Preparation And Study On Gas Sensing Properties Of Hierarchical Structure Metal Oxide Semiconductor/g-C₃N₄ Composite

The construction of three-dimensional hierarchical composite materials assembled from low dimensional nanomaterials is an effective strategy to improve the gas sensing performance of metal oxide semiconductors（MOS）.This article takes morphology control as the starting point,using metal oxide semiconductors Sn O₂,Zn O,and Co₃O₄as the matrix and graphite phase nitriding（g-C₃N₄）as the composite,constructs three hierarchical structures of Sn O₂/g-C₃N₄,Zn O/g-C₃N₄,and Co₃O₄/g-C₃N₄ composite materials.The structural characteristics of the prepared materials were explored through characterization methods such as XRD,SEM,EDS,and N₂ adsorption desorption,and the gas sensing performance of the prepared materials was tested using a gas sensing analysis system.The specific research content is as follows:（1）Two dimensional nanosheets of g-C₃N₄ were successfully prepared using thiourea as raw material through thermal polymerization and ultrasonic assisted liquid stripping.Pure Sn O₂ and Sn O₂/g-C₃N₄ composite materials with flower like hierarchical structure assembled by nanosheets were prepared by hydrothermal method and high-temperature calcination,and their gas sensing properties for ethanol were analyzed and compared.Gas sensitive studies have shown that the response of Sn O₂/g-C₃N₄-5 to 100ppm ethanol at 200℃is 18.88,2.09 times that of pure Sn O₂,and it has a fast response and recovery time of 2s and 13 s,respectively.In addition,Sn O₂/g-C₃N₄-5 also exhibits good repeatability,stability,and excellent selectivity for ethanol.The gas sensing properties of Sn O₂/g-C₃N₄-5 towards ethanol are attributed to the unique hierarchical structure and n-n heterojunction of the material.（2）Pure Zn O and Zn O/g-C₃N₄ microspheres with hierarchical structure assembled from nanoparticles were prepared using hydrothermal method and subsequent high-temperature calcination.Their gas sensing properties for ethanol were analyzed and compared.Gas sensitive studies have shown that the response of Zn O/g-C₃N₄-3 to100ppm ethanol at 260℃is 26.36,which is 2.19 times that of pure Zn O.The response and recovery times are 26s and 31s,respectively.Moreover,Zn O/g-C₃N₄-3 has good repeatability,stability,and excellent selectivity for ethanol.The excellent gas sensing performance is attributed to the good dispersion and uniformity of nanoparticles in the Zn O/g-C₃N₄-3 hierarchical structure,as well as the n-n heterojunction.（3）Porous flower-like hierarchical structures pure Co₃O₄ and Co₃O₄/g-C₃N₄composites derived from metal organic framework（MOF）cobalt were prepared by solvothermal method and high-temperature calcination.The gas sensitivity of the synthesized samples to ethanol was tested.Gas sensitive studies have shown that the response of Co₃O₄/g-C₃N₄-4 to 100ppm ethanol at 220℃is 33.48,which is 1.5 times that of pure Co₃O₄,the response time and recovery time were 199s and 201s respectively.Co₃O₄/g-C₃N₄-4 exhibits good repeatability,stability,and excellent selectivity for ethanol.The thin and porous nanosheets,large specific surface area,and p-n heterojunction in the hierarchical structure of Co₃O₄/g-C₃N₄-4 are the main reasons for the excellent gas sensing performance.This method provides a new research approach for the porous flower like hierarchical structure MOS derived from the MOF method.