Cheap catalyst made easy

Mar 22, 2011

Catalysts made of carbon nanotubes dipped in a polymer solution equal the energy output and otherwise outperform platinum catalysts in fuel cells, a team of Case Western Reserve University engineers has found.

The researchers are certain that they'll be able to boost the power output and maintain the other advantages by matching the best nanotube layout and type of polymer.

But already they've proved the simple technique can knock down one of the major roadblocks to use: cost.

Platinum, which represents at least a quarter of the cost of fuel cells, currently sells for about $65,000 per kilogram. These researchers say their activated carbon nanotubes cost about $100 per kilogram.

Their work is published in the online edition of at http://pubs.acs.org/doi/full/10.1021/ja1112904.

"This is a breakthrough," said Liming Dai, a professor of chemical engineering and the research team leader.

Dai and research associates Shuangyin Wang and Dingshan Yu found that by simply soaking carbon nanotubes in a water solution of the polymer polydiallyldimethylammoniumn chloride for a couple of hours, the polymer coats the nanotube surface and pulls an electron partially from the carbon, creating a net positive charge.

They placed the nanotubes on the cathode of an alkaline fuel cell. There, the charged material acts as a catalyst for the oxygen-reduction reaction that produces electricity while electrochemically combining hydrogen and oxygen.

In testing, the fuel cell produced as much power as an identical cell using a .

But the activated nanotubes last longer and are more stable, the researchers said. Unlike platinum, the carbon-based catalyst: doesn't lose catalytic activity and, therefore, efficiency, over time; isn't fouled by carbon monooxide poising; and is free from the crossover effect with . Methanol, a liquid fuel that's easier to store and transport than hydrogen, reduces activity of a platinum catalyst when the fuel crosses over from the anode to the cathode in a fuel cell.

The new process builds on the Dai lab's earlier work using nitrogen-doped carbon nanotubes as a . In that process, nitrogen, which was chemically bonded to the carbon, pulled electron partially from the carbon to create a charge. Testing showed the doped tubes tripled the energy output of platinum.

Dai said the new process is far simpler and cheaper than using nitrogen-doped carbon and he's confident his lab will increase the energy output as well. "We have not optimized the system yet."

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apex01
not rated yet Mar 22, 2011
This is great. Hopefully these new and more cost effective fuel cells using CNT catalysts will stimulate demand for them. Hence, maybe this will act as an engine to fund more CNT R&D.
Azpod
not rated yet Mar 22, 2011
Awesome! Cheap fuel cells is one of the biggest hurdles we have to overcome if we ever hope to move away from an oil-based economy. Even if we could produce alternative, zero-carbon fuels for free (a fantasy, I know), no one would use these fuels if doing so would make "economy" cars cost as much as luxury cars do today.