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Atomic-scale restructuring of hollow PtNi/C electrocatalysts during accelerated stress tests

Abstract : 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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Submitted on : Thursday, July 26, 2018 - 11:19:28 AM
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Laetitia Dubau, Miguel Lopez-Haro, Julien Durst, Frederic Maillard. Atomic-scale restructuring of hollow PtNi/C electrocatalysts during accelerated stress tests. Catalysis Today, Elsevier, 2016, 262, pp.146-154. ⟨10.1016/j.cattod.2015.08.011⟩. ⟨cea-01849433⟩



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