基于YSZ@CeO2微纳纤维和多孔氧化物敏感电极的高灵敏NOx传感器的研究

Stable-zirconia-based NOx sensor has excellent stability in high temperature working environment, so it has important application in vehicle exhaust treatment and emission monitoring. At present, how to improve the sensitivity of YSZ based NOx is still a difficult and hot-spot in the field of gas sensors. In this project, by preparing the YSZ@CeO2 micro-nano fiber and porous oxide electrode, the reactions on three-phase-boundary are to be enhanced, and the ionic conductivity of the electrolyte is to be improved. Moreover, the target gas diffusion can be accelerated due to the porosity of oxide electrode materials, and finally the sensitivity of the sensor can achieve significantly improvement. The project features are as followings: we plan to realize the micro-nano fiber of YSZ based solid electrolyte substrate with porous surface by coaxial electrospinning method, plan to solve the problem of electrode harden during the sintering process by taking advantage of the high carbon residue rate of PF nanoparticles sintering in inert atmosphere, and plan to adjust the porous electrode micro-structure by down-up multilayer coating technology. The implementation of this project not only can improve the sensitivity of the NOx sensor, but also can understand the relationship between the microstructure and sensing characteristics of the sensor material which has important scientific interest.

稳定氧化锆基NOx传感器在高温工作环境下具有优异的稳定性，因此在机动车尾气处理和排放监控中具有重要应用。目前，如何提高YSZ基NOx的灵敏度依然是气体传感器领域的难题和热点。本项目从制备多孔YSZ@CeO2微纳纤维固体电解质和多孔氧化物电极出发，利用电解质表面的多孔性增大三相反应界面的活性位点密度，通过YSZ的一维结构提高离子导电率，借助氧化物电极材料的多孔性加速目标气体的扩散，最终实现YSZ基NOx传感器灵敏度的显著提升。本项目的特色之处在于：利用同轴静电纺丝方法实现对YSZ基固体电解质基材的微纳纤维化和表面的多孔化修饰；利用PF纳米粒子在惰性气氛中烧结时高残炭率的特点，结合down-up多层涂覆技术，解决电极高温烧结过程中易板结的难题，实现电极多孔化。本项目的实施不仅可以研究提高NOx传感器灵敏度的新技术，而且能够深入理解传感材料的微观结构与传感特性的关联规律，具有重要的科学意义。

NO2等有毒气体对环境和人体健康的危害受到越来越多的关注。汽车尾气是大气中NO2的主要来源，为实现尾气中NO2的浓度，高性能的车载NO2气体传感器至关重要。本项目主要致力于开发具有高性能的车载汽车传感器。项目执行期间，我们探索了采用静电纺丝法制备YSZ纳米纤维膜，并尝试将其用于YSZ型气体传感器。静电纺丝法制备的YSZ纤维膜具有一维纳米结构，通过高温烧结后仍能保持其微观结构。但是得到YSZ板易碎不易加工，同时多孔疏松结构不利于氧空穴传输，气体敏感性能不佳。为了构建具有多孔结构的敏感电极，我们开发了一种采用有机模板法制备YSZ基混成电位传感器多孔敏感电极的方法，克服了一般有机模板剂在电极烧结过程中过早氧化失效的问题。我们采用水热法合成了尺寸均匀的酚醛树脂微球，利用酚醛树脂自身高温时高残炭率的优点，结合高温惰性气氛烧结低温氧化去模板的方法，成功地制备出了多孔敏感电极，制作的器件性能优异。电化学极化曲线测试结果表明，多孔电极有利于促进三相界面处电化学反应。另外我们还研究了具有微纳米结构的敏感电极材料，采用同轴静电纺丝法制备了具有核壳结构的氧化物敏感材料，具有异质结结构的一维纳米纤维增大了电子耗尽层厚度，增大了传感器在空气与测试气体中的阻值变化，提高了传感器响应。采用水热法制备了具有三维结构Ce掺杂氧化物材料（SnO2、WO3等），Ce的氧化物在高温还原性气氛中价态变化增强了敏感材料表面空穴，增加了表面吸附氧位点，提高了传感器响应值。本项目为制作高性能气体传感器用于有毒气体检测提供了理论依据，具有潜在的应用价值。