Preparation of highly selective, sensitive and stable hydrogen sensors based on Pd-doped tungsten trioxide

In this paper, highly selective, sensitive and stable hydrogen sensors based on Pd-doped tungsten trioxide were successfully prepared by promoting way. Two different morphologies of WO3 were obtained by chemical route synthesis (WO3 nano-particles and WO3 micro-lamellae), their morphologies were observed by SEM and TEM microscopy and their crystalline structures were determined by X-ray diffraction (XRD). To prepare Pd-doped WO3 films, palladium chloride salt/WO3 was highly dispersed in organic solution using sonication, the resultant Pd-WO3 dispersion was drop coated on the alumina substrate fitted with gold electrodes and annealed at 500 degrees C. The gas sensing properties of Pd-doped WO3 films to reducing gases (NH3, CO, H-2) were studied at different operating temperatures. The sensors have shown high sensitivity and selectivity to hydrogen at working temperature of 200 degrees C. The sensors with low Pd loading (0.4 wt %) has shown the best stability and reproducibility. In these last conditions, the sensors have shown no obvious response to ammonia (<= 1 ppm) and insignificant response to carbon monoxide (<= 200 ppm). (C) 2010 Published by Elsevier Ltd.