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  Structure-Activity-Stability Relationships for Space-Confined PtxNiy Nanoparticles in the Oxygen Reduction Reaction

Mezzavilla, S., Baldizzone, C., Swertz, A.-C., Hodnik, N., Pizzutilo, E., Polymeros, G., et al. (2016). Structure-Activity-Stability Relationships for Space-Confined PtxNiy Nanoparticles in the Oxygen Reduction Reaction. ACS Catalysis, 6(12), 8058-8068. doi:10.1021/acscatal.6b02221.

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Mezzavilla, Stefano1, Author           
Baldizzone, Claudio2, Author           
Swertz, Ann-Christin1, 3, Author           
Hodnik, Nejc2, 4, Author           
Pizzutilo, Enrico2, Author           
Polymeros, George2, Author           
Keeley, Gareth P.2, Author           
Knossalla, Johannes1, Author           
Heggen, Marc5, Author           
Mayrhofer, Karl J. J.2, 6, 7, Author           
Schüth, Ferdi1, Author           
1Research Department Schüth, Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_1445589              
2Electrocatalysis, Interface Chemistry and Surface Engineering, Max-Planck-Institut für Eisenforschung GmbH, Max Planck Society, ou_1863354              
3Service Department Lehmann (EMR), Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_1445625              
4National Institute of Chemistry, Hajdrihova 19, Ljubljana, Slovenia, ou_persistent22              
5Ernst Ruska Center for Microscopy and Spectroscopy with Electrons, Forschungzentrum Jülich GmbH, Jülich, Germany, ou_persistent22              
6Helmholtz-Institute Erlangen-Nuremberg for Renewable Energy (IEK-11), Forschungszentrum Jülich, Egerlandstrasse 3, 91058 Erlangen, Germany, ou_persistent22              
7Department of Chemical and Biological Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91058 Erlangen, Germany , ou_persistent22              


Free keywords: activity; dealloying; nanoparticles; oxygen reduction reaction; stability
 Abstract: This study focuses on the synthesis and electrochemical performance (i.e, activity and stability) of advanced electrocatalysts for the oxygen reduction reaction (ORR), made of Pt-Ni nanoparticles embedded in hollow graphitic spheres (HGS). The mechanism of the confined space alloying, that is, the controlled alloying of bimetallic precursors with different compositions (i.e., Pt3Ni, PtNi, and PtNi3) within the HGS mesoporous shell, was examined in detail. It was found that the presence of platinum during the reduction step, as well as the application of high annealing temperatures (at least 850 degrees C for 3.Sh in Ar), are necessary conditions to achieve the complete encapsulation and the full stability of the catalysts. The evolution of the activity, the electrochemical surface area, and the residual alloy composition of the Pt-Ni@HGS catalysts was thoroughly monitored (at the macro- and nanoscale level) under different degradation conditions. After the initial activation, the embedded Pt-Ni nanoparticles (3-4 nm in size) yield mass activities that are 2- to 3.5-fold higher than that of pure Pt@HGS (depending on the alloy composition). Most importantly, it is demonstrated that under the normal operation range of an ORR catalyst in PEM-FCs (potential excursions between 0.4 and 1.0 V-RHE) both the nanoparticle-related degradation pathways (particle agglomeration) and dealloying phenomena are effectively suppressed, irrespectively of the alloy composition. Thus, the initial enhanced activity is completely maintained over an extended degradation protocol. In addition, owing to the peculiar configuration of the catalysts consisting of space-confined nanoparticles, it was possible to elucidate the impact of the dealloying process (as a function of alloy composition and severity of the degradation protocols) separately from other parallel phenomena, providing valuable insight into this elusive degradation mechanism.


Language(s): eng - English
 Dates: 2016-12-02
 Publication Status: Published in print
 Pages: 11
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: ISI: 000389399400008
DOI: 10.1021/acscatal.6b02221
 Degree: -



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Title: ACS Catalysis
  Abbreviation : ACS Catal.
Source Genre: Journal
Publ. Info: Washington, DC : ACS
Pages: - Volume / Issue: 6 (12) Sequence Number: - Start / End Page: 8058 - 8068 Identifier: Other: 2155-5435
CoNE: https://pure.mpg.de/cone/journals/resource/2155-5435