Preparation Of ZnO-Based P-n Heterojunction Composites By Electrospinning And Their Gas Sensing Properties

The materials,prepared by electrospinning,have net structure and rich gas adsorption sites,which can be used as gas sensing materials.In this paper,ZnO nanofibers were prepared by electrospinning,and the optimal technological parameters were obtained by single factor experiment.Moreover,the effect of different calcination temperatures on gas sensing performance were investigated.In order to improve the sensitivity,selectivity and stability of the materials,p-type metal oxides?NiO and Co₃O₄?were doped with ZnO to prepare NiO-ZnO and Co₃O₄-ZnO nanofibers with p-n heterostructure,respectively.It would provide a new idea for the development of new gas sensing materials.The specific work is as follows:?1?ZnO precursor was prepared by electrospinning using ethanol and N,N dimethylformamide as solvent,and zinc acetate and polyvinylpyrrolidone as raw material.The effect of spinning parameters on fiber morphology and structure were investigated.Moreover,the network structure ZnO nanofibers were obtained by optimizing the calcination temperature.The gas sensitivity of samples at different calcining temperatures were tested and the gas sensing mechanism was discussed.The results showed that the precursor with good morphology can be obtained by electrospinning with PVP content of 13 wt.%,voltage applied by high-voltage device of 16 k V and curing distance of 16 cm.The ZnO nanofibers obtained by calcining at 700?,which had the highest response to ethanol.?2?NiO-ZnO composite nanofiber with p-n heterojunction were prepared by electrospinning.The effect of molar ratio of Ni and Zn on the structure and gas sensitivity of NiO-ZnO were investigated.The gas sensitivity test results showed that the NiO-ZnO with network structure had better gas sensitivity than ZnO.The NiO-ZnO with Zn/Ni molar ratio of 12:1 had the highest gas-sensitive performance to acetone.The response to acetone of 50 ppm reached 62 at the best operating temperature of 300?,which was 10 times than ZnO nanofibers.and the NiO-ZnO with Zn/Ni molar ratio of 12:1 showed good selectivity and stability.?3?The Co₃O₄-ZnO with p-n heterojunction was prepared by electrospinning,and the effect of the molar ratio of Co and Zn on the structure and gas sensitivity of Co₃O₄-ZnO were investigated.The results showed that when the molar ratio of Zn/Co was 10:1,Co₃O₄-ZnO nanofibers had significant gas sensitivity to ethanol.The response to 50 ppm ethanol reached 115 at the optimum operating temperature of 300?.The results showed Co₃O₄-ZnO nanofibers with molar ratio of Zn/Co of 10:1 had the fast response characteristics,good selectivity and stability.