Pulsed galvanostatic deposition of Pt particles on microcrystalline and nanocrystalline diamond thin-film electrodes I. Characterization of As-deposited metal/diamond surfaces

The pulsed galvanostatic deposition of nanometer-sized Pt particles on electrically conducting microcrystalline and nanocrystalline diamond thin-film electrodes is reported. The deposition was studied as a function of pulse number (10-50) and current density (0.50-1.50 mA cm(-2)) at the two morphologically different forms of diamond. The deposition of catalyst particles using ten 1 s pulses (duty cycle 50%) at a current density of 1.25 mA cm(-2) (geometric area) produced the smallest nominal particle size and the highest particle coverage on both diamond surfaces. Secondary electron micrographs revealed metal particle deposition over much of the diamond surface, a nominal particle size of 43 +/- 27 nm [relative standard deviation (RSD) = 63%] for microcrystalline and 25 +/- 25 nm (RSD = 100%) for nanocrystalline diamond, and a nominal particle coverage of 7.5 (+/- 0.9) x 10(9) cm(-2) for microcrystalline and 1.9 (+/- 1.0) x 10(10) cm(-2) for nanocrystalline diamond. Deposition under these conditions resulted in the most efficient utilization of the metal catalyst for H+ adsorption, based on the electrochemically active Pt area normalized to the estimated metal loading. Typical specific surface areas of 10-50 m(2)/g Pt were calculated, which compare favorably to values obtained at sp(2) electrodes, like carbon and graphite. The influence of the diamond electrode microstructural and electronic properties on the formation of dimensionally uniform metal adlayers is discussed. (c) 2005 The Electrochemical Society.