Study of palladium metal particle deposition on the conductive diamond surface by XRD, XPS and electrochemistry

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 (|ɛ| ≥ 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 〈1 1 1〉 and the consequent increase in the Pd interatomic spacing (to ∼2.79 Å) 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.