Position Title
University of California, Irvine
Prof. Xiaoqing Pan
Abstract
Revealing Dynamic Behaviors of Nanocatalysts by in situ Electron Microscopy
Platinum (Pt) based nanoparticles are widely used as catalysts for many chemical and electrochemical reactions such as the oxygen reduction reaction. In particular, M-Pt (M=Pd, Co, Ni, etc.) core-shell nanoparticles have proven to be promising systems yielding high activity, improved stability, and efficient utilization of Pt. Controlled formation of new and desirable shapes can further provide improved activity through access to unique facets. However, catalyst degradation during operation due to changes in morphology or shape, species loss caused by dissolution, and undesired migration of atoms remain an obstacle for these materials. Therefore, it is important to understand the dynamics of nanoparticle evolution in the liquid environment to reveal the cause and kinetics of catalyst changes. In this talk, we present in situ transmission electron microscopy (TEM) studies on the degradation of Pd@Pt nanoparticles. The etching process of core-shell nanoparticles with different shapes are imaged directly in real-time in a liquid cell in situ TEM. Different etching pathways were observed. The insights on the interaction of nanostructures with reactive liquid environments can help better engineer the surface structure to improve the stability of electrocatalysts as well as design a new porous structure that may provide more active sites for catalysis.
Biography
Xiaoqing Pan is the Henry Samueli Endowed Chair in Engineering, professor of materials science and engineering, and professor of physics and astronomy. He is also the inaugural director of the Irvine Materials Research Institute (IMRI), and founding director of the Center for Complex Active Materials – an NSF MRSEC. Pan is an internationally recognized materials scientist and electron microscopy expert due to his pioneering development and applications of novel transmission electron microscopy (TEM) methods for probing the atomic scale structure, properties and dynamic behaviors of materials. His work has led to the discoveries of new materials and novel functionalities. Pan has received the NSF CAREER Award and the Chinese NSF’s Outstanding Young Investigator Award. He is an elected fellow of the American Ceramic Society, American Physical Society, Microscopy Society of America, and the Materials Research Society. He has published over 400 peer-reviewed scientific papers in high impact journals.