Facile Electrochemical Synthesis of Pd Nanoparticles with Enhanced Electrocatalytic Properties from Surfactant-Free Electrolyte

Synthesis of low-dimensional metallic nanoparticles with a clean surface, high dispersibility, and enhanced atomic surface distribution is extremely important, as these factors strongly influence the electrocatalytic properties of the nanoparticles. In this study, the early stage electrochemical nucleation and growth of palladium nanoparticles (Pd NPs) under potentiostatic control has been investigated on a Au(111) textured substrate. The size distribution and structural characterization of the ex situ as-deposited Pd NPs by means of high-resolution field emission gun-scanning electron microscopy (FEG-SEM) at different stages combined with electrochemical measurements revealed that the cluster of nuclei grew independently through the reduction of metal ions. The electrodeposited Pd NPs were very pure, as confirmed by X-ray photoelectron spectroscopy (XPS), owing to the surfactant-free green electrodeposition process, and they exhibited a highly dispersed average particle size of 2–5 nm. The average nanoparticle size becomes smaller with higher overpotentials for the same deposition time. The synthesized Pd NPs demonstrated the largest specific surface area (four times that of commercial Pd−C) and electrocatalytic activity in ferrocyanide/ferricyanide redox and ethanol electrooxidation processes (35 times that of commercial Pd−C). This work represents an important step in achieving the fundamental understanding of nucleation and growth of nanoparticles correlating the electrocatalytic performances.