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Research on Fuel cell catalysts Faster Design – Better Catalysts: How a New Concept Combines Geometric and Adsorption Properties

Author / Editor: Prof. Dr. Aliaksandr S. Bandarenka, Technical University of Munich / Eilyn Dommel

Catalyst design plays a key role in improving many processes. An international team of scientists has now developed a concept that elegantly correlates geometric and adsorption properties. They validated their approach by designing a new platinum-based catalyst for fuel cell applications.

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The different number of similar neighbors has an important influence on the catalytic activity of surface atoms of a nanoparticle.
The different number of similar neighbors has an important influence on the catalytic activity of surface atoms of a nanoparticle.
(Image: David Loffreda, CNRS, Lyon)

Hydrogen would be an ideal energy carrier: Surplus wind power could split water into its elements. The hydrogen could power fuel cell-driven electric cars with great efficiency. While the only exhaust would be water, the range could be as usual. But fuel cell vehicles are still a rare exception. The required platinum (Pt) is extremely expensive and the world’s annual output would not suffice for all cars.

A key component of the fuel cell is the platinum catalyst that is used to reduce oxygen. It is well known that not the entire surface but only a few particularly exposed areas of the platinum, the so-called active centers, are catalytically active.

A team of scientists from Technical University of Munich and Ruhr University Bochum (Germany), the Ecole normale superieure (ENS) de Lyon, Centre national de la recherche scientifique (CNRS), Universite Claude Bernard Lyon 1 (France) and Leiden University (Netherlands) have set out to determine what constitutes an active center.

Studying the model

A common method used in developing catalysts and in modeling the processes that take place on their surfaces is computer simulation. But as the number of atoms increases, quantum chemical calculations quickly become extremely complex.

With their new methodology called “coordination-activity plots” the research team presents an alternative solution that elegantly correlates geometric and adsorption properties. It is based on the “generalized coordination number” (GCN), which counts the immediate neighbors of an atom and the coordination numbers of its neighbors.

Calculated with the new approach, a typical Pt (111) surface has a GCN value of 7.5. According to the coordination-activity plot, the optimal catalyst should, however, achieve a value of 8.3. The required larger number of neighbors can be obtained by inducing atomic-size cavities into the platinum surface, for example.

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