Artificial leaf turns sunlight, CO2 and water into synthetic gas .
Cambridge's artificial leaf uses two perovskite light absorbers and a cobalt catalyst to convert sunlight, water and carbon dioxide into syngas
The humble leaf is an incredible little machine, converting sunlight and carbon dioxide into energy for a plant. Artificial versions could be useful renewable energy sources, or even used to produce fuels. Now, researchers from the University of Cambridge have developed an artificial leaf that can produce synthetic gas (or syngas) without releasing carbon dioxide.
Syngas is made from hydrogen and carbon monoxide, sometimes with a bit of carbon dioxide thrown in. While it can technically be burned to generate electricity or for gas lighting and heating, it more often acts as an intermediate step in manufacturing products, including plastics, fertilizers, and fuels like diesel. Unfortunately, producing it can release carbon dioxide into the atmosphere.
“You may not have heard of syngas itself but every day, you consume products that were created using it,” says Erwin Reisner, senior author of the study. “Being able to produce it sustainably would be a critical step in closing the global carbon cycle and establishing a sustainable chemical and fuel industry.”
To help with that, the Cambridge team developed a new artificial leaf prototype that can produce syngas through photosynthesis. The new device contains two light absorbers made of perovskite, and a cobalt catalyst. When these are placed in water, one side produces oxygen, while the other reduces carbon dioxide and water into carbon monoxide and hydrogen. Those latter two gases can then be combined into syngas.
The team showed that the technology can still work even in relatively low light, like that on cloudy or rainy days. The perovskite was chosen because it’s good at absorbing light and creating a voltage, which is why it’s showing up in solar panels so much lately. Meanwhile the cobalt in the catalyst is lower cost and more efficient at creating carbon monoxide than other materials.
That said, the conversion efficiencies are still quite low – the new design currently produces hydrogen at an efficiency of 0.06 percent and carbon monoxide at 0.02 percent.
The new device joins a range of artificial leaf designs that are being developed to create a range of useful products, like electricity, drugs, fertilizers, and hydrogen fuel. Ultimately, the team hopes to be able to skip the middleman syngas stage.
“What we’d like to do next, instead of first making syngas and then converting it into liquid fuel, is to make the liquid fuel in one step from carbon dioxide and water,” says Reisner. “There is a major demand for liquid fuels to power heavy transport, shipping and aviation sustainably.”