Study On The Structural Design Of Porous Composite Semiconductor Oxide Material And The Gas Sensor Based On It

In recent years,with the continuous improvement of our country's economy,quality of people's life has also been correspondingly improved.But a large number of toxic emissions have caused great harm to environment and human health when the economy has been developed.Therefore,an increasing number of people pay more attention to environmental safety while living standard has been satisfying.In order to effectively detect the present toxic gas in real time,gas sensors have emerged and are widely used for indoor and outdoor gas detection.The semiconductor oxide,as the core part of the gas sensor,is widely researched because of its sensitive performance.However,due to the increasing detection requirement,the pristine material can't meet the demand.Thus,it is necessary to improve the performance of the sensor by adjusting the composition and morphology of the semiconductor oxide through an environmentally friendly and simple method.In this paper,the semiconductor oxide material with different morphologies and structures were successfully prepared by simple hydrothermal and solvothermal methods.In addition,in order to improve the gas sensitivity,the composition and structure of the materials were designed and constructed by calcination and doping.Then,a possible sensitivity mechanism is proposed.The details are as follow:1.The hierarchical porous and nonporous SnO₂ microflowers was successfully synthesized by a simple hydrothermal method and followed by calcination procedure.The microstructure and morphology of the product were characterized by X-ray diffraction?XRD?,energy dispersive X-ray spectroscopy?EDS?,scanning electron microscopy?SEM?and transmission electron microscope?TEM?.Gas sensors based on the two materials were fabricated and researched for their gas sensing properties.The results of comparison show that at the optimum operating temperature 240 °C,the sensors based on hierarchical porous SnO₂ microflowers which calcined at 500 ? possess a more preferable gas-sensing property.Specifically,the sensitivity of the hierarchical porous SnO₂ microflowers to 100 ppm ethanol is 205.6,while the hierarchical nonporous SnO₂ microflowers is 52.9.In addition,the response recovery time is 3 s?3 s?and 45 s?145 s?,respectively.What's more,the minimum concentration of ethanol that we can detect is 0.1?1.0?ppm,and the response value is 1.9?2.0?.2.Ga-doped and undoped SnO₂ porous microflowers were synthesized by a facile hydrothermal method.Their composition and structure were determined by X-ray powder diffraction?XRD?,energy-dispersive spectroscopy?EDS?,X-ray photoelectric spectroscopy?XPS?and scanning electron microscopy?SEM?.Gas sensors based on the two materials were fabricated and compared for their gas sensing properties.The results show that 230 ? is the best working temperature for both materials.At this temperature,the 3 wt% Ga-doped SnO₂ porous microflowers sensor to formaldehyde exhibits an improved sensitivity?95.8/50 ppm?,which is 4.5 times that of the pure SnO₂ porous microflowers sensor?21.2/50 ppm?,and the response-recovery time are 3 s and 39 s.what's more,it also owns the lower detection limit?3.0/0.1ppm?,and well selectivity.3.Pure Fe₂O₃ microspheres and Gd₂O₃/Fe₂O₃ loose microspheres were synthesized successfully by solvothermal method and followed with calcined.The structure and elemental composition were provided by X-ray powder diffraction?XRD?and energy-dispersive spectroscopy?EDS?.Additionally,the morphology was characterized by scanning electron microscope?SEM?and transmission electron microscope?TEM?.Gas sensors based on the two materials were fabricated and systemically compared for their gas sensing properties.The results show that the sensors based on Gd₂O₃/Fe₂O₃ loose microsphere exhibits excellent selectivity to acetone with a sensitivity of 268.6?100 ppm?at an optimum working temperature of 220 ?,which is 9.8 times that of pure Fe₂O₃ loose microsphere?27.5/100 ppm?,and the corresponding response-recovery times are 6 s and 36 s,respectively.In addition,the detection limit is as low as 0.1 ppm?2.3?.