Preparation And Gas Sensitive Properties Of Cobalt-based Composite Metal Oxides

In recent years,in order to get a better living environment,people are trying to improve the air quality,at this time,a kind of equipment can quickly and accurately detect the toxic and harmful gases in the environment is very important.And semiconductor gas sensor because of its compact size,low cost has been favored by more and more people.In order to obtain gas sensor with better performance,people use different complexing agents and modifiers to synthesize morpho-controllable semiconductor materials.In this research process,scholars have gradually shifted their focus from single metal oxide gas sensor to composite metal compound gas sensor.As a common solvent,triethylamine（TEA）is widely used in all walks of life,but its inflammable and toxic properties will threaten human life safety.Therefore,the development of a gas sensitive material that can quickly detect triethylamine content in the air can greatly reduce the safety hazard caused by triethylamine leakage.In this paper,three kinds of semiconductor gas sensing materials are prepared and used for the detection of TEA.The first is the serine-assisted hydrothermal synthesis of YF₃-Co₃O₄ composite material（Y-Co₃O₄-350）.In order to judge the effects of different calcination temperatures and YF₃ doping on material properties,Y-Co₃O₄-450 and N-Co₃O₄-350 control materials were prepared at the same time.The gas-sensitive tests of the three materials indicated that Y-Co₃O₄-350 has the best response（（Rg-Ra）/Ra）=93.2)to 100 ppm TEA at 170℃,and the response recovery time is 18s and 36s,respectively.In addition,the optimal adsorption position of the composite was obtained by DFT theory.All the results revealed that the good gas-sensitive response of the Y-Co₃O₄-350-based sensor may be due to the dual effects of morphology sensitization and electron sensitization.Finally,the gas-sensitive response mechanism and enhancement mechanism of composites were analyzed.The second is the arginine-assisted hydrothermal synthesis LaF₃-Co₃O₄ composite material.In order to judge the effect of La F₃ on the material properties,pure phase Co₃O₄ material without La F₃ was prepared.Gas sensitivity tests were performed on above materials and the final results indicated that La F₃-Co₃O₄ has a better response（（Rg-Ra）/Ra）=83.4)to 100 ppm TEA at 170℃.Finally,the gas sensitive response mechanism of the material was preliminarily analyzed.The third is the arginine-assisted hydrothermal synthesis LaF₃:Yb³⁺-Co₃O₄ composite.In order to compare the effect of Yb³⁺doping on the composite,La F₃-Co₃O₄ and pure phase Co₃O₄ were used as the control group.The results indicated that La F₃:Yb³⁺-Co₃O₄ has a good response（（Rg-Ra）/Ra）=156.9)to 100 ppm triethylamine gas at170℃.The doping of La F₃ by Yb³⁺leads to the further increase of fluorine defects in La F₃,which provides a good condition for the formation of adsorbed oxygen,thus achieving the improvement of material properties.In addition,La F₃:Yb³⁺-Co₃O₄ has a sea urchin-like hierarchical structure that will provide more active sites for the overall material,thereby improving the gas sensitivity of the preparation.Finally,the gas-sensitive response mechanism and the growth mechanism of the material are preliminarily analyzed.