K2CO3/Al2O3 Composite Pellet as Room-Temperature NO2 Sensor

K
₂
CO
₃
, an alkaline carbonate, is commonly used as lean NOx trap device at elevated temperatures. In this device, K
₂
CO
₃
along with some appropriate additives are coated on two interdigitated Au contacts, which previously patterned on an insulator support, such as Al
₂
O
₃
. Failure to spontaneous recovery in the sensor's operating conditions causes to a problem in the application of this structure as an NO
₂
sensor. In this letter, we show that if K
₂
CO
₃
is combined with Al
₂
O
₃
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 NO
₂
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 NO
₂
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 NO
₂
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 K
₂
CO
₃
/Al
₂
O
₃
composite pellet in the exposure of NO
₂
.