The Study Of High-performance H₂S Sensor Based On Metal Oxide Nanomaterials

It is well known that H₂S is poisonous gas,as well as atmospheric pollutants,and brings serious harm to the environment and people life.Therefore,the preparation of low temperature,high sensitivity and fast response of H2S sensor is of great significance.The simple preparation method were developmed to synthesize variety of nanoscale metal oxides for H2S gas sensors in this thesis.The gas sensitivities of the metal oxides to H2S at a low temperature were investagted and their gas-sensing mechanisms were also discussed.Various and different metal oxide nanomaterials have been synthesized by different methods,includeing one-step reduction method,sonochemistry method,solvothermal method and solvent thermal pyrolysis.There materials were invlolved in Cu2O/CuO microsphere structure,CuO nanobelt,ZnO nanoparticles?nano bundles and nanorods,ZnFe₂O₄nano-particles,porous Co₃O₄ nanosheet and?-Fe₂O₃ nanosheet ect.Especially the as-synethsized ZnO nanomaterials have different morphologies,including nanoparticle clusters with diameter of 300-500 nm,500-900 nm ZnO bundles composed of nanorods,and single-dispersed nanorods with diameter and length of 45 and 145 nm,respectively.The influence of synthesis conditions on the samples above were studied,and their growth mechanisms were discussed.For example,the growth mechanism of CuO nanobelts has been described below:Cu?OH?2 nanowires firstly form,and they were transformed into one-dimensional?1D?Cu?OH?2/CuO core–shell nanostructures and then into CuO nanobelts gradually.This two-step process priority growth has opened up a new way of preparation for the synthesis of nanomaterials.The H₂S sensing properties of the metal oxides above were investingated.The measurement results showed that they exhibited good sensing properties to H₂S gas at a low working temperature,including high response,fast response and recovery times,good repeatability and long-term stability.Based on the excellent sensitivity of H2S gas,the relationships between the sensing properties and structure and phase composition of sensitive materials at the nanoscale were studied,and thereby the enhanced mechanisms were given.For example,the sensor response of the Cu2O/CuO sub-microspheres to 50 ppb H2S is about2.1,the response and recovery times are 24 and 76 s at 95?,respectively.The sensing mechanism can be attributed to the transition state of Cu₂O_2-x formed in Cu₂O/CuO microspheres,which is more favorable of the interaction with H2S gas.At the same time,the effect of the reduced size of and the increased specific surface area of Cu2O/CuO sub-micron ball on the sensing performance are also important.Overall,the metal oxide nanostructures obtained in the thesis can detect trace H₂S gas detection at a low working temperature.Therefore,they are very promising for practical applications.