl radicals,and the weak oxidative causes the limited photocatalytic efficiency.The methods to enhence the photocatalytic performance include moving the band gap to improve the oxidative or reductive property,increasing the visible light absorption to high the utilization of light to excite more electrons or holes,and combining with other materials to reduce the recombination of the electrons and holes.The size and morphology of nano-ZnFe₂O₄ have significantly affected on the band gap and photocatalytic properties.The nano-ZnFe₂O₄ was prepared by the solvothermal method,and mainly studied the influence of solvent polarity on the morphology of ZnFe₂O₄.It was observed that the more polar of the solvent,the more favorable the reduction in product size,which may be due to the fact that the greater polarity is more easily to nucleate the crystals during the generation process of ZnFe₂O₄.The quantum size effect of the nano-ZnFe₂O₄ causes changes in the band gap and the recombination of the electronics and holes.Through the optimization of the synthesis conditions,the photocatalytic performance of the nano-ZnFe₂O₄ reached74.28%,and it shows room temperature ferromagnetism,which results in easily recycle and reuse.In order to further enhance the photocatalytic performance,the ZnFe₂O₄/?-Fe₂O₃photocatalyst was synthesized by a hydrothermal method.The?-Fe₂O₃ is a common semiconductor with a band gap of 1.9².2 eV.The heterojunction was formed with?-Fe₂O₃and nano-ZnFe₂O₄.It reduced the recombination of electrons and holes,and the degradation efficiency increased from 74.28%to 94.91%in 120 min.However,the surface defects after recombination still caused the recombination of the electrons and holes.Thus,it was necessary to regulate the flow of electrons and holes.The noble metal is a good conductor of electrons,and after compounding with the catalyst,it can effectively conduct electrons to the surface of the catalyst to increase the photocatalytic performance.Therefore,ZnFe₂O₄/?-Fe₂O₃/Pt was prepared by the photocatalytic method,and Pt is successfully loaded on the surface of the catalyst.In addition,the Schottky barrier can be form to further promote the unidirectional movement of electrons,and the photocatalytic degradation efficiency of ZnFe₂O₄/?-Fe₂O₃/Pt increased from 83.71%to 99.96%in 100 min.The composite catalyst ZnFe₂O₄/SnS₂ was prepared to increase the absorption of visible light and further to improve the photocatalytic efficiency.The composite catalyst inhibited the photochemical corrosion of SnS₂ and also high the photocatalytic effect of ZnFe₂O₄.In this work,ZnFe₂O₄ nanoparticles were successfully supported on the SnS₂ sheet by a solvothermal method,and it can completely degrade the methyl orange solution within 20 min.By effectively separating the electron-holes pares and the rapid destruction of nitrogen-nitrogen double bonds,the composite energy can significantly improve the photocatalytic performance.At the same time,the ferromagnetic property of the composite catalyst made it easy to recycle to perform a photocatalytic cycle.