PROGRAM

Tuesday 21 December; Leiden, Mark Saeys "First principle guided design of surfaces and interfaces: Catalysts and surface tunneling junctions

Date:

 

Informal Seminar

Time: 13:30 hrs

Location: 173 OORT

abstract:

Mark Saeys, Department of Chemical and Biomolecular Engineering, National University of Singapore

Kinetic modeling and catalyst design have long been based on chemical intuition, i.e., the combination of a large empirical database and qualitative concepts relating structure and composition to function and activity. In recent years, first principle based quantum mechanical modeling has become an important tool to guide the design of materials with desired functionality. In combination with experimental validation, such a first principle guided approach has enabled dramatic progress in our understanding of technologically important surfaces and interfaces.

In this presentation, I will discuss our recent progress in three areas. First, I will illustrate how first principle based modeling can help elucidate complex catalytic reaction mechanisms. Based on DFT calculations, CO insertion via a RCH + CO step is proposed as the dominant chain growth mechanism in Fischer-Tropsch Synthesis on Co catalysts. [1] Recent surface science studies by the group of Niemantsverdriet indeed confirm that C-O bond breaking is feasible on Co terraces if a CxHy-O moiety can be formed, [2] as proposed in the CO insertion mechanism. First principle calculations can also guide the design of improved catalysts. Supported Co catalysts slowly deactivate by carbon deposition during Fischer Tropsch Synthesis. Based on first principle calculations, boron was identified as a promising promoter to prevent nucleation and growth of resilient carbon deposits. [3] Subsequent experiments indeed confirmed that small amounts of boron enhance the stability of Co catalysts without affecting activity and selectivity.

In the second part of the talk, I will discuss our recent progress towards the design and fabrication of atom scale devices on a Si(001) platform using low temperature STM [5,6]. Dangling bond states can be introduced in the surface band gap of semiconductors such as hydrogen terminated Si(001) when surface atoms are extracted using the tip of an STM. In collaboration with the Atom Technology group in Singapore, we are exploring the design of wires, tunneling junctions, and logic gates using these dangling bond states.

 

References.

1. Zhuo, Tan, Borgna, Saeys, JPC C 113, 1947 (2009)

2. Weststrate, Gericke, Verhoeven, Ciobica, Saib Niemantsverdriet, JPC Lett. 1, 1767 (2010)

3. Xu, Chen, Tan, Borgna, Saeys, J. Catal. 261, 158 (2009); Tan, Xu, Chang, Borgna, Saeys, J. Catal. 274, 121 (2010)

4. Kawai, Yeo, Saeys*, Joachim*, Phys. Rev. B, 81, 195316, (2010); Manzano, Soe, Kawai, Saeys, Joachim, Phys. Rev. Lett. (under review)

Biography

Mark Saeys obtained his PhD from Ghent University with prof. Guy Marin in 2002. Since 2003 he is a professor of chemical engineering at the National University of Singapore. During his years at Ghent University, he was a visiting scientist with prof. Matt Neurock at the University of Virginia and with prof. Bill Green at the Massachusetts Institute of Technology. For his work on gas phase radical chemistry, he received the ExxonMobil Chemical Benelux Award in 2002 and the Richard A. Glenn Award in 2003. In Singapore, he is also the associate director for academics in the Singapore-MIT Alliance-Chemical and Pharmaceutical Engineering program, a visiting professor of chemical engineering at the MIT, and holds an adjunct appointment with the Institute for Materials Research and Engineering (IMRE). He enjoys working at the interface between chemistry, physics, and engineering. His research interests include first principle based catalyst design, complex radical kinetics, and atom scale design and fabrication of electronic devices on semiconductor surfaces.

Workshops

29 March 2011 - 1 January 2021

Casimir Course - Hot Topicslink