Course: Cellular Bio-363
Date: 12/12/2017
Artificial Photosynthesis
Introduction
Plants are living organisms that exist either in the wild form natural evolution or
domesticated by man through careful bias selection over many years. Plants are able to generate
the necessary food resources (oxygen and carbohydrates) required for energy creation through a
natural process called photosynthesis; plants convert light energy from sun light to chemical
energy through green pigmentations known as chlorophyll in leaves while bacteria under-go this
process in the plasma membranes. The chemical energy produced is released by the organisms to
facilitate their normal activities later on. This process occurs naturally. Man has found a way to
manipulate this process and mimic photosynthesis through a process known as artificial
photosynthesis. The aim of this paper is to critically analyze artificial photosynthesis.
General background
Artificial photosynthesis in not a sudden discovery as its conceptualization and
implementation occurred over a long time and involved several people. Giacomo Ciamician, a
chemist of Italian origin, is the first person credited with the formulation of the theory of
artificial photosynthesis. This was in 1912. He proposed the abandonment of the use of fossil
fuel to the more reliable use of energy captured from sunlight by using advanced photochemistry
technology. He envisioned that the use of such energy would lead to less pollution of the
environment arising from the burning of fossil fuels. Additionally, its spread and use would
lessen the gap between the producers of fossil fuels and the rest of the world as sunlight can
easily be accessed from anywhere in the world unlike the former whose distribution is limited
(Martin, 2016).
Akira Fujishima is credited with the discovery of Honda-Fujishima effect employed in
hydrolysis in the 1960s; he discovered that titanium dioxide had photo-catalytic properties. In
1994, the Swedish Consortium for Artificial Photosynthesis was created. Its sole aim was study
and analyze natural photosynthesis so that the discoveries could be replicated using artificial
systems. This field is currently experiencing a resurgence as more scientists and scientific
organizations take up keen interest in it; such as the Commonwealth Scientific and Research
Organization (CSIRO), the Brookhaven National Library and the United States Air Force Office
of Scientific Research. The first practical artificial leaf was created in 2011 by the Massachusetts
Institute of Technology’ Solar Revolution Project and chemist Daniel G. Nocera and his team
(Martin, 2016).
The mechanisms of artificial photosynthesis
Natural photosynthesis occurs in a two-step sequence that involves the harvesting of sun
light and the splitting up of water molecules using energy from the first step. The aim of natural
photosynthesis is the production of oxygen and glucose while for artificial photosynthesis
hydrogen is the resultant product. Plants are able to harvest sun light using chlorophyll. This is
combines carbon dioxide molecules (6) and water molecules (6) to produce a single glucose
molecule and 6 molecules of oxygen. In artificial photosynthesis energy used for splitting up the
water molecules is derived from the photocatalytic splitting of water using solar light. The
selected catalyst used in this process should be able to quickly react, absorbing a large amount of
the available incident photons from sunlight i.e. it should be very effective and efficient at
carrying out this process. This is a preferred method as a sustainable amount of hydrogen is
obtained as an alternate source of energy. This reaction splits water into hydrogen protons and
oxygen. The protons react with carbon dioxide to produce hydrogen in the presence of a catalyst
(The Drawdown Organization, 2017).
Design of the artificial leaf
A research group led by Daniel Nicora designed and created the most basic artificial leaf.
It consists of a solar cell made purely from silicon to produce the energy required for the
photocatalytic splitting of water. Photocatalytic materials are bound onto two of its sides. This
does away with the need for the use of control circuits or wires to operate the artificial leaf. The
leaf is made of is made up of cobalt, nickel and silicon which are both abundant on earth and
inexpensive in nature. The leaf design contains a sheet of silicon, this should be very thin and be
a semiconductor of electricity. This converts solar energy into electricity that is wirelessly
streamed throughout the leaf. A cobalt based catalyst is bound onto the silicon sheet; it releases
oxygen from water. An alloy of nickel-molybdenum and zinc is coated on the other side of the
silicon sheet. It serves to release hydrogen molecules bound in the water. This device is very
inexpensive at it can be easily created and used; it is placed on to a container of a container of
water which is then exposed to the sun and begins to immediately generate energy i.e. two
bubble streams are observed on each side of the cell, one containing oxygen and the other
hydrogen. The leaf should be designed such that a barrier exists to separate these two gases
collected to be stored. The device is heterogeneous such hat two separate electrodes exist, an
anode and a cathode. This ensures that oxygen and hydrogen are produced at different points in
the device making their production and collection easier and safer. The device is ready for the
market. However, researchers have not yet been able to create the necessary system for the
collection of the gases produced during the observed reactions (Martin, 2016).
Current research and development
Artificial photosynthesis is a developing field that constantly experiences advancements
as scientists seek to come up with more inexpensive ways of carrying out the process using the
cheapest and most affordable materials. In 2009, K. Dormen and F. del Valle demonstrated the
effective use thermal treatment within a closed atmosphere by using the photo-catalyst Cd1xZnxS. The solid catalyst showed a high rate of production of hydrogen from water (del Valle,
Ishikawa, & Domen, 2009). Scientists at the University of California, Santa Cruz separately
tested the use of cadmium selenide quantum dots sensitized and nitrogen doped titanium dioxide
nanowires and nanoparticles to achieve the same results in 2010 (Hensel, Wang, Li, & Zhang,
2010). In 2010, the United States Department of Energy established the Joint Center for
Artificial Photosynthesis. The organization aims to come up with cost-effective means of
producing safe energy using carbon dioxide, water and sunlight only (Solar Fuels Hub
Organization, 2012). Additionally, a team led by Professor David Windell from the University of
Cincinnati was able to demonstrate the photosynthesis by the use of enzymes (Beckman, 2010).
