Preparation And Gas Sensing Properties Of Porous SnO₂Microspheres

Porous semiconducting gas sensing materials often have high specific area, canprovide more reactive sites for the redox reaction between the material and objectives gas,that is beneficial to improve the sensibility of the gas sensor and hence have attractedmuch research interest. At the same time, the unique porous structures offer abundant gastransport channels, which help to improve response and recovery speed. The thermallyand chemically stable SnO2materials often have high response to the testing gas andseem to be one of promising oxide materials that can be employed in wide gas-sensingapplications. In this perspective, designing and preparing SnO2materials with excellentgas performance have been research hotspots and further designing SnO2with porousstructure has been a hot point in the hotspots. It is still a challenge to synthesize porousSnO2with uniform size and homogenous morphology via an environmentally friendlyfacile method. In this work, two economical controllable synthetic routes have beenreported to prepare porous SnO2microspheres with different morphology. We alsoinvestigated the growth mechanism, disclosed the relationship between gas sensingproperties and morphologies. The SnO2with porous constructure herein have enhancedsensitivity, response-recovery time, selectivity and stability.The main research content of this thesis includes the following two parts:(1) Using biopolymer sodium alginate (NaAlg) as the structure-directing agent, porousSnO2microsphere was successfully synthesized by a facile synthetic route. In order tostudy the regulating effects of sodium alginate and ethylene glycol on the porousstructure of SnO2, a series of compare experiments were carried out. The results showthat the as-obtained porous SnO2microsphere can serve as a highly sensitive material forethanol detection. The sensing response of the porous SnO2is～3and4times as high asthose of the solid SnO2microspheres (which are prepared in the absence ofsodiumalginate) and the commercially available SnO2nanoparticles, respectively. (2) We have successfully synthesized uniform nanoparticle-assembled SnO2microspheres with a highly porous structure via a template-free route, and the formationmechanism of such porous materials is discussed. The surface area, pore size,nanoparticle size can be tuned via the thermal treatment of the resulting SnO2microspheres. The organic amine was used as the target gas to evaluate the sensingproperties of the annealed samples, the materials show excellent gas performance towardTEA. Moreover, theoretical model was applied to study the gas diffusion as well as therelevance with their sensing properties.