Preparation Of Three-Dimensional RGO Aerogel/Metal Oxide Nanocomposite And Gas-Sensing Properties At Room Temperature

In recent years,toxic and harmful gases produced by industrial production,automobile exhaust and decoration have caused great harm to people’s health.Therefore,semiconductor gas sensor,as a convenient and simple gas detection equipment,has been gradually paid attention.Gas sensor based on single metal oxide has the advantages of high sensitivity and low price,and is widely used,but it still has the disadvantages of high operating temperature,high power consumption,poor selectivity and so on.Therefore,we hope to develop a new type of gas sensor with low power consumption,high sensitivity,high selectivity and good stability at low temperature or even room temperature.It was found that by depositing metal oxide nanocrystals on a conductive and stable carrier,the electrical conductivity and dispersion of nanocrystals could be improved effectively.Reduced graphene oxide（r GO）has been widely studied for its excellent stability,high electron migration rate and high specific surface area.The r GO/metal oxide semiconductor（MOS）composite was constructed.The r GO could act as a carrier to avoid the agglomeration of MOS nanocrystals.In addition,as an excellent conductive material,r GO can enhance electron transfer to the target gas（or inside the composite material）and improve gas diffusion,especially for three-dimensional r GO aerogels with interconnected porous structures and high specific surface area.In this paper,room temperature gas sensitive materials with three-dimensional r GO aerogel and different metal oxides composite were designed and synthesized by hydrothermal method.The research contents includes the following points:1.Firstly,the modified Hummers method was used to prepare GO,which was analyzed by scanning electron microscopy（SEM）and Raman spectroscopy（Raman）.It was confirmed that the prepared GO sheet were very thin,which laid a foundation for subsequent experiments.Then,three-dimensional r GO aerogels were prepared by hydrothermal assembly and freeze-drying methods.Three-dimensional r GO aerogels with different micro-morphology were prepared by exploring reaction time and adding different kinds of amine sources.The microstructure of the aerogel was characterized by SEM,the specific surface area and pore size distribution of the material were analyzed by BET,and the graphitization degree of r GO was analyzed by Raman spectroscopy to determine the best synthesis plan.2.Three-dimensional r GO aerogel/Zn O composites and three-dimensional r GO aerogel/Co₃O₄ composites were prepared by one-step method.The three-dimensional r GO aerogel/Zn O composites were analyzed by SEM and X-ray diffraction analysis（XRD）.It was found that the nanorod-like wurtzite Zn O was uniformly distributed on the surface of r GO sheet,and there was a cross-linked macroporous network structure inside the three-dimensional r GO aerogel.The gas sensitivity test showed that at room temperature the response value of the composite to 100 ppm NO₂ is 17.5%.The characterization results of three-dimensional r GO aerogel/Co₃O₄ composites confirmed that the cubic spinel Co₃O₄nanoparticles were uniformly distributed on r GO sheet,and the specific surface area is 306.5m²/g.The response to 100 ppm triethylamine gas at room temperature reaches 95%at room temperature.3.Three-dimensional r GO aerogel/Fe₂O₃ composite,three-dimensional r GO aerogel/Sn O₂ composite and three-dimensional r GO aerogel/In₂O₃ composite were assembled and synthesized by electrostatic gravity,and a series of characterization tests were carried out on the composites.The results show that the size of the Fe₂O₃ cube in the three-dimensional r GO aerogel/Fe₂O₃ composite is about 300 nm and the specific surface area is 223.8 m²/g.At room temperature,the response value of the Fe₂O₃ cube to 20 ppm NO₂ is 9.9%.The size of Sn O₂ microspheres which is in the prepared three-dimensional r GO aerogel/Sn O₂ composite is about 400 nm,and the specific surface area is 240.6 m²/g.The response value of the prepared three-dimensional r GO aerogel/Sn O₂ composite to 20 ppm NO₂ at room temperature is 11%.In the prepared three-dimensional r GO aerogel/In₂O₃ composite,the size of In₂O₃nanoparticles is about 150 nm,and the specific surface area of the composite is 241.9 m²/g.The response value of In₂O₃ nanoparticles to 20 ppm NO₂ at room temperature is 16.8%.