High-throughput Screening And Gas Sensitivity Of Metal Oxide Gas Sensing Materials Under Temperature Programmed Cooling

With the development of society and the improvement of people's living standards,the application of gas sensors is becoming more and more extensive.Metal oxide gas sensors of low cost,good sensitivity,simple signal processing and facile miniaturization has been widely used in detection of toxic gases,industrial exhausts and combustible or explosive gases.In the process of gas detection,the gas sensing response is an important parameter to evaluate the quality of metal oxide sensitive materials.There are two methods to improve the gas sensing response of metal oxides.One is to select materials with good gas sensing property or to develop new sensing materials.The other is to excite the potential gas sensitivity of the metal oxide materials by changing the test conditions,namely adjusting external conditions such as light,heat and force.To find high quality gas sensing materials and study their gas sensing mechanism are the most important steps in the development of metal oxide gas sensors.In this paper,it was attempted to select materials with excellent gas sensing properties through high throughput screening.The process mainly includes parallel synthesis of materials and high throughput screening.Firstly,two kinds of thin film-forming methods,namely screen printing technology and micro droplet premixed apparatus,were employed to synthesize two series of materials.The two series of materials are binary material surface modification system?including 72 surface modification materials?based on WO₃,SnO₂ and ternary composite system?including 45 ternary composite materials?based on SnO₂-WO₃-Co₃O₄,respectively.Next,a home-made Pump type smell analyzer network was used to characterize the gas sensing properties of the as synthesized materials and find the material with the best gas sensing properties.Then,the maximum of the gas sensing response under constant temperature test(S_{S Max})and the maximum of the gas sensing response under temperature programed cooling(S_{d Max})were defined.Finally,the maximum of the gas sensing response under temperature programed cooling was adopted to make a cluster analysis of these materials.All those analyses mentioned above presented a more intuitive view on the influences of modified elements and the composition proportion on the gas sensor properties.Moreover,in view of the fact that the S_{d Max} was much larger than S_{S Max},temperature programmed cooling was applied to improve the poor reducing gas sensing response of metal oxides here.Equilibrium chemisorbed oxygen and accumulated chemisorbed oxygen were defined under temperature programmed cooling.Firstly,two types of common and simple metal oxides,n-SnO₂ and p-Co₃O₄ have been chosen as the study object according to the difference in reducing gas sensitivity between n-and p-type materials.Then,the comparisons on the reducing gas sensitivity and chemisorbed oxygen between n-type SnO₂ and p-type Co₃O₄ under constant temperature test and temperature programed cooling have been made.It will contribute to a more thoroughly understanding on the gas sensitivity of metal oxide gas sensor under temperature programmed cooling.