Pt/Ni alloyed nanoparticles have been prepared via co-precipitation method on crystalline silica Support. The respective salt Solutions were reduced using sodium borohydride (NaBH4) in an inert atmosphere at 353 K. Various Pt/Ni molar ratios were studied. H-2-TPR studies revealed that total reduction of the metal ions occurred during the reduction stage while H-2-TPD profiles show that there are four different types of the catalysts. Catalytic studies of these bimetallic catalysts demonstrate enhancements in the activity compared to Ni-100. Catalyst with the best activity, Pt72Ni28, exhibits specific metal sites not seen in other catalysts. The existence of these metal sites is explained as clue to the interaction between Pt and Ni nanoparticles. STEM analysis strongly indicates that the nature of the interaction is the formation of alloys between the metal Particles while XPS demonstrates that Pt segregation Occurs On the surface of the bimetallic Particles. (C) 2009 Elsevier B.V. All rights reserved.