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 ∘C. The gas sensing properties of Pd-doped WO3 films to reducing gases (NH3, CO, H2) were studied at different operating temperatures. The sensors have shown high sensitivity and selectivity to hydrogen at working temperature of 200 ∘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).