Investigation of chemisorption of oxygen on platinum nanoparticles with density functional theory calculations

Abstract

Platinum nanoparticles are one of the most commonly used catalysts in proton exchange membrane fuel cells (PEMFCs). One of most important catalytic processes is the oxygen reduction reaction, and this is known to be affected by the size and structure of the platinum catalysts. Recent advances in the linear scaling DFT code ONETEP [1], have made it possible to investigate stages of the oxygen reduction reaction occurring on nanoparticles consisting of over a hundred atoms. In this thesis, these newly implemented techniques are tested and calibrated by comparing with similar calculations performed in plane-wave DFT code CASTEP [2]. Following this calibration, the chemisorption of atomic and molecular oxygen on different platinum structures was investigated through calculation of chemisorption energies, electron density differences, and local densities of states. Good qualitative agreement was found between the results obtained in this thesis, and those found in the available experimental and computational literature. Size effects, including variation in the strength of O-Pt binding, and the contraction of Pt-Pt bonds in smaller PtN and OPtN nanoparticles relative to bulk, are observed and discussed with respect to their relevance to the oxygen reduction reaction.

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ORCID for Chris-Kriton Skylaris: orcid.org/0000-0003-0258-3433

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