Effect of carbon nonoxide on hydrogen permeation in some palladium-based alloy membranes

The effect of poisoning by carbon monoxide in hydrogen gas on hydrogen permeation through Pd-rich Pd-Y(Gd)-Ag and Pd-Y-In(Sn,Pb) alloy series has been investigated. The hydrogen permeability in all the alloys decreases with time due to the adsorption of the contaminant gas on the surfaces. In particular, the reduction in permeability For high Y(Gd) content Pd-Y(Gd)-Ag alloys, which have higher permeability under pure H-2 gas, is larger than that in the Pd-Y-In(Sn,Pb) alloys series. The reduction rates for the Pd-Cid-Ag alloy series decrease with increasing temperature, whereas for the Pd-Y-Ag alloy series and also Pd-24.0 at. % Ag alloy the reduction rates increase with temperature. The XPS analysis on the alloy surfaces before and after the permeation experiments showed no carbides or oxides. The intensities of C-1s spectrum for all the alloys decrease with increase of Ar+ sputter etching time. The reduction in hydrogen permeability for these alloys can be attributed to the decrease in effective area for dissociation of hydrogen molecules due to the adsorption of CO on the alloy surfaces. Copyright 1996 International Association for Hydrogen Energy