The spontaneous deposition of Pd metal particles on a conductive boron-doped diamond film supported on silicon substrate was achieved by immersing the diamond/silicon in solutions of 100 ppm Pd2+ with various HF concentrations (0.0049-4.9%). Scanning electron microscopy showed that HF strength affects the deposition morphology (size and density) of Pd particles on polycrystalline diamond surfaces. X-ray photoelectron spectroscopy confirmed the zero valence of Pd particles. X-ray diffraction characterization of Pd particles prepared from 0.0049% HF showed significant lattice strain (vertical bar epsilon vertical bar >= 1.4%) compared to those from [HF] >= 0.049%. The unstrained Pd showed similar electrocatalytic behavior as a Pd disk. While a tensile strain along (111) and the consequent increase in the Pd interatomic spacing (to similar to 2.79 angstrom) could explain the enhanced hydrogen evolution electrocatalytic behavior of Pd metal particles prepared from 0.0049%, the same strained Pd on diamond exhibit no electrocatalytic activity toward HCHO oxidation. (c) 2005 Elsevier B.V. All rights reserved.