Microstructure Control And Hydrogen Sensing Enhancement Mechanism Of ZnO/SnO₂ Based Nanofibers

As a kind of clean energy throughout the industrial production,hydrogen has been widely developed in the power grid.It can be used as the coolant of hydrogen cooled generator set,can also be used as energy to be converted and stored by generator set,and can also be used as a fault characteristic gas,which plays an important role in DGA analysis.Hydrogen is colorless and odorless,easy to leak,low explosion limit and difficult to detect,which always poses a threat to the safe operation of power grid.Hydrogen detection involves a wide range of equipment,many different needs.Therefore,the research on high performance and low-cost controllable preparation of hydrogen sensor is also a strong guarantee for the safe operation of power grid.ZnO and SnO₂ are both wide band gap n-type metal oxide semiconductors,which have been widely studied as ideal hydrogen sensing materials due to their excellent thermal and chemical stability.The results show that the materials with low dimensional structure will show more excellent electrical properties because of their nano effect,which makes the nanofiber structure have more potential in hydrogen sensing.Noble metal doping is often used to break through the problem of gas selectivity,but it will also increase the manufacturing cost,and cannot coordinate the contradiction between high performance and low-cost.Therefore,it is one of the important ways to realize the deep excavation and controllable preparation of nanofiber hydrogen sensor performance.Based on the advantages of one-dimensional nanomaterials in gas sensing,this paper is devoted to the experimental research on the performance enhancement of Zn O/Sn O₂based nano-structured hydrogen sensors by electrospinning.Aiming at the target of improving the performance of Zn O/Sn O₂ based hydrogen sensing materials,the multi-level composite microstructure control and hydrogen sensing performance enhancement mechanism of Zn O/Sn O₂ based nanofibers were studied.Firstly,aiming at the problem of low catalytic efficiency of solution doping and other traditional noble metal doping methods,a method of magnetron sputtering doping surface microstructure calcination reconstruction was proposed.This method can make noble metal dopants efficiently disperse on the surface of electrospun nanofibers,and improve the performance of hydrogen sensor from the perspective of surface microstructure and morphology control of nanofibers.The response R_a/R_g of Pd doped Sn O₂ nanofiber rods prepared by this method to 100 ppm hydrogen is 28.5,and the response time is only 4 s.compared with the undoped samples,the hydrogen response is increased by 2.5 times when the optimum operating temperature is reduced by about50%.Then,by deeply regulating the spinning solution and calcination parameters,a one-step synthesis method from electrospun fiber precursor to hollow nanofibers was obtained.The ternary heterojunction Pd/Zn O/Sn O₂ hollow nanofibers based on this method obtained optimum response of 171 to 200 ppm hydrogen,and the real-time response was greatly improved.Furthermore,the correlation between Ar plasma post-treatment and hydrogen sensing properties of materials was studied.From the perspective of lattice defect structure control,the mechanism of oxygen control and hydrogen sensing properties enhancement on the surface of materials by plasma treatment was obtained.The materials were promoted from Pd/Sn O₂ to Zn O/Sn O₂,and the application of non-noble-metal performance enhancement method with low-cost was realized.Finally,aiming at the bottleneck of poor selectivity of non-noble-metal doped hydrogen sensor,the functional structure modified nano composite structure was successfully synthesized from the precursor of electrospun nanofibers by controlling the calcination process.The synergistic effect of the composite structure significantly improved the performance and selectivity of the sensor.The Zn O(0001)single crystal facet functionalized Zn O-Sn O₂ heterojunction nanorod composite structure was fabricated.Response at 150?for 200 ppm hydrogen is more than 400,and it also has excellent performance in real-time response and hydrogen selectivity.The technology of electrospinning has been transformed from a single morphology and homogeneous composition to a functional heterogeneous composite structure,solving the contradiction between high performance and low-cost preparation successfully.