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Simulations of the Oxidation and Degradation of Platinum Electrocatalysts
Author(s) -
Kirchhoff Björn,
Braunwarth Laura,
Jung Christoph,
Jónsson Hannes,
Fantauzzi Donato,
Jacob Timo
Publication year - 2020
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.201905159
Subject(s) - reaxff , platinum , catalysis , materials science , oxide , electrochemistry , platinum nanoparticles , nanoparticle , density functional theory , chemical physics , chemical engineering , molecular dynamics , electrode , nanotechnology , chemistry , computational chemistry , organic chemistry , interatomic potential , engineering , metallurgy
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 [Pt 6 O 8 ] 4− clusters is observed. Density functional theory calculations confirm that [Pt 6 O 8 ] 4− is indeed stable and hydrophilic. These results suggest that the formation of [Pt 6 O 8 ] 4− may play an important role in platinum catalyst degradation as well as the electromotoric transport of Pt 2+/4+ ions in fuel cells.