Sustainable Energy Source: Artificial Photosynthesis

As concerns about energy supply emerge in the mainstream, alternatives to fossil fuels are becoming more and more sought after technologies.  One of the consultants that scientists have turned to is nature. 

If the smartest energy source is one that's abundant, cheap and clean, then plants are a lot smarter than humans. Over billions of years, they developed perhaps the most efficient power supply in the world: photosynthesis, or the conversion of sunlight, carbon dioxide and water into usable fuel, emitting useful oxygen in the process.

Natural Photosynthesis

Photosynthesis is a process by which green plants and certain other organisms use the energy of light to convert carbon dioxide and water into the simple sugar glucose. In so doing, photosynthesis provides the basic energy source for virtually all organisms. An extremely important byproduct of photosynthesis is oxygen, on which most organisms depend.

Artificial Photosynthesis

Artificial photosynthesis is a chemical process that biomimics the natural process of photosynthesis to convert sunlight, water, and carbon dioxide into carbohydrates and oxygen. The term artificial photosynthesis 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 and oxygen and is a major research topic of artificial photosynthesis.

Artificial photosynthesis is a promising source of energy for the future and has the ability to produce solar fuels efficiently. Currently, there is much room for improvement in all the basic steps utilised for converting solar energy into electric power energy. The major bottlenecks in the process of AP are the catalytic steps, which are needed for oxidation of water and production of fuels. It is expected that within the next 10 years, small demonstration scale systems will be launched, based on the AP that can make solar fuels [1]. Research in the field of AP is at a fascinating stage.

Nanotechnology

The major source for driving AP is the advancements in the field of nanotechnology. Nanotechnology is a part of science and technology about the control of matter on the atomic and molecular scale - this means things that are about 100 nano-metres in size. Nanotechnology includes making products that use parts this small, such as electronic devices, catalysts, sensors, etc.

In artificial photosynthesis, scientists are essentially conducting the same fundamental process that occurs in natural photosynthesis but with simpler nano-structures.  The fabrication of these nano-structures has only recently been possible due to breakthroughs in nanotechnology in the areas of imaging and manipulation.  With the core processes in photosynthesis being light gathering, charge separation, and recombination, the goal of scientists has been to create efficient synthetic nano-structures that can function as antennae and reaction centres.

Nanotechnology has been considering several areas of AP like light capturing, transportation of electrons, splitting of water and storage of hydrogen [2]. There is a race between different metals like haematite, cobalt, and manganese for an inexpensive electrode. There are still several safety concerns over the hydrogen storage and transportation due to the low energy density of hydrogen gas. Other research areas in this area are the production of methanol and how to make the AP system capable of using the hydrogen generated from water splitting and atmospheric CO2 to store in the form of formic acid.

Drawbacks

Similar to other emerging renewable energy sources, AP also has a huge potential and a lot of research is carried out on improving various aspects of this technology. However, there are some potential drawbacks of this technology also. There are safety concerns over the hydrogen storage and transportation due to the low energy density of hydrogen gas. Most of the hydrogen catalysts are sensitive to oxygen hence their performance is degraded or inactivated. Secondly, the materials used for AP often corrode in water and cause stability issues.[3]

Future Works

While current artificial photosynthesis methods are far less efficient than the natural process, there has been continual progress in the field.  One of the reasons that the technology is being pursued is that, compared to current solar panel technology, molecular nanoparticles are cheaper, lighter, and more environmentally sound.[4] Aside from providing a renewable energy source and eliminating our reliance on rapidly diminishing fossil fuels, it has also been suggested that artificial photosynthesis on a large industrial scale could reverse global warming since the process consumes carbon dioxide and releases oxygen.  With the potential of such beneficial impacts on the environment and our energy supply, continued research into combining nanotechnology and natural processes should remain a central goal.

Need for this article:

The need of the hour is to support these renewable technologies and especially emerging renewable technologies to make the earth a clean and hazard-free place for living beings. The support could be by creating awareness, helping in overcoming the technological barriers, subsidised and tax-free policies by local governments and by mandating the use of environment-friendly energy sources.

References:

[1] ‘Artificial photosynthesis -- solar fuels: current status and future prospects’ (2010)Biofuels (17597269), 1(6), p. 861. Available at: http://search.ebscohost.com.elib.tcd.ie/login.aspx?direct=true&db=edb&AN=67066080 (Accessed: 29 March 2020).

[2] Y.S. Nam. (2010) 'Virus-templated assembly of porphyrins into light harvesting nanoantenne' J Am Chem Soc, 135 (5), pp. 1462-1463

[3] Hussain, A., Arif, S. M. and Aslam, M. (2017) ‘Emerging renewable and sustainable energy technologies: State of the art’,Renewable and Sustainable Energy Reviews, 71, pp. 12–28. doi: 10.1016/j.rser.2016.12.033.

[4] ‘Nanotechnology: A Gentle Introduction to the Next Big Idea’ (2003)Materials Today, 6(2), p. 50. doi: 10.1016/S1369-7021(03)00236-0.