Inhibition of hydrogen absorption in bulk Pd by the formation of Ru–Pd surface alloy

Abstract

Thermal programmed desorption (TPD) of hydrogen was performed in Pd and 5% Ru–Pd foils. The foils were inspected with Auger Electron Spectroscopy and Ar ion-sputter cleaned. Hydrogen dosage was 1000L at 10−3Pa. Hydrogen evolving from Pd (TPD curves) was 12 times larger than for the 5% Ru–Pd foil. A 1.8μm thick Ru–Pd surface alloy was grown on the surface of Pd and the TPD curves were very similar to those of the 5% Ru–Pd bulk alloy. The lattice parameter of the Pd fcc crystal structure decreased by 2.8%, when alloying with 5% Ru. The lattice parameter of the fcc cell of Pd increased by 2.3% when absorbing hydrogen. Hydrogen saturation amount at 4655Pa was obtained using a quartz crystal microbalance in a 24nm Pd film and in a 5% Ru–Pd film. A hydrogen–metal ratio (x=H/Pd) was calculated from these measurements yielding a ratio of xPd=0.68 for Pd and xRuPd=0.27 for ~2% Ru–Pd film.