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Danerol A.S.,University of Savoy | Bas C.,University of Savoy | Flandin L.,University of Savoy | Claude E.,Axane | Alberola N.D.,University of Savoy
Journal of Power Sources | Year: 2011

The changes in properties within membrane electrode assemblies (MEAs) aged in a stack functioning at constant-power operation (0.12 W cm-2) for several durations (0, 347, 892, and 1397 h) were characterized. An important effort was placed into better understanding interfaces. Two tests were thus developed to investigate the changes in each active layer/membrane interface. Both techniques demonstrated that the mechanical bounding of both cathode and anode to the polymer membrane improve with the functioning time in fuel cell. This phenomenon was further attributed to Pt dissolution and diffusion/precipitation within the polymer membrane and to a diffusion/crystallization of the binding agent in the vicinity of the electrode/membrane interfaces. © 2010 Elsevier B.V. All rights reserved. Source

Axane | Date: 2011-06-07

Fuel cell system for generating electricity, in particular for lighting and sound recording during the filming of cinema. Installation, maintenance, servicing, and repair of fuel cell electric generators. Rental of fuel cell electric generators.

Dubau L.,Joseph Fourier University | Lopez-Haro M.,Joseph Fourier University | Castanheira L.,Joseph Fourier University | Durst J.,Joseph Fourier University | And 6 more authors.
Applied Catalysis B: Environmental | Year: 2013

Long-term (3422h) operation of proton exchange membrane fuel cell in stationary conditions causes two regimes of degradation of the cathode catalytic layer. Firstly, from the beginning of life until the first membrane electrode assembly sampling, at t=1163h, fast degradation of the fresh Pt3Co/C nanoparticles is monitored; classical degradation mechanisms of Pt-based electrocatalysts occur, such as carbon corrosion, crystallite migration, dissolution of the less noble metal (Co), and 3D Ostwald ripening. A second degradation regime sets up from 1163h to 3422h, during which the changes in composition and morphology are slower. At the end of the ageing test, three distinct populations of Pt-Co/C nanoparticles coexist: (i) Pt-Co/C core-shell particles characterized by an alloyed (but depleted, compared to the fresh material) core surrounded by a 3-5 monolayer thick Pt-rich shell, (ii) Pt-Co/C "hollow" particles containing a central cavity surrounded by a Pt-Co shell containing limited amount of Co atoms distributed at the atomic scale and (iii) pure Pt/C "hollow" particles, from which Co dissolution has been completed. Experimental evidences are provided that the Pt-rich phase remains stable, and maintains constant ORR activity over more than 2000h of operation in real PEMFC conditions. © 2013 Elsevier B.V. Source

Lopez-Haro M.,Joseph Fourier University | Dubau L.,Joseph Fourier University | Guetaz L.,CEA Grenoble | Bayle-Guillemaud P.,Joseph Fourier University | And 6 more authors.
Applied Catalysis B: Environmental | Year: 2014

The oxygen reduction reaction (ORR), which is the cathodic reaction in a proton-exchange membrane fuel cell (PEMFC) and in several other important processes, is a widely studied reaction. From the kinetics viewpoint, Pt is the best electrocatalyst and its activity can be increased upon alloying with a 3d-transition metal (Co, Ni, Fe, Cu). Aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy prove that the structural and compositional changes of Pt3Co/C nanoparticles during real-life PEMFC operation are much richer than previously thought from accelerated stress tests. Four different nanostructures are observed after 3422h of operation in stationary mode: Pt, Pt-Co/C "hollow", Pt-Co core-shell and Pt "bulk" nanoparticles. The presence of "hollow" nanoparticles in the aged catalytic layer is accounted for by the nanoscale Kirkendall effect, a vacancy-mediated diffusion mechanism in binary alloys where one species diffuses faster than the other. The oxygen reduction reaction specific activity of the "hollow" nanostructures is 1.5-fold that of the fresh Pt3Co/C cathode catalyst and 3-fold that of Pt/C nanoparticles, thereby offering a new route to synthesize highly active and durable PEMFC electrocatalysts. © 2014 Elsevier B.V. Source

Dubau L.,Joseph Fourier University | Durst J.,Joseph Fourier University | Maillard F.,Joseph Fourier University | Guetaz L.,CEA Grenoble | And 3 more authors.
Electrochimica Acta | Year: 2011

This paper provides further insights into the degradation mechanisms of nanometer-sized Pt3Co/C particles under various proton-exchange membrane fuel cell (PEMFC) operating conditions. We confirm that Co atoms are continuously depleted from the mother Pt3Co/C electrocatalyst because they can diffuse from the bulk to the surface of the material. The structure of the Pt-Co/C nanoparticles in the long-term is determined by a balance between Co surface segregation and formation of oxygenated species from water splitting. When the PEMFC is operated at high current density (low cathode potential, below the onset of surface oxide formation from water), a steady-state is reached between the rate of Co dissolution at the surface and Co surface segregation. Consequently, Co and Pt atoms remain homogeneously distributed within the Pt-Co/C particles and the thickness of the Pt-shell is maintained to a small value not detectable by atomic-resolution high-angle annular dark-field scanning transmission electron microscopy. When the PEMFC is operated at low current density (high cathode potential), the formation of surface oxides from water and the resulting "place-exchange" mechanism enhance the rate of diffusion of Co atoms to the surface. Consequently, the fresh Pt 3Co/C particles form core/shell particles with thick Pt-shells and Co content < 5 at% and, ultimately, "hollow" Pt nanoparticles (Kirkendall effect). To the best of our knowledge, this is the first report on the formation of "hollow" Pt particles in a PEMFC. © 2011 Elsevier Ltd. All rights reserved. Source

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