Size-Controlled Synthesis of Palladium Nanospheres by Pulse Electrodeposition in 1-Butyl-3-methylimmidazolium Chloride Ionic Liquid

Abstract

Pd electrodeposition in ionic liquids has been mostly limited to the formation of thin films, which has restricted its potential application to the electronics and decorative industry only. The electrochemical synthesis of nanostructured Pd could broaden its applications to the catalyst industry as well. In 1-butyl-3-methylimmidazolium chloride, the Pd deposits reported so far have had uncontrolled growth without any well-defined morphology. In this study, we report controlled synthesis of Pd nanoparticles with well-defined morphology on pre-etched Ni electrodes. Potentiostatic pulse deposition was used to synthesize these Pd nanoparticles, which had spherical shape and unimodal size distribution. In contrast, thin film-like morphology was deposited during direct electrodeposition. The size of the Pd nanospheres was controlled by controlling the duty cycle; the size of the Pd nanospheres increased from 14.8 ± 3.5 to 30.8 ± 6.6 nm when the duty cycle decreased from 0.5 to 0.2. The size of the Pd nanospheres showed linear dependence on the duty cycle giving excellent control. X-ray diffraction analysis revealed face-centered cubic crystalline microstructure for the Pd particles. The analysis also suggested that the amount of Pd increased by decreasing the duty cycle. The surface of the Pd deposits was dominated by metallic state as revealed by X-ray photoelectron spectroscopy.