Preparation Of Sno₂ Nano-materials And Their Gas-sensing Properties

SnO2 is a kind of typical n-type semiconducting metal oxide with a wide band gap of 3.6 eV.For its unique nature from nanodimensional and semiconductor features,SnO2 nano-materials show vast potential applications in the field of transparent conducting oxide(TCO)materials,oxidation catalysts and solid-state gas sensors.Therefore,the synthesis and applications of nanostructured SnO2 have aroused great interest in the nano-materials field.In this thesis,the morphology controls of nanostructured SnO2,as well as their gas-sensing properties are the main research contents.Hydrothermal method and solvothermal method were used to synthesize SnO2 microspheres,SnO2-Pd-Pt-In2O3 nanocomposite,noble metals(Pt,Pd)/SnO2 composite microspheres,SnO2 nanoparticles,and noble metals(Pt,Pd)/SnO2 nanometer composite nanoparticles,respectively.The resultant products were used as sensing materials for gas sensors to detect the virulent,inflammable and explosive gases,respectively,and the sensing mechanisms of also were discussed.The main contents could be summarized as follows:(1)Synthesis,characterization and gas-sensing properties of SnO2 microspheresSnO2 microspheres were successfully obtained through a facile solvothermal method.The structure,morphology,surface chemical state and specific surface area of SnO2 microspheres were analyzed by XRD,SEM,TEM,XPS and BET,respectively,and the corresponding formation mechanism was supposed.The as-synthesized SnO2 microspheres were used as sensing materials for gas sensor to detect the formaldehyde gas.It is found that the gas sensor has excellent gas-sensing properties toward formaldehyde gas at the operating temperature of 200 ?.(2)Preparation and gas-sensing properties of SnO2-Pd-Pt-In2O3 nanocompositeAs a new methanol sensing material,the SnO2-Pd-Pt-In2O3 nanocomposite was obtained by facile solvothermal method and solid-phase reaction method.The phase composition and the unique structure of as-prepared Sn02-Pd-Pt-In2O3 nanocomposite were comprehensively characterized using the techniques such as XRD,SEM and TEM,respectively.The results of gas sensing properties indicate that the sensor based on SnO2-Pd-Pt-In2O3 nanocomposite shows the low operating temperature,ultra-high response,and minimum detection limit toward methanol gas.(3)Preparation and gas-sensing properties of noble metals(Pt,Pd)composited SnO2 microspheresSnO2 microspheres in a composite with noble metals(Pt,Pd)were synthesized by a facile solvothermal method.The crystal structure,morphology,composition,surface chemical state and specific surface area were thoroughly characterized.The as-synthesized noble metals(Pt,Pd)/SnO2 nanocomposite microspheres were used to fabricate gas sensor devices.The gas sensor based 5.0 mol%Pt-SnO2 nanocomposite not only shows a lower operating temperature of 80 ?,but also exhibits ultra-high response,faster response and recovery speeds,remarkable repeatability,selectivity and reliable stability toward methanol gas.10 mol%Pd-SnO2 nanocomposite shows excellent gas-sensing properties toward hydrogen at the operating temperature of 200?.(4)Synthesis,characterization and gas-sensing properties of SnO2 nanoparticlesSnO2 nanoparticles with various shapes were synthesized by a simple hydrothermal method,and its crystal structure,morphology,surface chemical state and specific surface area have been thoroughly characterized.The as-synthesized SnO2 nanoparticles were used as sensing materials in the sensor to detect the butane.Gas sensing tests exhibit that the SnO2 nanoparticles are highly promising for gas sensor applications.The SnO2 nanoparticles base gas sensor display a high response,faster response and recovery speeds,excellent repeatability,and reliable stability.(5)Preparation and gas-sensing properties of noble metals(Pt,Pd)composited SnO2 nanoparticlesNoble metals(Pt,Pd)composited SnO2 nanoparticles have been directly prepared via a simple hydrothermal method.The structure,morphology,composition,surface chemical state and specific surface area of the noble metals(Pt,Pd)/SnO2 nanocomposite nanoparticles were analyzed with XRD,SEM,EDX,TEM,XPS,BET,respectively.The gas-sensing characteristics of the resulted products for carbonic oxide and methane were investigated,respectively.1.5 mol%Pt-SnO2 nanocomposite exhibits a superior sensitivity toward carbonic oxide at the operating temperature of 80 ?.2.5 mol%Pd-SnO2 nanocomposite not only shows a lower operating temperature of 340 ?,but also exhibits ultra-high response,faster response and recovery speeds,and reliable stability toward methane.