Research On High Performance YSZ-based Gas Sensor By Using Template Method

In this paper,our research mainly focus on mixed potential type gas sensor,which used yttrium stabilized zirconia（YSZ）as solid electrolyte.This kind of sensor has good mechanical and chemical stability,and is widely used in the field of automobile exhaust detection.There might be two ways to improve the sensitivity of the sensor.One is to find new sensing electrode materials,the other is to fabricate high efficient thriple phase boundary.It is a classic method to fabricate nanostructure array on flat by using template method,and PS sphere and AAO are most widely used template.Many nanostructure such as nanotube and nanobowl array has successfully fabricated on the silicon and glass flat.And there are many reports about the application of these structure in the field of fuel cell and solar cells.This paper mainly explores the use of template method to build high efficient three-phase interface on YSZ substrate,and then improve the performance of the sensor.Firstly,Well-ordered porous three-phase boundary（TPB）was prepared by using polystyrene sphere as template and examined to improve the sensitivity of mixed-potential-type NO₂ sensor based on yttria-stabilized zirconia（YSZ）due to the increase of the active electrochemical reaction sites.The morphology of the pore array on YSZ substrate surface can easily be controlled by the concentration of the precursor solution(Zr⁴⁺/Y³⁺=23 mol/L:4 mol/L)and treatment conditions.An ordered hemispherical array was obtained when C_Zr⁴⁺=0.2 mol/L.The processed YSZ substrates were used to fabricate the sensors and their sensing properties were tested.The measuring results indicated that the sensor with well-ordered porous TPB exhibited the highest sensitivity to NO₂ with a response value of 105 mV to 100 ppm NO₂,which is approximately twice as much as the smooth one.In the monitoring range of 10-400 ppm NO₂,the sensitivity of the sensors increased from 30.3 mV/decade to 53 mV/decade.In addition,the sensor also showed good stability and speedy response kinetics.All these enhanced sensing properties might be due to the structure and morphology of the enlarged TPB.Secondly,the nano-bowl shaped structure and gold nanoparticle array were successfully fabricated on the YSZ substrate and examined to improve the sensitivity of mixed potentialtype NH₃ gas sensor.The nano-bowl shaped structure was constructed by solution-dipping template（polystyrene spheres）strategy and gold nanoparticle inlaid in the nanostructure was fabricated by vacuum evaporation plating technology.The present study mainly explored the influence of gold layer's thickness on the nanostructure.The perfect ordered gold nanoparticle array inlaid in nano-bowl shaped structure was obtained when the evaporated gold film thickness was about 50nm.The mixed potential type gas sensor which based on processed YSZ substrate displayed the improved sensitivity and selectivity to NH₃ at elevated temperature.All the enhanced sensing properties might due to the enlarged three phase boundary（TPB）and inlaid gold nanoparticle array.At last,we also try to build nanotube and nanodot array on the YSZ substrate by using AAO as the template combined with hot press method.And using NiO as sensing electrode material fabricating the sensor.The results show that the response value of the sensor based on processed YSZ substrate by the anodic alumina（AAO）template increased from 40 mV to 62 mV for 100 ppm NO₂,and the sensitivity also increases from 35 mV/decade to 41 mV/decade in the range of 10-400 ppm NO₂.The above results show that the nanostructure array can significantly improve the performance of sensor.And AAO template method is an effective way to build efficient three-phase interface.All in all,we try to use template method to fabricate the high performance thriple phase boundary,and improve the sensitivity of the sensor.Meanwhile,the polarization curves and the response under different oxygen partical pressure were also measured to verify the sensing mechanism.