A highly dispersed and ultrafine carbon supported Pd nanoparticles (Pd/C) catalyst is synthesized by a facile homogeneous precipitation-reduction reaction method. Under the appropriate pH conditions, [PdCl(4)](2)-species in PdCl(2) solution are slowly transformed into the insoluble palladium oxide hydrate (PdO center dot H(2)O) precipitation by heat treatment due to a slow hydrolysis reaction, which results in the generation of carbon supported PdO center dot H(2)O nanoparticles (PdO center dot H(2)O/C) sample with the high dispersion and small particle size. Consequently, a highly dispersed and ultrafine Pd/C catalyst can be synthesized by PdO center dot H(2)O -> Pd(0) in situ reduction reaction path in the presence of NaBH(4). As a result, the resulting Pd/C catalyst possesses a significantly electrocatalytic performance for formic acid electrooxidation, which is attributed to the uniformly sized and highly dispersed nanostructure. (C) 2011 Elsevier B.V. All rights reserved.