Making Carbon Dioxide Useful

Tuesday, July 16, 2013 @ 06:07 PM gHale

A water-soluble catalyst can electrocatalytically transform carbon dioxide into a useful chemical feedstock.

With the global demand for fuel is rising along with carbon dioxide levels in the atmosphere, this new development could actually fall into the category of a win-win situation.

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Studies attempted to address the global carbon imbalance by exploring ways to recycle carbon dioxide into liquid fuels. Formate, the anion of formic acid, is an intermediate of carbon dioxide reduction and can end up used as a fuel in formic acid fuel cells.

The catch is, however, the selective production of formate, without using organic solvents, is challenging. Water, being inexpensive and environmentally-friendly, is obviously preferred over organic solvents as a reaction medium. On the other hand, the reduction of carbon dioxide in water ends up complicated by the reduction of water to hydrogen being a more kinetically favorable process.

Researchers from the University of North Carolina designed an iridium pincer catalyst.

But that all may change as Thomas Meyer, Maurice Brookhart and Peng Kang at the University of North Carolina designed an iridium pincer catalyst that can selectively reduce carbon dioxide into formate in almost pure water. Formate ends up made in a 93 percent yield with no other reduced carbon products formed at the same time. Notably, the catalyst does not catalyze proton reduction to form hydrogen molecules although a small amount of background hydrogen ends up at the electrode.

Wenzhen Li, an expert in the electrochemical reduction of carbon dioxide at Michigan Technological University said this exciting work reports such a catalyst for the first time. The only problem he sees is that formate and the catalyst are both water-soluble, so an input of energy would end up required to separate formate from the solution.

“It would be even more interesting to develop a [similar] catalyst to further reduce carbon dioxide to carbon monoxide or even hydrocarbons,” he said.

The group is now hunting for more efficient catalysts and ways to immobilize them on electrodes.

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