Journal
CATALYSIS TODAY
Volume 262, Issue -, Pages 146-154Publisher
ELSEVIER
DOI: 10.1016/j.cattod.2015.08.011
Keywords
Platinum; Hollow metal nanoparticles; Galvanic replacement; Oxygen reduction reaction; Proton exchange membrane fuel cell; Durability
Funding
- Investments for the Future programme [AN-10-LABX-44-01]
- University of Grenoble-Alpes through the AGIR programme [LL1492017G]
- French National Research Agency through the HOLLOW project [ANR-14-CE05-0003-01]
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Hollow nanomaterials composed of a Pt-rich shell surrounding a central void have demonstrated promising electrocatalytic activity for the oxygen reduction reaction (ORR). However, their long-term stability remains understudied, and is the focus of the present paper. Here, we followed the temperature-dependent morphological and compositional trajectories of hollow PtNi/C nanoparticles during accelerated stress tests (AST) of interest for proton-exchange membrane fuel cells (PEMFC) applications. The combined physical, chemical and electrochemical results showed that: (i) the PtNi/C nanoparticles preserve a hollow nanostructure during accelerated stress testing at T=25 degrees C, but collapsed in real PEMFC operating conditions (solid electrolyte - T=80 degrees C), (ii) the dissolution of Ni atoms is drastically enhanced with an increase of the temperature, almost all Ni atoms being leached after the AST conducted in a single PEMFC, (iii) a lattice strain of ca. 0.4% persists in the aged hollow PtNi/C nanocatalysts, (iv) whatever the AST conditions, hollow PtNi/C nanocatalysts show improved ORR activity over solid Pt/C nanocatalysts of the same crystallite size. The catalytic enhancement is believed to result from the presence of subsurface vacancies in the dealloyed hollow PtNi/C nanoparticles. In a more global perspective, the present contribution emphasizes the crucial role of temperature on the stability of shape-controlled particles (far from their equilibrium shape). (C) 2015 Elsevier B.V. All rights reserved.
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