Sensitive and rapid hydrogen sensors based on Pd–WO3 thick films with different morphologies

WO3 loaded with noble metals is well-known to be sensitive to reducing gases and can be used as hydrogen sensor. This paper presents a simple and attractive method concerning the preparation of hydrogen sensors based on Pd-loaded WO3 nanocomposites with different morphologies. The influences of the morphology of WO3 and the palladium growth on its surface on the hydrogen sensing performances are studied. WO3 nanospheres, nanowires and nanolamellae were synthesized by different methods starting from the same precursor (H2WO4·nH2O) which has been obtained by acidification of sodium tungstate (Na2WO4). The prepared WO3 nanostructures were modified with the Pd by dispersing them in a PdCl2 containing solvent using sonication (giving Pd-WO3 inks). The sensors were prepared by screen-printing thick films (∼10 μm) of these inks on alumina substrates fitted with gold electrodes. The response of Pd-loaded WO3 sensors to hydrogen was checked for the different morphologies at working temperatures ranging from 180 to 240 °C. The sensors prepared from nanolamellae showed the highest response while the nanowires presented the shortest response time to hydrogen.