Scientists from the University of Michigan have been working together with scientists from McGill and McMaster Universities in Canada to develop a new artificial photosynthesis that uses sunlight to turn carbon dioxide CO2 into green methane. This can help make natural-gas-powered devices carbon neutral.
Photosynthesis is a process when green plants use sunlight to make food for themselves out of carbon dioxide and water, releasing oxygen as a byproduct.
The team created a catalyst made up of nanoparticles of copper and iron. The copper and iron hold onto the molecules by their carbon and oxygen atoms. This allows time for the hydrogen atoms to leap from the water onto the carbon atoms.
The device they created uses an electrical current, or the sun’s energy, to break down the carbon dioxide and water on a type of solar panel that’s studded with nanoparticles of copper and iron. The base is made of a silicon wafer, similar to average solar panels, where a layer 300 nanometers tall and 30 nanometers wide acts as a semiconductor with gallium nitride.
This creates a large, though microscopic, surface area for the reactions to take place and the nanoparticle-flecked nanowires are covered with a thin film of water.
The team’s invention is made from readily abundant materials and is easy enough to make that would allow for mass production. The researchers said they think that within 5-10 years they can be recycling smokestack carbon dioxide into clean-burning fuel.
The researchers were able to harness relatively large electrical currents, which are especially good at channeling that electricity towards forming methane. This enables half of the available electrons to go toward methane-producing methods, versus byproducts such as carbon monoxide or hydrogen.
Methane happens to be the main component of natural gas. This artificial photosynthesis looks to produce hydrocarbon fuels, that are similar to natural gas or gasoline, from the same starting materials.
University of Michigan professor of Electrical Engineering and Computer Science Zetian Mi said:
Thirty percent of the energy in the U.S. comes from natural gas. If we can generate green methane, it’s a big deal.
Generally speaking, turning CO2 into green methane is a difficult process, CO2 is one of the more stable molecules and the carbon must be harvested from the CO2. Water also needs to be broken down to attach the hydrogen to the carbon. Each one of the carbon atoms needs four hydrogen atoms to become methane, which makes this so complicated. Each carbon-hydrogen bond has two electrons in it, to create four bonds.
Post-doctoral researcher Baowen Zhou talks about the team’s exciting discovery here:
Previous artificial photosynthesis devices often operate at a small fraction of the maximum current density of a silicon device, whereas here we operate at 80 or 90% of the theoretical maximum using industry-ready materials and earth-abundant catalysts.
The team’s artificial photosynthesis device may end up being best used connected to industrial smokestacks that produce highly concentrated amounts of carbon dioxide. They can be designed to run on solar power alone, or they can be designed to operate in the dark as well by being connected to electricity.
Hopefully, the team can continually produce these results and find the best recipe to have them produced on a large scale due to the large number of smokestacks polluting the world with CO2 emissions.
