408
11 Templated Systems
The materials used for dual template synthesis are essentially the same as used in
other lyotropic deposition methods. Pt with high surface area due to the hierarchical
pore system obtained an outstanding interest because of its catalytic properties [357,
363]. The high surface area and the hierarchical pore structure of transition metal
oxides (like MnO 2 [359]) and hydroxides (like Co(OH) 2 [360, 361]) are beneficial
for the supercapacitor properties. The analysis of dual template-synthesized Ni alloys
showed that besides the composition, the particle size of the alloys plays a fundamental role in the determination of the electrochemical and corrosion properties of
these alloys [356, 358].
11.4.6 Micelle Templates
The category of micelle templates involves a large variety of materials. The group of
micelle templates ranges from those assembled from either relatively small surfactant
molecules or large multiblock copolymers to colloidal particles precipitated in situ
in the plating solutions. The latter can be distinguished from the previous sorts of
micelles with the feature that no dynamic equilibrium with the solution prevails;
hence, their shape and size are determined by the precipitation conditions and can
be taken as constant. In this respect, they show some resemblance to the colloidal
particle templates but differ from them in size and aggregation mechanism. Finally,
reverse micelles must be listed here as finite domains that can regulate the special
constraints of the electrodeposition process. A few examples will be shown below
for each category. The micelle-forming material is a sacrificial component in each
case that can be removed by washing the deposit with and appropriate solvent and
that no longer has any influence on the deposit properties after being removed. The
electrodeposition process is usually very simple, involving potentiostatic polarization
for a fixed time. The deposition potential was often reported to have a significant
impact on whether the deposit showed a reverse micelle mesoporous structure or not;
therefore, the optimization of the deposition process is indispensable.
Micelle templates formed by the association of small surfactant molecules.
Anionic, neutral and cationic surfactant all can form micelles in aqueous solutions
above the critical micelle-forming concentration but below the limit of the occurrence
of the H 1 phase. The most commonly applied materials in each category are sodium
dodecylsulphate [364, 365], octaethylene glycol monohexadecyl ether [366] and
cetyltrimethylammonium bromide [367], respectively. The impact of the micellar
solutions on the deposition process has been demonstrated in various ways. The
change in the micrometre-scale morphology of the deposits may be an indicator
of the micelle templating process, even if the micelle imprints at the sub-10 nm
scale cannot be detected with SEM observations [364]. When TEM observations
are available, the mesoporous nature of the deposits can be identified, showing that
a disordered pore arrangement was formed [365–367]. A transition from random
to hexagonally ordered deposits with the increase of the surfactant concentration is
demonstrated in Fig. 11.21.
11 Templated Systems
The materials used for dual template synthesis are essentially the same as used in
other lyotropic deposition methods. Pt with high surface area due to the hierarchical
pore system obtained an outstanding interest because of its catalytic properties [357,
363]. The high surface area and the hierarchical pore structure of transition metal
oxides (like MnO 2 [359]) and hydroxides (like Co(OH) 2 [360, 361]) are beneficial
for the supercapacitor properties. The analysis of dual template-synthesized Ni alloys
showed that besides the composition, the particle size of the alloys plays a fundamental role in the determination of the electrochemical and corrosion properties of
these alloys [356, 358].
11.4.6 Micelle Templates
The category of micelle templates involves a large variety of materials. The group of
micelle templates ranges from those assembled from either relatively small surfactant
molecules or large multiblock copolymers to colloidal particles precipitated in situ
in the plating solutions. The latter can be distinguished from the previous sorts of
micelles with the feature that no dynamic equilibrium with the solution prevails;
hence, their shape and size are determined by the precipitation conditions and can
be taken as constant. In this respect, they show some resemblance to the colloidal
particle templates but differ from them in size and aggregation mechanism. Finally,
reverse micelles must be listed here as finite domains that can regulate the special
constraints of the electrodeposition process. A few examples will be shown below
for each category. The micelle-forming material is a sacrificial component in each
case that can be removed by washing the deposit with and appropriate solvent and
that no longer has any influence on the deposit properties after being removed. The
electrodeposition process is usually very simple, involving potentiostatic polarization
for a fixed time. The deposition potential was often reported to have a significant
impact on whether the deposit showed a reverse micelle mesoporous structure or not;
therefore, the optimization of the deposition process is indispensable.
Micelle templates formed by the association of small surfactant molecules.
Anionic, neutral and cationic surfactant all can form micelles in aqueous solutions
above the critical micelle-forming concentration but below the limit of the occurrence
of the H 1 phase. The most commonly applied materials in each category are sodium
dodecylsulphate [364, 365], octaethylene glycol monohexadecyl ether [366] and
cetyltrimethylammonium bromide [367], respectively. The impact of the micellar
solutions on the deposition process has been demonstrated in various ways. The
change in the micrometre-scale morphology of the deposits may be an indicator
of the micelle templating process, even if the micelle imprints at the sub-10 nm
scale cannot be detected with SEM observations [364]. When TEM observations
are available, the mesoporous nature of the deposits can be identified, showing that
a disordered pore arrangement was formed [365–367]. A transition from random
to hexagonally ordered deposits with the increase of the surfactant concentration is
demonstrated in Fig. 11.21.