Preparation And Photocatalytic Properties Of TiO₂ Nanofibers-Based Composite

With the continuous growth of the world population and the rapid development of industry,environmental pollution and energy depletion have become two major problems hindering the progress of human society.Solar energy as a clean,free,inexhaustible energy has been considered to be the most promising renewable energy.Inspired by natural photosynthesis,the researchers studied semiconductor photocatalysis.Semiconductor photocatalysis technology,which can convert solar energy into chemical energy,is developing rapidly in the field of energy and environmental protection and has become a research hotspot.Among many semiconductor photocatalysts,titanium dioxide(TiO₂)has attracted extensive attention because of its advantages such as mature process,low cost,high chemical stability and non-toxicity.However,TiO₂ can only absorb ultraviolet light,and the photogenerated carriers are easy to recombine,which affects its practical application.We tried to improve the photocatalytic performance of TiO₂ by dye sensitization,supported co-catalyst,morphology control,semiconductor material composite and other methods.In this paper,TiO₂ nanofibers synthesized by electrospinning method were used as the matrix to prepare a series of TiO₂-based composites,which realized the effective separation of photogenerated electrons and holes,and improved the photocatalytic performance of TiO₂:1.TiO₂/Bi₂S₃ composites were prepared by electrospinning combined with hydrothermal method.Bi₂S₃ nanowires in the composites were uniformly distributed on the surface of TiO₂ nanofibers,which obtained a higher specific surface area and exposed more active sites,which was conducive to dye adsorption and photocatalytic reaction.The results showed that when the concentration of rhodamine B(Rh B)solution was 10 mg/L and the content of as-prepared sample was 10 mg/L,the degradation rate of Rh B reached 99%within 60 min.The degradation experiments of methyl orange(MO)showed that the degradation of dyes on the composites was the result of the combined action of dye sensitization and photocatalysis.Due to appropriate energy band matching,synergistic interaction exists between Rh B dye,TiO₂ nanofibers and Bi₂S₃ nanowires,resulting in an ultrafast electron transfer process assisted by dye sensitization.At the same time,the direct Z-type heterojunction formed between TiO₂and Bi₂S₃ promotes the dye sensitization and the transfer of photogenerated carriers,which improves the photocatalytic performance of the composites under visible light.2.TiO₂/MoSe₂ composites were prepared by electrospinning combined with hydrothermal method.MoSe₂ is in close contact with TiO₂ nanofibers,forming a good contact surface,and photogenerated carriers can be transmitted at the interface.In the process of photocatalytic reaction,due to the existence of MoSe₂ with good electrical conductivity,the electrons in TiO₂ can be transferred to the MoSe₂ co-catalyst.The results show that when the content of MoSe₂ is 5 wt%,the hydrogen production rate is545?mol·h^-1·g^-1,which is 34.1 times higher than that of pure TiO₂.The reason for the increase of photocatalytic activity is that the MoSe₂ co-catalyst with good electrical conductivity acts as an electron"trap"in the complex system,which promotes the separation of photogenerated carriers.3.TiO₂/NiS₂ composites were prepared by electrospinning combined with in-situ sulfurization.In the process of photocatalytic reaction,the good electrical conductivity and large work function(Wc?5.7185 e V)of metallic phase NiS₂ enable the electrons in TiO₂ to flow to the NiS₂ co-catalyst,the photogenerated carriers are separated effectively,and the Schottky barrier can also prevent the photogenerated electrons from flowing back to TiO₂.The results show that the photocatalytic performance of the composites is significantly improved.When the content of NiS₂ is 5 wt%,the best rate of hydrogen production is 9291.8?mol·h^-1·g^-1.The reason for the improvement of photocatalytic activity is that the NiS₂ co-catalyst has good electrical conductivity and forms a Schottky junction with TiO₂,which can effectively separate the photogenerated carriers.