Construction And Gas Sensing Properties Of SnO₂@TiO₂ Heterojunction Nanorods

One-dimensional TiO2 nanomaterials are regarded as a highly potential gas sensing material due to unique linear charge conduction channel.However,the gas sensors based on one-dimensional TiO2 nanomaterials usually show low response to target gas at high operating temperature.Constructing heterojunctions is an efficient approach to enhance their gas sensing properties of one-dimensional TiO2 nanomaterials.Semiconductor materials with low work function are widely selected to be acted as the decorating materials to construct heterojunctions in recent works,while the corresponding semiconductor materials with high work function are rarely investigated.Therefore,SnO2@TiO2(ST)heterojunctions were optimally constructed based on one-dimensional TiO2 nanorods and SnO2 nanoparticles in this thesis,aiming to synthesize a gas sensing material with rapid response ability and high sensitivity at low operating temperatures to target gas.The quasi-array-structured TiO2 nanorods were firstly fabricated on diatomite-based porous substrates by a hydrothermal method.The optimal preparation conditions were determined by combining with XRD and SEM characterization results.SnO2@TiO2 heterojunction nanorods were then prepared by a solution-coating method.The effects of volume ratios of tin-source to TBT on the morphologies and structure properties of SnO2@TiO2 heterojunction nanorods were studied,and the influences of structure change on their gas sensing properties and the corresponding reaction mechanism were also investigated.The gas sensing properties of SnO2@TiO2 heterojunction nanorods revealed that the response of TiO2 nanorods to H2 was improved significantly by constructing heterojunctions.The responses of SnO2@TiO2 heterojunction nanorods with different volume ratios of tinsource to TBT to 0.05%H2 at 100℃ followed in order of pure TiO2<5.0 ST<3.0 ST<0.5 ST<1.0 ST.Under the same test condition,1.0 ST sample exhibited the highest response of 15.4 to 0.05%H2 with shortest response time of 3 s and recovery time of 125 s,as well as good reproducibility and selectivity.Based on the structural characterization results,the growth mechanism of SnO2@TiO2 heterojunction nanorods was analyzed.Combining the changes of microstructure and gas sensing performance,the gas sensing mechanisms of pure TiO2 nanorods and SnO2@TiO2 heterojunction nanorods were systematically discussed.The enhanced sensing mechanism of SnO2@TiO2 heterojunction nanorods to H2 was discussed in relation to modulation of conduction channel,potential barrier and chemical sensitization as well as electron sensitization.