Construction Of Copper Matrix Composites And Study Of NO_x Gas Sensitivity Properties

In order to prepare copper-based composites with low cost and excellent gas-sensing properties,the flower-like CuO-NiO composites with mesoporous structure and the porous CuO-ZnO composites were prepared by simple refluxing and hydrothermal methods in this paper.The structure of the composite film was characterized by XRD,BET,SEM,TEM and XPS etc..The relationship between the structure of the material and the gas-sensing properties was also explored,and the NOx gas sensitivity of composite materials was tested at room temperature..Firstly,CuO-NiO composites with different molar ratios were prepared by controlling reflux reaction of different quality nickel hydroxide nanosheets(hydrothermal synthesis)and copper hydroxide precursors,the characterization of CuO-NiO composites were tested.The results showed that CuO-NiO composites with flower-like hierarchical structure are prepared,where nickel hydroxide is a nanosheet structure.At room temperature,the prepared samples of CuO-NiO composites were tested for NOx(nitrogen oxide)gas sensitivity,and the gas-sensing mechanism of the composites was analyzed.The results showed that the gas-sensing performance of the sample with a molar ratio of 1:1(CN-1)was best among the samples compared with the molar ratio of 2:1(CN-2)and 4:1(CN-4),which was 82.88%for 100 ppm NOx(nitrogen oxide)gas and the corresponding response time was only 2 s,the minimum detection limit was 1 ppm and the stability test time was up to 9 weeks.The reason of their good gas-sensing properties was attributed to the flower-like hierarchical structure CuO-NiO composites have more gas surface adsorption sites,and the NOx could be more easily adsorbed and desorbed on the surface of the material.At the same time,the formation of p-p heterostructures makes the electrons in NiO faster and efficiently transferred to CuO,this also helps to speed up the gas-sensing response.Secondly,the porous CuO-ZnO composites were synthesized by simple refluxing-calcination method without using the templating agent.By adjusting the quality of ZnO,CuO-ZnO composites with different molar ratios were prepared.The structural characterization and gas-sensing properties of the synthesized CuO-ZnO composites were investigated,and the formation mechanism and gas-sensing mechanism were also discussed.The results showed that the sample with the molar ratio of 4:1(CZ-4)has the best gas-sensing property compared with the samples with molar ratio of 2:1(CZ-2)and 1:1(CZ-1),which was 63.04%for 100 ppm NOx(nitrogen oxide)gas and the corresponding response time is only 2 s,the minimum detection limit was 1 ppm and the stability test time was up to 6 weeks.In addition,through the selective test,the CuO-ZnO composite has a gas-sensitive response to the NH3 gas excepted the super performance to the NOx(nitrogen oxide).Its excellent gas-sensing properties can be attributed to the combined action of the high specific surface,highly porous structure,and the high conductivities of the interaction between CuO and ZnO.In summary,the flower-like CuO-NiO composites with mesoporous structure and the porous CuO-ZnO composites have higher sensitivity,faster response time,lower detection limits,better stability and selectivity to NOx(nitrogen oxide)at room temperature,and they have the potential application value in the field of gas sensors.