Projekt

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Degradation mechanisms of electro-catalysts used in polymer electrolyte fuel cells

Gesuchsteller/in Foelske-Schmitz Annette
Nummer 121719
Förderungsinstrument Projektförderung (Abt. I-III)
Forschungseinrichtung Labor für Elektrochemie Paul Scherrer Institut
Hochschule Paul Scherrer Institut - PSI
Hauptdisziplin Physikalische Chemie
Beginn/Ende 01.10.2008 - 30.09.2011
Bewilligter Betrag 164'158.00
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Alle Disziplinen (2)

Disziplin
Physikalische Chemie
Materialwissenschaften

Keywords (10)

polymer electrolyte fuel cell; PEFC; degradation; platinum; carbon; corrosion; electro-catalysis; electrochemistry; scanning tunneling microscopy; x-ray photoelectron spectroscopy

Lay Summary (Englisch)

Lead
Lay summary
Polymer electrolyte fuel cells (PEFC) are regarded as one key technology for future applications in energy conversion. In this project degradation mechanisms of the catalyst used in PEFC will be systematically studied in order to contribute to its lifetime improvement. Scientists have been working for years on adequate alternatives to fossil fuels and one of the most promising candidates is hydrogen. It can function as an energy carrier, converting chemical into electrical energy, e.g. in PEFC which are especially well designed for transport, stationary and mobile applications. PEFC are based on a simple chemical reaction of hydrogen with oxygen, thus turning chemical energy into electrical energy. The electrochemical reactions occur at a platinum catalyst surface of a three phase boundary (electrode, electrolyte and gas phase). However, platinum is very expensive and a lot of effort is directed towards reducing the cost of the PEFC, e.g. by using platinum nanoparticles dispersed on carbon support, while simultaneously increasing its lifetime, as catalyst degradation via sintering and corrosion of platinum in PEFC is a widely known phenomenon.In this project degradation mechanisms on model electrodes that consist of platinum nanoparticles with various sizes dispersed on defined carbon substrates will be systematically studied using in situ electrochemical scanning probe microscopy in combination with x-ray photoelectron spectroscopy. This approach will allow us to investigate chemical and structural changes in dependence on the substrate, particle size and applied electrode potential in real time and down to the atomic scale. Overall, the collected data shall lead to a basic understanding of the degradation mechanisms that take place on carbon and platinum under defined reaction conditions (potential, time, temperature) and might help to design improved catalysts for PEFC by adjusting both the support and the catalytically active compound.
Direktlink auf Lay Summary Letzte Aktualisierung: 21.02.2013

Verantw. Gesuchsteller/in und weitere Gesuchstellende

Mitarbeitende

Publikationen

Publikation
Fabrication of large scale arrays of metallic nanodots by means of high resolution e-beam lithography
(2011), Fabrication of large scale arrays of metallic nanodots by means of high resolution e-beam lithography, in MICROELECTRONIC ENGINEERING, 88(8), 1972-1974.
In situ STM study of Pt-nanodot arrays on HOPG prepared by electron-beam lithography
(2011), In situ STM study of Pt-nanodot arrays on HOPG prepared by electron-beam lithography, in ELECTROCHEMISTRY COMMUNICATIONS, 13(5), 484-487.
Study of Platinum Deposition on Untreated and Thermally Modified Glassy Carbon
(2011), Study of Platinum Deposition on Untreated and Thermally Modified Glassy Carbon, in JOURNAL OF THE ELECTROCHEMICAL SOCIETY, 158(7), D420-D425.
Extreme ultraviolet interference lithography for generation of platinum nanoparticles on glassy carbon
(2010), Extreme ultraviolet interference lithography for generation of platinum nanoparticles on glassy carbon, in ECS Transactions, 25(24), 175-184.

Wissenschaftliche Veranstaltungen

Aktiver Beitrag

Titel Art des Beitrags Titel des Artikels oder Beitrages Datum Ort Beteiligte Personen
Electrochemistry 2010, GDCh Fachtagung 13.09.2010 Bochum
216th Meeting of the Electrochemical Society 04.10.2009 Wien, Oesterreich
EMPA PhD Symposium 13.11.2008 St. Gallen


Abstract

The polymer electrolyte fuel cell (PEFC) has been proven to be an alternative power source for stationary and portable applications as well as for sustainable individual mobility. Currently, cost, reliability, and lifetime are the most important issues for practical use of this power source. In PEFCs the electrochemical reactions occur at catalyst surfaces of a three-phase boundary (electrolyte / electrode / gasphase) at operating temperatures between 60 and 100°C. Due to high efficiency and potentially high corrosion resistance the catalyst used in conventional PEFCs consists of nanoparticles of platinum and its alloys dispersed on a carbon support, and, therefore, is one of the major cost drivers. As a consequence, one key challenge in fuel cell development is to decrease the platinum content by maximizing its utilization and lifetime. Under steady state conditions platinum and carbon show high corrosion resistance. However, depending on the duty cycle, it is proposed that a considerable loss in cell performance refers to sinter and/or corrosion processes of the catalyst and/or its support. Investigations leading to an understanding of these processes are of fundamental interest for the optimization of the catalyst. In most of the relevant studies in this research field complex composite electrodes under different working conditions (temperature, time, potential, stoichiometry etc.) were investigated. Systematic studies in which state-of-the-art in situ analytical methods are applied to study the corrosion and sinter properties of model materials are missing. In this project degradation mechanisms on model electrodes that consist of platinum nanoparticles with various sizes (from 1 to 100 nm) dispersed on defined carbon substrates will be systematically studied using in situ electrochemical scanning probe microscopy in combination with x-ray photoelectron spectroscopy. This approach will allow us to investigate chemical and structural changes in dependence on the substrate, particle size and composition, and applied electrode potential in real time and down to the atomic scale. The model electrodes serving the larger particles (> 10nm) are going to be prepared in collaboration with the Laboratory for Micro- and Nanotechnology at PSI aiming to produce periodic dot-structures via extreme ultraviolet interference at the unique XIL-beamline at the SLS. The smaller particles will consist of colloids and are going to be prepared in collaboration with H. Schulenburg from the Fuel Cells Group of the Electrochemistry Laboratory and G. Khelashvili from H. Bönnemanns Group at the Forschungszentrum Karlsruhe.Overall, the collected data shall lead to a basic understanding of the degradation mechanisms that take place on carbon and platinum under defined reaction conditions (potential, time, temperature) and might help to design new catalysts by adjusting both the support and the catalytically active compound.
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