introduction to photosynthesis, artificial photosynthesis, history, photolytic cell, how does AP work, artificial leaf, applications, pros and cons of the technology.

1. ARTIFICIAL
PHOTOSYNTHESIS

2. What is Photosynthesis?
Photosynthesis is the process by
which plants and other things make
food. It is a chemical process that
uses sunlight to turn carbon dioxide
into sugars the cell can use as energy.
Photosynthesis maintains
atmospheric oxygen levels and
supplies all of the organic
compounds and most of the energy
necessary for life on Earth.

3. Artificial Photosynthesis
 Artificial Photosynthesis is a chemical process that
replicates the natural process of photosynthesis, a
process that converts sunlight, water, and carbon dioxide
into carbohydrates and oxygen.
 The term is commonly used to refer to any scheme for
capturing and storing the energy from sunlight in the
chemical bonds of a fuel (a solar fuel).
 Photocatalytic Water Splitting, converts water into
Hydrogen Ions and oxygen, and is a main research area in
artificial photosynthesis.

4. History
 Visible light water splitting with a one piece multijunction
cell was first demonstrated and patented by William Ayers
at Energy Conversion Devices in 1983.
 This group demonstrated water photolysis into hydrogen
and oxygen, now referred to as an "artificial leaf” with a
low cost, thin film amorphous silicon multijunction cell
directly immersed in water.
 Hydrogen evolved on the front amorphous silicon surface
decorated with various catalysts while oxygen evolved off
the back metal substrate, which also eliminated the
problem of mixed hydrogen/oxygen gas evolution.

5. A sample of a
photoelectric cell in a lab
environment. Catalysts
are added to the cell,
which is submerged in
water and illuminated by
simulated sunlight. The
bubbles seen are oxygen
(forming on the front of
the cell) and hydrogen
(forming on the back of
the cell).

6. How it works!
 To recreate the photosynthesis that plants have perfected, an
energy conversion system has to be able to do two crucial
things: harvest sunlight and split water molecules.
 Plants accomplish these tasks using chlorophyll, which
captures sunlight, and a collection of proteins and enzymes
that use that sunlight to break down H2O molecules into
hydrogen, electrons and oxygen (protons).
 For an artificial system to work for human needs, the output
has to change. Instead of releasing only oxygen at the end of
the reaction, it would have to release liquid hydrogen (or
perhaps methanol) as well. That hydrogen could be used
directly as liquid fuel or channeled into a fuel cell.

7.  Getting the process to produce hydrogen is not a problem, since
it's already there in the water molecules. And capturing sunlight is
not a problem, current solar-power systems do that.
 The hard part is splitting the water molecules to get the electrons
necessary to facilitate the chemical process that produces the
hydrogen.
 Splitting water requires an energy input of about 2.5 volts. This
means the process requires a catalyst -- something to get the
whole thing moving. The catalyst reacts with the sun's photons to
initiate a chemical reaction.

8. The Solution:- Catalyst
 Manganese: Manganese is the catalyst found in the
photosynthetic core of plants. A single atom of manganese
triggers the natural process that uses sunlight to split water.
Using manganese in an artificial system is a biomimetric
approach -- it directly mimics the biology found in plants.
 Cobalt oxide: One of the more recently discovered catalysts,
clusters of nano-sized cobalt-oxide molecules (CoO) have
been found to be stable and highly efficient triggers in an
artificial photosynthesis system. Cobalt oxide is also a very
abundant molecule -- it's currently a popular industrial catalyst.

10. The Artificial Leaf

11.  The artificial leaf consist of two connected semiconducting
electrodes placed in water. The electrodes absorb light and
use the energy to split the water into its basic components,
oxygen and hydrogen. The oxygen is released into the
atmosphere, and the hydrogen is stored as fuel.

12. Applications /Advantages
 Fossil fuels are in short supply, and they're contributing
to pollution and global warming. Artificial photosynthesis
could offer a new, possibly ideal way out of our energy
predicament.
 It has benefits over photovoltaic cells, found in today's
solar panels. The direct conversion of sunlight to
electricity in photovoltaic cells makes solar power a
weather- and time-dependent energy, which decreases
its utility and increases its price. Artificial photosynthesis,
on the other hand, could produce a storable fuel.

13.  Unlike most methods of generating alternative
energy, Artificial photosynthesis has the potential to
produce more than one type of fuel.
 Artificial Photosynthesis produces a clean fuel
without generating any harmful by-products, like
greenhouse gasses and makes it an ideal energy
source for the environment.

14. The Hiccups
 The manganese that acts as a catalyst in plants doesn't work
as well in a man-made setup, mostly because manganese is
somewhat unstable.
 The other big obstacle is that the molecular geometry in plants
is extraordinarily complex and exact -- most man-made setups
can't replicate that level of intricacy.
 One of the major disadvantages of the artificial
photosynthesis today is the fact that materials used often
corrode in water, as most hydrogen catalysts are very sensitive
to oxygen, being inactivated or degraded in its presence.