Preparation And Properties Research Of CeO₂/Ce_1-xZr_xO₂Sensing Electrode Materials For Ammonia Sensor

With the rapid development of Automobile industries, gas pollution is increasinglyserious.In order to reduce NOx in automobile exhaust,many countries enacted stringentemission standards.In the practical application,NOx in the exhaust is reduced throughchemical reactions of ammonia and NOx, generating pollution-free nitrogen and water andeventually reducing the levels of NOx in the exhaust. However, excessive ammonia willbe exsited and lead to air pollution,which is called "ammonia leakage".Ammonia sensor isessential to detect ammonia concentration, many countries are doing large numbers ofresearch works about ammonia sensors.However,sensibility of sensitive electrode isinsufficient,the structure of the sensor is complex,the stability is poorer.Therefore thisthesis focuses on the electrode material of ammonia sensor.According to the catalyticoxidation of material electrochemical principle,we study the performance of ammoniasensors with simple structure based pure CeO₂and Ce1-xZrxO2electrode,our specificwork is as follows:Pure CeO₂powder is prepared by hydrothermal method, the test results show that theaverage particle size of CeO₂powder is about100nm,and have uniform grain sizedistribution and good crystallinity. we study the performance of the ammonia sensor basedCeO₂sensitive electrode,the sensitivity is about29mv/decade and sensitivity is best at450℃.when temperature is higher than450℃,the performance of ammonia sensordecline rapidly,therefore,the modification of the electrode materials is necessary.Byadding different content of Zr in CeO₂,Ce1-xZrxO2solid solution is prepared to improvethe performance of the ammonia sensor,different proportions of Ce_1-xZr_xO₂powder wasprepared by hydrothermal method,the testing result shows the average particle size ofCe_1-xZr_xO₂is about100nm,Ce_1-xZr_xO₂powder have uniform grain size distribution andgood crystallinity,Zr is in the CeO₂lattice,we test the performance of the ammonia sensorbased Ce1-xZrxO2sensitive electrode,the results show that the addition of ZrO2improvedsignificantly the performance of the sensor.X=0.6the performance of the sensor is best; Working temperature increase from450℃to550℃;Sensitivity improved from29mv/decade up to80mv/decade, about2³times;Sensor signal have good repeatability;When X=0.6or higher, at550℃,the impact of ZrO2for response/recovery time is notobvious,the response time is about5s,the recovery time is controlled in10s,recovery timewere longer than the response time.We study the surface and cross-section morphology of Ce_1-xZr_xO₂electrode and findthat the addition of ZrO2in the electrode make grain refiner,and at the same time alsochange microstructure of the electrode,when X=0.6,surface of the electrode form a good3d mesh structure,so the sensor performance is best,when X=0.8,3d holes get smallerand electrode become dense, the performance of the sensor consequently decline,it can beseen that the ZrO2in CeO₂lattice changes the electrode microstructure, thereby change theperformance of the sensor.