Role of nanostructured WO sub(3 in ion-conducting sensors for the detection of NOx in exhaust gases from lean combustion engines)

Sensitivity to nitrogen monoxide (NO) is studied when implementing nanostructured tungsten trioxide (WO sub(3) in the electrodes of potentiometric sensors for detecting exhaust gases in lean combustion engines. The sensors are made of an YSZ electrolyte covered by two catalytic electrodes. Several groups of sensors have been prepared with different materials over one of the electrodes: layers of nanostructured WO) sub(3), YSZ, WO sub(3 and YSZ mixed and Pt-YSZ cermet electrodes are studied. Differences on sensing responses for each electrode configurations have been found when exposed to several NO concentrations in gas mixtures typical of exhaust gases from lean combustion engines. The role of each layer configuration has been attributed to a diffusive or a catalytic dominant behaviour. Maximum sensitivity to NO is found for electrodes made of thin layers of nanostructured WO) sub(3) over Pt.