Seminar Abstract:
My research group develops optical and electrochemical approaches to uncover how local structure, composition, and electronic properties govern charge transport and reactivity in energy conversion and storage materials. In the first part of this talk, I will highlight our spatially resolved studies of solar energy conversion materials, including photoelectrochemical imaging of transition metal oxide photocatalysts and optical measurements of individual quantum dots. These studies illustrate how nanoscale heterogeneity can produce substantial variations in photochemical and electrochemical behavior and motivate the need to connect local materials properties with macroscopic function.
I will then turn to two-dimensional (2D) semiconductors, where atomically thin dimensions give rise not only to spatial heterogeneity but also to electronic properties that can change dramatically under operating conditions. I will discuss our imaging studies of charge separation and reactivity in 2D materials and our recent efforts to understand how giant band-gap renormalization in monolayer transition-metal dichalcogenides contributes to their unique electrochemical behavior compared to bulk materials. Using in situ spectroelectrochemistry, electrochemistry, spatially resolved measurements, and many-body theory, we find that changes in carrier concentration can substantially renormalize the electronic band gap and alter energy-level alignment and interfacial electron-transfer rates. These results challenge conventional pictures of semiconductor interfaces in which the band structure is treated as fixed and suggest new opportunities to control reactivity, charge transport, and energy conversion through the unusual many-body physics of two-dimensional materials.
Speaker Bio:
Justin Sambur is the Monfort Associate Professor of Chemistry at Colorado State University. Justin earned his B.S. degree in 2006 from the State University of New York (SUNY)-Binghamton. His undergraduate honors thesis work under the direction of Dr. David Doetschmann focused on the degradation mechanisms of chemical warfare agents within zeolite pores. Justin traveled west to graduate school and earned his PhD under the direction of Dr. Bruce A. Parkinson at Colorado State University (CSU). Justin studied the photoelectrochemical energy conversion properties of semiconductor nanocrystals and light absorbing polymers on single crystal electrode surfaces. In 2011, Justin traveled back to NY to join Prof. Peng Chen’s lab at Cornell University. Justin’s NSF ACC-F Postdoctoral Fellow work integrated single molecule imaging methods in the area of photoelectrochemistry. Justin returned to CSU in 2016 as an Assistant Professor of Chemistry and the School of Advanced Materials Discovery (SAMD). His research has been recognized with the Royce Murray Young Investigator Award, Air Force Young Investigator Award, NSF CAREER Award, and DOE Early Career Award. Justin was also named a Sloan Research Fellow and a Scialog Fellow in Advanced Energy Storage.
