Issue 1, 2023

Co and Ni single sites on the (111)n surface of γ-Al2O3 – a periodic boundary DFT study

Abstract

The influences of increasing the number of d-electrons in the single metal (Fe-like) substituted (111)n surface of γ-Al2O3 on its possible catalytic effects were explored. The energetic properties, local structures, and in-site electron configurations of the most active tri-coordinated Co and Ni single-site (111)n surface of γ-Al2O3 have been studied using the density functional theory (DFT) approach under periodic boundary conditions. The replacement of Al by a Co or Ni atom on the I position of the (111)n surface leads to significant elongations of metal–O distances. The energy released from the substitution process on the AlI site of the (111)n surface follows the sequence NiI (164.85 kcal mol−1) > CoI (113.17 kcal mol−1) > FeI (44.30 kcal mol−1). The triplet and quintet (ground state) of the CoI substituted complex are energy degenerate. Also, the doublet and quartet (ground state) of the NiI substituted complex have the same stable energy. This energy degeneracy comes from the α–β electron flipping on the p-orbital of the neighboring O that is next to the substituted CoI or NiI site on the (111)n surface of γ-Al2O3. Different from the FeI substituted single-site (111)n surface, in which the electron configuration of FeI varies according to its spin-multiplicity state, substituted NiI has a unique d8 electron configuration in all three spin states, and similarly, CoI has a unique d7 electron configuration in all three open shell spin states. An increase of the population of d-electrons in the single metal substituted (111)n surface of γ-Al2O3 is likely to provide a more stable electron configuration in the metal catalytic center.

Keywords: Co substituted surface of γ-Al2O3; Ni substituted surface of γ-Al2O3; (111)n surface; Periodic boundary DFT approach; Metal catalytic center.

Graphical abstract: Co and Ni single sites on the (111)n surface of γ-Al2O3 – a periodic boundary DFT study

Supplementary files

Article information

Article type
Paper
Submitted
03 nov 2022
Accepted
05 jan 2023
First published
10 jan 2023
This article is Open Access
Creative Commons BY license

Ind. Chem. Mater., 2023,1, 117-128

Co and Ni single sites on the (111)n surface of γ-Al2O3 – a periodic boundary DFT study

J. Gu, J. Wang and J. Leszczynski, Ind. Chem. Mater., 2023, 1, 117 DOI: 10.1039/D2IM00039C

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