Researches On Modification Of Titanium Dioxide Aerogels And Its Hydrogen Sensitivity Performance

Hydrogen may play a key role in a future sustainable energy system as a carrier of renewable energy to replace hydrocarbons.In order to steadily promote the development of the hydrogen economy era,the preparation,transportation,storage and use of hydrogen need to be greatly safeguarded.Therefore,it is imperative to research and develop hydrogen sensors with high sensitivity,rapid response recovery and high stability.In this thesis,TiO₂ aerogels with high specific surface area and high porosity were prepared by sol-gel method and supercritical carbon dioxide（CO₂）drying technology to"aerogels"TiO₂ materials with hydrogen sensitivity.And TiO₂ aerogels with anatase and rutile crystal types were obtained by high-temperature calcination.According to the analysis of micro-morphology,specific surface area and oxygen vacancies,the TiO₂aerogels before and after high-temperature crystallization have three-dimensional network structure,but the pore walls of the crystallized TiO₂ aerogels are severely damaged,the specific surface area is greatly reduced,and the number of oxygen vacancies is increased.In addition,the influence of the change of TiO₂ aerogel crystal form on the performance of hydrogen sensor was also explored.The results show that the anatase TiO₂ aerogel hydrogen sensor has the highest sensitivity（3.1271）,2.09 times that of the commercial TiO₂ nanoparticle hydrogen sensor,and also has a short response recovery time（4 s/29 s）,good stability（less sensitivity change in 30 days）,and linearity（100ppm～1000 ppm hydrogen）.On the basis of the above research,the anatase TiO₂ aerogel was modified by noble metal Pd to further improve the sensitivity of the hydrogen sensor and reduce its operating temperature.In the TiO₂ sol stage,Pd Cl₂ solution after ultrasonic dispersion was introduced,and then gel,supercritical CO₂ drying and high-temperature calcination were used to obtain anatase TiO₂ aerogels with different Pd content doping.According to the hydrogen sensitivity test results,when the molar ratio of Pd to Ti is 2%,the sensitivity of the hydrogen sensor is 4.8671,1.56 times that of the anatase TiO₂ aerogel hydrogen sensor;Compared with the optimal operating temperature of anatase TiO₂ aerogel hydrogen sensor（450℃）,the optimal operating temperature of the sensor is significantly reduced（from 450℃to 300℃）,and it also has an extremely short response recovery time（2 s/19s）,good linearity,good stability and selectivity.More recently,the Sn O₂-Pd-TiO₂ composite aerogel was successfully prepared by combining electrospinning with the sol-gel method and supercritical CO₂ drying technology.The purpose is to build a hollow Sn O₂ nanofiber and TiO₂ network skeleton heterostructure to optimize the performance of the hydrogen sensor.Similarly,according to the hydrogen sensitivity test results,when the molar ratio of Sn to Ti is 21%,the hydrogen sensor has the best sensitivity（6.3178）,2.02 times the sensitivity of the anatase TiO₂ aerogel hydrogen sensor（3.1271）.In addition,the sensor has shorter response recovery time（1 s/20 s）,better linearity（100 ppm～700 ppm hydrogen）,good stability,and better hydrogen selectivity in complex gas environments.