Current fuel cell technology uses carbon black, an inexpensive and electrically conductive carbon material, as a support for platinum particles. The carbon transports electricity, while the platinum is the catalyst that drives the production of electricity. The more platinum particles the fuel is exposed to, the more electricity is produced. Yet carbon black is porous, so the platinum inside the inner pores may not be exposed. Carbon black also tends to corrode over time.

As a result, the researchers note, fuel cells suffer from meager performance due to poor efficiency and durability of the catalysts; these suboptimal characteristics have hampered widespread commercialization.

In order to produce more efficient fuel cells, you want to increase the active surface area of the catalyst, and you want your catalyst to last.

—André Taylor

At 13 nanometers in scale (about 1/10,000 the width of a human hair), the BMG nanowires that Schroers and Taylor developed are about three times smaller than carbon black particles. The nanowires’ long, thin shape gives them much more active surface area per mass compared to carbon black. In addition, rather than sticking platinum particles onto a support material, the Yale team incorporated the platinum into the nanowire alloy itself, ensuring that it continues to react with the fuel over time.

Electrocatalytic performance of the Pt-BMG nanowires toward (A) carbon monoxide (CO) oxidation, (B) methanol 1 mol L-1 oxidation, and (C) ethanol 1 mol L-1 oxidation. Cyclic voltammograms in 0.5 mol L-1 H2SO4, normalized to the electrode geometric area. Scan rate: 20 mV s-1. Credit: ACS, Carmo et al. Click to enlarge.

The nanowires’ unique chemical composition makes it possible to shape them into such small rods using a hot-press method, said Schroers, who has developed other BMG alloys that can also be blow molded into complicated shapes. The BMG nanowires also conduct electricity better than carbon black and carbon nanotubes, and are less expensive to process.

In summary, Pt-BMG nanowire architecture exhibits superb durability combined with high electrocatalytic activity toward CO, methanol, and ethanol oxidation. The demonstrated performance suggests widespread commercial use and applicability, which is easy, scalable, and economical in fabrication. Developing specifically tailored alloys of BMGs for electrocatalytic applications could result in transformative improvements in a multitude of areas such as energy conversion/storage and sensors.

—Carmo et al.

Other authors of the paper include Marcelo Carmo, Ryan C. Sekol, Shiyan Ding and Golden Kumar (all of Yale University).

Resources

• Marcelo Carmo, Ryan C. Sekol, Shiyan Ding, Golden Kumar, Jan Schroers, André D. Taylor (2011) Bulk Metallic Glass Nanowire Architecture for Electrochemical Applications. ACS Nano doi: 10.1021/nn200033c