An ultrafine Pd/C catalyst with a uniformly sized and highly dispersed nanostructure was synthesized by an improved liquid phase reduction method; in this process a complexone (trans-1,2-diamino-cyclohexane-N,N,N',N'-tetraacetic acid, C(y)DTA) was used as an alternative stabilizer for the first time. Physicochemical characterizations indicated that the resulting Pd nanoparticles possessed ideal structural characteristics, including an average diameter of 2.1 nm, narrow size distribution ranging from 0.5 to 4.0 nm, no visible agglomerations, and no residual C(y)DTA. Electrochemical tests showed that the catalytic activity of the obtained Pd/C catalyst for formic acid electrooxidation was 2.2 times greater than that of Pd/C catalyst prepared in the absence of C(y)DTA. This improvement in the electrocatalytic performance was attributed to the uniformly sized and highly dispersed nanostructure, which provided a larger overall electrochemical active surface area. (C) 2009 Elsevier Ltd. All rights reserved.