Catalytic Dissociation of Water on the (001), (011), and (111) Surfaces of Violarite, FeNi2S4: A DFT-D2 Study

Abstract

The iron–nickel sulfide mineral violarite is relevant in origin of life theories and has potential catalytic activity. Here we present density functional theory simulations with a correction for the long-range interactions (DFT-D2) of the bulk and surfaces of violarite, and subsequent adsorption and dissociation of water. Relaxation of the low-Miller index surfaces shows the (001) surface to be energetically the most favorable, while the (111) is the least stable surface, but also the least reactive with respect to water. Calculation of the reaction energy pathways reveals that water adsorption is most likely to occur on the (011), as this stabilizes the low-coordinated atoms. Stronger adsorption energies are found for Fe octahedral sites, over tetrahedral Ni sites, with the dissociation of an adsorbed water molecule on the surface facilitating the adsorption of a subsequent molecule. Dissociation of water is also most likely to occur on the (011) surface, as reflected by negative values calculated for the overall reaction energies. The results ultimately show that associative adsorption of water is preferred over dissociative adsorption.