Papanikolaou, Konstantinos G.; (2021) On the Surface Restructuring of Highly Dilute Alloys and its Effects on Catalytic Performance. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Recent studies have shown that highly dilute alloys of platinum group metals (PGMs: Pt, Rh, Ir and Pd) with coinage metals (Cu, Au, and Ag) serve as highly selective and coke–resistant catalysts in a number of important chemical reactions. These materials are composed of trace amounts of a PGM or Ni, whose atoms are embedded in a coinage metal surface, and their catalytic behaviour is governed by the size and shape of the surface clusters of PGM atoms. Therefore, establishing a means of control over the topological architecture of highly dilute alloy surfaces is crucial to achieving catalytic performance tailored to a specific application. This Thesis employs density functional theory, kinetic Monte Carlo and microkinetic modelling in order to investigate ways of manipulating the surface architecture of a number of dilute alloy surfaces towards optimal performance for key catalytic reactions. The latter include the direct dissociations of NO, CO2 and N2, and the reverse events, which are important in, among others, emission control technologies. Also examined is the potential of a Ni/Cu dilute alloy for the NO + CO chemistry, and it is demonstrated that the selectivity toward the desired products can be manipulated by tuning the size of the Ni clusters in the ensemble. The results can guide future theoretical, surface science and catalysis studies on highly dilute alloys, towards the development of superior catalysts that can efficiently accelerate chemistries of industrial significance.

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