An experimentally simple process is reported in aqueous solution and under ambient conditions to prepare highly dispersed and active Pd/C catalyst without the use of a stabilizing agent. The [Pd(NH3)(4)](2+) ion is synthesized with gentle heating in aqueous ammonia solution without formation of Pd(OH)(x) complex intermediates. The adsorbed [Pd(NH3)(4)](2+) on the surface of carbon (Vulcan XC-72) is reduced in situ to Pd nanoparticles by NaBH4. The Pd/C catalyst obtained is characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show that highly dispersed Pd/C catalyst with 20 wt.% Pd content and with an average Pd nanoparticle diameter of 4.3-4.7 nm could be obtained. The electrochemical measurements show that the Pd/C catalyst without stabilizer has a higher electro-oxidation activity for formic acid compared to that of a Pd/C catalyst prepared in a traditional high temperature polyol process in ethylene glycol. (C) 2010 Elsevier B.V. All rights reserved.