An impregnation method has been proposed to prepare Pd-loaded WO3 nanolamellae for the gas sensing application. WO3 nanolamellae were synthesized via an acidification method and impregnated with H2Pd2Cl4 solution followed by an ammonia washing treatment. The microstructure and H2 sensing characteristics of the Pd-loaded WO3 nanolamellae were investigated. Electron microscopy studies revealed that PdO particles have been deposited on the surfaces of WO3 with a diameter ranging from 3 to 15 nm. With quite a small amount of Pd, the sensor resistivity was greatly enhanced and it demonstrated an extremely large response to the reduced gas. It was found that sensing response at low temperature increased dramatically with a rise in the gas concentration for Pd-loaded sensors. However, the sensor response at high temperature quickly saturated with increasing the H2 concentration for larger amount of Pd loading. An enhanced combustion effect of Pd and chemical adsorbed water could be responsible for such a saturation of sensing response at high temperatures.
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