Developing a heating procedure to optimise hydrogen permeance through Pd–Ag membranes of thickness less than 2.2 μm

The Pd–Ag films, with a total thickness of <2.2 μm, were deposited by electroless plating on the inside of α-alumina membranes from SCT. The H2 permeances through separated Pd–Ag layers were poor and heating conditions were investigated to improve the H2 permeances through the metal films. The heating temperature, heating time and heating environment all had a significant effect on the H2 permeance and the H2 to N2 selectivity of the Pd–Ag films. The films were oxidised at 310°C for 1 h after heat treatment in Ar at 550°C, and then reduced in H2. This additional surface modification step more than doubled the H2 permeance through the film and only created a moderate amount of membrane defects as indicated by the increase in the N2 permeance. After the heating process, the membranes were characterised from 250 to 410°C using both a sweep gas and a positive pressure difference.