Otegbade, O.A.; (2012) Theoretical investigations of surface oxides on platinum and platinum alloy catalysts for fuel cell applications. Doctoral thesis , UCL (University College London).

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Abstract

The interaction of oxygen with metal surfaces can lead to various structures; these include surface oxide films, oxygen penetration in the subsurface region and bulk oxides, at certain partial pressures and temperatures. This research focuses on the oxygen reduction reaction (ORR) within the proton exchange membrane fuel cell (PEMFC). PEMFC are believed to be kinetically limited for the ORR due to a loss of surface area at the cathode as a result of oxidation. One explanation for this phenomenon is the “so called place exchange mechanism” which leads to a thin surface oxide being formed. In an attempt to understand and verify this hypothesis, Pt and Pt/Ni alloys have been modelled in order to determine the relative propensity of surface oxide film formation. Density functional theory (DFT) has been used to model various facets of the catalyst particles, in particular the (111) and (100) surfaces. In addition, a range of oxygen coverages at high symmetry sites and oxide thin films have also been modelled as intermediates in the place exchange mechanism. The DFT data obtained from these calculations have been used in a statistical thermodynamics model. This allows one to bridge the temperature and pressure gap between the technological relevant conditions of the PEMFC and the electronic structure calculations.

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