The Preparation And Room Temperature Hydrogen Sensing Properties Of TiO₂/MoO₃ Nanofibers

Hydrogen（H₂）is an ideal clean energy,flammable,explosive,colorless and odorless,so it poses a major safety hazard during storage,transportation and use.Therefore,real-time detection of hydrogen using highly sensitive and stable hydrogen sensors is an important prerequisite for ensuring the safety of hydrogen energy.Metal oxide-based sensors are low cost,stable,sensitive,and easy to integrate,but they need to operate in a high-temperature environment,have high power consumption,and have poor device stability.Therefore,the development of hydrogen sensors that operate stably at room temperature is a hot spot in this field.One-dimensional materials such as Ti O₂,WO₃,Mo O₃,Sn O₂ and other metal oxide semiconductors have the advantages of large specific surface area and many active points on the surface,making them the best materials for the development of room temperature hydrogen sensors.Mo O₃ is an n-type semiconductor with a layered structure with excellent catalytic hydrogen dissolving ability.Mo O₃ nanofibers have a large specific surface area and many surface active points,while Mo O₃ has a slow response speed and poor sensitivity at room temperature.Therefore,this paper takes Mo O₃ as the object of study,uses Ti O₂ nanoparticles to composite Mo O₃ nanofibers（Ti O₂/Mo O₃）through in situ recombination process,and based on this,assembles hydrogen-sensitive devices using Ti/Pt as electrodes,analyzes the influence of the form,phase,and valence state of the composite system on the electrical characteristics and hydrogen sensitivity performance at room temperature,and By changing the amount of Ti O₂ recombination,annealing temperature,and time,we will improve the performance of hydrogen-sensitive devices and analyze the hydrogen sensitivity enhancement mechanism.The research results are as follows:（1）Ti O₂ composite Mo O₃ nanofibers were obtained by hydrothermal method and impregnation firing method,and the effect of composite ratio on the surface morphology and phase of the nanofiber was investigated.A nanofiber composite material of Ti O₂/Mo O₃（0.5 wt%,1 wt%,1.5 wt%,2 wt%,2.5 wt%）was prepared by an impregnation firing method and the composite ratio was controlled.The results show that the nanoparticles are uniformly attached to the surface of the nanofibers,have good dispersion,and the diameter of the nanoparticles is about 75 nm.When the recombination of Ti O₂ is 0.5 wt%to 2.5 wt%,with the increase of the composite ratio,the ultraviolet absorption spectrum shows redshift,and the Raman spectrum shows blue shift,indicating that there are oxygen vacancies on the surface of the nanofiber.（2）Hydrogen-sensitive devices based on Ti O₂/Mo O₃ nanofibers were assembled,the effects of Ti O₂ recombination on the electrical and hydrogen-sensitive properties of materials were studied,and the mechanism of hydrogen sensitivity enhancement of materials was analyzed.The results show that good contact is formed between the obtained nanofiber and the Ti/Pt electrode.When the amount of Ti O₂ recombination is 0.5 wt%to 2.5 wt%,all nanofibers show good hydrogen sensitivity characteristics at room temperature,and with the increase of recombination volume,the hydrogen sensitivity characteristics of the device gradually improve,and in 2000,with a response time of 15 seconds and a recovery time of 390 seconds,the best performance of nanofibers with a Ti O₂ mass fraction of 2 wt%.The room temperature response under hydrogen ppm concentration is 41.5,and the cycle stability test of the device also shows that the device has good cycle stability for hydrogen,different reducing gas tests were carried out on the device,and the selectivity of the equipment was good.（3）The effect of argon annealing on the hydrogen sensitivity properties of 2 wt%Ti O₂/Mo O₃ nanofibers was investigated,and the hydrogen sensitivity enhancement mechanism of materials was analyzed.The results show that in the range of 300-500°C,the crystallinity of the material increases with increasing annealing temperature.After annealing,the sample showed better sensitivity characteristics than unannealed samples in the temperature range of300-500°C,and showed the best hydrogen sensitivity performance of argon annealing for 1hour at 400°C,the response time was 10 seconds,the recovery time was 90 seconds,and the room temperature response reached 43.2 at 2000 ppm concentration hydrogen,which was improved compared with unannealed samples.Through the cycle stability test of the device,it has also been shown that the device has good cycle stability for hydrogen,and different reduction gas tests have been carried out on the device,showing that the selectivity of the device is good,and the device has good applicability.