Kinetics and Mechanism of Tin Electrodeposition from Fluoroborate Bath onto Pencil Graphite Electrode

摘要

In this work, the nucleation and growth mechanism of tin electrodeposition from a fluoroborate bath onto pencil graphite electrode (PGE) has been investigated by cyclic voltammetry (CV) and chronoamperometry (CA) techniques, along with scanning electron microscopy (SEM). Here, cyclic voltammograms reveal that tin reduction is a diffusion-controlled process. The diffusion coefficient, charge transfer coefficient, and the kinetic constant of tin cations reduction are found to be 1.35 x 10(-5) cm(2)/s, 0.28, and 1.94 x 10(-3) cm/s, respectively. Current transients analysis using Scharifker-Hills and Palomar-Pardave et al. models indicate that initial nucleation is instantaneous, followed by typical three-dimensional growth. Fitting the experimental data against the mentioned models unveils that hydrogen evolution on tin and PGE substrates co-occurred with tin cations reduction. Furthermore, the number of active sites, tin nucleation rate constant, and the proton reduction rate constant on the graphite surface were shown to increase with overpotential. Results also reveal that the proton reduction rate constant is lower on the grown tin centers than on the PGE surface. Moreover, the diffusion coefficient of tin species is derived using the Cottrell equation and Palomar-Pardave et al. model, which is in agreement with CV measurements. Finally, SEM imagery indicates the formation of spherical 3D nuclei with uniform distribution, as result of instantaneous deposition and dendritic growth compatible with diffusion-controlled conditions.