Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Review
. 2018 Jan 13;376(2110):20170065.
doi: 10.1098/rsta.2017.0065.

Reactivity of CO 2 on the Surfaces of Magnetite (Fe 3 O 4), Greigite (Fe 3 S 4) and Mackinawite (FeS)

Affiliations
Free PMC article
Review

Reactivity of CO 2 on the Surfaces of Magnetite (Fe 3 O 4), Greigite (Fe 3 S 4) and Mackinawite (FeS)

David Santos-Carballal et al. Philos Trans A Math Phys Eng Sci. .
Free PMC article

Abstract

The growing environmental, industrial and commercial interests in understanding the processes of carbon dioxide (CO2) capture and conversion have led us to simulate, by means of density functional theory calculations, the application of different iron oxide and sulfide minerals to capture, activate and catalytically dissociate this molecule. We have chosen the {001} and {111} surfaces of the spinel-structured magnetite (Fe3O4) and its isostructural sulfide counterpart greigite (Fe3S4), which are both materials with the Fe cations in the 2+/3+ mixed valence state, as well as mackinawite (tetragonal FeS), in which all iron ions are in the ferrous oxidation state. This selection of iron-bearing compounds provides us with understanding of the effect of the composition, stoichiometry, structure and oxidation state on the catalytic activation of CO2 The largest adsorption energies are released for the interaction with the Fe3O4 surfaces, which also corresponds to the biggest conformational changes of the CO2 molecule. Our results suggest that the Fe3S4 surfaces are unable to activate the CO2 molecule, while a major charge transfer takes place on FeS{111}, effectively activating the CO2 molecule. The thermodynamic and kinetic profiles for the catalytic dissociation of CO2 into CO and O show that this process is feasible only on the FeS{111} surface. The findings reported here show that these minerals show promise for future CO2 capture and conversion technologies, ensuring a sustainable future for society.This article is part of a discussion meeting issue 'Providing sustainable catalytic solutions for a rapidly changing world'.

Keywords: density functional theory; iron oxide; iron sulfides; reaction mechanisms; spinel; surface science.

Conflict of interest statement

We have no competing interests.

Figures

Figure 1.
Figure 1.
(a) Conventional unit cell of Fe3S4 showing the cubic spinel crystal structure. Note that Fe3O4, the isostructural oxide counterpart of Fe3S4, is not displayed. (b) Schematic of the tetragonal unit cell of FeS. Tetrahedral FeA atoms are in light blue, octahedral FeB atoms are in dark blue and S atoms are in yellow. Atoms belonging to the neighbouring unit cells are represented as sticks. (Online version in colour.)
Figure 2.
Figure 2.
CO2 adsorbed to the Fe3O4{111} surface, showing (a) top view and (b) side view. Tetrahedral FeA atoms are in light blue, octahedral FeB atoms are in dark blue, C atoms are in cyan and O atoms are in red. Surface atoms are represented as sticks and the CO2 molecule is represented as balls and sticks. Interatomic distances are shown in Å and angles are shown in °. (Online version in colour.)
Figure 3.
Figure 3.
CO2 adsorbed to the Fe3S4{111} surface, showing (a) top view and (b) side view. Tetrahedral FeA atoms are in light blue, octahedral FeB atoms are in dark blue, S atoms are in yellow, C atoms are in cyan and O atoms are in red. Surface atoms are represented as sticks and the CO2 molecule is represented as balls and sticks. Interatomic distances are shown in Å and angles are shown in °. (Online version in colour.)
Figure 4.
Figure 4.
CO2 adsorbed to the FeS{111} surface, showing (a) top view and (b) side view. Tetrahedral FeA atoms are in light blue, S atoms are in yellow, C atoms are in cyan and O atoms are in red. Surface atoms are represented as sticks and the CO2 molecule is represented as balls and sticks. Interatomic distances are shown in Å and angles are shown in °. (Online version in colour.)
Figure 5.
Figure 5.
Charge density flow (ρ) for the CO2 molecule adsorbed on (a) the Fe3O4{111} and (b) the FeS{111} surfaces. Electron density gain and depletion surfaces are in orange and purple, respectively. Isosurfaces display a value of ±0.009 e Å−3. Tetrahedral FeA atoms are in light blue, octahedral FeB atoms are in dark blue, S atoms are in yellow, C atoms are in cyan and O atoms are in red. Surface atoms are represented as sticks and the CO2 molecule is represented as balls and sticks. (Online version in colour.)
Figure 6.
Figure 6.
Reaction profile for the dissociation of the CO2 molecule on the Fe3O4{001} and {111} and FeS{001} surfaces. (Online version in colour.)

Similar articles

See all similar articles

Cited by 1 article

Feedback