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Over-limiting current and control of dendritic growth by surface conduction in nanopores.

Han JH, Khoo E, Bai P, Bazant MZ - Sci Rep (2014)

Bottom Line: Copper electrodeposits 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 positive surface charge, dendrites avoid the surfaces and are either guided along the nanopore centers or blocked from penetrating the membrane.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.

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 nanopores, without any such instabilities, and used to control dendritic growth during electrodeposition. Copper electrodeposits 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.

No MeSH data available.


Related in: MedlinePlus

(a) Effect of SC on electrodeposition in charged nanopores during OLC. (b) V-t curves of AAO(+) and AAO(−) for an applied current of −6 mA. (c) Magnification of data of (b) for first 200 s. SEM images of electrodeposited Cu nanowires in (d) AAO(+) and (e) AAO(−).
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f4: (a) Effect of SC on electrodeposition in charged nanopores during OLC. (b) V-t curves of AAO(+) and AAO(−) for an applied current of −6 mA. (c) Magnification of data of (b) for first 200 s. SEM images of electrodeposited Cu nanowires in (d) AAO(+) and (e) AAO(−).

Mentions: Our physical picture (Figure 2B) is further supported by the morphology of copper deposits grown during OLC, which reveals for the first time the dramatic effects of nano-template surface charge (Figure 4A). In the SC-dominated regime, we expect AAO(+) to block copper penetration into the nanopores, while AAO(−) should promote growth of a nanowire array following a deionization shock that is stable to shape perturbations55. For sufficiently high voltage and low salt, SC-guided electrodeposition should conformally coat the surfaces, leading to an array of nanotubes.


Over-limiting current and control of dendritic growth by surface conduction in nanopores.

Han JH, Khoo E, Bai P, Bazant MZ - Sci Rep (2014)

(a) Effect of SC on electrodeposition in charged nanopores during OLC. (b) V-t curves of AAO(+) and AAO(−) for an applied current of −6 mA. (c) Magnification of data of (b) for first 200 s. SEM images of electrodeposited Cu nanowires in (d) AAO(+) and (e) AAO(−).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4231330&req=5

f4: (a) Effect of SC on electrodeposition in charged nanopores during OLC. (b) V-t curves of AAO(+) and AAO(−) for an applied current of −6 mA. (c) Magnification of data of (b) for first 200 s. SEM images of electrodeposited Cu nanowires in (d) AAO(+) and (e) AAO(−).
Mentions: Our physical picture (Figure 2B) is further supported by the morphology of copper deposits grown during OLC, which reveals for the first time the dramatic effects of nano-template surface charge (Figure 4A). In the SC-dominated regime, we expect AAO(+) to block copper penetration into the nanopores, while AAO(−) should promote growth of a nanowire array following a deionization shock that is stable to shape perturbations55. For sufficiently high voltage and low salt, SC-guided electrodeposition should conformally coat the surfaces, leading to an array of nanotubes.

Bottom Line: Copper electrodeposits 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 positive surface charge, dendrites avoid the surfaces and are either guided along the nanopore centers or blocked from penetrating the membrane.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.

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 nanopores, without any such instabilities, and used to control dendritic growth during electrodeposition. Copper electrodeposits 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.

No MeSH data available.


Related in: MedlinePlus