Insights in Controlling Reactivity from Atomic Level Characterization of Surfaces and Interfaces

Bruce E. Koel
Professor of Chemical and Biological Engineering
Princeton School of Engineering and Applied Science

Interfacial chemical reactions in a wide range of applications including heterogeneous catalysis, electrochemistry, sensing, and sequestration are controlled by the composition and nanoscale structure of surfaces and interfaces. New insight into the nature of reactive sites at metal alloy surfaces and oxide-metal interfaces can be obtained by exploiting the ability to characterize both practical materials and single-crystal surfaces at the atomic level. Dr. Koel will present illustrative results for two energy and environmental materials applications: (i) Pd-Fe alloys for the oxygen reduction reaction (ORR) in PEM fuel cells, and (ii) iron nanoparticles for arsenic sequestration in environmental remediation. Scanning tunneling microscopy (STM) of Pd3Fe(111) surfaces revealed the formation of Pd adatoms on top of the outmost alloy layer, in contrast to other well-studied binary alloy systems, which may play a role in enhancing ORR kinetics on this alloy. Investigations of reactions between nanoscale zero-valent iron (nZVI) and arsenite (As(III)) using high-resolution X-ray photoelectron spectroscopy (HR-XPS) demonstrated for the first time stratified distributions of multiple arsenic valence states within the iron nanoparticles and revealed that As(III) oxidation and reduction can occur in parallel in separate regions of the nanoparticles.

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Sponsored by the Department of Chemistry.