Single Atom Nucleation of Cobalt over Graphene Oxide: Theory and Experimental Study

Gupta, A and Srivastava, C (2020) Single Atom Nucleation of Cobalt over Graphene Oxide: Theory and Experimental Study. In: Langmuir, 36 (27). pp. 7824-7834.

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Abstract

Nucleation and growth mechanism of Co electrodeposition over graphene oxide (GO) was studied using cyclic voltammetry (CV) and chronoamperometry techniques. The studies were performed over an aqueous electrolyte containing 10 mM CoSO4·7H2O maintained at an initial pH of 2.5. CV studies established that the deposition mechanism was diffusion-controlled and irreversible. Chronoamperometry studies revealed the presence of three concurrent processes: an initial adsorption current, which indicated adatom layer formation, 3D nucleation and growth of Co islands over GO, and hydrogen evolution over the deposited Co nanoclusters. It was observed that the nucleation rate increased with increasing the overpotential (η) for deposition (from 2.71 × 104 cm-2 s-1 at η = 0.35 V to 3.62 × 106 cm-2 s-1 at η = 0.90 V). Application of the classical theory of nucleation over the chronoamperometry results suggested that the free energy of formation of the critical nucleus was lower than room temperature thermal energy. This indicated that the nucleation and growth process was not activation-controlled but rather a kinetically controlled process. Application of Milchev's atomistic theory revealed that every single atom of Co deposited over the GO sheet was a supercritical nucleus that could grow into a cluster irreversibly. Copyright © 2020 American Chemical Society.

Item Type:	Journal Article
Publication:	Langmuir
Publisher:	American Chemical Society
Additional Information:	The copyright for this article belongs to American Chemical Society.
Keywords:	Chronoamperometry; Cobalt compounds; Crystallization; Cyclic voltammetry; Deposition; Electrolytes; Free energy; Graphene; Nucleation, Aqueous electrolyte; Chronoamperometry techniques; Co-electrodeposition; Deposition mechanism; Diffusion controlled; Free energy of formations; Kinetically controlled; Nucleation and growth, Process control
Department/Centre:	Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	03 Feb 2023 05:11
Last Modified:	03 Feb 2023 05:11
URI:	https://eprints.iisc.ac.in/id/eprint/79828

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