Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Catalyst structure identified in an operating PEM fuel cell

07.10.2016

Research at the group of Dr Moniek Tromp of the University of Amsterdam's research priority area Sustainable Chemistry has revealed the structure of the palladium catalyst for hydrogen oxidation in proton exchange membrane (PEM) fuel cells. Contrary to current views the results, obtained by applying X-ray spectroscopy under operating conditions, indicate the existence of a hydride phase throughout the operating range.

The research, performed in collaboration with the Technical Electrochemistry research group of Prof. Dr Hubert Gasteiger at the Technical University of Munich (Department of Chemistry), has recently been published in ACS Catalysis.


Photograph and schematic lay-out of the experimental setup, featuring an improved flow field design and a reduced thickness of the graphite window (500 µm). The latter is transparent to X-rays at the K edge energies (6 8 keV) of transition metal catalysts such as manganese, iron, cobalt and nickel. The improved cell design therefore also enables operando XAS studies of commonly investigated fuel cell catalysts based on these 3d transition metal alloys with platinum, or of PGM-free iron-based catalysts.

Investigating palladium

In proton exchange membrane fuel cells (PEMFC) electrons are generated by means of the electrochemical oxidation of hydrogen, thus producing the electrical power to drive an electric car or provide electricity for industry or households. The best currently known electro-catalysts for this electron-generating oxidation reaction are the so-called platinum-group metals, with platinum itself as the most active catalyst.

Palladium provides an interesting alternative for platinum since it is only slightly less active but more widely available and less expensive. However, in practice the activity of palladium decreases at high anodic potentials. This has until now been explained by a change in its catalytic properties, mainly hydride decomposition in the bulk of the material and oxide formation at the surface.

These explanations are disputable, however, since they are based on laboratory experiments at room temperature. Typical operating conditions of a low temperature PEMFC involve temperatures up to 80 °C. Both for a fundamental understanding of the performance and for the development of non-Pt based catalysts it is important to characterize the catalyst under real reaction conditions.

Improved experimental set-up

The current Amsterdam/Munich research cooperation bridges the gap between electrochemical studies in liquid electrolytes at room temperature and real operating fuel cells at 80 °C. In ACS Catalysis the researchers present electrochemical isotherms for the absorption of hydrogen into a Pd catalyst as a function of applied potential, temperature, and reaction atmosphere.

They were obtained with a new, improved X-ray absorption spectroscopy (XAS) electrochemical fuel cell, allowing the investigation of PEMFC electrodes during operation (operando spectroscopy). The research was performed at the BM30B/FAME beamline of the European Synchrotron Radiation Facility in Grenoble.

Hydride phase maintained

The operando spectroscopic characterization during hydrogen oxidation unequivocally demonstrates that the hydride phase is maintained under practical operating conditions of a fuel cell anode, even at high anodic potentials. The transition from a hydride to a metallic state, previously observed in electrochemical cells based on a liquid electrolyte, does not occur.

The researchers argue that the reaction environment of operating PEMFC's is so much unlike that in room-temperature liquid electrolytes cells that the chemical state of the Pd catalyst is completely different. One important feature explaining this is the orders of magnitude higher mass-transport rates in PEMFC's.

The recent findings highlight the necessity of characterizing the properties of electro-catalysts under realistic operating conditions. Furthermore the researchers argue that in fact for all electro-catalytic reactions in which the reactant is supplied in a gaseous form - not just for the hydrogen oxidation in a fuel cell - it is of utmost importance to maintain appropriate mass transfer regimes when establishing structure-activity relationships.

Full bibliographic information

Armin Siebel, Yelena Gorlin, Julien Durst, Olivier Proux, Frédéric Hasché, Moniek Tromp, and Hubert A. Gasteiger: Identification of Catalyst Structure during the Hydrogen Oxidation Reaction in an Operating PEM Fuel Cell ACS Catal., 2016, 6, pp 7326–7334 DOI: 10.1021/acscatal.6b02157

For further information, please contact:

Johan Rheeder

+31 20 525 3591

J.P.S.Rheeder@uva.nl

Johan Rheeder | AlphaGalileo
Further information:
http://www.uva.nl

More articles from Life Sciences:

nachricht World’s Largest Study on Allergic Rhinitis Reveals new Risk Genes
17.07.2018 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt

nachricht Plant mothers talk to their embryos via the hormone auxin
17.07.2018 | Institute of Science and Technology Austria

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

World’s Largest Study on Allergic Rhinitis Reveals new Risk Genes

17.07.2018 | Life Sciences

Electronic stickers to streamline large-scale 'internet of things'

17.07.2018 | Information Technology

Behavior-influencing policies are critical for mass market success of low carbon vehicles

17.07.2018 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>