378
P. Kumar
and wind power in areas without backup of grid connections. Therefore, the capacity
to store converted solar and wind energy is an urgent requirement of renewable
energy.
As the electrical energy has to be used immediately, therefore, it is difficult to
match electrical energy demand with the intermittent source of renewable energy
without cheap storage. At present the researcher is working on two main concepts to
address this problem. The first is based upon photocatalytic processes where the solar
energy is directly converted into storable fuels. In the second concept the batteries are
used to store energy. A lot of research efforts are being made by researchers across the
world to develop an capable electrode materials to store energy. For that a high-energy
storage capacity electrode is needed. Electrode designs that have a very large surface
area, highly conducting, and long durability are required. Modified nanostructured
surface of nanostructured materials might be few of the key materials to develop
high-energy storage electrode. There have been wide ranges of porous material, e.g.,
metal-organic frameworks (MOFs) (Furukawa et al. 2013), mesoporous materials
(Schuth and Schmidt 2002), and electrochemically etched porous semiconductors
(Foll et al. 2006) where fine control over physical properties of porous materials is
achieved utilizing controlled techniques, such as directing molecular building blocks
into porous structures for MOFs.
One-dimensional nanostructured materials are promising building blocks for next
generation photovoltaic, optoelectronic, batteries and photonic devices due to their
dimensional dependence physical, optical, and electronic properties. Silicon is a high
density material compared to carbon materials, therefore the silicon-based batteries
have higher volumetric energy density and can easily be integrated on chip with
silicon devices, which would make the silicon battery electrode potential candidates
for energy storage applications. Further the porous matrix offers high volumetric
storage characteristics that are required for transportation applications and mobile
technology (Gogotsi and Simon 2011). This underlines a structural advantage of
controllable porous materials and one-dimensional nanostructured materials, such
as nanoporous silicon (PS), since the chemical and electrochemical etch process that
forms the active material structure dictates the volumetric energy storage properties
and enables this metric to be easily assessed and controlled (Gaur et al. 2013; Granitzer and Rumpf 2010). However, PS suffers from high reactivity due to its relatively
high resistance resulting in poor stability and low power density. Coating of graphene
on PS has been possible solution to increase the stability by reducing the resistance
of PS (Desplobain et al. 2007; Min-Gi et al. 2016; Oakes et al. 2013), but even for
coated electrodes the performance has still been many orders of magnitudes lower
that of carbon-based batteries. This has been attributed to the fact that the power
density is finally controlled by the resistance of the complex Si nanostructure and,
therefore, in addition to the stability the coating also has to provide high conductivity.
Graphene coating on PS is an alternative to provide very large surface area, stability
as well as high conductivity.
The physical properties, e.g., the lateral width, randomness, length scale, and
chemical functionality of PS host matrix can easily be controlled and graphene coating protects the PS from electrochemical degradation with the electrolyte, resulting in
P. Kumar
and wind power in areas without backup of grid connections. Therefore, the capacity
to store converted solar and wind energy is an urgent requirement of renewable
energy.
As the electrical energy has to be used immediately, therefore, it is difficult to
match electrical energy demand with the intermittent source of renewable energy
without cheap storage. At present the researcher is working on two main concepts to
address this problem. The first is based upon photocatalytic processes where the solar
energy is directly converted into storable fuels. In the second concept the batteries are
used to store energy. A lot of research efforts are being made by researchers across the
world to develop an capable electrode materials to store energy. For that a high-energy
storage capacity electrode is needed. Electrode designs that have a very large surface
area, highly conducting, and long durability are required. Modified nanostructured
surface of nanostructured materials might be few of the key materials to develop
high-energy storage electrode. There have been wide ranges of porous material, e.g.,
metal-organic frameworks (MOFs) (Furukawa et al. 2013), mesoporous materials
(Schuth and Schmidt 2002), and electrochemically etched porous semiconductors
(Foll et al. 2006) where fine control over physical properties of porous materials is
achieved utilizing controlled techniques, such as directing molecular building blocks
into porous structures for MOFs.
One-dimensional nanostructured materials are promising building blocks for next
generation photovoltaic, optoelectronic, batteries and photonic devices due to their
dimensional dependence physical, optical, and electronic properties. Silicon is a high
density material compared to carbon materials, therefore the silicon-based batteries
have higher volumetric energy density and can easily be integrated on chip with
silicon devices, which would make the silicon battery electrode potential candidates
for energy storage applications. Further the porous matrix offers high volumetric
storage characteristics that are required for transportation applications and mobile
technology (Gogotsi and Simon 2011). This underlines a structural advantage of
controllable porous materials and one-dimensional nanostructured materials, such
as nanoporous silicon (PS), since the chemical and electrochemical etch process that
forms the active material structure dictates the volumetric energy storage properties
and enables this metric to be easily assessed and controlled (Gaur et al. 2013; Granitzer and Rumpf 2010). However, PS suffers from high reactivity due to its relatively
high resistance resulting in poor stability and low power density. Coating of graphene
on PS has been possible solution to increase the stability by reducing the resistance
of PS (Desplobain et al. 2007; Min-Gi et al. 2016; Oakes et al. 2013), but even for
coated electrodes the performance has still been many orders of magnitudes lower
that of carbon-based batteries. This has been attributed to the fact that the power
density is finally controlled by the resistance of the complex Si nanostructure and,
therefore, in addition to the stability the coating also has to provide high conductivity.
Graphene coating on PS is an alternative to provide very large surface area, stability
as well as high conductivity.
The physical properties, e.g., the lateral width, randomness, length scale, and
chemical functionality of PS host matrix can easily be controlled and graphene coating protects the PS from electrochemical degradation with the electrolyte, resulting in