Preparation And Photocatalytic Properties Of Electrospun ZnO/In₂O₃ And In GaZnO₄ Nanofibers

Due to the excellent physical-chemical properties and unique one-dimensional structural characteristics,inorganic nanofibers have a wide range of applications such as sensor applications,energy storage,optoelectronic devices,environmental purification,biotechnology and chemical catalysis.Electrospun inorganic nanofibers become a hot topic in the field of photocatalysis because of the adjustable components,uniform fiber diameters,large length to diameter ratio and high surface area,as well as their easy for designing new photocatalytic materials with high activity and better reusability.ZnO is a direct band gap semiconductor which has excellent ultraviolet light absorption characteristics and suitable energy position of conduction band and valence band.However,the photocatalytic quantum yield of ZnO is very low due to the high electron-hole recombination rate.To solve these problems,we designed and fabricated In₂O₃-ZnO heterojunction composite nanofibers and InGaZnO₄ nanofiber by electrospinning to improve the photocatalytic properties of ZnO-based materials,and the main results are as follows:?1?In₂O₃-ZnO heterojunction composite nanofibers with uniform diameters were obtained by electrospinning technique.The obtained samples were characterized by the analytical methods of Scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,X-ray powder diffraction?XRD?,X-ray spectroscopy?XPS?,Nnitrogen adsorption-desorption isotherms and Uv-Vis diffuse reflectance?Uv-Vis/DR?etc.The results indicate that the diameter of In₂O₃-ZnO heterojunction composite nanofibers is in the range of 40-60 nm which is much less than pure In₂O₃ and ZnO nanofibers.Their specific surface area is about 69 m2/g with the average pore size of about 8 nm.Photocatalytic studies show that In₂O₃-ZnO heterojunction composite nanofibers present much higher performance for the degradation of dyes and the hydrogen production rate,which illustrate that the formation of In₂O₃-ZnO heterojunction can inhibit the electron-hole recombination in ZnO and improve photocatalytic activity.?2?InGaZnO₄ nanofibers with uniform diameters were prepared by electrospinning.Scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,X-ray powder diffraction?XRD?,X-ray spectroscopy?XPS?,Nitrogen adsorption-desorption isotherms and Uv-Vis diffuse reflectance?Uv-Vis/DR?were used to characterize the obtained samples.The results show that InGaZnO₄ nanofibers calcined at 550?have smooth surface and uniform diameters of 50-70 nm.Their pore size distribution is in the range of 2-10 nm and their specific surface area can be achieved 116 m2/g.InGaZnO₄ nanofibers have much better photocatalytic activity than pure ZnO and In₂O₃ nanofibers,while the absorbance properties of InGaZnO₄ nanofibers are lower than ZnO and In₂O₃ nanofibers.Thus,InGaZnO₄ nanofibers may have higher separation efficiency of electrons and holes due to their characteristic crystal structure of native superlattice structure.Furthermore,the grain size of InGaZnO₄ nanofibers is enlarged from 5 nm to 22 nm with increasing the calcination temperatures,but their photocatalytic activities are reduced.