报告人：斯坦福大学崔毅教授的博士生孔德圣博士
时间：2014年2月25日上午10：00
地点：唐楼A313
ABSTRACT
Metal chalcogenides is a large family of functional materials with rich physical and chemical properties depending on their compositions, dimensions and phases, which find broad range applications in electronics, optoelectronics and energy conversion/storage. In my PhD research, I developed several techniques to synthesize nanostructures of several chalcogenide materials in a horizontal tube furnace reactor. These nanomaterials are applicable for topological insulator electronic devices and hydrogen evolution reaction as electrocatalysts.
In the first part of my talk, I will introduce my research on chalgoenide topological insulators. Topological insulators are narrow-gap semiconductors with metallic electronic states always present at their surfaces. The unique property of topological surface states is that the spins of electrons are determined by their moving direction. Such unusual spin texture gives rise to many unusual properties of surface carriers. Several chalcogenides are indentified as topological insulators based on theoretical calculations and spectroscopic measurements. However, there are many challenges to make use of their exotic properties in functional devices. In my research, I developed several synthesis techniques to grow nanostructures of these chalcogenides with controlled morphology and compositions. These nanomaterial are used in electronic device studies. My research addressed some key material challenges to probe and access the surface electronic properties of these chalcogenides.
The second part of my talk will focus on developing chalcogenide materials as electrocatalyst for water splitting. With the increasing interest in using hydrogen as a sustainable and carbon-free energy carrier, there is a great need to explore and optimize new catalysts suitable for electrochemical water reduction. Some layered dichalcogenides, such as MoS2 and WS2, are chemically active electrocatalysts for hydrogen evolution reaction (HER), with the promise to replace noble metal catalysts like Pt. Previous studies have identified the edges of the molecular layers are catalytically, which opens up a rational pathway to boost the catalytic activity by increasing the exposed edge sites. My research is on developing edge-terminated thin films and nanostructures as hydrogen evolution reaction catalysts. In addition, I discovered a group of first-row transition metal dichalgenide (ME2, M = Fe, Co, Ni ; E = S, Se) catalytically active for HER. These catalysts exhibit excellent activity and stablilty that expands the family of non-precious HER catalysts.