[CCoE Notice] [CCOE Notice] MS Thesis Presentation

[Abercrombie, Irene F]

MS Thesis Defense
Carbon Monoxide Adsorption on Pt Monolayer on Pd(hkl) Surface Studied by Subtractivelly Normalized Interfacial Fourier Transform Infra-red Spectroscopy
Milan Slavkovic
Date: Monday, July 30, 2012

Location: Electrical & Computer Engineering Conference Room - N-328
Time: 12:30 PM

Committee Co-chair: Dr. Metin Akay
Committee Co-Chair: Dr. Stanko Brankovic
Committee Member: Dr. Ting Chen


The progress of our civilization is critically dependent on the discovery of new materials and structures with better properties, novel functionality and applications. In the last two decades, the world has seen significant progress in synthesis of low-dimensional structures with properties considerably different from those of the bulk materials. The ultra-thin metal overlayers represent one class of such structures with increasing application in fuel cells. The physical and chemical behavior of ultra-thin metal overlayers is altered due to different structural and electronic effects dominating their properties. The ultimate configuration of ultra-thin catalyst overlayers in terms of their specific activity is the monolayer configuration where every catalyst atom is on the surface. In monolayer configuration the catalyst "feels" ligand effect most strongly identifying substrate importance to achieve the desired catalyst properties.
In our work, the two-dimensional Pt monolayers on Pd(hkl) (PtML/Pd(hkl)) were used as model system to study CO adsorption. The PtML/Pd(hkl) were obtained using surface limited red-ox replacement reaction (SLRR) of underpotentially deposited Cu monolayers on Pd(hkl) with, and without presence of citrate in the reaction solution. The morphology of Pt monolayer was characterized by exsitu scanning tunneling microscopy combined with statistical image analysis identifying significance of citrate ions for improved uniformity of Pt monolayers.  The strength of the CO adsorption on Pt monolayer (CO-PtML/Pd(hkl) bond) was studied by subtractivelly normalized interfacial fourier transform infra-red spectroscopy (SNIFTIRS). The SNIFTIRS results indicate synergistic effect of both; Pt monolayer and Pd(hkl), yielding a qualitatively new phenomenon where the bond of adsorbed CO on PtML/Pd(hkl) is weaker than the corresponding CO bond on each of the bulk metal surfaces (CO-Pt(hkl) and CO-Pd(hkl)). This result has fundamental importance when catalysts for oxygen reduction and hydrogen oxidation reactions are considered where the surface poisoning by intermediates or impurities is responsible for reduced catalyst activity.


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