Morphological Evolution of Nanocluster Aggregates and Single Crystals in Alkaline Zinc Electrodeposition

Abstract

The morphology of Zn electrodeposits is studied on carbon-coated transmission electron microscopy grids. At low overpotentials (η = −50 mV), the morphology develops by aggregation at two distinct length scales: ∼5 nm diameter monocrystalline nanoclusters form ∼50 nm diameter polycrystalline aggregates, and the aggregates form a branched network. Epitaxial (000̅2) growth above an overpotential of |ηc| > 125 mV leads to the formation of hexagonal single crystals up to 2 μm in diameter. Potentiostatic current transients were used to calculate the nucleation rate from Scharifker et al.’s model. The exp(η) dependence of the nucleation rates indicates that atomistic nucleation theory explains the nucleation process better than Volmer–Weber theory. A kinetic model is provided using the rate equations of vapor solidification to simulate the evolution of the different morphologies. On solving these equations, we show that aggregation is attributed to cluster impingement and cluster diffusion while single-crystal formation is attributed to direct attachment.

Controlling electrochemical growth of metallic zinc electrodes: Toward affordable rechargeable energy storage systems

“…4C-3. The observation of ZnO on the surface of Zn metal anode is supported by other ex situ electron microscopy studies (91,92) and in situ characterization techniques, e.g., electrochemicalacoustic time-of-flight analysis (93).…”

“…We hypothesize that this is because of the ratio between SEI-forming reaction rate and the Zn deposition rate; at a small deposition current, the parasitic reaction can proceed steadily and form the SEI layer, which results in the moss-like deposition morphology. Initial experimental evidence for this hypothesis was provided by a highresolution TEM study of the Zn electrodeposits formed in alkaline electrolytes at a low overpotential (50 mV) and at a moderate overpotential (150 mV) (92). Existence of ZnO crystallites is consistently detected under these two conditions but in different geometries and quantities.…”

“…The crystallographic texture of metal electrodeposits is determined by two main factors: the substrate and the overpotential (87,92,137). The influence of substrate can be most fruitfully interrogated using the concept of heteroepitaxy, which describes a group of crystal growths in which the epilayer forms a semi-/coherent interface with the substrate and therefore shows locked orientation relation with the substrate (138).…”

Impact of anode substrates on electrodeposited zinc over cycling in zinc-anode rechargeable alkaline batteries

“…For example, the preferred orientation of zinc on brass (112 2) correlates with a high coulombic efficiency (95%+) during battery cycling [25]. The early stage of compact zinc electrodeposition was also studied on carbon-coated TEM grids [27], where it was demonstrated that (000 2) zinc single-crystals merge to form polycrystalline compact zinc thin films. It has also been reported [19] that crystallographic mismatch between the substrate and zinc deposit affects the zinc adhesion and subsequent morphology, in particular that islands of zinc form on substrates of larger crystallographic misfit.…”

Improvement in Corrosion Protection of Zinc by A Natural Inhibitor Incorporated with Zinc Oxide Nanoparticles in an Acidic Medium Evaluated using Gravimetric Measurement, Electrochemical Method and Atomic Force Microscopy

“…All the test systems were open to the air. After 30 min, the specimens were taken out, washed with distilled water and re-weighed 15,16 . To obtain good reproducibility, experiments were carried out in triplicate, and the average values were obtained.…”