High sensitive gas sensor based on Pd-loaded WO₃ nanolamellae

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.