Over-limiting Current and Control of Dendritic Growth by Surface Conduction in Nanopores

TL;DR

This paper demonstrates that over-limiting current in nanopores can be achieved through surface conduction, enabling control over dendritic growth during electrodeposition without relying on chemical or hydrodynamic instabilities.

Contribution

It introduces a surface conduction mechanism in nanopores that sustains over-limiting current and allows for precise control of dendritic growth during electrodeposition.

Findings

Surface conduction enables over-limiting current in nanopores.

Surface charge influences dendritic growth and morphology.

Control of dendrites is achieved without chemical or hydrodynamic instabilities.

Abstract

Understanding over-limiting current (faster than diffusion) is a long-standing challenge in electrochemistry with applications in desalination and energy storage. Known mechanisms involve either chemical or hydrodynamic instabilities in unconfined electrolytes. Here, it is shown that over-limiting current can be sustained by surface conduction in nano pores, without any such instabilities, and used to control dendritic growth during electrodeposition. Copper electrode posits are grown in anodized aluminum oxide membranes with polyelectrolyte coatings to modify the surface charge. At low currents, uniform electroplating occurs, unaffected by surface modification due to thin electric double layers, but the morphology changes dramatically above the limiting current. With negative surface charge, growth is enhanced along the nanopore surfaces, forming surface dendrites and nanotubes behind a deionization shock. With positive surface charge, dendrites avoid the surfaces and are either guided along the nanopore centers or blocked from penetrating the membrane.