Preparation Of Tungstate Nanomaterials And Gas Sensing Properties At Room Temperature

Aiming at the existing gas sensor has paid fewer researches on the simultaneous identification for detection of NO_x or NH₃ gases in SCR technology,the electrospinning method was used to prepare modified Tungstate nanomaterials by changing the atomic ratio of the doped element,which endly realized the detection of both oxidizing gases and reducing gases.Firstly,the pure tungstate cobalt,cobalt tungstate,and tungsten trioxide composites were prepared with tungstic acid and cobalt acetate as raw materials by using electrospinning method,and the gas sensing performances of ammonia gas and nitrogen oxide were tested at room temperature.XRD and IR results showed that the synthesized sample had good crystallinity and no other substances generated in the sample.The CoWO₄-CoWO₄ heterojunction and WO₃-CoWO₄ homojunction structures of the material could be seen by taken TEM technique,and the lattice plane of cobalt tungstate and tungsten trioxide were?011?,?110?,?111?for CoWO₄ and?122?,?114?for WO₃,respectively.The synthesized material Co-W-3 with mole ratio Co and W 3:10exhabited higher gas sensing performance than the pure cobalt tungstate and the other cobalt tungstate composite material.The sensitivity to 1 000 ppm ammonia at room temperature was 2.17,the response time was 3 s,and the sensitivity to 100 ppm nitrogen oxide was 4.65,the response time was 1.33 s.XPS analysis showed that the increased adsorbed oxygen content in the synthesized sample was the main reason for the gas sensitivity improvement.Secondly,the pure nickel tungstate,nickel tungstate and tungsten trioxide compositeswere prepared with tungstic acid and nickel acetate as raw materials by using the same synthesis method,and the gas sensing properties of ammonia and nitrogen oxides were also tested at room temperature.The results of XRD and IR indicated that the synthesized samples had good crystallinity and there was no misfit peaks in it.The NiWO₄-NiWO₄ homojunction structure and WO₃-NiWO₄heterojunction structure of the material were characterized by TEM,and lattice planes of nickel tungstate and tungsten trioxide could be seen clearly?-121?,?110?were for NiWO₄ and?042?,?024?for WO₃,respectively.The gas sensitivity properties of Ni-W-3sample with mole ratio Ni and W 3:10 was more obviously better than the pure tungstate nickel and the other cobalt tungstate composite material.The sensitivity to 1000 ppm ammonia at room temperature was 1.8,the response time was 3.7 s,and for100 ppm NO_x,the sensitivity was 4.05,the response time was 2 s.It was found that the excellent gas detection properties of the modified tungstate composites not only provided a certain theoretical basis for solving ammonia and nitrogen oxide pollution detection which was caused by industrial production and other human activities,but also lower cost in simultaneous monitoring.