11210E500100 College of Engineering Seminar

TOPIC
▸　Construction and Catalytic Application of a Nanocrystal Library of High-Entropy Alloys

Abstract
❝　High-entropy-alloy (HEA) nanocrystals consisting of a minimum of five elements have recently emerged as a versatile family of catalysts due to immense chemical space and tunability. However, there are no effective strategies for synthesizing libraries of HEA nanocrystals with controlled surface atomic structures of exposed facets for boosting catalytic performance. Due to the distinct nucleation and growth kinetics of constituent metals and their distinctive crystal structures, it is incredibly challenging to confine five or more different metal species situated on the nanocrystal surface with a specific arrangement but also in a high-entropy random mixing state. I will present a straightforward strategy to craft a library of facet-controlled HEA nanocrystals with up to ten dissimilar metallic elements by solution-phase layer-by-layer epitaxial growth, enabling the design of 638 distinct catalysts with 5 to 10 elements in equimolar ratios. The subnanometer-thick solid-solution HEA atomic layers can be deposited epitaxially on nanocrystal seeds with {100} and {111} facets, thus achieving HEA shells with square and hexagonal atomic arrangements, respectively. The hollow HEA nanocages with ultrathin walls along a specific direction can be further fabricated via post-synthetic chemical etching. Three facet-dependent catalytic actives of HEA nanocrystals are discovered in electrocatalysis and photocatalysis, and their catalytic facets with real active sites are also identified by in situ synchrotron X-ray absorption spectroscopy and density-functional theory calculations. Our work enables facet engineering in the multi-elemental space and unveils the critical needs for their future development toward catalysis.　❞

SPEAKER
▸　Prof. Tung-Han YANG *
▸　Department of Chemical Engineering, National Tsing Hua University

Short Bio
❝　Dr. Tung-Han Yang is an assistant professor in Department of Chemical Engineering, National Tsing Hua University, Taiwan. He has published 36 journal articles and 21 of them are as first and corresponding authors in Chemical Reviews, Science Advances, PNAS, Nano Letters, ACS Nano, Angewandte Chemie International Edition, Advanced Functional Materials, Small, Chemical Science, Acta Materialia, and many others. His research works have been highlighted by NSRRC (Taiwan), Georgia Tech Research News, NSF Research News, and many other news media. Tung-Han received his B.S. in Department of Chemical Engineering from National Cheng Kung University in 2009. He then studied in Department of Materials Science and Engineering, National Tsing Hua University, and received his M.S. and Ph.D. in 2011 and 2017, respectively. In 08/2015–08/2017 and 08/2019–02/2021, he spent 3.5 years to work as a research scholar and postdoctoral fellow at Georgia Institute of Technology (with Prof. Younan Xia and Prof. Dong Qin), respectively. He starts his independent research career in Department of Chemical Engineering, National Tsing Hua University from 02/2021.　❞

TIME
▸　2023/12/05 (TUE) 13:20 ~ 15:10

VENUE
▸　Classroom 202, Chemical Engineering Building