Size-selective electrochemical preparation of surfactant-stabilized Pd-, Ni- and Pt/Pd colloids

A detailed study concerning the size-selective electrochemical preparation of R4N+Br- -stabilized palladium colloids is presented. Such colloids are readily accessible using a simple electrolysis cell in which the sacrificial anode is a commercially available Pd sheet, the surfactant serving as the electrolyte and stabilizer. It is shown that such parameters as solvent polarity, current density, charge flow, distance between electrodes and temperature can be used to control the size of the Pd nanoparticles in the range 1.2-5 nm. Characterization of the Pd colloids has been performed using transmission electron microscopy (TEM), small angle X-ray scattering (SAXS) and X-ray powder diffractometry (XRD) evaluated by Debye-function-analysis (DFA). Possible mechanisms of particle growth are discussed. Experiments directed towards the size-selective electrochemical fabrication of (n-C6H13)4N+Br- -stabilized nickel colloids are likewise described. Finally, a new strategy for preparing bimetallic colloids (e.g., Pt/Pd nanoparticles) electrochemically is presented, based on the use of a preformed colloid (e.g., (n-C8H17)4N+Br- -stabilized Pt particles) and a sacrificial anode (e.g., Pd sheet).