High performance and negative temperature coefficient of low temperature hydrogen gas sensors using palladium decorated tungsten oxide

Gas sensors based on a noble metal-semiconductor are widely used, and they show a positive temperature response to hydrogen below 400 degrees C. In this study, a catalytically activated hydrogen sensor is obtained based on Pd decorated WO3 nanoplates constructed by a solvothermal method. An insight into the role of Pd catalyst in the outstanding performance is provided by comparing the sensing properties of this sensor with those of a traditional one made from the same pristine WO3. The pure WO3 sensor exhibits poor selectivity and low sensitivity to hydrogen. In contrast, the observed response of the as-produced sensor is up to 843 at a low operating temperature of 80 degrees C; the response value is even greater than that of WO3 sensors at high temperatures (250-400 degrees C). In addition, the Pd-loaded WO3 sensors show excellent selectivity towards H-2 in comparison to other common gases (CH4, C3H6O, C2H6, C3H8O and NH3). The significantly improved performance is thoroughly explained in terms of the adsorption-desorption mechanism and chemical kinetics theories. Furthermore, an interfacial model demonstrated in this report indicates that the interfacial barrier between WO3 nanoparticles can be a novel effect for excellent gas sensing performance.