Fabrication And Hydrogen Sensing Performance Of MoO₃-based Nano Materials

The characteristics of H₂ as a clean energy have entered people’s eyes,but because of its easy explosion in the air,there will be many unsafe factors in the process of H₂production,storage,transportation,and use.It is imminent to accurately detect H₂leakage with a hydrogen sensor with fast response to H₂,good selectivity and excellent stability.Although single-phase MoO₃ has poor mechanical stability,and the detection range is narrower than that of other materials.However,in this paper,H-MoO₃/NiO nanosheets with good response to H₂ were obtained through the synergy of three modification methods,namely,MoO₃ step by step morphology control,heterojunction construction and hydrogen treatment.selectivity and stability.This study has important implications for the hydrogen sensing performance of MoO₃.The main research contents are as follows:1.High-purity MoO₃ samples were synthesized,with a thickness of about 100 nm,MoO₃ nanosheets with a length and width of about 500 nm,and MoO₃ nanorods with a diameter of about 250 nm.Detect its response to H₂ at room temperature.The test results show that the MoO₃ nanosheet sample has a larger response value,and the response value increases with the increase of the concentration.It is 1.08 times and 1.38times that of MoO₃ nanorods.At the same time,MoO₃ nanosheets also have a relatively short response/recovery time and a more favorable choice for H₂.The BET results prove that MoO₃ nanosheets have better hydrogen sensing performance because of their larger specific surface area,more gas can be adsorbed,and both electron capture and release are increased,resulting in a greater response to H₂.2.The solvothermal method was used to successfully composite NiO onto MoO₃nanosheets,and MoO₃/NiO nanosheets were obtained.The hydrogen sensing performance test at room temperature shows that the composite does not change the n-type response of the nanomaterials,and the 5 mol%MoO₃/NiO sample has the highest response value,and the response value to H₂ at 200 ppm and 1000 ppm is the pure MoO₃ nanosheets,respectively.1.11 times and 1.8 times higher than that,while maintaining the selectivity to H₂,good recyclability and good stability.The hydrogen sensing performance of MoO₃/NiO nanosheets is better.On the one hand,it is because some high-valent Mo⁶⁺ions are replaced by low-valent Ni²⁺ions,resulting in a relatively high oxygen vacancy concentration,which makes the sensor response better.The mass junction adjusts the band gap,forms an electron depletion layer and a hole accumulation layer,traps an increase in the number of O₂ molecules adsorbed,and also forms a"built-in electric field",which improves the separation efficiency of electron-hole pairs and increases the The number of charge carriers ultimately improves the performance of the hydrogen sensor.3.On the basis of preparing MoO₃/NiO in the previous step,hydrogen treatment is performed to prepare H-MoO₃/NiO nanomaterials.The H-MoO₃/NiO composites were characterized by tests,and the hydrogen-treated samples at 300℃had the best performance.The responses to H₂ at 200 ppm and 1000 ppm are 1.24 and 3.31 times higher than those of pure MoO₃,respectively,while also having relatively short response/recovery times.After analysis,it is believed that,on the one hand,nanomaterials can introduce suitable concentration of oxygen vacancies on the surface of metal oxide semiconductors after hydrogen treatment under suitable conditions.On the other hand,the hydrogen treatment causes Ni⁰ to appear in the material,and Ni0further reduces Mo⁶⁺in MoO₃to Mo⁵⁺,and at the same time produces Ni MoO₄,α-MoO₃ and Ni MoO₄ form a p-n junction,and a"built-in electric field"is formed inside,which reduces the The recombination efficiency of electron-hole pairs is improved,the density of charge carriers is increased,and the performance of hydrogen sensor at room temperature is further improved.This research on MoO₃ hydrogen sensor at room temperature lays a solid foundation for further hydrogen sensing research at room temperature.