SnO₂-based Micro/nanomaterials: Fabrication, Photocatalysis And Gas Sensing Properties

Semiconducting oxide nanomaterials have been intensively studied in the fields of catalytically decomposing organic compounds and detecting volatile and toxic gases. SnO₂, a typical n-type semiconductor with a wide band gap?3.6 eV?, have been widely investigated with gas sensors and catalysis, because of its unique optical, electrical, and catalytic properties. It is widely accepted that both photocatalytic and gas-sensing reactions generally occurr on the materials' surfaces based on the adsorption-reaction-desorption processes. This thesis mainly focuses on SnO₂-basedmicro/nanomaterials, especially on the enhancement of their photocatalytic and sensing performances by Zn doping and compositing with other materials. The main results are as follows:1. A facile and simple hydrothermal method has been developed for preparing undoped and Zn-doped SnO₂ nanostructures by optimizing the growth conditions. The morphology of SnO₂ nanospheres was transformed into ultrathin nanosheets assembled architectures after Zn doping. The Zn-doped SnO₂ gas sensors exhibit highly sensitive and selective sensing properties to glycol gas. The response can reach to be 90 for 100 ppm glycol, which is much higher than that of undoped SnO₂. The as-prepared Zn-doped SnO₂ hierarchical nanostructures were also used as efficient photocatalysts and exhibited excellent degradation for MO, which is much higher than that of undoped SnO₂ at the same UV irradiation time.2. A facile and simple hydrothermal method has been developed for preparing SnO₂/Fe₂O₃ nanocomposites on a carbon cloth. The as-prepared SnO₂/Fe₂O₃ nanocomposites were also used as efficient photocatalysts and exhibited excellent degradations for MB, which are much higher than those of undoped SnO₂ and Fe₂O₃ at the same UV irradiation time. Zn₂SnO₄ can be used as a recyclable catalyst for the degradation of MB. We proposed the enhanced photocatalytic mechanism by compositing with other materials.3. Polyhedral Zn₂SnO₄ have been successfully fabricated with a facile hydrothermal method by optimizing the growth conditions. The gas sensing properties on triethylamine?TEA? for octahedral Zn₂SnO₄?24 h? microstructures showed that the sensor response?S=Ra/Rg? reach to be 37 at 100 ppm, which is much larger than that of cubic Zn₂SnO₄?16 h?. When the irradiation time is 60 min, the degradation of the Zn₂SnO₄ microstructures?24 h? is about 90%, higher than those of Zn₂SnO₄?16 h, 40%? and Zn₂SnO₄?36 h, 50%?. The photocatalytic activities of hollow cubic Zn₂SnO₄ sub-microstructures were evaluated by the degradation of methylene blue?MB?, methylene orange?MO?, and rhodamine B?RhB? and the results exhibit a much higher selectivity to the degradation of MB?95%? by Zn₂SnO₄ than those of MO?70%?, Rh B?81%? and ZnSn?OH?6?MB 20%? in 20 min.