Pore Structure Manipulation Of Ordered Mesoporous Metal Oxide In The Nanocasting Route:from Single-to Multi-modal Mesoporous Systems And Their Application For Gas Sensor

Ordered mesoporous metal oxides have attracted great interest in areas including gas sensor, catalysis, energy conversion and storage, since the ordered periodical porous structure and large specific surface area allow for improved performances.Nanocasting is an important method for preparing ordered mesoporous metal oxides with crystalline walls. In this method, suitable recursors are introduced into the pores of mesoporous templates. Subsequent heating to obtain the desired crystalline metal oxides and selective removal of the template could leave a negative mesoporous metal oxide replica. The mesopore of these replicas generates from those space by originally occupied by pore walls of mesoporous templates and thus its structural type and distribution are relatively simple. The thesis proposed that one can adjust the porous structure of ordered mesopous metal oxide and imporove their performance in pratical apllications by controlling the confined growth of metal oxides in the mesoporous channel of mesoporous templates.A series of ordered mesoporous indium oxides with different porous structures have been prepared by using ordered mesoporous silica KIT-6 as hard templates and indium nitrate as precursor. KIT-6-x contains two sets of interpenetrating gyroid mesopores, which are bridged by. some secondary pores within their walls. By increased the hydrothermal aging temperatures, the mesopore sizes gradually increased, companied by the enlarging of secondary pores. These results suggested that under certain conditions, it will be generated the tri-modal mesoporous indium oxide. Moreover, it is found that the porous structure of mesoporous iniudm oxides could be adjusted by changing other parameters such as the filling degree (the volume ratio of indium nitrate and pore volume of KIT-6), filling times, heating rate.Similarly, single-, bi-, tri- and multi-modal mesoporous manganese oxide and hematite by using manganese nitrate and iron nitrate as precursor and KIT-6 as hard template, suggesting the feasibility of this strategy for adjust porous structures of mesoporous metal oxide at a wide range.The gas sensing properties for formaldehyde (HCHO) of the tri-modal mesoporous indium oxide specimens were examined. The results reveal those tri-modal mesoporous indium oxide possess much stronger responses to HCHO even at low concentrations than other indium oxide counterparts.