Sometimes, Mother Nature knows best. When it comes to harnessing the power of the sun, scientists are developing systems that mimic the processes found in nature.
Scientists with consumer electronics giant Panasonic recently developed an artificial photosynthesis system that can create a useful industrial chemical for the agricultural and textile industry.
The key to the system is a nitride semiconductor and a metal catalyst. These two work in a two step process generate energy and to capture carbon dioxide and convert it to formic acid.
Formic acid is used in the cattle and poultry industry to preserve feed and also as an antibacterial agent. It is also used in cleaning products and in the production of leather, the dyeing and finishing of textiles and as a coagulant in the production of rubber.
So, in Panasonics artificial photosynthesis system, light shines in water and hits the nitride semiconductor triggering a water splitting reaction, separating water molecules into their two components – hydrogen and oxygen.
The metal catalyst then triggers another reaction known as carbon dioxide reduction, and it is also reduced to its respective elements. The carbon, oxygen and hydrogen combined create formic acid.
Panasonic envisions using this artificial photosynthesis technology in a system that will capture and convert carbon dioxide from incinerators, power plants or other industrial sources to create a valuable resource from “waste”. This would also have the added benefit of keeping industrial carbon dioxide from reaching the atmosphere and contributing to the world’s rising emission levels.
Currently, the system can convert the carbon dioxide into formic acid with a 0.2 percent conversion rate. While this may not be high enough for commercial use, it is higher than any other similar technology. Panasonic also believes that the device is easily scalable as the reaction rate is completely proportional to the light power. Concentrating or increasing the light conversion levels should increase the formic acid production.
Panasonics latest technological breakthrough is actually an attempt to copy a process that plants and certain other organisms such algae and bacteria have been doing since life first appeared on earth.
Using and storing sun for fuel
Plants, algae and bacteria are photosynthetic organisms, which means they can capture and convert light energy – usually from the sun and convert it into storable fuel. Through photosynthesis, these organisms can create their own food from carbon dioxide and water. Not only does photosynthesis allow the organism to live and grow, but it also allows for life on earth. Photosynthesis produces oxygen as a “waste product” that is then released into the atmosphere.
Artificial photosynthesis basically takes the idea that, using nothing but sunlight as an energy input, something useful can be created. Mostly what’s created is referred to as solar fuel and it allows the energy of the sunlight to be produced and also stored for later usage, however, they are also working in creating other useful chemicals and products – much like Panasonic used it to create formic acid.
Photochemical carbon dioxide reduction is the general term for what Panasonic was able to do – the production of useful chemicals from carbon dioxide, water and sun light.
Most of the research in this area focuses on the creation of fuel products such as carbon monoxide, methanol and methane. These carbon-based fuels are not as clean and green as methane but they are lower emitting. Also most research into this technology involves the use of carbon capture, with the idea that the carbon dioxide to be used in the process would be captured from fossil-fuel burning technologies.
The main area of research into artificial photosynthesis though is for the creation of hydrogen. Photocatalytic water splitting is one of the main ways being investigated for use in hydrogen fuel production. Basically, sunlight and a catalyst are used to separate water into its component parts of hydrogen and water. The hydrogen can then be used as a clean, renewable fuel.
Water splitting was first demonstrated in the 1950s and has been enjoying a revival recently. So far, the most promising device has been an “artificial leaf” developed at the Massachusetts Institute of Technology. This is basically a silicon solar cell with different catalytic materials bonded onto its two sides. When place in a container of water and exposed to sunlight, generates two streams of bubbles – one of oxygen and the other of hydrogen.
The biggest attraction of these solar created products – the fuels and the chemicals – is that it’s a way to use solar power even when there is no sun. One of the challenges of solar is what to do when there is little or no sun.
For solar energy to become a practical and widespread component of the world’s energy mix, new technologies to store it are vital. With artificial photosynthesis, scientists are looking towards a natural process perfected in the earth’s past to see the way towards creating the fuels of humanities future.
By Katrice R. Jalbuena