Changes in CO2 Adsorption Affinity Related to Ni Doping in FeS Surfaces: A DFT-D3 Study

Abstract

Metal sulphides constitute cheap, naturally abundant, and environmentally friendly materials for energy storage applications and chemistry. In particular, iron (II) monosulphide (FeS, mackinawite) is a material of relevance in theories of the origin of life and for heterogenous catalytic applications in the conversion of carbon dioxide (CO2) towards small organic molecules. In natural mackinawite, Fe is often substituted by other metals, however, little is known about how such substitutions alter the chemical activity of the material. Herein, the effect of Ni doping on the structural, electronic, and catalytic properties of FeS surfaces is explored via dispersion-corrected density functional theory simulations. Substitutional Ni dopants, introduced on the Fe site, are readily incorporated into the pristine matrix of FeS, in good agreement with experimental measurements. The CO2 molecule was found to undergo deactivation and partial desorption from the doped surfaces, mainly at the Ni site when compared to undoped FeS surfaces. This behaviour is attributed to the energetically lowered d-band centre position of the doped surface, as a consequence of the increased number of paired electrons originating from the Ni dopant. The reaction and activation energies of CO2 dissociation atop the doped surfaces were found to be increased when compared to pristine surfaces, thus helping to further elucidate the role Ni could have played in the reactivity of FeS. It is expected that Ni doping in other Fe-sulphides may have a similar effect, limiting the catalytic activity of these phases when this dopant is present at their surfaces.

Theoretical Research on the Reduction of CO2 with H2S on Pyrite FeS2 Surfaces

“…Therefore, based on the results presented in this study, it can be concluded that the reactivity of Fe atoms around the S vacancy is significantly higher compared to those on the perfect pyrite surface. Živković et al [22] studied the adsorption behaviors of the CO 2 molecule on the FeS (011) surface-terminated Fe atoms and also found the Fe-O and Fe-C bonds. The difference in Fe atoms between the pyrite surface and the FeS surface is the amount of coordination.…”

“…Previous studies have extensively investigated the adsorption of CO 2 on various metal oxide [34,35] and sulfide surfaces [22,36]. For instance, Khaledialidusti et al [36] studied the adsorption behavior of CO 2 on the chalcopyrite (110) surface and reported both molecular and dissociative adsorption.…”

“…As a widely occurring sulfide ore in nature, pyrite has been a hot topic of research [14][15][16][17][18][19][20][21][22][23][24][25][26]. However, defects such as impurity-bearing and vacancy are often observed in the mineralization of pyrite.…”

Is the reactivity of calcium carbonate fully understood?

“…Nonetheless, AIMD and DFT are used to study for instance relative stabilities (Li et al, 2009), adsorption behavior (Zivković et al, 2021), and crystal defects (Živković and De Leeuw, 2020). In the need to study larger-scale problems where AIMD methods fall short, atomistic force fields are generally a suitable alternative.…”