Preparation Of WO₃/PANI Nanocomposites And Their Ammonia-Sensitive Properties

Ammonia(NH3)is a toxic and harmful gas,which not only affects human health and safety,but also is one of the factors forming haze.At the same time,the trace breath gas ammonia as a kind of human body,in the aspect of medical detection,disease diagnosis has important potential applications.Therefore,accurate,real-time and rapid detection of ammonia has important practical significance.At present,the metal oxide material based ammonia gas sensor has high sensitivity,but high working temperature and high energy consumption.Conduct ammonia gas sensor based on conductive polymer material can work at room temperature,but the sensitivity is not high and the stability is poor.Material modification and construction of composite gas sensitive materials is one of the main methods to improve the performance of gas sensors.Based on this background,the author prepared WO3,Pt-WO3 and WO3-PANI composite gas sensitive materials respectively,characterized and analyzed the micro morphology,crystal structure and elemental composition of the sample materials,and fabricated ammonia sensors based on different gas sensitive materials.The gas sensitivity property of the prepared material was tested and its gas sensitivity mechanism was analyzed.The main content summary is as follows:(1)A three-dimensional spherical WO3 gas sensitive material with diameter of about 3 μm was prepared by hydrothermal method.The gas sensitivity test results show that the ammonia sensor based on spherical WO3 has a sensitivity of 15.94 to 100ppm NH3 at the operating temperature of 150℃,and has good response/recovery characteristics.(2)Spherical WO3 gas sensitive materials modified by noble metal Pt nanoparticles were prepared by co-grinding method.The gas sensitivity test results show that when the mass fraction of Pt is 1%,the Pt-WO3 ammonia gas sensor shows excellent gas sensitivity.At the working temperature of 120℃,the sensitivity of 100ppmNH3 is 53,which is three times that of pure WO3 nanomaterials.In addition,the WO3 ammonia sensor modified by precious metals has enhanced the selectivity of ammonia.(3)The prepared by in-situ polymerization oxidation method WO3/PANI composite gas sensitive materials.Gas sensitive test results show that when the molar ratio of Pt-WO3 and PANI is 3:1,The gas sensitivity performance of the composite ammonia gas sensor prepared at is relatively excellent,and the sensitivity of 100 ppm NH3 at room temperature can reach 25.62,while the sensitivity of pure PANI material is only 3.18 under the same test conditions.In addition,the composite ammonia gas sensor also has wonderful selectivity and stability.The enhanced gas sensitivity was attributed to the p-n junction formed between PANI and WO3 microspheres and the catalysis of the noble metal Pt.