Breakthrough Solar Cell Converts CO2 into Fuel

Solar Daily reported that researchers at the University of Illinois in Chicago have engineered a potentially game-changing solar cell that cheaply and efficiently converts atmospheric CO2 directly into usable hydrocarbon fuel, using only sunlight for energy.

This finding was reported in the July 29th issue of “Science” and was funded by the National Science Foundation and the U.S. Department of Energy. A temporary patent application has been filed. Unlike conventional solar cells which convert sunlight into electricity that must be stored in heavy batteries, this new device does the work of plants, converting atmospheric CO2 into fuel, solving two problems at once. A solar farm with these high-tech cells could remove significant amounts of carbon dioxide from the atmosphere and create energy-dense fuel efficiency.

According to Amin Salehi-Khojin, assistant professor of mechanical and industrial engineering at UIC and senior author of the research, the new solar cell is not photovoltaic; it’s photosynthetic. Instead of producing energy in an unsustainable one-way route from traditional fossil fuels to greenhouse gas, they can now reverse the process and recycle atmospheric carbon into fuel using the power of the sun. The artificial solar leaves deliver syngas or synthesis gas, which is a mixture of carbon monoxide and hydrogen gas. Syngas can be burned directly or it can be converted into diesel or any other hydrocarbon fuel. The ability to convert CO2 into fuel at a cost that is comparable to a gallon of gasoline would make traditional fossil fuels obsolete.

The chemical reactions that convert CO2 into fuel or other burnable forms are called reduction reactions, which is the reverse of oxidation or combustion. Engineers have been exploring different catalysts to drive CO2 reduction, but so far, reactions have been inefficient and usually rely on expensive precious metals like silver. The research and development team focused on a family of nanostructured compounds called transition metal dichalcogenides (TMDC) as the catalyst. They paired them with an ionic liquid as the electrolyte inside a two-compartment, three-electrode electrochemical cell.

The best of the several catalysts they have studied turned out to be nanoflake tungsten diselenide. It’s 1,000 times quicker than noble-metal catalysts and about 20 times more affordable. The UIC artificial leaf is made up of two silicone triple-junction photovoltaic cells of 18 square centimetres used to capture light from the Sun. The rest of the process is completed using the tungsten diselenide, the ionic liquid co-catalyst system on the cathode side and the cobalt oxide in potassium phosphate electrolyte on the anode side.

The technology can be adapted for large-scale uses like solar farms as well as small-scale applications for houses and office buildings in the future. Salehi-Khojin states that in the future it may prove useful on Mars, whose atmosphere is mostly CO2.

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