Mono- and bimetallic catalytic membranes were prepared via deposition of Pd and Cu onto macroporous polymeric membrane. The membranes were employed to catalyze the reaction of nitrate ions reduction by hydrogen in water. Monometallic Pd- and Cu-loaded membranes were poorly active in the reaction, while bimetallic (Pd + Cu)-loaded membranes exhibited high catalytic activity. Combination of monometallic Pd- and Cu-loaded membranes in one stack resulted in high catalytic activity, similar to that of bimetallic (Pd + Cu)-loaded membranes. The results of this study provide experimental support for a hypothesis on hydrogen spillover as a part of the molecular mechanism of nitrate ions reduction by hydrogen in water over palladium-copper catalytic system. (C) 2003 Elsevier B.V. All rights reserved.