AN AMPEROMETRIC CARBON-MONOXIDE SENSOR-BASED ON THE STEADY-STATE DIFFERENCE RESPONSE TECHNIQUE

A solid-state CO sensor has been fabricated by coating the cathode of a Pt/yttria-stabilized zirconia/Pt cell with a layer of copper oxide/zinc oxide/aluminium oxide catalyst mixture. The sensor response is defined as the difference between the two steady-state currents prior to and after the introduction of CO into the O-2-N-2 carrier-gas mixture. The two steady-state current measurements are made in one continuous time course including the stabilization of the sensor in the carrier gas, the injection of CO and finally the stabilization period for the sensor to reach its second steady-state condition. A linear response is obtained with this difference response technique up to 0.18 mol% CO, with a sensitivity increasing from 4.93 mA (mol% CO)(-1) at 1003 K to 9.54 mA (mol% CO)(-1) at 1103 K. The sensor response is verified to be a direct measure of the rate of catalytic oxidation of CO in the catalyst layer by the good correlation of the linear range sensitivity according to pseudo first-order kinetics of the catalytic oxidation of CO.