Electrocatalytic activity of Ni-Pt electrocatalysts fabricated by electrolytic deposition for ammonia oxidation as well as the nucleation mechanism of electrodeposited Pt on Ni substrate was investigated by cyclic voltammetry, potentiostatic current-time transient, electrolytic cell polarization curve measurement and atomic force microscopy techniques. Nucleation of Pt on Ni substrate is time and potential dependent, following a mixed 3-D progressive and instantaneous mechanism. With nucleation and growth of Pt as well as the enhanced uniformity of Pt distribution, the electrocatalytic activity of Ni-Pt electrode is enhanced. The threshold value of applied voltage to oxidize ammonia on the fabricated Ni-Pt electrocatalyst in alkaline solution is 0.55 V, which is comparable to those noble metal-modified Pt electrocatalysts. Furthermore, the ammonia electrolytic efficiency on Ni-Pt electrocatalyst is as high as 75%, which is much higher than that on bright Pt and Pt-Ru electrodes, and is comparable to Pt-Ir electrode. Fabrication of Ni-Pt electrocatalysts by electrolytic deposition provides an economic, high-performance alternative for ammonia oxidation and production of hydrogen. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.