Highly active and stable electrocatalysts for the reduction of nitrate ions were prepared by the adsorption of PdCl42- ions onto a tin monolayer on Au(111) followed by reduction of the adsorbed PdCl42-. The maximum atomic ratio of Pd to Sn, and hence the surface Au. determined using a quartz crystal microbalance, X-ray photoelectron spectroscopy and cyclic voltammetry, was 0.87, which corresponds to 0.3 mug-Pd cm(-2). Despite such an extremely low loading of Pd, the Pd/Sn/Au electrodes showed high electrocatalytic activity (-3.5 mA cm(-2) at -0.1 V vs. Ag\AgCl) and N-2 selectivity (37%), both of which are comparable to the highest values reported at different electrodes. In addition, the reduction current on the Pd/Sn/Au electrodes remained constant for hours and decreased only due to the exhaustion of nitrate ions in solution. (C) 2004 Elsevier B.V. All rights reserved.