Materials Science Research Lecture

***Refreshments at 3:45pm in Noyes lobby

Abstract:

Nanoscale materials often change morphology, crystal structure, or chemical states, especially in solution processes, which impact properties of the materials. Thus, an understanding of nanoscale materials transformations is significant to the synthesis and various applications of materials, such as batteries, catalysis, and so on. We have developed an in-situ liquid phase transmission electron microscopy (TEM) platform to investigate materials transformation dynamics at the atomic level and to elucidate how atomic scale heterogeneity and fluctuations at solid-liquid interfaces influence the transformation pathways. In this talk, I will highlight some breakthroughs in our ability to capture the atomic level structural and chemical changes of materials in solution processes, which have provided unprecedented opportunities to resolve the underline mechanisms. In the first part of my talk, I will show by tracking single particle growth trajectories our in-situ studies reveal the significance of heterogeneity and defects, as well as kinetic factors, in the formation of nanoscale materials. Insights garnered from this research have contributed to finding new strategies for controlling nanoscale reactions in materials synthesis. The second part of my talk will be focused on dynamic phenomena at electrified solid-liquid interfaces, such as catalyst evolution during electrocatalytic reactions. With our development of novel electrochemical liquid cell TEM, we track Cu-based catalysts evolution and atomic dynamics of electrified solid-liquid interfaces during CO2 reduction reaction (CO2RR). Intermediate structures, mass loss of Cu, and unique transformation pathways of the Cu-based catalysts have been captured. Control experiments have also demonstrated that intermediates can be utilized for enhanced carbon-carbon coupling, thus improving the catalytic performance.

More about the Speaker:

Haimei Zheng is a senior scientist in Materials Sciences Division at Lawrence Berkeley National Laboratory (LBNL), and she is also an adjunct professor in Department of Materials Science and Engineering at University of California (UC), Berkeley. She received her Ph.D. degree from University of Maryland, College Park in Material Science and Engineering, advised by Prof. Lourdes Salamanca-Riba and Prof. Ramamoorthy Ramesh (2001-2004). She moved with Prof. Ramesh to UC Berkeley and completed her Ph.D. study at Berkeley (2004-2006); subsequently, she did her postdoctoral research (2006-2010) with Dr. Ulrich Dahmen in National Center for Electron Microscopy at LBNL and Prof. Paul Alivisatos in Chemistry Department at UC Berkeley. In 2010, she started her independent research group in Materials Sciences Division at LBNL.

Her research interests are broadly in physical and chemical processes of materials, with a focus on nanoscale materials transformations and dynamic phenomena at solid-liquid interfaces by developing and applying in-situ liquid phase transmission electron microscopy (TEM). She received DOE Office of Science Early Career Award in 2011, LBNL Director's Award for exceptional scientific achievements in 2013, MRS Medal Award in 2019. She was named an MRS Fellow in 2021, and a Fellow of Microscopy Society of America (MSA) in 2023.