Assessment of the Nucleation and Growth Mechanism of Copper Electrodeposition Over Graphene Oxide

The characteristics of copper electrodeposition over graphene oxide (GO) were studied using cyclic voltammetry (CV), chronoamperometry (CA), and microscopy techniques. CV results established the diffusion-controlled nature of Cu reduction over GO. Mathematical modeling of CA data revealed the simultaneous occurrence of three competing reactions at the electrode-electrolyte interface: adsorption/double-layer charging, 2D instantaneous nucleation, and 3D nucleation and growth of Cu islands. The steady-state nucleation rates (I_st) for Cu island formation increased with an increase in the cathodic voltage from − 0.40 V (I_st = 4.23 × 10⁶ cm⁻² s⁻¹) to − 0.60 V (I_st = 14.04 × 10⁶ cm⁻² s⁻¹). Application of the classical theory of nucleation revealed that under the overpotential ranges provided in the experiment, the critical Gibb’s free energy required for Cu nucleation over GO substrate is lower than the room-temperature thermal energy. It means that the Cu deposition mechanism is not activation-controlled but rather a kinetically controlled mechanism. Application of Milchev’s atomistic theory reveals that the critical nucleus size is one atom, which implies that every Cu atom depositing over GO is a supercritical nucleus that can grow irreversibly.