A GdAlO(3) Perovskite Oxide Electrolyte-Based NO(x) Solid-State Sensor

NO(x) is a notorious emission from motor vehicles and chemical factories as the precursor of acid rain and photochemical smog. Although zirconia-based NO(x) sensors have been developed and showed high sensitivity and selectivity at a high temperature of above 800 °C, they fail to show good performance, and even don’t work at the typical work temperature window of the automotive engine (<500 °C). It still is a formidable challenge for development of mild-temperature NO(x) detector or sensor. Herein, a novel amperometric solid-state NO(x) sensor was developed using perovskite-type oxide Gd(1−x)Ca(x)AlO(3−δ)(GCA) as the electrolyte and NiO as the sensing electrode. NO(x) sensing properties of the device were investigated at the temperature region of 400–500 °C. The response current value at −300 mV was almost linearly proportional to the NO(x) concentration between 300 and 500 ppm at 500 °C. At such a temperature, the optimal sensor gave the highest NO(2) sensitivity of 20.15 nA/ppm, and the maximum response current value reached 5.57 μA. Furthermore, a 90% response and 90% recover time to 500 ppm NO(2) were about 119 and 92 s, respectively. The excellent selectivity and stability towards NO(x) sensing showed the potential application of the sensor in motor vehicles.