Preparation Of Molybdenum Oxide-based Nanomaterials And Research On Its Gas-sensing Properties

As an n-type semiconductor metal oxide with a layered structure,MoO₃ has attracted much attention in the field of gas sensing in recent years.However,problems such as high operating temperature,unsatisfactory detection limits,poor selectivity and stability have limited the practical application of molybdenum oxide in the field of gas sensors,and there is still a lot of exploratory work to be done in its preparation methods and gas sensing mechanisms.Therefore,this paper designed and synthesized three kinds of materials:multilevel structure flower-like?-MoO₃,oxygen-vacancy-enriched porous?MoO₃ nanosheets,and Ag/?-MoO₃ nanobelts.Application of the above synthesized MoO₃ nanomaterials in gas sensor,and they can be used to detect toxic and harmful gases such as,trimethylamine and hydrogen sulfide.And design experiments to study the sensing mechanism in detail.The main content of this paper is divided into the following three sections:?1?Multilevel structure flower-like?-MoO₃ was synthesized by solvothermal method,which was used molybdenum acetylacetonate and acetonitrile.The precursor was calcined at 450? to obtain the final product.The material was assembled into a gas sensor.The sensor has the best gas sensing performance for organic amines?MMA,DMA,TMA?at a working temperature of 170?.The detection limits for MMA,DMA,and TMA are 3 ppm,1 ppm,and 0.1 ppm,respectively.This shows that flower-like?-MoO₃ sensor has a better response to organic amines,and all gases show good linear relationship.?2?oxygen-vacancy-enriched porous?MoO₃ nanosheets was synthesized by a simple one-step solvothermal method using MoO₃ as the molybdenum source and methanol as the solvent.The precursor was calcined at 300,400,500? to obtain the final products.The gas sensor shows the best gas sensing performance for TMA when the annealing temperature is 400?.20 ppb TMA gas can be detected at working temperature of 133? and the response reaches 1.21.A new sensing mechanism is proposed by designing experiments,GC-MS characterization,and combining DFT theory calculation.?3?The?-MoO₃ nanobelts were synthesized by a one-step hydrothermal method using MoO₃ and deionized water,and adding 5wt%Ag to form 5wt%Ag/?-MoO₃composite by photoreduction method.The gas sensing test shows that the 5wt%Ag/?-MoO₃ composite gas sensor has higher selectivity for H₂S gas than pure?-MoO₃nanobelts.The detection limits for H₂S is100 ppb at a lower working temperature of 133^?.Response time of sensor to 100 ppm H₂S is 8 seconds with good long-term stability.In addition,the sensitive materials after H₂S adsorption were analyzed by means of IR,XRD,and XPS characterization to explore their sensing mechanism to H₂S.