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Simulations of the Oxidation and Degradation of Platinum Electrocatalysts

Simulations of the Oxidation and Degradation of Platinum Electrocatalysts

Title: Simulations of the Oxidation and Degradation of Platinum Electrocatalysts
Author: Kirchhoff, Björn   orcid.org/0000-0002-8600-7806
Braunwarth, Laura
Jung, Christoph
Jónsson, Hannes   orcid.org/0000-0001-8285-5421
Fantauzzi, Donato
Jacob, Timo
Date: 2019-12-26
Language: English
Scope: 1905159
University/Institute: Háskóli Íslands
University of Iceland
School: School of Engineering and Natural Sciences (UI)
Verkfræði- og náttúruvísindasvið (HÍ)
Department: Raunvísindastofnun (HÍ)
Science Institute (UI)
Series: Small;16(5)
ISSN: 1613-6810
1613-6829 (eISSN)
DOI: 10.1002/smll.201905159
Subject: Electrocatalysis; Fuel cells; Oxidation; Platinum catalysts; ReaxFF; Oxun; Efnarafalar; Ryð; Hermun
URI: https://hdl.handle.net/20.500.11815/1549

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Kirchhoff, B., Braunwarth, L., Jung, C., Jónsson, H., Fantauzzi, D., Jacob, T., Simulations of the Oxidation and Degradation of Platinum Electrocatalysts. Small 2020, 16, 1905159. https://doi.org/10.1002/smll.201905159


Improved understanding of the fundamental processes leading to degradation of platinum nanoparticle electrocatalysts is essential to the continued advancement of their catalytic activity and stability. To this end, the oxidation of platinum nanoparticles is simulated using a ReaxFF reactive force field within a grand-canonical Monte Carlo scheme. 2–4 nm cuboctahedral particles serve as model systems, for which electrochemical potential-dependent phase diagrams are constructed from the thermodynamically most stable oxide structures, including solvation and thermochemical contributions. Calculations in this study suggest that surface oxide structures should become thermodynamically stable at voltages around 0.80–0.85 V versus standard hydrogen electrode, which corresponds to typical fuel cell operating conditions. The potential presence of a surface oxide during catalysis is usually not accounted for in theoretical studies of Pt electrocatalysts. Beyond 1.1 V, fragmentation of the catalyst particles into [Pt6O8]4− clusters is observed. Density functional theory calculations confirm that [Pt6O8]4− is indeed stable and hydrophilic. These results suggest that the formation of [Pt6O8]4− may play an important role in platinum catalyst degradation as well as the electromotoric transport of Pt2+/4+ ions in fuel cells.


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