[CCoE Notice] Seminar: Layered MoS2 materials: Catalysis and Beyond! * AH108 * 10:30 am, Friday, February 28, 2020 * Manuel Ramos * UACJ-Instituto de Ingeniería y Tecnología, México *

[Knudsen, Rachel W]

***** Seminar *****
Department of Electrical and Computer Engineering
Materials Engineering Program
Center for Integrated Bio and Nano Systems
  February 28, 2020
10:30 a.m., Room: AH108
Layered MoS2 materials: Catalysis and Beyond!
Manuel Ramos
Departamento de Física y Matemáticas
UACJ-Instituto de Ingeniería y Tecnología, México
Abstract: The catalytic sites of cobalt promoted MoS2 catalytic materials is present in here by meaning of field emission transmission electron microscopy in scanning and transmission mode. The aim is to depict crystallographic and electronic structure on those materials. Our results indicate that sulfur termination sites are more idealistic (energetic favorable [eV]) for adsorption of sulfur-content molecules as reflected by density functional theory computer assisted calculations.
The usage of electron microscopy to determine structure/function relationships on nano-scaled catalytic materials has brought great insights, mainly when studying cobalt-promoted MoS2 unsupported catalyst1,2. On the other hand, the development of computer assisted code to determine electronic structure as based in “density” methods allows to understand many aspects such as electronic donation from cobalt into molybdenum as both shared sulfur bonding1, oxidation process and carburization aspects3. In that regards, we present in here two fundamental aspects: 1) Molecular structure of mixed phase of Cobalt sulfide and Molybdenum Sulfide (Co9S8/MoS2) based on experimental observations made by electron microscopy. 2) The catalytic sites of the as proposed molecular bulk model1. Our results indicate vertical contact between MoS2 slabs onto (111)-Co9S8 planes and the electronic structure reveals a high metallic character with sulfur termination as most active sites for adsorption of sulfur content molecules as calculated using transitional states by Halgren-Lipscomb algorithm. 3) Co/MoS2 were also synthesized by hydrothermal methods and final products highly investigated by both as mentioned techniques. Along with other investigations using atom probe tomography for MoS2/ITO Interfaces for photovoltaic engineering applications.
Our findings indicate a bulk structure as reveal by high-resolution transmission electron microscopy with (101)-MoS2 planar contact onto (111)-Co9S8 causing the slabs to nucleate vertically. The structure was subjected to carbonization in a “in-situ” operando TEM experiment and we find that carbon undergoes at sulfur edge termination provoking bending of layered material2. By density of states it was possible to determine a metallic character near Fermi level with irreducible point value of kF ~0.56Å-1 as indicated by Band Structure. The carbide phase as observed by TEM indicate carbon located at the edge, in agreement with DFT computations performed in Co/MoS2 crystal and inclusion of cobalt atoms were observed from Rietveld refinement for Co/MoS2 microspheres with radius distance of 3.17Å to 2.2Å in Mo-Mo bonding expanding the lattice3.
REFERENCES
[1] Manuel A. Ramos et al., Catal. Sci. Technol., 2012, 2, 164–178.
[2] Manuel Ramos et al. Ultramicroscopy 127:64-69 (2012).
[3] Manuel Ramos et al. Nature Scientific Reports | 7: 12322
[4] Manuel Ramos et al. MRS Communications (2019), doi:10.1557/mrc.2019.150.
 Biosketch: Prof. Dr. Manuel Ramos is a native of Cd. Juárez, Chihuahua and currently a research professor at Physics and Mathematics Department of Universidad Autónoma de Cd. Juárez. He is currently a member of Materials Research Society-USA and Sociedad Mexicana de Materiales. He has completed about 44 research JCR manuscripts in the literature. His research topics comprehends usage of microscopy and microanalysis in combination with DFT computational methods for understanding of structure/function and electronic states of catalytic materials. In 2010 obtained a Doctoral degree in Material Science and Engineering from University of Texas at El Paso, in 20006 a Master´s degree in Mechanical Engineering from Florida A&M-Florida State University and in 2003 a Bachelor in Science-Physics from UT-El Paso. He is currently a review contributor for Catalysis Today, Catalysis Science and Technology, ACS-Catalysis and FUEL. Member of Sistema Nacional de Investigadores from CONACyT-México and independent research consultant in USA.  And has served as special issue guest editor for Journal of Materials Research, Catalysis Today and MRS-Advances.
Contact Prof. Robles Hernandez at fcrobles at Central.UH.EDU<mailto:fcrobles at Central.UH.EDU> if you would like to meet with Prof. Ramos.
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