Wide range H2 sensors for process streams, based on multilayered Pd thin films dispersed with Ag nanoparticles and chromium as buffer layer

Performance of a wide range H-2 sensor made of thin film of Pd dispersed with silver nanoparticles and a buffer layer of Cr for Al2O3 substrate having a typical working range of 800 ppm-4% H-2 in argon, is presented. Thin films of Cr, Pd and nanop articles of Ag have all been deposited sequentially as multilayers using pulsed laser deposition method. GI-XRD confirms the formation of face centered cubic Pd. Pd is in elemental state in the asdeposited multilayer while Ag exhibits both elemental and +1 oxidation state in Ag-Pd/Cr which upon H-2 conditioning at 200 degrees C becomes elemental Ag. Cr buffer layer despite very effective in preventing delamination of Pd films during hydrogen intake, it leads to the loss of H-2 sensing properties. Dispersion of silver nanoparticles on the sensing surface of Pd restores the H-2 sensing properties of Pd/Cr. The results of Ag-Pd/Cr/Al2O3 are compared with those of Pd/Cr/Al2O3 and Pd/Al2O3 and the role of Ag nanoparticles in sensing is highlighted. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.