Study On The Doping And Modification Of SnO₂ Nanorods And Room-Temperature Hydrogen Sensing Properties

With the particularly rapid development of science and technology nowadays,more and more non-renewable resources mainly oil are gradually consumed.Great damage to the environment has been caused,the use of fossil fuels leads to the development of cleaner and more green new energy.It’s an important strategy for the development of all countries.Hydrogen energy,as one of clean energy sources,has wide sources.It is widely used,but hydrogen molecules is small and has low ignition energy.Leakings of hydrogen are prone to occur in the process of transportation and storage applications.Explosion of hydrogen leads to casualties and property losses.Therefore the research and study of sensitive and reliable room temperature hydrogen sensor to monitor real-time detection of hydrogen is particularly important to ensure the safety of the hydrogen related industry.Transition metal doping and composite construction of heterojunctions are proved to be effective means to improve the performance of hydrogen sensors.In the field of gas sensing,SnO₂ is a kind of commen n-type metal-oxide semiconductor material,but the performance of the traditional SnO₂ material cannot meet the needs of actual conditions.It is necessary to improve its sensitivity through transition metal doping and composite construction of heterojunction to obtain better gas sensors.In this paper,SnCl₄·5H₂O and Na OH were used to synthesize SnO₂ nanorods by simple one-step hydrothermal method,TiO₂ composite SnO₂nanorods by hydrolysis,SnCl₄·5H₂O and NiCl₂·6H₂O,Ni doped SnO₂ nanorods with high specific surface area by simple one-step hydrothermal method,and the hydrogen sensor based on doping-modified SnO₂ nanorods was analysed by magnetron sputtering and lithography,and the sensitivity of the device to hydrogen was tested.The research contents are as follows:（1）SnO₂ nanorods with tetragonal rutile structure were synthesised,and the diameter of each nanoflower was about 3μm.TiO₂ nanoparticle-modified SnO₂ nanorod materials were prepared by hydrothermal synthesis technique and in situ hydrolysis method,and the effects of the ratio of water to alcohol,hydrolysis temperature,hydrolysis time and the concentration of precursor TiCl₄ solution on the surface morphology of SnO₂ nanorods modified by TiO₂ were studied,and the mechanism of the hydrolysis reaction was explored.The morphology,element distribution and crystal structure of SnO₂ nanorods modified with the same proportion of TiO₂were analyzed.TiO₂ modified SnO₂ nanorods maintain tetragonal rutile structure,and the size of individual nanorods does express significantly change.TiO₂ modified on the surface of SnO₂nanorods mainly exists in the form of thin films and small short cones.When the amount of TiO₂ modified is excessive,the SnO₂ nanorods will completely cover the SnO₂ nanorods.（2）Hydrogen sensor devices based on TiO₂-modified SnO₂ nanorods were assembled,and the effects of the proportion of TiO₂ modification on the electrical properties of the sensors and on the gas-sensitive properties were investigated.The experimental results show that an increase in the amount of TiO₂ modification leads to a significant increase in the resistance value of the material.The experimental results show that for a precursor solution concentration of 0.3 mmol/mL,the device achieves a response of 1.73 for 3000 ppm H₂ at room temperature,with a response time of 367 s and a recovery time of 603 s.The best hydrogen-sensitive performance is achieved at this time.The repeatability and selectivity of the material were tested at room temperature and humidity,and the experimental results showed that the sensor based on this material has good repeatability and selectivity.The mechanism of TiO₂ modification on the optimization of hydrogen sensing of SnO₂ nanorod material was investigated.The gas-sensitive response of the hydrogen sensor devices based on TiO₂ modified SnO₂ nanorods was improved with excellent selectivity and repeatability,but the humidity resistance stability needs to be enhanced.（3）Ni-doped SnO₂ nanorods with high specific surface area were synthesized by a simple one-step hydrothermal method using SnCl₄·5H₂O and NiCl₂·6H₂O reagents as raw materials,and the effects of different Ni doping ratios on the nanorod size and morphology were investigated.With the increasing Ni doping content,the size of SnO₂ nanorods changed significantly,and the diameter of individual nanoflower decreased from 3μm to about 1μm.The Ni doping significantly reduced the nanorod size and increased the aspect ratio,while a higher aspect ratio would have a larger specific surface area.At the same time,the lattice constant increases in the a-axis direction and decreases along the c-axis as the Ni doping ratio increases.Hydrogen sensor devices based on Ni-doped SnO₂ nanorods were assembled,and the effects of the Ni doping ratio on the electrical and gas-sensitive properties of the sensors were investigated.The experimental results show that the change in the doping ratio significantly affects the gas-sensitive performance of the material,and the best hydrogen-sensitive performance is achieved for Ni/Sn=3.7 at%,with the device achieving a response of79.11 for 3000 ppm H₂ at room temperature with a response time of 71 s and a recovery time of 797 s,which is related to the highest adsorbed oxygen content on the surface of the sample at room temperature and humidity.The material was tested for selectivity at room temperature and humidity,and the experimental results indicated that the sensor has great selectivity for hydrogen.The mechanism of the doping of Ni on the optimization of hydrogen sensitivity of SnO₂ nanorod material was investigated.The gas-sensitive response of the hydrogen sensor devices based on Ni-doped SnO₂ nanorods achieved a significant improvement of 70 times compared to the undoped SnO₂ nanorod hydrogen sensor devices,with excellent selectivity.