Argonne Researchers Develop New Concept in Nanoscale Catalyst Engineering; Could Advance Commercialization of Fuel Cells

5 March 2007

Researchers at the US Department of Energy’s Argonne National Laboratory have developed an advanced concept in nanoscale catalyst engineering that could bring polymer electrolyte membrane (PEM) fuel cells for hydrogen-powered vehicles closer to commercialization.

The Argonne researchers, Nenad Markovic and Vojislav Stamenkovic, published related results last month in Science and this month in Nature Materials on the behavior of single crystal and polycrystalline platinum alloy surfaces. The researchers discovered that the nanosegregated platinum-nickel alloy surface has unique catalytic properties, opening up important new directions for the development of active and stable practical cathode catalysts in fuel cells.

The results of their findings identify a clear trend in the behavior of extended and nanoscale surfaces of platinum-bimetallic alloy. Additionally, the techniques and concepts derived from the research program are expected to make contributions to other areas of science well beyond the focus on electrocatalysis.

Their experiments and approach sought to substantially improve and reduce platinum loading as the oxygen-reduction catalyst. The research identified a fundamental relationship in electrocatalytic trends on surfaces between the experimentally determined surface electronic structure (the d-band center) and activity for the oxygen-reduction reaction. This relationship exhibits “volcano-type” behavior, where the maximum catalytic activity is governed by a balance between adsorption energies of reactive intermediates and surface coverage by spectator (blocking) species.

The electrocatalytic trends established for extended surfaces explain the activity pattern of nanocatalysts and provide a fundamental basis for the enhancement of cathode catalysts. By combining experiments with simulations in the quest for surfaces with desired activity, the researchers developed an advanced concept in nanoscale catalyst engineering.

In the past, theoretical connections have been suggested between electronic behavior and catalytic activity. Our work represents the first time that the connections have been identified experimentally. For us, this development constitutes the beginning of more breakthrough advances in nanocatalysts.

—Nenad Markovic

Our study demonstrates the potential of new analytical tools for characterizing nanoscale surfaces in order to fine tune their properties in a desired direction. We have identified a cathode surface that is capable of achieving and even exceeding the target for catalytic activity with improved stability. This discovery sets a new bar for catalytic activity of the cathodic reaction in fuel cells.

—Vojislav Stamenkovic

Collaborators on the research were Bongjin Mun and Philip Ross at DOE’s Lawrence Berkeley National Laboratory, Matthias Arenz and Karl Mayrhofer from Technical University of Munich, Christopher Lucas from the University of Liverpool and Guofeng Wang from the University of South Carolina.

This research was funded by DOE’s Office of Basic Energy Sciences and by General Motors.

Resources:

• “Trends in electrocatalysis on extended and nanoscale Pt-bimetallic alloy surfaces”; Vojislav R. Stamenkovic, Bongjin Simon Mun, Matthias Arenz, Karl J. J. Mayrhofer, Christopher A. Lucas, Guofeng Wang, Philip N. Ross and Nenad M. Markovic; Nature Materials 6, 241 - 247 (2007)doi:10.1038/nmat1840

• “Improved Oxygen Reduction Activity on Pt3Ni(111) via Increased Surface Site Availability”; Vojislav R. Stamenkovic, Ben Fowler, Bongjin Simon Mun, Guofeng Wang, Philip N. Ross, Christopher A. Lucas, Nenad M. Markovic; Science 26 January 2007: Vol. 315. no. 5811, pp. 493 - 497 DOI: 10.1126/science.1135941