基于非化学计量钙钛矿型敏感电极的NOx传感器及原位脱溶敏感增强

Mixed-potential type sensors are widely applied in the monitoring and controlling of NOx pollutants in harsh environments. The sensing electrode with good sensitivity, selectivity and stability is important for the mixed-potential type NOx sensors. In this proposal, perovskite oxides will be used as the sensing electrode of the mixed-potential type NOx sensors in view of the good structural stability and sensing performance of the perovskite oxides. The non-stoichiometry will be applied to improve the sensitivity and selectivity of the perovskite-type electrode. The nanoparticles will be in-situ exsolved on the surface of the perovskite-type electrodes by the electrochemically promoted vapor phase reduction to further improve the performance of the sensing electrode. Furthermore, the influences of the electrolyte and sensing electrode on the performance of the sensors will be investigated from the perspective of the gas/sensing electrode/electrolyte triple phase boundary (TPB). By the proposed research work, the mechanism of the effects of non-stoichiometry on the properties of the sensing electrode will be investigated to achieve the controlling of the sensing performances of the sensing electrodes. The influence of the electrochemically promotion on the vapor phase reduction exsolution will be discussed. The new method for the preparation of the composite sensing electrode will be set up. The relationship between the TPB and sensing performance will be obtained for effectively improving the sensing performance of the sensor by modulating the TPB. New ideas and methods for the development of gas sensors will be provided in the ways of material design, preparation method and structure regulation.

混合位型传感器在恶劣环境下NOx污染物的监测与控制领域应用广泛。兼备良好灵敏度、选择性和稳定性的敏感电极对混合位型NOx传感器至关重要。基于钙钛矿型氧化物结构稳定和气敏性能好的特点，本项目提出将其作为混合位型NOx传感器的敏感电极，利用非化学计量改善钙钛矿型电极的灵敏度和选择性；采用电化学促进气相还原法，在敏感电极表面原位脱溶纳米金属颗粒，进一步提高其气敏性能；在此基础上，从气体/敏感电极/电解质三相界面视角出发，探究电解质、敏感电极对传感器性能的影响规律。通过研究，探明非化学计量对敏感电极性能的影响机制，实现对其气敏性能的调控；明确电化学促进对气相还原脱溶的作用规律，建立复合敏感电极制备新方法；揭示三相界面与气敏性能的内在关系，更有效地通过调控三相界面改善传感器的气敏性能。从材料设计、制备方法、结构调控等方面，为气体传感器的研究与开发提供新思路和新方法。

汽油机在稀薄燃烧运行可有效降低污染物排放，提高热效率，但需"吸藏还原催化剂"来解决NOx的去除问题。而该催化剂对NOx脱除和再生过程必须由在线NOx传感器控制，因此开发可满足上述要求的固体电解质型NOx传感器十分必要。本项目主要从以下几方面开展了相关研究工作：（1）基于钙钛矿型氧化物结构适应性强和组成调控性好的特点，利用非化学计量改变晶格中的离子价态，推动氧晶格无序化，有效改善了钙钛矿型敏感电极的催化、吸附和传导能力，提高了传感器对NOx的灵敏度和选择性，为传感器性能调控提供了新策略。（2）采用还原脱溶法原位合成了高分散金属纳米颗粒修饰的钙钛矿基复合敏感电极，探究了原位脱溶选择性和物理化学条件，建立了复合敏感电极制备新方法，有效克服了传统复合方法存在的颗粒易团聚和用量大等缺点。（3）从气体/敏感电极/电解质三相界面视角出发，探究了电解质、敏感电极对传感器性能的影响规律。设计了基于氧离子/电子混合导体的多孔骨架层，增加了界面的催化能力。（4）利用交流阻抗参数丰富的优点，系统研究了传感器多信号响应特征及使用条件，以恒相位角元素作为固体电解质型气体传感器的响应信号，显著改善了传感器的响应稳定性和速度，丰富了传感器的工作模式。通过上述研究工作，实现了敏感材料设计、界面调控及工作模式的综合优化，使传感器性能得到明显改善。为气体传感器的研究与开发提供新思路和新方法。