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May 2011

Nano Fuel Tanks Driving Electric Vehicle Technology

Novel synthesis of bi-metallic catalysts for use in direct methanol fuel cells

Natalie Ray

Transmission electron micrograph of the nanoparticles studding the surface of the aluminum oxide.

For the first time, atomic layer deposition was used to synthesize nanoparticle catalysts that contain two metals: ruthenium and platinum. ALD has already been commercialized by the semiconductor industry and is easily transferable to the energy production industry as a way to fabricate catalysts.

Scientists led by Jeffery Elam with the Institute for Atomic-efficient Chemical Transformations published their multidisciplinary approach for designing and characterizing ruthenium-platinum nanoparticles in Nano Letters.

Catalysts facilitate chemical transformations and are essential for converting energy feedstocks into useable, clean energy. For instance, platinum catalysts in direct methanol fuel cells convert methanol into hydrogen fuel for electric vehicles. Mixing ruthenium in the platinum catalyst increases performance. “Improved ruthenium-platinum nanoparticle catalysts will accelerate the deployment of methanol-powered electric vehicles,” says Elam.

Unlike other catalyst synthesis methods, ALD has atomic-scale control during nanoparticle growth. “This ability to engineer catalytic nanoparticles at the atomic level will have tremendous benefits for clean energy technologies,” says Elam.

Learning about nanocatalysts: Institute scientists alternately deposited ruthenium and platinum atoms onto a nanoporous support using ALD. A quartz crystal microbalance verified growth during deposition, and electron microscopy revealed discrete ~1.2-nanometer metal nanoparticles.

Improved catalytic performance is achieved only when platinum and ruthenium are mixed at the atomic scale. To determine this, the team turned to one of Argonne’s unique facility resources: the Advanced Photon Source. Using synchrotron radiation, the scientists analyzed the nanoparticles’ x-ray absorption spectrum and were able to tease out two distinct chemical bonds: ruthenium-ruthenium and ruthenium-platinum. This confirmed that the nanoparticles were bi-metallic.

At temperatures above 210 °C, ruthenium-platinum nanoparticles yielded higher methanol conversions, up to 45% higher, than a single mixture of the two metals. This better catalytic behavior further supports the bi-metallic nature of the particles.

Future work: With the support of IACT, the group is investigating the ALD synthesis of other bi-metallic catalytic systems. They are also focused on resolving the nanoparticles’ inner atomic structure, hoping the understanding leads to more efficient catalyst design.

More Information

Christensen ST, H Feng, JL Libera, N Guo, JT Miller, PC Stair, and JW Elam. 2010. “Supported Ru-Pt bimetallic nanoparticle catalysts prepared by atomic layer deposition.” Nano Letters 10, 3047-3051. DOI: 10.1021/nl101567m.

Acknowledgments

This ongoing project is supported by the Institute for Atom-efficient Chemical Transformations, an Energy Frontier Research Center funded by the Department of Energy, Office of Science, Office of Basic Energy Sciences.

About the author(s):

  • Natalie Ray conducts research in palladium catalysis and is a member of IACT, an Energy Frontier Research Center. Under the guidance of Professors Peter Stair and Richard Van Duyne, she is studying how to design catalysts for selective hydrogenation using atomic layer deposition.

Two Metals Are Better than One

Novel approach produces bi-metallic materials for turning alcohol into electricity

Transmission electron micrograph of the nanoparticles studding the surface of the aluminum oxide.

Given their high cost, platinum catalysts can be pretty lazy. In certain devices, the precious metal inefficiently drives or catalyzes a reaction that turns a simple alcohol into fuel. This six-atom alcohol is called methanol. Adding ruthenium atoms to the platinum could turn more of the methanol into fuel, maybe enough to develop electric vehicles powered by methanol instead of the nation’s energy grid. But precisely placing the ruthenium atoms to create the perfect catalyst has eluded scientists, until they put a new twist on an old technology. They used atomic layer deposition, a well-known approach from the semiconductor industry, to alternately set ruthenium and platinum atoms on a surface. The resulting multi-metal particles were more efficient than platinum alone. The Institute for Atomic-efficient Chemical Transformations, a DOE Energy Frontier Research Center led by Argonne National Laboratory in Illinois, conducted this research.

More Information

Christensen ST, H Feng, JL Libera, N Guo, JT Miller, PC Stair, and JW Elam. 2010. “Supported Ru-Pt bimetallic nanoparticle catalysts prepared by atomic layer deposition.” Nano Letters 10, 3047-3051. DOI: 10.1021/nl101567m.

Disclaimer: The opinions in this newsletter are those of the individual authors and do not represent the views or position of the Department of Energy.