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

Abstract

Performance of a wide range H2 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% H2 in argon, is presented. Thin films of Cr, Pd and nanoparticles 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 as-deposited multilayer while Ag exhibits both elemental and +1 oxidation state in Ag–Pd/Cr which upon H2 conditioning at 200 °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 H2 sensing properties. Dispersion of silver nanoparticles on the sensing surface of Pd restores the H2 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.