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L1.03 - Nucleation and Growth of Secondary Phases on Electrochemically-Active, Perovskite-Oxide Surfaces 
April 22, 2014   9:15am - 9:30am

The oxygen evolution (OER) and reduction reactions (ORR) are ubiquitous in many energy conversions. Of particular interest are reactions that take place over the solid/gas interface, for example, in elevated-temperature solid oxide fuel cells and electrolyzers operating at 500-800°C. Despite that OER and ORR generally dominate the overpotential in these electrochemical cells, an in-depth understanding of what controls reaction rate has not been achieved yet. In particular, the formation of secondary phases at the surface of electrocatalysts due to cation segregation and phase separation are believed to influence OER and ORR rates strongly.Here, we combine in-situ and ex-situ microscopy and spectroscopy techniques to follow the formation and growth of such secondary phases at the surface of perovskite (ABO) electrocatalysts. A compositional range of dense, epitaxial thin film electrodes were grown by pulsed-laser deposition. The nucleation and growth of secondary phases were observed by in-situ environmental SEM as a function of temperature and oxygen partial pressure. Auger microscopy was also used to link surface morphology to the nanoscale chemical composition. These results were combined with current-voltage measurements to assess the formation pathway of secondary phases and their impact on OER and ORR rates.

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Keynote Address
Panel Discussion - Different Approaches to Commercializing Materials Research
Business Challenges to Starting a Materials-Based Company
Fred Kavli Distinguished Lectureship in Nanoscience
Application of In-situ X-ray Absorption, Emission and Powder Diffraction Studies in Nanomaterials Research - From the Design of an In-situ Experiment to Data Analysis