K2CO3/Al2O3 Composite Pellet as Room-Temperature NO2 Sensor

Abstract

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.