Nucleation and growth mechanism of tin electrodeposition on graphene oxide: A kinetic, thermodynamic and microscopic study

Abstract

Nucleation and growth mechanism of Sn deposition over graphene oxide (GO) was investigated by cyclic voltammetry, chronoamperometry and transmission electron microscopy (TEM) using an aqueous electrolyte containing 10 mM SnSO4 at pH 2.0. Chronoamperometry studies revealed adsorption phenomena of Sn atoms over GO electrode before the nucleation. Simultaneous reactions that happened over the GO electrode were hydrogen ion reduction along with 3D diffusion-controlled nucleation and growth of Sn. The reaction rates of nucleation and hydrogen reduction increased with increase in the applied potential towards more negative values. Application of atomistic theory of nucleation revealed the fact that a supercritical nucleus can be formed even with one Sn atom over GO sheet which implied that every single atom of deposited Sn can act as a stable nucleus which can grow with further addition of Sn atoms. Further application of classical nucleation theory suggested that the thermodynamic activation energy barrier for nucleation under the applied potential ranges is comparable to that of room temperature thermal energy, kT (2.476 kJ/mol) implying that the deposition was heavily governed by formation of initial adsorption layer of Sn adatoms. Characterization of surface morphology, size and distribution of Sn nanoparticles over GO was performed using TEM and a quantitative comparison of number density of nucleation sites has been presented.