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Case Western Team Finds CNTs Could Dramatic Cut Fuel Cell Costs

by Editor1 last modified March 26, 2011 - 12:07

Case Western Research University scientists are unlocking catalytic powers of carbon nanotubes, and may bring commercial fuel cells closer to reality. The team has proven fuel cell catalysts made of CNTs dipped in a polymer solution can equal the energy output of much more expensive platinum catalysts.

Case Western Team Finds CNTs Could Dramatic Cut Fuel Cell Costs

Case Western finds CNTs dipped in a polymer solution can perform on par with platinum for fuel cells.

Platinum comprises at least 25% the cost of a fuel cell and now sells for about $65,000 per kilogram. Case Western’s “activated” CNTs would cost about $100 per kilogram, according to Dr. Liming Dai, a CWU professor of chemical engineering and the research team leader.

"This is a breakthrough," Dr Dai said. His team members include research associates Shuangyin Wang and Dingshan Yu.

The researchers found by simply soaking CNTs in a water solution of the polymer polydiallyldimethylammoniumn chloride for a couple of hours, that polymer will coat the nanotube surface. The coating pulls an electron partially from the carbon in the tube, creating a net positive charge.

They placed the “activated” CNTs 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. During tests, the CNT-powered fuel cell produced as much power as an identical cell using a platinum catalyst, Dr. Dai said.

Even more encouraging, the “activated” CNTs lasted longer and proved to be more stable than platinum, they added.

In specific, the team found the carbon-based catalyst:
  • Does not lose catalytic activity over time;
  • Will not be fouled by carbon monoxide poising;
  • Remains free from the crossover effect with methanol, a liquid fuel that's easier to store and transport than hydrogen. (In platinum catalysts, methanol can reduce activity when fuel crosses over from the anode to the cathode in a fuel cell.)

The latest CWRU finding builds on the Dai lab's earlier work, which found nitrogen-doped CNTs could also be a catalyst. In that process, nitrogen chemically bonded to the carbon pulled electrons partially from the carbon to create a charge. Testing showed the “doped” CNTs could triple the energy output of platinum.

Despite the higher efficiencies, Dai and his team continued to press for a low-cost and simpler CNT-based process, and found the latest “activated” CNT approach.

The Case western team will continue their work to increase the energy output, while maintaining other advantages by looking to optimize the nanotube layout and type of polymer.
The work is published in the online edition of Journal of the American Chemical Society at http://pubs.acs.org/doi/full/10.1021/ja1112904.