Palladium Nanoparticles Electrodeposition onto Glassy Carbon from a Deep Eutectic Solvent at 298 K and Their Catalytic Performance toward Formic Acid Oxidation

Abstract

From potentiodynamic and potentiostatic electrochemical methods it was assessed, for the first time, the kinetics and mechanism involved during the electrochemical synthesis of palladium nanoparticles, PdNPs, from a deep eutectic solvent, DES, formed by the choline chloride and ethylene glycol eutectic mixture at 298 K. It was found that the potentiostatically electrodeposited PdNPs were formed through multiple 3D nucleation with diffusion-controlled growth. The nucleation frequency and the nucleation active sites increased linearly and exponentially with applied potential, respectively, and the Pd(II) ions diffusion coefficient, D, in DES was D = (2.77 ± 0.19) 10 −7 cm 2 s −1 . The morphology and composition of the PdNPs were characterized by SEM and XPS, respectively. The PdNPs were homogeneously dispersed onto the GCE surface, with monodispersed size ((41 ± 5) nm) and were formed mainly by metallic palladium with small amounts of PdO and PdO 2 . Furthermore, it was also shown that the GCE-PdNPs modified electrode depicts a high catalytic activity toward formic acid electrochemical oxidation reaction, revealing a mass activity of (4200 ± 100) mA mg Pd −1 at the peak potential, much greater than those reported so far for other PdNPs synthesized by means of sophisticated, time-consuming methods.

Mechanism and Kinetics of Palladium Nanoparticles Electrochemical Formation onto Glassy Carbon, from a Deep Eutectic Solvent (Reline)

“…The best-fit parameters obtained from the analyses of some of the j–t plots in Figure b are reported in Table along with the diffusion coefficient of the Pd­(II) ions in this system, estimated from parameter P 1 (D = (1.65 ± 0.10) × 10 –7 cm 2 s –1 ). This value is smaller than that found for Pd­(II) ions in ethaline DES, (2.77 ± 0.19) × 10 –7 cm 2 s –1 , at 298 K but greater than the value reported, 0.19 × 10 –7 cm 2 s –1 , at 322 K, by Lanzinger et al, using the Randles–Sevcik equation.…”

“…A typical CV recorded with the GCE immersed in reline containing Pd(II) ions is shown in Figure 1. It is important to mention that the system conditions differ from those observed in choline/ethylene glycol DES 20 on several things, like the viscosity of DES and the temperature imposed on the system. During the cathodic scan, a well-resolved peak, associated with the reaction Pd(II) Reline + 2e − = Pd (s) , is depicted.…”

“…So far, we have clearly shown that residual water reduction occurs on the growing surface of the Pd(0) nanoparticles concurrently with palladium deposition and that using eq 10, for the analysis of the potentiostatic current density transients, we have been able to quantify both contributions to the total current. This is not a minor finding at all; for instance, if the PdNPs would be used as a catalyst toward some electrode reaction, namely the formic acid oxidation reaction, 20 the mass activity of these nanoparticles (obtained as the ratio between the formic acid oxidation current and the mass of the catalyst) must be estimated. If these nanoparticles were supported on the carbon electrode by means of electrodeposition process, then using the first Faraday law, it would be possible to estimate the palladium mass amount used to modify the electrode surface.…”

“…DES have been used for Ni, Cr, Fe, , and Al electrodeposition. Recently, we have shown that palladium nanoparticles, PdNPs, electrodeposited at 298 K, from a choline chloride:ethylene glycol mixture (ethaline) exhibited an outstanding performance toward formic acid oxidation reaction. In this work, we studied, for the first time, the mechanism and kinetics involved during PdNPs electrodeposition onto a glassy carbon electrode (GCE) from a different DES, reline, formed by the eutectic mixture of choline chloride and urea.…”

A Novel Electrochemical Glassy Carbon Electrode Modified with Carbon Black and Glyceline Deep Eutectic Solvent within a Crosslinked Chitosan Film for Simultaneous Determination of Acetaminophen and Diclofenac

“…DES properties have continuously been compared to those exhibited by IL [11]. Due to the ability to solubilize metal oxides [12], DES has been used as electrolyte solution in metal electrodeposition processes [13] and nanomaterials synthesis [14, 15]. Electrosynthesis of conductive polymers receives special attention [16].…”