The Development of Gas Sensors Based on Multivalent Cation Conducting Solid Electrolyte

氮氧化物是造成大气污染的有毒气体，抑制氮氧化物向环境大气排放是一个迫切需要解决的问题。为了实现有效的抑制，需要对每个排放点的NOx气体进行现场传感，研制一种实用的小尺寸、高灵敏度、高选择性的智能NOx气体传感器具有重要意义。在本研究中，我们研制了一种基于三价Al^&lt；3+&gt；导电固体电解质和O^&lt；2-&gt；负离子导电Yttria稳定氧化锆(YSZ)的NOx气敏元件，其辅助电极是KNO2掺杂的Gd_2O_3固溶体的水不溶辅助电极。目前的NOx气敏传感器对450℃的NO检测具有很高的灵敏度，对NOx气体浓度变化的响应时间在15min以内。另一方面，该传感器在理论上也可以对NO_2气体做出类似于NO气体检测的响应。此外，由于即使混合气体中NO含量的比例改变，传感器输出的总NOx气体(NO+NO2)浓度在2000ppm也是恒定的，因此本传感器能够检测环境空气中的总NOx气体浓度。以KNO2掺杂Gd2O3固溶体为辅助电极的导电固体电解质是一种智能的NOx气体传感器，不仅可以检测NO和NO2的单独氮氧化物，而且可以检测总的NOx气体。由于该传感器即使在高温下也具有较高的热稳定性和化学稳定性，因此目前的NOx气体传感器在每个NOx排放点的实际应用都被寄予了极大的期望。

Nitrogen oxides are toxic gas species which cause air pollution, and the suppression of Nox gas emission into ambient atmosphere is an urgent issue. For an effective suppression, the on-site sensing of Nox gas at every emitting site is necessary and the development of a practical smart Nox gas sensor with a small size, a high sensitivity and a high selectivity is greatly important. In this research, we newly developed a Nox gas sensor based on trivalent Al^<3+> conducting solid electrolyte and O^<2-> anion conducting yttria stabilized zirconia (YSZ) with a water insoluble auxiliary electrode of the KNO_2 doped Gd_2O_3 solid solution.The present Nox gas sensor shows a high sensing performance according to the theoretical Nemst relationship for the NO detection at 450℃ and its response time for Nox gas concentration variation was within 15 min. On the other hand, the sensor can also respond to the NO_2 gas theoretically similar to the case for the NO gas detection. Furthermore, since the sensor outputs for total Nox gas (NO + NO_2) concentration of 2000 ppm were constant even if the ratio of NO amount in mixed gas changed, the present Nox gas sensor was found to be able to detect the total Nox gas concentration in the ambient atmosphere.In conclusion, the present sensor based on both divalent Al^<3+> and divalent O^<2-> conducting solid electrolytes with water insoluble auxiliary electrode of the KNO_2 doped Gd_2O_3 solid solution was found to be a smart NOx gas sensor which can detect not only individual nitrogen oxides of NO and NO_2 but also total NOx gas. Since the sensor also possesses both the high thermal and chemical stabilities even at elevated temperatures, the practical application of the present NOx gas sensor is greatly expected at every NOx gas emitting site.