Seminar:

Friday April 10, 2020, 4:00 PM

Dr. Justin Sambur - Assistant Professor, Department of Chemistry, School of Advanced Materials Discovery (SAMD), Colorado State University, Fort Collins

Photo: Seminar:

Profile: Dr. Justin Sambur returned to his alma mater in August 2016 as an Assistant Professor in Analytical Chemistry.  His research focuses on using single-molecule imaging methods to study single-particle photoelectrocatalysis.Dr. Sambar was a NSF ACC-F Postdoctoral Fellow  at Cornell University in the laboratory of Dr. Peng Chen. He earned a Ph.D. in chemistry in 2011 at Colorado State University under the guidance of Dr. Bruce Parkinson.  He earned a B.S. in chemistry at SUNY-Binghamton in 2006. Check out some of his articles: Influence of single-nanoparticle electrochromic dynamics on the durability and speed of smart windowsand  Probing Charge Carrier Transport and Recombination Pathways in Monolayer MoS2/WS2 Heterojunction Photoelectrodes

Abstract: Energy needs and environmental trends demand a large-scale transition to clean, renewable energy. Nanostructured materials are poised to play an important role in this transition. However, nanomaterials are chemically and structurally heterogeneous in size, shape, and surface structural features. My research group focuses on understanding the correlation between nanoparticle chemistry/structure and functional properties. The first part of my talk will focus on characterizing charge storage mechanisms in single nanoparticles. My lab has developed a high-throughput electro-optical imaging method to selectively probe the battery-like and capacitive-like (i.e., pseudocapacitive) contributions to overall charge stored in single metal oxide nanoparticles. Pseudocapacitors are a promising class of electrochemical energy storage materials that behave electrochemically like capacitors even though the underlying charge storage mechanism is faradaic in nature (like a battery). Pseudocapacitors have the potential to charge/discharge at capacitor-like rates and maintain high energy density. A major challenge in the field is to demonstrate that pseudocapacitors behave electrochemically like a capacitor and the charge storage process is faradaic in nature. It is challenging to do so because pseudocapacitive charging has the same electrical signatures as non-faradaic electrical double layer charging. I will present our recent single particle-level measurements that reveal structure-property relationships that are hidden in ensemble-level measurements. The second part of my talk will focus on solar energy conversion using ultrathin semiconductors such as monolayer-thick (ML) two-dimensional (2D) materials such as MoS2 and WS2. ML semiconductors represent the ultimate miniaturization limit for lightweight and flexible power generation applications. However, the underlying solar energy conversion processes in 2D materials are not entirely understood. We developed a correlated laser reflection and scanning photocurrent microscopy approach to study how layer thickness and surface structural features (edges versus basal planes) influence solar energy conversion efficiency. I will highlight our recent wavelength-dependent photocurrent microscopy and current-voltage measurements that revealed charge separation, transport, and recombination pathways in monolayer heterojunction ITO/MoS2/WS2 and ITO/WS2/MoS2 photoelectrodes.