Chapter 8
Porous Nanostructured Materials
8.1 The Dynamic Bubble Template Method
8.1.1 Overview of the Dynamic Bubble Template Method
During the electrodeposition of a compact film, side reactions are usually much
undesired. In aqueous solutions, the typical side reaction during metal deposition is
the evolution of hydrogen. The harmful fingerprint of the hydrogen evolution is a pit
on the surface where a hydrogen bubble could stay attached for a sufficiently long
time so that the deposit growth is obstructed at the bubble-covered area. Here, both
the structure and, in the case of alloy deposition, the local deposit composition differ
from the rest of the surface. Such imperfections are the starting points of the coating
damage, originating from either wear or corrosion. Therefore, the application of both
wetting agents and a sufficiently intense solution agitation are the common countermeasures against the hydrogen bubble attachment. Concerning structural integrity
and durability, the hydrogen absorbed into the metal coating being deposited may
cause hydrogen-induced embrittlement.
Unlike in the processes leading to smooth coatings, the dynamic bubble template
method requires an intense gas evolution on the cathode. Since the most common
solvent is water, the bubbles are formed of hydrogen, and the method is often called as
the dynamic hydrogen bubble template (DHBT) technique. The growing metal fills
up the voids between the bubbles, and the solution remaining in the space between
the growing dendritic or foamy metal soon becomes depleted with respect to the
precursor of the deposit being formed. Therefore, the growth proceeds near the
solid–liquid–gas triple-junction zones. The dynamic nature of the bubble template
methods means that the bubbles form at the surface of the cathode and then leave it.
Hence, neither the size of the bubbles nor their attachment site at the surface is fixed
during the process, although it is much influenced later by the morphology of the
deposit itself. The scheme of the process can be seen in Fig. 8.1.
In all literature resources offering a schematic image on the DHBT method, a
transition from small-bubble to large-bubble templating can be seen as the porous
© Springer Nature Switzerland AG 2021
L. Péter, Electrochemical Methods of Nanostructure Preparation,
Monographs in Electrochemistry, https://doi.org/10.1007/978-3-030-69117-2_8
259
Porous Nanostructured Materials
8.1 The Dynamic Bubble Template Method
8.1.1 Overview of the Dynamic Bubble Template Method
During the electrodeposition of a compact film, side reactions are usually much
undesired. In aqueous solutions, the typical side reaction during metal deposition is
the evolution of hydrogen. The harmful fingerprint of the hydrogen evolution is a pit
on the surface where a hydrogen bubble could stay attached for a sufficiently long
time so that the deposit growth is obstructed at the bubble-covered area. Here, both
the structure and, in the case of alloy deposition, the local deposit composition differ
from the rest of the surface. Such imperfections are the starting points of the coating
damage, originating from either wear or corrosion. Therefore, the application of both
wetting agents and a sufficiently intense solution agitation are the common countermeasures against the hydrogen bubble attachment. Concerning structural integrity
and durability, the hydrogen absorbed into the metal coating being deposited may
cause hydrogen-induced embrittlement.
Unlike in the processes leading to smooth coatings, the dynamic bubble template
method requires an intense gas evolution on the cathode. Since the most common
solvent is water, the bubbles are formed of hydrogen, and the method is often called as
the dynamic hydrogen bubble template (DHBT) technique. The growing metal fills
up the voids between the bubbles, and the solution remaining in the space between
the growing dendritic or foamy metal soon becomes depleted with respect to the
precursor of the deposit being formed. Therefore, the growth proceeds near the
solid–liquid–gas triple-junction zones. The dynamic nature of the bubble template
methods means that the bubbles form at the surface of the cathode and then leave it.
Hence, neither the size of the bubbles nor their attachment site at the surface is fixed
during the process, although it is much influenced later by the morphology of the
deposit itself. The scheme of the process can be seen in Fig. 8.1.
In all literature resources offering a schematic image on the DHBT method, a
transition from small-bubble to large-bubble templating can be seen as the porous
© Springer Nature Switzerland AG 2021
L. Péter, Electrochemical Methods of Nanostructure Preparation,
Monographs in Electrochemistry, https://doi.org/10.1007/978-3-030-69117-2_8
259