Available online at www.springerlink.com Acta Metall. Sin. (Engl. Lett.) Vol.26 No. 4 pp. 361—365 August 2013 Preparation and Characterization of Ultra-thin Pd-Ag Alloy Membranes Renguo SONG 1)† , Zhanguo ZHANG 2) , Chao WANG 1) , Hai LI 1) and Zhixiu WANG 1) 1) School of Materials Science and Engineering, Changzhou University, Changzhou 213164, China 2) National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba, Ibaraki 3058569, Japan [Manuscript received 18 March 2013, in revised form 28 March 2013] c  The Chinese Society for Metals and Springer–Verlag Berlin Heidelberg Ultra-thin Pd-Ag alloy membranes were prepared initially by cold rolling, and it was found that there exist a large number of defects such as pinholes or cracks in the as-rolled membranes. Subsequently, these defects were repaired using electroless plating technique. The morphologies of the membranes have been examined by scanning electron microscopy (SEM). It was observed in some as-repaired membranes that the defects were disappeared. A hydrogen permeation study has demonstrated that the as-repaired Pd-Ag alloy membranes were of high hydrogen permeation flux and hydrogen selectivity. KEY WORDS: Pd-Ag alloy membrane; Cold rolling; Electroless plating; Hydrogen permeation 1. Introduction Hydrogen is essential for the production of clean fuel. Faced to lower-grade crude oil and stricter en- vironmental standards, refinery will need more hy- drogen to reduce the amounts of metals, sulfur and nitrogen in the hydrocarbon fuel. Also, the tougher legislation for air pollution emissions is expected to in- crease the use of hydrogen as an alternate fuel for zero- emission vehicles. In order to meet these challenges, improvements must be made in the production, sep- aration, purification and utilization of hydrogen. Hy- drogen selective membranes have been the focus of in- tensive study in recent years [1-5] . The potential appli- cations of hydrogen selective membranes include sepa- ration and recovery of hydrogen from process stream, purification of hydrogen for fuel cell application and membrane reactors. Membrane reactors have the ad- vantage of combining chemical reaction and separa- tion in a single unit. It has been demonstrated that the selective removal of hydrogen across the mem- brane during the dehydrogenation can result in supra- † Corresponding author. Prof., Ph.D.; Tel: +86 519 86330069; Fax: +86 519 86330069; E-mail: songrg@cczu.edu.cn (Renguo SONG) DOI: 10.1007/s40195-013-0151-7 equilibrium conversions. Moreover, high purity hy- drogen can be recovered from the reaction. Pd and Pd alloy membranes exhibit very high performance in terms of hydrogen permeability be- cause of the high solubility and diffusivity of the hy- drogen isotopes in their lattice. In particular, Pd- Ag alloy with silver content of 23–25 at.% shows a very high chemical and mechanical stability. The ad- dition of Ag into the Pd membrane has been used to improve their resistance to hydrogen embrittle- ment. Therefore, Pd and Pd-Ag membranes have re- ceived growing attention for catalytic membrane reac- tor and hydrogen purification applications during the past three decades [6-14] . Up till now, many methods have been proposed and developed to prepare Pd and Pd-based membranes including physical vapor depo- sition (PVD), sputtering and magnetron sputtering, chemical vapor deposition (CVD), electroless plating, cold rolling and so on [15] . Among these techniques, electroless plating is the most attractive preparation method because it provides strong advantages such as uniformity of deposits on complex shapes, low cost as well as very simple equipment [16-18] . For Pd mem- brane preparation using electroless plating technique, Pd particles are generally reduced from the plating solution of amine complex of Pd in the presence of reducing agents and then grow on Pd nuclei which