The Syntheses Of NiO,SnO₂ Nanostructure Composites And Their Gas Sensing Properties

VOCs(volatile organic compounds)emissions are rising with economic development,and it is essential for the quality of human life environment to detect VOCs effectively.Metal oxide materials(NiO and SnO₂)are ideal gas-sensitive materials with low costs,excellent physical and chemical properties.However,it is poor to detect acetaldehyde and ethylene glycol.The shortcomings of NiO and SnO₂ in the gas-sensing performances can be improved through nanometerization,surface modification and composite.Therefore,we synthesize the flower-like hierarchical NiO architecture and the butterfly-like hierarchical SnO₂ architecture to realize nanometerization.In addition,NiO nanomaterials are modified by Pt and graphene respectively,and compounded with SnO₂of different dimensions.Finally,the gas-sensing properties are studied.Hydrothermal/solvothermal methods are main methods in the paper.The specific research results are as follows:(1)We synthesize Ni₃(NO₃)₂(OH)₄ by adjusting a series of parameters,and NiO nanostructures are synthesized by calcination.NiO nanoflakes are rich in surface structure,such as pore structure and large surface area.The NiO materials have a response of 118to 50 ppm ethylene glycol at the optimal working temperature(150 ^oC),which have excellent gas-sensing properties.(2)The flower-like hierarchical of NiO architectures are modified by the noble metal Pt,and Pt adheres to the surface of the NiO nanoflakes.With the addition of Pt increasing,the NiO nanoflakes are severely damaged,leading in special defect structures.The modification of Pt improves the sensitivity and selectivity of the NiO sensor to ethylene glycol.0.5 at.%Pt-NiO has a response of 558 to 50 ppm ethylene glycol at the working temperature of 150 ^oC,and the sensor has stronger selectivity and shorter response time.(3)The flower-like hierarchical NiO architectures are modified with r GO.The morphology of samples varies with the amount of r GO,and with the amount of r GO modification gradually increasing,the proportion of NiO flowers on the surface decreases.About 10 wt.%r GO-NiO,small flakes of NiO appear on the surface of r GO.Compared with pure NiO,the working temperature to ethylene glycol(125 ^oC)is lower,and the response(174.89)is higher.(4)The butterfly-like hierarchical SnO₂ architectures are synthesized.SnO₂nanoplatelets have a rich surface structure,including dislocations,protruding islands,mesoporous structures and oxygen vacancies.The SnO₂ nanostructure has a higher response to acetaldehyde at the low working temperature,good selectivity and the detection as low as ppb.Moreover,the response of the sensor to 500 ppb acetaldehyde can reach 78.7.(5)The flower-like hierarchical NiO architectures are compounded with the SnO₂ of different dimensions(0D,1D and 2D)by diffrerent hydrothermal/solvothermal methods.SnO₂ is successfully attached to the surface of NiO nanoflakes as nanoparticles,nanorods and nanoplatelets,but SnO₂ affects the morphology and defects of NiO nanoflakes,changing the surface activity of NiO and the number of gas molecules during the progress of the reactions.Comparing with pure NiO nanoflakes,the responses of three materials have changed.For 1D-SnO₂/2D-NiO and 2D-SnO₂/2D-NiO,the responses are higher,the selectivities are stronger,and the response times are shorter.