The Preparation And Photoelectric Properties Of Fe₂O₃/C Composite Nanomaterials

At present,on the road of vigorously developing industry and exploring science and technology,water pollution caused by excessive use of toxic compounds such as pesticides,dyes and organic solvents has become a global problem that needs to be solved urgently.Photocatalytic technology is different from other organic pollutant treatment technologies,in terms of application cost,only the preparation of appropriate photocatalyst can achieve large-scale application.In addition,environmental friendly,green and non-toxic,high efficiency and energy saving characteristics become one of the most effective ways to degrade pollutants.Among many photocatalysts,iron oxide（Fe₂O₃）has many excellent properties.It is an environment-friendly N-type semiconductor and one of the most stable transition metal oxides in the natural environment.In addition,its narrow band gap,high absorption rate of solar energy,low price and abundant reserves are considered to be one of the most promising semiconductor materials for photocatalytic degradation of pollutants.However,pure Fe₂O₃ material has a series of problems such as low electron mobility,short life of excited state,poor electrical conductivity and so on.This article will simply Fe₂O₃ materials and carbon composite material form heterogeneous interface,can be to give full play to the advantage of the two materials:On the one hand,the composite carbon materials and other materials,contact interface easier to transport transferred electron,has a good electron transfer properties,inhibition of charge carrier recombination,extend the life of the light life carrier;on the other hand,carbon-based materials can provide a large number of active sites for the smooth reaction due to their large specific surface area.Theoretically speaking,the more active sites involved in the reaction,the faster the reaction rate will be.Under the influence of photoelectric synergistic effect,the advantages between the two can be given full play,which is embodied in the improvement of photoelectric current,the expansion of visible light absorption spectrum,and the improvement of degradation efficiency of organic pollutants.Two kinds of ferric oxides（α-Fe₂O₃ andγ-Fe₂O₃）with different phases were prepared by one-step hydrothermal method using nano-Fe₂O₃ as substrate.After further modification ofα-Fe₂O₃,CNTs/α-Fe₂O₃ doped with different content of carbon tubes andα-Fe₂O₃@C core-shell structure withα-Fe₂O₃ as core were prepared.In order to further optimize the photodegradati on performance of pure Fe₂O₃,γ-phase Fe₂O₃ nanomaterials were prepared,and compared withα-Fe₂O₃,γ-Fe₂O₃@C core-shell structure was prepared by a similar method.The photocatalytic performance of the heterogeneous interface was further explored,and the photocatalytic enhancement mechanism of Fe₂O₃ matrix composites was summarized based on the experimental results.（1）CNTs/α-Fe₂O₃ photocatalyst was synthesized by a simple one-step hydrothermal method with mixing FeCl₃,CH₃COONa and MWCNTs.The photocurrent test shows that the photocurrent intensity ofα-Fe₂O₃ is significantly improved after the carbon tube loading,especially when the mass ratio of CNTs andα-Fe₂O₃ is 5%（CNTs/α-Fe₂O₃-S₂）,the photocurrent intensity is 0.34 m A/cm²,which is 1.8 times higher than that ofα-Fe₂O₃ alone.The comparison experiments of dye degradation showed that CNTs/α-Fe₂O₃-S₂ composite nanomaterials had significant effects on the degradation of cationic organic dyes Rhodamine B and methylene blue.（2）After mixing FeCl₃ and CH₃COONa by hydrothermal method,pure Fe₂O₃nanoparticles were first synthesized,and then the appropriate proportion of C₆H₁₂O₆was added.After the reaction at 220^oC,α-Fe₂O₃@C was prepared.In the photocurrent test results,the photocurrent intensity ofα-Fe₂O₃ increased significantly after carbon coating,especially when the molar ratio of C₆H₁₂O₆ toα-Fe₂O₃ was 0.1,α-Fe₂O₃@C-0.1M with the photocurrent intensity of 0.24 m A/cm².The results showed thatα-Fe₂O₃@C-0.1M had better photocatalytic activity enhancement efficiency for the cationic dyes Rhodamine B and methylene blue.（3）Primaryγ-Fe₂O₃ was synthesized by one step hydrothermal method,and thenγ-Fe₂O₃ as the nucleus,the outer layer through the hydrolysis of C₆H₁₂O₆,on the surface ofγ-Fe₂O₃,coated with carbon to get theγ-Fe₂O₃@C core-shell structure.The maximum photocurrent value ofγ-Fe₂O₃@C-0.3M composite nano-material is 0.43m A/cm²,which is 3.6 times that ofγ-Fe₂O₃.Through different thickness of carbon coatedγ-Fe₂O₃ in visible light irradiation degradation of Rh B photocatalytic experiments found that the sampleγ-Fe₂O₃@C-0.3M showed the best photocatalytic degradation efficiency of 86%.