Design And Properties Study Of Gas Sensing Materials Based On Porous Metal Oxide

In this thesis,three gas sensing materials based on ZnO or SnO2 were synthesized by template method,hydrothermal method and ultrasonic chemical deposition method.The structural characterizations and gas sensing properties of the prepared materials were studied.The main contents of the researches are as follows:Using ordered porous ZnO as precursor,a kind of original 3D ball-flower-like ordered mesoporous ZnO was prepared through a hydrothermal reaction method.The ordered mesoporous with 5.2 nm diameter were regularly distributed on the surface of the ball-flower-like ZnO,which led to the specific surface area of the material reached to 108.69 m2·g-1.At room temperature,the ball-flower-like ZnO material showed excellent gas sensing response to NOx,whose response to 100 ppm NOx gas reached to 68.9%,the response time was only 6 s,and detection limit was as low as 1 ppm.It broke the tradition that pure ZnO showed gas sensing response to NOx only in relative higher temperature.Using ordered porous ZnO as matrix,the ordered porous Cr2O3/ZnO gas sensing material with p-n heterojunction was successfully prepared by ultrasonic chemical deposition method.The influence of different ultrasonic chemical deposition time on gas sensing property was investigated.When ultrasonic chemical deposition time was 2 h,the prepared ordered porous Cr2O3/ZnO material showed excellent gas sensing response toward NOx gas at room temperature.When concentration of NOx gas was 100 ppm,the gas sensing response could reach to 86.7%,response time was only 4 s,and detection limit was as low as 0.05 ppm.The superior gas sensing properties of the Cr2O3/ZnO material could been attributed to the loose and ordered porous structure,the catalysis of Cr2O3,and the synergistic effect of p-n heterojunction.Under the hydrothermal environment,a kind of novel and uniform 3D aloe-like ordered porous SnO2 material was successfully synthesized by template method,and the breadth,thickness and length of the aloe-like petals were about 230±10 nm,30±5 nm and 600±10 nm,respectively.The ordered mesoporous with average pore diameter of 3.6 nm were distributed on the surface of the 3D aloe-like SnO2 material,the specific surface area of the material reached to 79.952 m2·g-1.The optimum synthesis conditions were determined by a series of experiments,and the morphology,structure and gas sensing performance toward H2S of the prepared material were tested.The 3D aloe-like SnO2 material showed much excellent gas sensing performance to H2S at 190?,whose response to 100 ppm H2S reached to 48.3(Ra/Rg),response time was only 3 s,and detection limit was as low as 0.5 ppm.