A DFT-based study of carbon monoxide adsorption on osmium (0001) and osmium (1121) surfaces for Fischer-Tropsch synthesis

• Main Author: Rivas, Hiromi
• Format: text
• Language: English
• Published: Animo Repository 2019
• Subjects: Carbon monoxide—Absorption and adsorption; Fischer-Tropsch process; Osmium; Biological and Chemical Physics
• Online Access: https://animorepository.dlsu.edu.ph/etd_masteral/6177; https://animorepository.dlsu.edu.ph/context/etd_masteral/article/13226/viewcontent/Rivas_Revised_Thesis2.pdf
• Institution: De La Salle University

The most commonly used catalysts in FT synthesis are transition metals, which involves iron, cobalt, and ruthenium. On the other hand, osmium (Os) belongs to group 8 elements together with iron and ruthenium a hexagonal close-packed crystal structure like cobalt and ruthenium, with greater lattice parameters. This study focused on the initiation stage of the FT synthesis where carbon monoxide (CO) is adsorbed on the metal surface. This study determined adsorption energy of CO/Os system for each adsorption site on both surfaces of osmium, the dissociation energy of the oxygen, their corresponding density of states and charge difference profiles with the use of Density Functional theory implemented by VASP. The results showed that the density of states of osmium exhibits symmetry between the spin up and spin down states. Presence of states in the Fermi level was also observed, indicating that osmium is a non-magnetic metal. The calculated adsorption energy on the most preferred site for each surface was -2.04 eV and -2.07 eV respectively, while the calculated dissociation energy was -8.44 eV and -9.31 eV for Os (0001) and Os 1121 respectively. Osmium (0001) was a better surface for FT synthesis compared to Os 1121