AVS 66th International Symposium & Exhibition
    Surface Science Division Thursday Sessions
       Session SS+2D+AP+AS+OX+SE-ThA

Paper SS+2D+AP+AS+OX+SE-ThA7
Oxide Surface Formation on Rh Nanoparticle during O2 Exposures Observed by Atom Probe Microscopy

Thursday, October 24, 2019, 4:20 pm, Room A220-221

Session: Dynamics at Surfaces/Reactions and Imaging of Oxide Surfaces
Presenter: Sten Lambeets, Pacific Northwest National Laboratory
Authors: S.V. Lambeets, Pacific Northwest National Laboratory
T. Visart de Bocarmé, Université Libre de Bruxelles, Belgium
N. Kruse, Washington State University
D.E. Perea, Pacific Northwest National Laboratory
Correspondent: Click to Email
Metallic surfaces may undergo a series of surface and subsurface structural and chemical transformations while exposed to reactive gases that inevitably change the surface properties. Understanding such dynamics from a fundamental science point of view is an important requirement to build rational links between chemical/structural surface properties and design new catalysts with desired performance or new materials with enhanced resistance to corrosion. The research presented here addresses the early oxide formation dynamics on a rhodium (Rh) single nanoparticle during O2 exposures and reveals the inter-facet cooperation between Rh{012} and Rh{113} facets, as well as the important role that the subsurface plays.

Field Ion and Field Emission Microscopies (FIM and FEM) enable correlative atomic to nanoscale imaging of the surface of a very sharp Rh needle, the apex size and shape of which models that of a Rh nanoparticle. FIM is used to map, with atomic lateral resolution, the Rh surface revealing a complex network of crystallographic facets, while FEM is used to observe and record O2 dissociative adsorption and subsequent reaction with H2 over this same surface of Rh in real-time with nano-scale lateral resolution. Since FEM imaging relies on local work function variations, it notably can be used to follow the fate of adsorbed oxygen atoms (O(ads)) on the Rh surface. As a result, we directly observe that the O2 dissociative adsorption is mainly active on the Rh{012} regions. The application of Atom Probe Tomography (APT) provided a means to map the fate of the absorbed oxygen leading to bulk oxide formation through Rh{113} facets. Thus the correlative combination of FIM, FEM, and APT provides unique insight into the mechanism of bulk oxide formation starting from the dissociative oxygen absorption occurring at {012} facets and subsurface penetration of the adsorbed oxygen occurring through {113} facets. leading to a preferential accumulation of the oxygen within the bulk along the [111] direction. This work offers a unique methodology to explore the interactions between the different crystal facets of a complex surface, to explore the complex dynamics linking the surface and the bulk, and finally, offers exciting perspectives leading to a better understanding of heterogeneous catalysis and corrosion dynamics.