Electrodeposition of Co and Pd Onto Carbon Fiber and Platinum Ultramicroelectrodes
Authors: Corona Castro Jair Azael , Mendoza Huizar Luis Humberto 
Published: February 2020

The synthesis of Co and Pd structures with tuned magnetic properties have scarcely been investigated from the electrochemical point of view [1-7]. Probably, this is due that, these properties are highly dependent on their shape, size and composition. In this sense, the use of ultramicroelectrodes (UME) allow to form a limited number of nuclei onto its surface, which is useful to analyse the electrochemical variables that modify the shape, size and specific composition of these particles [8-11]. In order to analyze the influence of the electrochemical variables during the synthesis of Co and Pd materials employing ultramicroelectrodes; in this work we conducted voltamperometric and chronoamperometric studies from two aqueous solutions. The first one containing PdCl2 0.01 M + NH4Cl 0.1 M and the second one CoCl2 0.01 M + NH4Cl 0.1 M. The working electrodes were a platinum UME (Pt-UME) of 10 μm of diameter and a carbon fiber UME (CUME) of 11 μm of diameter. A graphite bar was used as a counterelectrode and all potentials are reported against an Ag/AgCl electrode. The electrochemical experiments were controlled by mean a bipotentiostat UNISCAN M370. Fig. 1a shows a set of transients obtained in the potential range [-0.8 – -0.95] V applying a potential pulse during 32 s from the system Pt-UME/CoCl2 0.01 M + NH4Cl 0.1 M, while in Fig. 1b are depicted the transients obtained from the system Pt-UME /PdCl2 0.01 M + NH4Cl 0.1 M in the potential range [-0.4 – -0.7] V. Figure 1c and 1d, shows the transients obtained onto CUME for the case of Co and Pd, respectively. All the transients reported in Fig. 1 were compared with the theoretical ones predicted by the mathematical model proposed by Correia et al [12], by means a nonlinear fitting employing the Levenberg-Marquardt algorithm. In all cases, the kinetic parameters such as the nucleation rate (A) and the number of active nucleation sites (N0) were potential dependent. Also, the N0 values in each potential allowed us to simulate the AFM image associated to each potential considering a random distribution on the UME surface.

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Figure 1