Study On The Preparation Of Multi-morphic Fe₂O₃/g-C₃N₄ Heterojunction Composite Photocatalyst For Photocatalytic Removal Of Indoor Formaldehyde

Photocatalytic oxidation is a kind of gas pollutant purification technology that is very suitable for indoor conditions.However,as the core of photocatalytic oxidation technology,most catalysts have many following problems,non-response under visible light,low photocatalytic efficiency and unstable photocatalytic activity when the catalysts were used indoors.In order to solve the above-mentioned problems,this study proposed the methods to change the morphologies of g-C₃N₄ and constructed heterojunction with Fe₂O₃ to overcome the above mentioned shortcomings,and then used the Fe₂O₃/g-C₃N₄ heterojunction composite photocatalyst to purify indoor formaldehyde.The study used multiple characterization method to investigate the morphology,composition and structure of catalysts,and further to study the photocatalytic efficiency of the composite catalyst under different environmental conditions.The main research contents were as follows:（1）Preparation and characterization of multi-morphic Fe₂O₃/g-C₃N₄heterojunction composite photocatalystsThis study used a simple hydrothermal method to prepare three different morphologies of g-C₃N₄ with block,nanosphere and nanotube.In order to improve the g-C₃N₄ photocatalytic efficiency,this study further loaded Fe₂O₃ on g-C₃N₄ to produce Z-type heterojunction.Comparing the three morphologies of Fe₂O₃/g-C₃N₄ composite catalysts,nanospheres（33.5 m²/g）and nanotubes（27.5 m²/g）successfully improved the shortcomings of the small specific surface area of the bulk（14.1 m²/g）structure.At the same time,the light absorption band edges of bulk,nanosphere and nanotube Fe₂O₃/g-C₃N₄ red-shifted to 461 nm,484 nm,and 500 nm,respectively,which successfully broadened the visible light absorption range of ordinary g-C₃N₄（450 nm）.The transient photocurrent measurements showed that the electron hole pair separation efficiency of Fe₂O₃/g-C₃N₄with nanotube had the highest value.In addition,the free radical test presented that Fe₂O₃/g-C₃N₄ composite photocatalyst could continuously and stably produce·OH and·O₂^-oxidation substances of formaldehyde under visible light.（2）Study on performance of Fe₂O₃/g-C₃N₄ heterojunction composite catalyst for photocatalytic degradation of indoor formaldehydeThe study used the photocatalytic degradation of formaldehyde experiment to investigate the effect of the formaldehyde initial concentration,iron oxide loading,humidity and illumination on the catalytic efficiency of Fe₂O₃/g-C₃N₄.The results showed that the catalytic efficiency was the highest when the Fe₂O₃loadings on the bulk,nanosphere and nanotube Fe₂O₃/g-C₃N₄ composite catalysts were 1 wt%,3 wt%,and 3 wt%,respectively.Under the same formaldehyde concentration,the catalytic efficiency of Fe₂O₃/g-C₃N₄ composite catalyst was more than 15%higher than that of g-C₃N₄ without Fe₂O₃.The nanotube Fe₂O₃/g-C₃N₄ exhibited higher catalytic activity than the bulk and nanosphere Fe₂O₃/g-C₃N₄ under most conditions.Five cycles of experiments have proved that the catalyst has good stability and the catalytic efficiency is always higher than 60%.The effect of the application of photocatalysts on the efficiency of the catalyst was studied.Nanotubes Fe₂O₃/g-C₃N₄ were selected to combine with the coating to form a photocatalytic coating.The experimental results showed that the way the photocatalyst is added has a significant impact on the catalytic efficiency and the catalytic efficiency of adding catalyst after painting is 48%higher than that before painting.