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Lessons from Tree? New Photosynthesis Model Develops Fuel from Sunlight

Just learning a leaf of learning from trees around us, researchers at the University of Illinois at Chicago have developed a solar cell that can convert carbon dioxide in air into usable hydrocarbon fuel, using only sunlight for energy.

In their device, solar cells instead of converting sunlight into electricity, works on the lines of the work done by plants by converting atmospheric carbon dioxide into fuel. It can solve two crucial problems at once — climate change as the solar farm of such “artificial leaves” could remove significant amounts of carbon from the atmosphere and secondly, produce energy-dense fuel efficiently.

“The new solar cell is not photovoltaic — it’s photosynthetic,” said Amin Salehi-Khojin at UIC and lead 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.

Unlike plants which produce fuel in the form of sugar, the artificial leaf here delivers synthesis gas, a mixture of hydrogen gas and carbon monoxide called Syngas that can be burned directly.Amin Salehi-Khojin & Mohammad Asadi

The ability to turn CO2 into fuel at anegligible cost would make fossil fuels obsolete. Moreover, there is no complaint from climate change advocates, if this succeeds to overcome resistence from the established vested interests and petro-dollar Arab money.

The new catalyst is 1,000 times faster than noble-metal catalysts — and about 20 times cheaper. Other researchers have used TMDC catalysts to produce hydrogen by other means, but not by reduction of CO2. The catalyst couldn’t survive the reaction.

“The active sites of the catalyst get poisoned and oxidized,” Salehi-Khojin said. The breakthrough, he said, was to use an ionic fluid called ethyl-methyl-imidazolium tetrafluoroborate, mixed 50-50 with water.

The UIC artificial leaf consists of two silicon triple-junction photovoltaic cells of 18 square centimeters to harvest light; the tungsten diselenide and ionic liquid co-catalyst system on the cathode side; and cobalt oxide in potassium phosphate electrolyte on the anode side.

When average light of 100 watts per square meter reaches the Earth’s surface, it energizes the cell, hydrogen and carbon monoxide gas bubble up from the cathode, while free oxygen and hydrogen ions are produced at the anode.

The finding is reported in the July 29 issue of Science and was funded by the National Science Foundation and the U.S. Department of Energy. A provisional patent application has been filed.

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