Decoding Structure -ORR Activity Relationships Thanks to Surface Distortion

Abstract : The electrochemical activation of oxygen is the cornerstone of energy storage and conversion devices, such as metal-air batteries, electrolysers and fuel cells. In proton-exchange membrane fuel cells, the high cost and scarcity of Pt continues to drive research aimed at enhancing its mass activity (the current produced per gram of Pt) for the oxygen reduction (ORR). Recent studies have shown that the ORR kinetics is maximal on bimetallic alloys and at (111) facets 1 , hence, PtNi/C octahedra are still envisioned as the dream ORR catalyst 2. Strikingly, it was also found recently that structurally-disordered PtNi nanocatalysts feature highly desirable and sustainable ORR activity 3. However, to date, the mechanisms of this unexpected ORR activity enhancement remain unclear. To shed fundamental light onto this, state-of-the art PtNi/C nanocatalysts with distinct atomic composition, size, shape and density of disorder were synthesized. Their disorder was quantified experimentally, using the values of microstrain (a parameter accessible by the Rietveld refinement of wide-angle X-ray scattering patterns). Thanks to experimental measurements and ab initio calculations, the contributions of chemical and structural disorder were disentangled and a new parameter, the surface distortion (SD), was established. The SD descriptor was used to rationalize the ORR activity enhancement of the two classes of materials (structurally-ordered and structurally-disordered), and to probe their stability in simulated PEMFC cathode operating conditions
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Conference papers
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Submitted on : Wednesday, November 6, 2019 - 3:27:53 PM
Last modification on : Wednesday, November 13, 2019 - 8:01:42 AM

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Raphaël Chattot, O. Le Bacq, A. Pasturel, Pierre Bordet, J. Drnec, et al.. Decoding Structure -ORR Activity Relationships Thanks to Surface Distortion. EFCF 2019 Fuel Cells, Electrolysers H2 Processing Forum, Jul 2019, Lucerne, Switzerland. ⟨hal-02351817⟩

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