Hydrogen sensing using impedance measurements of nanocrystalline palladium

The objective of this work has been the development of a low cost method of sensing explosive levels of molecular hydrogen gas. The challenge in designing an inexpensive sensor has been to implement an inexpensive manufacturing process with a repeatable and accurate response. A sensor design has been implemented which uses a ceramic based interdigitated structure containing a thin layer of vacuum-sputtered palladium. Early tests with this structure showed that testing using direct current meters resulted in a catastrophic failure at or around 4% H₂. Reassessment of this method determined that alternating current excitation and impedance spectroscopy methods provided the basis for a high reliability device. The palladium sensing film required an initial pretreatment of H₂. Upon initial pretreatment, the sensor was tested and cycled from 9% to 33% and found to be repeatable.