This developing field will continue to attract more interest as man seeks to turn away from fossil
fuel and switch to the use of inexpensive and safe clean alternative energy sources.
Comparison to “organic” photosynthesis
Artificial photosynthesis borrows a lot of its concepts from “organic” photosynthesis. As
such, most of its primary components are similar. The two processes involve similar raw
materials; water, carbon dioxide and sunlight, and end products; carbohydrates and oxygen. Both
reactions use sunlight as their primary energy source. Both processes occur in two stages; the
first step involves the acquisition of energy from the sun while the second part involves the use
of the acquired energy in the reaction between carbon dioxide and water. Both processes have
catalysts, chlorophyll in green plants and cobalt-based catalysts in artificial leaves, which control
the rates of reactions and the amount of energy produced. Both reactions occur in specialized
sites; in the chloroplasts for green plants and photo-catalytic sites containing cobalt, nickel or
silicon in artificial leaves. In both these instances, water is split into its basic components;
hydrogen and oxygen molecules. Photosynthesis is dependent on the availability of sun light as
the primary source of energy. As such both processes are limited by the availability and intensity
of sun light in the environment (Olmos, 2015).
Contrast between “organic” and artificial photosynthesis
Organic photosynthesis is a natural process that occurs in green plants, algae and bacteria
as the primary source of energy used to facility metabolism and other body functions. On the
other hand, artificial photosynthesis is a process that is instituted and manipulated by man to for
the provision of an alternate source of clean energy. The former therefore occurs whenever
sunlight is available in green plants while the latter requires man’s input. Natural photosynthesis
occurs in specialized sites such as the leaves and plasma membranes of bacteria. Artificial
photosynthesis can be instituted wherever is most convenient to man; it only requires the
artificial leaf and water. The former uses sun light directly as its primary source of energy while
the later has to change sun light in to solar energy in order to for incorporation into the reaction.
Natural photosynthesis produces glucose and oxygen as its primary products while artificial
photosynthesis produces water and hydrogen as the end products. The hydrogen produced is
converted to a fuel source on its own or is farther combined with carbon dioxide to produce
organic fuels. The latter reaction is complete when water molecules are split into its constituent
components while the former goes a step farther by incorporating carbon dioxide into the
reaction to form glucose (Materials for a Sustainable Future, 2014).
Real-world application of artificial photosynthesis
The main purpose for the development of artificial photosynthesis is the production of
clean energy from readily and easily available resources thus doing away with the expensive and
limited fossil fuels. As such all that is required is the availability of water, whether clean or dirty
and a solar energy source that can easily be acquired to generate hydrogen and oxygen as
alternative energy sources. Alternatively, artificial photosynthesis can be used to generate clean
water for safe drinking and other uses from dirty or contaminated sources; water is split into its
constituent elements that can later be recombined to produce clean water free of contaminants
albeit relatively expensive as compared to conventional water treatment methods (Martin, 2016).
Advantages and disadvantages of artificial photosynthesis
Advantages
It uses solar energy that can easily be generated, stored and used for a later purpose hence
is relatively inexpensive. This means that the process is institutable at any time hence making it
very convenient to the user. The construction of an artificial leaf requires relatively cheap and
easily available materials hence making it a worthwhile venture. It is to use and is portable as all
it requires is a collection point for the products. The user is sure of the products he is acquiring
hence making it both an effective and efficient energy source; very little energy is lost during
production. The products of this process are environmentally friendly as it uses carbon-neutral
raw materials (Barber & Tran, 2013).
Disadvantages
The material used is easily lost over time due to corrosion while in water as they are
relatively unstable. Additionally, most hydrogen catalysts are very sensitive to the presence of
oxygen as they are either degraded or inactivated hence interfering with the whole process. There
is also the chance occurrence of photo-damage to the components of the machine. Presently,
production costs outweigh the benefits derived from the technology as compared to the
extraction and use of fossil fuels. This rules it out as a viable alternative as a source of
commercial fuel (Barber & Tran, 2013).
The future of artificial photosynthesis
The rapidly growing field that is expanding beyond just the production of clean energy
sources; it is being incorporated into other scientific fields such as the production of alcohols and
other chemicals. The use of fossil fuels is unreliable due to the diminishing levels of available
stock; it is also being discouraged as it is a constant source of environmental pollution. This
gives room to the rise of clean energy sources that easily be undertaken by the use of artificial
photosynthesis. Research currently conducted by various individuals and institution seeks to
come up with better and more sustainable materials to be used in the production of the artificial
leaf. This ensures that the process is more reliable as its components are able to produce more
energy over a longer period (Kim, Lee, Baek, & Park, 2017).
The relationship between artificial photosynthesis and molecular biology
Living organisms continually take up large amounts of compounds which they use to
facilitate provision of metabolic energy and biosynthesis. Photosynthesis is one such chemical
reaction studied under molecular biology. It demonstrates how living organisms have formulated
organic pathways and processes that ensure they use what is naturally available to them to
survive. Molecular biology seeks to understand how such actions take place so that man can
easily replicate these into useful everyday components which in the end make life easier to live.
Artificial photosynthesis is an example of a real-world application of the principles studies in
molecular biology.
Conclusion
Artificial photosynthesis is a practical example of how man is constantly learning from
nature on the basic aspects required to survive the ever evolving world. It mimics natural
photosynthesis to produce clean energy which is both sustainable and durable under the right
conditions and setting. Nature is the best place where man can easily learn how to adapt and use
basic components readily available to create items that are essential for everyday uses. Molecular
biology allows us the ability to study and easily understand biological processes in nature. More
time and infrastructure should be invested in this field.
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