Study On Gas Sensing Properties Of Hollow SnO₂/ZnO Microspheres

Metal oxide semiconductor materials are the most widely used gas sensing materials in the field of gas sensors.The sensors based onSn O₂,ZnO have the characteristics of good stability,low cost,and easy accessibility.They are widely used in gas sensing.However,SnO₂ and ZnO based gas sensors are difficult to work under normal temperature conditions and require high temperature excitation above 150°C.Moreover,the most important norm of gas sensors such as selectivity are poor,which makes them difficult to apply under room temperature conditions.Furthermore,the metal oxide material can obtain a larger specific surface area and better gas-sensing properties after being combined with the nanostructures,but nanomaterials work at a high temperature will causes the nanostructures to easily change and can not work stably.In this paper,Hollow Zn O spheres,SnO₂ spheres,and Core-Shell ZnO?SnO₂Heterojunction Spherical Shell Materials were prepared by template hydrothermal method,and the use of SEM,TEM,XPS,XRD and other means for its surface morphology,and then using the interdigital electrodes make sensors for gas sensitivity testing.Under random experimental conditions,the response and selectivity of the composite heterojunction spherical shell material to formaldehyde gas are better than those of the two oxide hollow spheres.The response of the composite material to the 100 ppm formaldehyde gas under ultraviolet irradiation is as high as 76%,which is much higher than which is 26%for ZnO hollow spheres and 11%for SnO₂ hollow spheres.In addition,the response of three materials to formaldehyde under UV excitation is much higher than that under heating conditions.The response of the composite to formaldehyde at the same concentration under heating conditions is only 28%,which is about one-third of that under UV light irradiation.It can be proved that light excitation is an effective method that can make the metal oxide semiconductor sensor work at relatively low temperature.There are many advantages to work at a lower temperature,for example,a higher concentration of ionized oxygen ions can be adsorbed on the sensor surface,thereby increasing the sensitivity,and because the temperature is lower,the power consumption is reduced,and the nano-microscopic structure is not easily destroyed,and at the same time,the photocatalysis improves the selectivity to the volatile organic compound.Based on the above experiment,UV excitation is a better method of metal oxide sensor excitation than thermal excitation.Hollow ZnO/SnO₂ heterojunction material is a good room temperature formaldehyde sensor material.