K2CO3/Al2O3 Composite Pellet as Room-Temperature NO2 Sensor

K2CO3, an alkaline carbonate, is commonly used as lean NOx trap device at elevated temperatures. In this device, K2CO3 along with some appropriate additives are coated on two interdigitated Au contacts, which previously patterned on an insulator support, such as Al2O3. Failure to spontaneous recovery in the sensor's operating conditions causes to a problem in the application of this structure as an NO2 sensor. In this letter, we show that if K2CO3 is combined with Al2O3 in the form of a pellet and Au contacts are transferred to the top of the structure, a new device is obtained that can detect NO2 at room temperature in both resistometric and potentiometric modes. In resistometric mode, this sensor exhibits response and recovery time of 65 and 473 s upon exposure to 900 ppb NO2 at room temperature. Under the same conditions, these times reduce to 16 and 62 s, respectively, when the sensor is operating in potentiometric mode. Using both measurement modes, the relative accuracy of the sensor for prediction of NO2 concentration level from 15 ppb to 900 ppb is less than 25%. Brick-wall modeling of the grains for resistometric mode and Nernstian electrochemical cell for potentiometric mode could successfully interpret the experimental behavior of the K2CO3/Al2O3 composite pellet in the exposure of NO2.