Selectivity Research Of Zeolite Modified Pd-WO₃ Gas Sensors

Acetone gas is closely related to industry,environment and health.Pd-WO₃ material has simple preparation process,low cost and well gas sensitive response.Its miniaturized sensor array structure is conducive to the integration of equipment,making it an important choice for detecting acetone gas.In this paper,the surface of Pd-WO₃ material was coated with zeolite filter membrane to reduce the interference of other gases and improve the sensitivity and selectivity of sensor response to acetone gas.Pd-loaded WO₃ nanoparticles gas-sensing materials were prepared by impregnation method.Commercial HZSM5 and HY zeolites and precious metals Pt,Rh,Ru impregnation modification zeolites were used as gas filter layer.Characterization analysis of materials is made by different characterization means.The results showed that Pd was uniformly loaded on the surface of monoclinic WO₃ nanoparticles in oxidized state,which had no obvious effect on the surface morphology of WO₃nanoparticles.Zeolites had loose structure,large specific surface area and pore volume structure,which had great influence on gas desorption.Zeolites modified by different noble metals had different morphologies.There is no obvious difference between the morphological structure and the unmodified zeolites.Different noble metals show different chemical states on the surface of the zeolite,which is closely related to the catalytic activity of the zeolites.The response characteristics of sensors in different atmospheres were tested by dynamic testing system.The selectivity of Pd-WO₃ materials to gases was changed by modifying the sensor with zeolite.The response characteristics of different sensors to gases were closely related to the catalytic properties of zeolite,not only with the efficiency of zeolite catalytic gases,but also with the products after catalysis.Sexual response is closely related to working temperature.Including,Pt-HY zeolite modified sensor has the best sensitivity and selectivity for acetone gas.In addition,the porous characteristics of zeolites affect the surface structure and gas desorption properties of Pd-WO₃ materials,which significantly increases the resistance and response and recovery time of sensors.Different noble metal loaded zeolites sensors have different mechanisms in acetone response process.The resistance behavior of under oxygen pressure is related to the modification of metal.The experimental results show that oxygen is adsorbed on the surface of sensitive materials in the form of O^—and O^—is the fundamental origin of acetone gas sensing response.The response mechanism of HZM5?HY and Rh?Ru modified zeolites sensors to acetone is the same as that of Pd-WO₃,while the response mechanism of Pt modified zeolite sensor to acetone is different from that of other sensors.With the introduction of precious metal Pt,the adsorption characteristics,catalytic activity and interaction with sensitive materials have changed,which shows that the fitting coefficients of sensor resistance and oxygen partial pressure deviate.