Versatile 1-D Nanostructures for Green Energy Conversion …
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as future generation energy sources. It is very clear from Fig. 1 that currently solar
energy accounts just about 1% of the total energy consumption which is quite low.
But from Fig. 1b, we see that the demand for solar energy will increase exponentially
and it will surpass all other sources of energy to be the most prominent alternative
energy source by the end of this century. What do you think is responsible for such
a large-scale growth in solar energy sector? The primary reason for the same lies in
the fact that current annual world energy consumption is nearly 1.6 × 10
5 TW, while
in one hour the earth receives 1.73 × 10
5 TWh of energy from the sun (Goswami
and Besarati 2013).
Thus, the earth receives more energy from the sun in a single hour than the whole
of humanity consumes in an entire year. With advent in technologies, low-cost solar
cell fabrication, one-time investment, government incentives and greater awareness,
world is trying to shift toward solar energy. Studying the end use distribution of
PSC generated energy, it is found that after generation storage of energy is the
second important issue; in view to resolve it, intense research work is required for the
development of efficient energy storage devices like rechargeable and high-capacity
batteries and supercapacitors. Therefore, energy conversion, as well as energy storage
research, is at the focal point of current research activities.
The fabrication of efficient energy generation and storage devices cannot be completed without the use of nanomaterials. As the recent studies in various disciplines
such as biology, chemistry or physical sciences, and technologies have shown that
when particles approach their nanoscales, they show completely different properties
as compared to their bulk material. For example, gold which we see yellow appears
red or purple in nanoscale. In nanoparticles, quantum effects dominate the behavior
and properties of particles. Secondly, “tunability” of properties can be done, that
is, one can fine-tune the properties of material of interest by changing the size and
shape at nanoscale. The key importance of making nanostructures is they have far
large surface areas as compared to similar bulk material. To be more precise, consider an example of solid cube with sides of 1 cm; its surface area is of 6 cm
2 . If
the same cube is filled with 1 nm-sized cubes, they cover an effective area of about
600,000 cm
2 , which is about one-third size of a football field. This key property
of having a very large surface area in small volume, that is, high surface to volume ratio of nanomaterials boosts the performance of devices (Thaxton et al. 2009).
Recent research shows that along with size, the shape of nanostructure also plays a
crucial role in modifying electrical, magnetic, optical and mechanical properties of
material (Kamble et al. 2016). The nanomaterials in energy conversion and storage
devices perform photovoltaic interactions as well as the chemical reactions at the
surfaces/interfaces, so the surface energy, specific surface area, charge transportation, light harvesting and surface chemistry play a very important role. To grab all
these properties in nanomaterials, the one-dimensional (1-D) nanostructure is the
best option; hence the 1-D nanomaterials have stimulated an increasing interest in
research and industries of PSC and ESS. Various 1-D nanostructures like nanofibers,
nanorods, nanowires, nanobelts, nanotubes, hierarchical nanostructures and so on, as
shown in Fig. 2, seem to be grown by different techniques. Such 1-D nanostructures
331
as future generation energy sources. It is very clear from Fig. 1 that currently solar
energy accounts just about 1% of the total energy consumption which is quite low.
But from Fig. 1b, we see that the demand for solar energy will increase exponentially
and it will surpass all other sources of energy to be the most prominent alternative
energy source by the end of this century. What do you think is responsible for such
a large-scale growth in solar energy sector? The primary reason for the same lies in
the fact that current annual world energy consumption is nearly 1.6 × 10
5 TW, while
in one hour the earth receives 1.73 × 10
5 TWh of energy from the sun (Goswami
and Besarati 2013).
Thus, the earth receives more energy from the sun in a single hour than the whole
of humanity consumes in an entire year. With advent in technologies, low-cost solar
cell fabrication, one-time investment, government incentives and greater awareness,
world is trying to shift toward solar energy. Studying the end use distribution of
PSC generated energy, it is found that after generation storage of energy is the
second important issue; in view to resolve it, intense research work is required for the
development of efficient energy storage devices like rechargeable and high-capacity
batteries and supercapacitors. Therefore, energy conversion, as well as energy storage
research, is at the focal point of current research activities.
The fabrication of efficient energy generation and storage devices cannot be completed without the use of nanomaterials. As the recent studies in various disciplines
such as biology, chemistry or physical sciences, and technologies have shown that
when particles approach their nanoscales, they show completely different properties
as compared to their bulk material. For example, gold which we see yellow appears
red or purple in nanoscale. In nanoparticles, quantum effects dominate the behavior
and properties of particles. Secondly, “tunability” of properties can be done, that
is, one can fine-tune the properties of material of interest by changing the size and
shape at nanoscale. The key importance of making nanostructures is they have far
large surface areas as compared to similar bulk material. To be more precise, consider an example of solid cube with sides of 1 cm; its surface area is of 6 cm
2 . If
the same cube is filled with 1 nm-sized cubes, they cover an effective area of about
600,000 cm
2 , which is about one-third size of a football field. This key property
of having a very large surface area in small volume, that is, high surface to volume ratio of nanomaterials boosts the performance of devices (Thaxton et al. 2009).
Recent research shows that along with size, the shape of nanostructure also plays a
crucial role in modifying electrical, magnetic, optical and mechanical properties of
material (Kamble et al. 2016). The nanomaterials in energy conversion and storage
devices perform photovoltaic interactions as well as the chemical reactions at the
surfaces/interfaces, so the surface energy, specific surface area, charge transportation, light harvesting and surface chemistry play a very important role. To grab all
these properties in nanomaterials, the one-dimensional (1-D) nanostructure is the
best option; hence the 1-D nanomaterials have stimulated an increasing interest in
research and industries of PSC and ESS. Various 1-D nanostructures like nanofibers,
nanorods, nanowires, nanobelts, nanotubes, hierarchical nanostructures and so on, as
shown in Fig. 2, seem to be grown by different techniques. Such 1-D nanostructures