Artificial photosynthesis replicates the process of photosynthesis to harness the sun’s energy in an environmentally friendly way. Research has yielded two results: photoelectrochemical cells and dye-sensitized solar cells. Both aim to achieve artificial photosynthetic energy that can be stored for later use. The most effective catalysts are cobalt and rhodium. Gratzel cells are the cheapest to produce, but liquid dyes can cause temperature problems. Ongoing research is looking for better catalysts and energy transport mechanisms to reduce the world’s dependence on non-renewable fossil fuels.
Plants get their energy in a very different way than the way people get energy. When a human being needs energy, he eats food. When a plant needs energy, it uses the process of photosynthesis to absorb carbon dioxide from the environment and uses sunlight to convert it into sugars, which is the type of energy it needs to survive. Scientists have worked to replicate the process of photosynthesis, trying to harness the sun’s energy in a new, effective and environmentally friendly way, and research into artificial photosynthesis has yielded interesting results.
The ability to produce artificial photosynthesis was first announced in 2000, although research was already in the planning stages before then. The researchers relied on the Honda-Fujishima effect, discovered in 1953 and which uses titanium dioxide as a photocatalyst. A photocatalyst accelerates processes related to light and, in this case, energy.
Due to scientific and commercial interest in artificial photosynthesis and the desire for potential new products that could result from it, the research field has split into two parts. This yielded two different results: photoelectrochemical cells and dye-sensitized solar cells. Each cell operates on different principles but seeks to achieve the same result: artificial photosynthetic energy that can be harnessed and stored for later use, which would reduce the world’s dependence on non-renewable energy sources.
Photoelectrochemical cells, also called PECs, use the electric current in water to create hydrogen and oxygen in a process called electrolysis. The electricity can then be stored in hydrogen, which is an ‘energy carrier’, and the energy can be used later, such as in batteries. There are two types of PECs, one that uses semiconductor surfaces to absorb solar energy and one that helps split water molecules for energy use. The other variety uses dissolved metals to absorb solar energy and start the process of artificial photosynthesis. The most common metal catalysts for this type of reaction are cobalt and rhodium. Researchers at the Massachusetts Institute of Technology (MIT) have found that these metals are the most effective for this type of work.
The other type of cell being researched, the dye-sensitized solar cell, is sometimes called a Gratzel cell or Graetzel cell. Like PECs, dye-sensitized artificial photosynthesis cells use a semiconductor to harvest energy, usually silicon. In dye-sensitized cells, the semiconductor is used to carry the collected energy and photoelectrons, or particles of energy, are separated and harnessed using special dyes. Gratzel cells are considered to be the most effective form of artificial photosynthesis currently available, as well as the cheapest to produce. The disadvantages are mainly due to temperature problems associated with liquid dyes, because they can freeze at lower temperatures and stop producing energy, expand at higher temperatures and break.
Research is still ongoing in the field of artificial photosynthesis, especially looking for better catalysts and energy transport mechanisms. While they are not the most efficient form of energy production available, there is still great interest in them due to their high potential yield, low production costs and possible implications for the environment. If man-made photosynthesis could be made affordable and reliable, the world’s dependence on non-renewable fossil fuels could be greatly reduced.
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