Fabrication of palladium nanotubes and their application in hydrogen sensing

A new electroless plating method was used to deposit palladium nanotubes within the pores. of track-etched polycarbonate membranes. The morphology of the deposited palladium nanostructures were characterized with the use of field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectrometry (EDX), and transmission electron microscopy (TEM). The largely expanded surface area and granular nature of the nanotubes make them ideal for applications that require high surface area. One of the applications investigated here is hydrogen sensing. Palladium nanotubes excel in high sensitivity, low detection limit, and fast response times in hydrogen sensing compared to sputtered Pd thin film on glass. The response time ranges from a few seconds to tens of seconds depending on the concentration of hydrogen. The hydrogen sensing behavior can be understood with the Langmuir adsorption isotherm theory at very low hydrogen concentration. The high sensitivity and fast response time in the nanotube imbedded samples imply that the nanostructures create not only larger surface areas but also many more favorable sites for hydrogen adsorption to occur. These new nanostructured sensing elements are superior to the conventional thin film sensors especially in the low hydrogen concentration region.