The highly dispersed and ultrafine carbon-supported Pd nanoparticles (Pd/C) catalyst is synthesized by using an improved precipitation-reduction method, which involves in Pd-II -> PdO center dot H2O Pd-0 reaction path. In the method, palladium oxide hydrate (PdO center dot H2O) nanoparticles (NPs) with high dispersion is obtained easily by adjusting solution pH in the presence of 1,4-butylenediphosphonic acid (H2O3P-(CH2)(4)-PO3H2, BDPA). After NaBH4 reduction, the resulting Pd/C catalyst possesses high dispersion and small particle size. As a result, the electrochemical measurements indicate that the resulting Pd/C catalyst exhibits significantly high electrochemical active surface area and high electrocatalytic performance for formic acid electrooxidation compared with that prepared by general NaBN4 reduction method. (C) 2011 Elsevier Ltd. All rights reserved.