A Study of the adsorption of CO on cobalt nanostructures: Cubic and hexagonal crystalline phases

Subject Areas :

Fatemeh Dolati ¹ , ali nakhaeipoura ² , vahidreza darugar ³ , zohre Dolati ⁴ , vagehe afkhamy ⁵

1 - chemistry, ferdowsi university of mashad, mashhad, Iran
2 - Department of Chemistry, Ferdowsi University of Mashhad
3 - Department of Chemistry, Ferdowsi University of Mashhad, P.O.Box: 9177948974, Mashhad, Iran
4 - Department of Polymer, Ferdowsi University of payyam Noor, Mashhad, Iran
5 - Department of Chemistry, University of Azad Mashhad, Mashhad, Iran

Received: 2017-11-15 Accepted : 2019-04-28 Published : 2018-08-23

Keywords: Cobalt catalyst, Cubic crystalline phase, Hexagonal crystalline phase, Adsorption, DFT, Fischer&ndash, Tropsch synthesis,

Abstract :

In the present work, the adsorption energies and structures of carbon monoxide (CO) on cubic and hexagonal crystalline phases of cobalt nanoparticles has been evaluated using density functional theory (DFT) calculations. However, the general trend in Fischer- Tropsch synthesis (FTS) activities on cobalt-based catalysts is reproduced by comparing adsorption energies. The catalysts with higher fractions of hcp phase exhibited higher conversion in FTS reaction than those cobalt fcc metallic phase. For evaluation of CO adsorption energies on cobalt surfaces, we have calculated the activation energy of adsorption of CO at 1 ML (ML=monolayers) on top of cobalt atoms on cubic and hexagonal crystalline phases of cobalt nanostructures. The results predicted that, the largest adsorption energies are found for the fcc crystalline phases and hcp surface adsorbed CO with lower energies. Since the lower energy of the adsorption of CO on cobalt hcp top sites may explain the higher activity of cobalt catalysts with hexagonal crystalline phases in FTS reaction.