ABSTRACT: While the properties of catalytic surfaces are often dramatically different from those of the homogenous bulk, we have incomplete knowledge of the precise atomic scale structures that give rise to unique properties even though the bulk structures are nearly always known. A two-pronged approach is necessary towards the goal of forming predictive rules for the direct design of catalytic materials. First, the activity of catalytic materials must be correlated with the atomic structures of their surfaces and support interfaces. Second, precise processing conditions must be established in order to understand the kinetics of transition pathways between structures. In both aspects of this approach, knowledge of the atomic structure of a surface is of critical importance. In this presentation, I will discuss a range of topics from UHV surface science of model systems through atomic resolution in-situ environmental imaging of real mixed-metal oxide catalytic nanoparticle systems.

Through combined experimental and theoretical studies the conditions under which the structures are formed on MgO and NiO (111) surfaces I will describe a generalizable route for the transformation between kinetically-limited metastable reconstructions involving mobile hydroxyl groups and relatively immobile cations. Furthermore, I will present results from in-situ atomic resolution environmental TEM that have been leveraged to determine the structure of the sub-monolayer oxide reconstructions that are the precursor to bulk copper oxidation, and provide insight into the kinetics of such transitions. Finally, I will discuss some recent results correlating the interfacial structure and bonding of CeOx/TiO2 interfaces of real catalytic nanoparticles with their performance in the oxygen evolution component of photocatalytic water splitting.

Prof.

ABSTRACT:
The stresses developed when soft solids are swelled in the presence of constraints can lead to a variety of different elastic shape instabilities, depending on the constraining geometry. In one example, we study the surface ‘creasing’ instability of thin layers confined in two-dimensions by attachment to a rigid substrate. We have verified that the conditions for instability are quite insensitive to both material properties and layer thickness, in agreement with simple predictions. Using temperature-responsive gels, we seek to elucidate the mechanisms of crease formation and growth, and take advantage of this instability as a way to create dynamic polymer surfaces with reconfigurable chemical patterns. In a second example, we consider the behavior of gel sheets internally constrained in their swelling through lateral variations in crosslinking. A newly developed method for patterning these materials provides access to opportunities for studying the controlled folding and buckling of gel micro-objects.

5-Apr (348 HMMB)
Prof. Darrin Pochan, Univ. Delaware

19-Apr (Sibley auditorium)
Prof. Yat Li, U.C. Santa Cruz

26-Apr (348 HMMB)
Prof. Nancy Haegel, Naval Postgraduate School