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. Electrodeposited Pd has applications as catalysts, interconnects, jewelry and ornaments.1 Electrodeposition has also been considered for recovery of fission palladium.2 Ionic liquids (ILs) are considered promising electrolytes for Pd electrodeposition because hydrogen embrittlement, which is commonly a problem for Pd electrodeposition in aqueous systems, could be avoided by proper choice of IL. Different types of ILs have been studied for this purpose such as chloroaluminates, 20 Some of the work has also been done with the deep eutectic solvents (DES) choline chloride/urea and choline chloride/ethylene glycol.14,21 Pd-containing liquid metal salts (LMS), which are ILs with metal ions coordinated to the cations are also being explored for Pd electrodeposition. 22 However, these works were mostly limited to the study of Pd thin films. This limits the usability of Pd electrodeposition in ILs to the electronic and decorative industry.Controlled synthesis of nanostructures would make Pd electrodeposition in ILs applicable towards heterogeneous catalysis, where catalysts are usually metal nanoparticles. However, controlling size, shape and distribution of metal nanostructures are not straightforward in either aqueous-based solutions or ILs. Although significant progress has been made in aqueous-based solution regarding the synthesis of Pd nanostructures, the same could not be said for ILs. One of the issues is that the ILs behave differently than that of water; therefore, the knowledge could not be directly transferred from aqueous solutions to ILs. Another prominent issue is that each IL has unique chemistry. Despite these disadvantages, ILs hav...

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“…The recovery of the diffusion rate of SiCl 4 molecules to the electrode surface resulted in the concentration of SiCl 4 at the substrate surface being retained at a relatively high level. Notably, the conditions of the electrodeposition and rest period were selected in consideration of an appropriate duty ratio, [40][41][42] allowing a relatively smooth surface to be obtained (Fig. 5).…”

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“…Additionally, the Pd layer on the Cu 2 O surface is quite thin, especially when considering the thickness of the oxide material, and beyond the detection limit of the technique. 22 − 24 …”

“…Such results suggest that Cu 2 O is the dominant species present in the composite materials, consistent with the SEM, TEM, and EDS results. Additionally, the Pd layer on the Cu 2 O surface is quite thin, especially when considering the thickness of the oxide material, and beyond the detection limit of the technique. − …”

“…While the XRD measurements indicate that only Cu 2 O is present in the samples, EDS and ICP-OES confirmed the presence of surface Pd for all of the samples, which was visually observed by TEM. This effect is attributed to the thinness of the Pd layer on the surface of the oxide cube …”

“…This effect is attributed to the thinness of the Pd layer on the surface of the oxide cube. 24 Photocatalytic Reactivity. The photocatalytic reductive dechlorination of PCBs was examined using the Cu 2 O/Pd 1, 3, 6, 9, and 15% particles irradiated with a Hg-vapor lamp in a photochemical cabinet.…”