Journal of Membrane Science 182 (2001) 195–203 Effects of electroless plating chemistry on the synthesis of palladium membranes Y.S. Cheng, K.L. Yeung * Department of Chemical Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, PR China Received 5 January 2000; received in revised form 23 August 2000; accepted 30 August 2000 Abstract The effects of plating chemistry on palladium deposition, plating efficiency and membrane microstructure have been studied for two palladium electroless plating solutions, hydrazine-based and hypophosphite-based plating baths. The electroless plating kinetics of palladium onto seeded supports have been determined for hypophosphite-based plating bath, and a simple kinetic model has been developed. The model provides an accurate prediction of deposition rate and film thickness as a function of plating parameters. Most importantly, the experimental results demonstrated that plating chemistry plays a vital role on both plating performance and film microstructure. © 2001 Elsevier Science B.V. All rights reserved. Keywords: Electroless plating chemistry; Palladium membranes; Hypophosphite-based plating bath; Membrane preparation and structure; Hydrazine-based plating bath 1. Introduction The applications of palladium membrane [1,2] include hydrogen separation and purification [3,4], hydrogen recovery from process streams [5,6] and membrane reactor for H 2 -related reactions (e.g. hy- drogenation [7–9], dehydrogenation [10,11], methane reforming [12], ammonia decomposition [13], etc.). Early palladium-based membranes are made of thin walled tubes or free-standing foils [14,15]. Recent efforts to increase H 2 permeation rates have led to the development of Pd-based composite membranes. Several recognized film deposition techniques have been successfully used in fabricating thin supported palladium membranes. These include the thermal * Corresponding author. Tel.: +852-2358-7123; fax: +852-2358-0054. E-mail address: kekyeung@ust.hk (K.L. Yeung). deposition [16], sputter coating [8], chemical vapor deposition [17], electrochemical plating [18] and electroless plating [19]. Electroless plating is a simple and inexpensive method for depositing palladium. It provides uniform dense coatings on both conducting and non-conducting surfaces [20–22]. A substantial amount of works has been published on Pd membrane synthesis via elec- troless plating [23–26]. However, only a few of these papers address the plating kinetics of palladium metal and little is known regarding the effects of plating chemistry on the palladium deposition and membrane microstructure. In this paper, the hydrazine and hypophosphite- based palladium plating baths were selected to demon- strate the effects of plating bath chemistry on the plating efficiency and film quality of the deposited palladium membrane. In addition, the deposition kinetics of palladium from hypophosphite-based 0376-7388/01/$ – see front matter © 2001 Elsevier Science B.V. All rights reserved. PII:S0376-7388(00)00563-9