Preparation Of W₁₈O₄₉ And WO₃·0.33H₂O Nanostructures And Study On Their Gas-sensing Properties Of Hydrogen

There is higher demand for energy resource as the growing population.Traditional fossil energy is not only limited,but produces toxic,harmful,flammable and explosive gases during use.To avoid these gas from hurting people,it is necessary to develop gas sensors with good performance and real time monitoring.With the development of nanotechnology,various nanomaterials with different properties have been used to make gas sensors.Among them,metal oxide semiconductor(MOS)nanomaterials have received great attention from researchers because of its outstanding advantages of simple fabrication process,wide application field,easy carrying and high detection accuracy.Hydrogen as a new clean energy has huge development potential with an increasingly focus on environmental protection.Hydrogen has the advantages of low density,non-toxic and wide application range.At the same time,hydrogen also has many potential threats.In many industrial production,sensors are required to detect hydrogen in real time at room temperature.Therefore,we urgently need to develop MOS-based gas sensors for hydrogen detection to adapt to the rapid development of hydrogen energy.However,the properties of MOS-based gas sensors are greatly affected by their structure.For the above reasons,our research direction is determined to improve hydrogen sensor performance by controlling the structure of different MOS materials.The main research work of this thesis is as follows:1.Preparation of hollow porous W18O49 nanospheres with micro Pd and study of its gas sensitivity to hydrogenWe first synthesized hollow porous W18O49 by simple hydrothermal method,and then synthesized Pd-W18O49 by impregnation and subsequent high temperature calcination.Comparing W18O49 sensor performance with different concentrations of Pd,we found that W18O49 with 2 wt.%Pd has relatively good performance.Moreover,the structure of W18O49 is preserved perfectly due to the small amount of modification.That is,the short response and recovery time is preserved.The response of 2 wt.%Pd-W18O49 to 1000 ppm H2 is as high as 1531,the response time is 3.5 seconds and the recovery time is 2.6 seconds.2.Preparation of mixed crystal phase WO3·0.33H2O with dandelion-like structure and study of its gas sensitivity to hydrogenBecause hydrogen is prone to explosion,working temperature has become the most important parameter in hydrogen sensing process.For the purpose of reducing the operating temperature and increasing the response recovery rate of hydrogen sensors,we synthesized the WO3·0.33H2O of the mixed crystal phase with the dandelion-like structure which has not been reported by other literatures.It has a transparent,interconnected,porous and reticular nanostructure,which helps H2 reach the active sites within the material quickly,increasing the response and recovery rate.The results show that the sensitivity of WO3·0.33H2O gas sensor to 1000 ppm H2 is 2.16,and its response time is 1.8 seconds and the recovery time is 2.0 seconds at room temperature.