Ethanol synthesis and water gas shift over bifunctional sulfide catalysts. Technical progress report, March 1993--May 1993
Study of preparation of MoS{sub 3}, decomposition to form MoS{sub 2}, and the Cs-containing reagents and techniques to achieve surface doping of the MoS{sub 2} with Cs was begun. Goal is to achieve a high surface area catalyst containing lower quantities of the Cs promoter in a highly dispersed state. Using high resolution electron spectroscopy for chemical analysis and solid state Extended Hueckel (EH) theory investigation and interpretation of electronic structure of MoS{sub 2} (hexagonal 2H form, 2 MoS{sub 2} molecules/unit cell) was carried out. The theoretical valence band of MoS{sub 2} was obtained by modification of density of states. Qualitative agreement theoretical and experimental MoS{sub 2} valence bands was obtained after parameterization of EH input ionization potentials H{sub ii} and Slater-type orbital (STO) double zeta coefficients c{sub i}. Theoretical energy dispersion curves 2-D and 3-D MoS{sub 2} also compared well with experimental energy dispersion curves. Highest occupied band of valence band is shown to consist of contributions not only from Mo 4d{sub z2} orbitals but also from Mo 4d{sub xy} and Mo 4d{sub x2-y2} orbitals. The theoretical systems 2-D MoS{sub 2} and 3-D MoS{sub 2}, containing zero for the former and an infinite number of Van der Waals gaps for the latter, exhibit direct and indirect gaps, respectively. Nature of 2H-MoS{sub 2} indirect gap is found to be directly linked to the interaction of crystal orbitals across Van der Waals gap between adjacent layers of MoS{sub 2} in the realistic 3-D model. Thus, the electronic properties and ability of adsorbing and activating hydrogen of very small and thin particles of MoS{sub 2} might be expected to be different from large bulk particles of MoS{sub 2}.
- Research Organization:
- Lehigh Univ., Bethlehem, PA (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG22-91PC91301
- OSTI ID:
- 10178813
- Report Number(s):
- DOE/PC/91301-7; ON: DE93040616
- Resource Relation:
- Other Information: PBD: Jun 1993
- Country of Publication:
- United States
- Language:
- English
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