| It is an important topic to design gas sensors with high sensitivity,fast response,good stability,portability and low cost because of the intensified environmental pollution and production needs.The gas-sensing material determines the quality of the sensor.Among them,graphene has attracted wide attention due to its extremely high electron mobility and large specific surface area.However,the sensitive structures of graphene have bottlenecks such as low response sensitivity,slow response and low selectivity.Generally,compounding graphene with metal oxides to form heterostructures is one of the effective ways to solve this problem.At present,there have been a lot of research reports on graphene binary composites,but few reports on ternary composite heterostructures.The construction of graphene-based ternary composite heterostructures and the study of the gas-sensing properties are of great significance for clarifying the gas-sensing mechanism of graphene-based multi-composite heterostructures.To this end,based on the Hummers method for preparing graphene oxide(GO)and the sensing mechanism of surface-controlled semiconductor sensitive materials,two ternary composites tin oxide/nickel oxide/reduced graphene oxide(SnO2/NiO/rGO)and tin oxide/nickel oxide/reduced graphene oxide nanosieves(SnO2/NiO/HrGO)are obtained by solvothermal method,oxidation etching,high temperature annealing,and their room temperature gas sensing properties to NO2 were investigated.The research results are as follows:(1)A ternary P-N-P composite structure of two-dimensional reduced graphene oxide supported nickel oxide and tin oxide is proposed,which exhibits excellent room temperature gas sensing performance for NO2 gas..Firstly,NiO nanoflowers and SnO2 nanospheres with uniform particle size and complete morphology were prepared by solvothermal method under high temperature and high pressure at 180℃.Finally,the SnO2/NiO/rGO ternary composite was obtained by annealing at 200℃.The sensing test results show that the response value of SnO2/NiO/rGO to 1 ppm NO2 is 16.2%when the mass ratio is(SnO2:NiO:GO)10:2:1,and the response values are 1.6,2,and 3.5 times higher than those of SnO2/rGO binary composite,NiO/rGO binary composite,and single rGO,respectively.The gas-sensing response values of SnO2/NiO/rGO ternary composites at NO2 concentrations of 200 ppb,500 ppb,1 ppm,5 ppm,and 10 ppm are 10.9%,13.7%,16.2%,17.3%,and 18.0%,respectively.The change is obvious and the lower detection limit is very low.Compared with formaldehyde,ethanol,acetone and other gases,SnO2/NiO/rGO ternary composite has excellent selectivity to NO2 gas.(2)A ternary composite structure based on a novel reduced graphene oxide nanosieve(HrGO)and loaded with nickel oxide and tin oxide is obtained through structural control,and exhibits better sensing performance for NO2.Graphene oxide nanosieve(HGO)is prepared by oxidation etching.Then the SnO2/NiO/HrGO is obtained by high temperature annealing.The sensing test results show that the highest response value of SnO2/NiO/HrGO to 1 ppm is 23.4%,which is 1.7,2 and 3.2 times that of SnO2/HrGO binary composite,NiO/HrGO binary composite and single HrGO,respectively.As the mass ratio of SnO2 to NiO increases,the response of SnO2/NiO/HrGO first increases and then decreases.In addition,the response value of HrGO series products is higher than that of rGO series.When the mass ratio of oxide to graphene is 10:1,the response of NiO/HrGO to 1 ppm NO2 is 11.8%,which is much higher than the NiO/rGO response value of 8.1%.This indicates the porous structure of HrGO contributes to the sensing performance of the material.This project successfully overcomes the shortcomings of low gas-sensing response and high operating temperature of single graphene and metal oxide gas sensors through the ternary compounding and structural control of graphene and metal oxides,and achieves high response to NO2 at room temperature.It has a good guiding role for the design,preparation and NO2 gas sensing test of multi-component composite materials. |
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