Preparation and characterization of Pd-Ag alloy membranes via simultaneous plating by continuous addition of Ag to the electroless plating solution

摘要

Because of their high permeability and exclusive selectivity for hydrogen, palladium-based thin membranes have attracted great interest as promising materials for the continuous separation and purification of hydrogen [1]. In addition, palladium-based membranes are potential candidates for use in integrated membrane reactors where the separation process is coupled with catalytic membrane reactors such as hydrogenation and dehydrogenation, hydroxylation of benzene and methane steam reforming. Pure palladium membrane is often damaged by hydrogen embrittiement due to α-β phase transition of the palladium hydride at below the critical temperature (293 °C) and pressure (2 MPa); this is accompanied by a lattice expansion and the resulting internal stress generates defects, which often cause fatal fracture of the membrane. Alloying of metals to palladium often increases the hydrogen permeability and enhances the mechanical properties. It has been pointed out that the α-β phase transition is considerably suppressed by alloying with silver [2]. Therefore Pd-Ag alloy membranes have been recognized as the promising membrane for the practical application in separation and purification of hydrogen.