Study Of Hydrogen Sulfide Gas Sensor Based On Metal Oxides Nano-Composites

Hydrogen sulfide(H2S),a toxic gas with unpleasant smell produced by animal and plant corruption,volcanic eruption,oil and gas extraction refining,chemical manufacturing and waste treatment process.For intensively corrosive,H2S will deactivate the catalyst,trigger environmental pollution,and damage industrial equipment which lead to energy loss,low efficiency.H2S is also very harmful to the human,which has irritating effects on the eye,respiratory system and nervous system when the concentration is low with rotten eggs.When the concentration is high,the olfactory nerve center of the human being is numb and unable to smell.H2S will stimulate the eyes,respiratory tract and lungs,resulting in a variety of inflammation,and may even lead to death if exposed to high concentration instantaneously.Therefore,it has been paid a great attention to develop a sensitive,rapid and portable gas sensor for safe production,human health and environmental protection.The gas sensor based on metal oxide semiconductors have attracted increased interest as a new kind of adsorbent owing to high sensitivity,long-term stability and fast response-recovery rate,as well as facile separation,low cost,easy miniaturization and integration.In this paper,we focus on improving the specific surface area of the metal oxide semiconductor material by adjusting the structural morphology,doping modification and so on,so as to expose more active sites,which improve the H2S gas sensing performance.The main contents are as follows:Chapter 2:In this paper,tin dioxide hollow microspheres(SnO2 HMS)were successfully prepared using amino-phenol/formaldehyde resin spheres as templates.A novel thin-film type hydrogen sulfide gas sensor was constructed by coating SnO2 HMS onto an alumina ceramic tube with two Au electrodes.The morphology and the phase structure of different nano-materials were characterized by TEM and XRD.The gas sensing results showed that SnO2 HMS had good sensing properties for H2S.At the optimum operating temperature of 200 ℃,the response of the sensor to 100 ppm H2S was as high as 97.13%,and the response time was very short,i.e.22 s.The response linear range to H2S was from 0.2 to 100 ppm,with a detection limit of 0.1086 ppm,and the correlation coefficient was 0.9931.Almost no effects on the sensor were observed from the environmental humidity and temperature.Also,the sensor possessed good reproducibility and selectivity.The sensor response signal reduced by 5.4%after 10 months of continuous monitoring of H2S gas in a pig farm,indicating that the sensor has a long-term stable lifetime with valuable application for remote monitoring.Chapter 3:In this chapter,ZnO@CuO hollow microspheres(ZnO@CuO HMS)were prepared by template method.The results of TEM showed that as-prepared ZnO@CuO HMS has regular morphology and uniform size.Interestingly,there are many pores with different sizes in the shell of microspheres.And then the H2S gas sensing of as-prepared material HMS was investigated.The sensor exhibited a fast response-recovery rate to H2S at a working temperature of 260℃,that response and recovery time was 81 s and 85 s for 25 ppm H2S respectively.Good linear relationships between the response of the sensor and the logarithm of H2S concentration was obtained in the ranges from 10 to 100 ppm,with slope of 117.92 and correlation coefficient of 0.9929.The sensor has good reproducibility and stability,at least 60 days of continuous working in environmental monitoring,indicating that the proposed method is valuable in practical application.Chapter 4:In this chapter,gold nanoparticles/tin oxide/reduced graphene(AuNPs/SnO2/rGO)ternary nanocomposites were successfully synthesized through an aqueous-phase route.The as-synthesized nanomaterials were characterized by UV-Vis and FT-IR spectroscopy.AuNPs/SnO2/rGO was coated on the surface of the alumina ceramic tube to form a novel thin film hydrogen sulfide(H2S)gas sensor.The gas-sensing results showed that the response of AuNPs/SnO2/rGO was 1.5 times of that of SnO2/rGO to 100 ppm H2S,and the response speed was much faster,which may be due to the catalytic effect of AuNPs.The response and recovery time of AuNPs/SnO2/rGO gas sensor for H2S at room temperature were 34s and 78s,respectively.The response linear range to H2S was from 25 to 150 ppm,and the correlation coefficient was 0.9940.Moreover,the gas sensor had good repeatability,reproducibility and stability for practical application.