Solar cells are widely known as a way to reduce one's electricity bills. However, its uses aren't limited to just that. Recently, researchers from the University of Illinois at Chicago have engineered a solar cell that converts atmospheric carbon dioxide directly into usable hydrocarbon fuel.
Take this new device as a plant. The solar cells are the leaves that absorb CO2 but unlike the nature's way, these don't release oxygen as a byproduct but just directly convert CO2 into fuel. Hence, creating a solar farm means having a lot of leaves, consequently reducing more CO2 and producing more fuel.
“The new solar cell is not photovoltaic — it’s photosynthetic,” says Amin Salehi-Khojin, assistant professor of mechanical and industrial engineering at UIC and senior author on the study. “Instead of producing energy in an unsustainable one-way route from fossil fuels to greenhouse gas, we can now reverse the process and recycle atmospheric carbon into fuel using sunlight,” he said.
Plants generate fuel in the form of sugar. These solar cells, on the other hand, create syngas or synthesis gas. Syngas is a mixture of hydrogen gas and carbon monoxide that can either be burned directly or converted into diesel and other hydrocarbon fuels. And in order to convert CO2 into burnable fuel, an efficient catalyst is needed.
So, researchers utilized nanoflake tungsten diselenide, a chemical from a family of nano-structured compounds called transition metal dichalcogenides or TMDCs, as a catalyst. They then paired this with ionic liquid as the electrolyte inside a two-compartment, three-electrode electrochemical cell. This catalyst is actually 1,000 times faster than noble-metal catalysts and about 20 times cheaper.
However, when reacting to CO2, such catalyst would "get poisoned and oxidized". Fortunately, they were able to pioneer a technique that prevents this from happening. They found that mixing an ionic fluid called ethyl-methyl-imidazolium tetrafluoroborate with water (50-50) would do the job. “The combination of water and the ionic liquid makes a co-catalyst that preserves the catalyst’s active sites under the harsh reduction reaction conditions,” Salehi-Khojin said.
Only 100 watts of light per square meter- about the average intensity reaching the Earth’s surface- is even needed to make this work! For short, we have here a cheap and efficient solar panel that could not only resolve the existing carbon crisis but could efficiently produce energy-dense fuel as well. Plus it only needs the ever free sunlight for energy. Kudos, researchers!