P Ndungu

Contactless Tip‐Selective Electrodeposition of Palladium onto Carbon Nanotubes and Nanofibers

Abstract Palladium was electrodeposited onto the tips of isolated carbon nanofibers and carbon nanopipes using an electric field. The amount of Pd deposited on the tips was controlled by varying the field application time. The morphology obtained varied from agglomerate of small particles that just covers the end of the nanotube to large ramified deposits that grow off the tip of the nanotube. The influence of the orientation of the carbon nanostructures with respect to the applied electric field and the quantity of the metal deposited is discussed. Electron microscopy was used to characterize the morphology and location of the deposits.

Pulsed Bipolar Electrodeposition of Palladium onto Graphite Powder

The pulsed bipolar electrodeposition of palladium onto 1-2 μm graphite particles was investigated. The amount of palladium deposited was strongly correlated with field intensity, showing an abrupt increase at 2-3 kV/cm. The electrodeposition was successful for frequencies ranging from 500 Hz to 20 kHz, and the amount of deposited palladium was independent of the frequency used. These results demonstrate that the preparation of bipolar electrodeposited catalysts can be achieved within a very large frequency window. Palladium surface area measurements indicate an increase in dispersion with increasing frequency. Sonication of the graphite prior to deposition leads to significantly greater palladium dispersion. Electron microscopy characterization reveals three types of growth: surface-bound, ramified, and amorphous. The surface-bound growth appears as spherical deposits on the order of 5 nm in both dc and pulsed-field experiments. The ramified deposits consist of interconnected 25-50 nm diam spherical structures extending from the graphite particles and appear in the samples prepared at all studied frequencies.