Research Of Gas Sensor Based On The Flower-like Hierarchical ZnO Material

Nowadays, in order to meet the demand of the era, science and technology in all fields have rapidly developed, therefore, in-depth understanding of the material, the development of new energy, new material plays an important role.In this process, the sensor can get large amounts of information that human senses can’t directly access to, which makes it play an important role in daily life and in the research field and.Gas sensor, as one of them, plays a very important role in detecting harmful toxic gases and flammable and explosive gases in order to ensure the safety of people production and living. For gas sensors, sensing materials are the key factors to influence the sensor performance. ZnO is one of the earlier used sensing materials, it is because that it has an unique physical and chemical properties, without toxic and the low cost of preparation, etc. Large amounts of evidence suggest that the crystal phase, morphologies, and the porosity have a significant impact on properties. Therefore, designing and preparing ZnO materials with different morphology and structure are greatly important in order to improve the performance of materials.Three-dimensional hierarchical structure composed of one dimensional and two dimensional material have a large surface area, which can provide more active sites, and the hierarchical architecture provides favourable transport pathways for electrons and holes. As a consequence, the properties superior to congeneric nanometer materials generated, which attract wide attention.ZnO materials with porous and hierarchical flower-like structure were synthesized through mild hydrothermal and simple calcination approach, in which the flower-like layered zinc oxalate hydroxide(Zn C2O4·3Zn(OH)2) precursor was first synthesized and then calcined at 600℃. The obtained products were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopic(TEM), Brunauer-Emmett-Teller(BET) and thermogravimetric(TG). We proposed the possible growth mechanism of the material via studying the time evolution experiment results. In the process of reaction, oxalic acid as a structure-directing agent hydrolyzed and then formed primarily sheets-like intermediate Zn C2O4·2H2O as an intermediate which could slow down the rate of hydrolysis reaction. With Hexamethylenetetramine(HMT)hydrolysis to produce hydroxy reaction,leads to the formation of layered zinc oxalate hydroxide precursor and provide basic materials for forming the hierarchical flower-like porous ZnO materials.Furthermore, the gas sensitivity also can be characterized based ZnO materials, whose results indicated that the synthesized materials had a preferable selectivity to ethanol gas. The fast response rate and reversible performance can be attributed to the produced greater specific surface area caused by the porous and hierarchical structure, showing that this kind of material has a certain application value in the field of gas sensor.