DFT Study of Oxidation States on Pyrite Surface Sites

Abstract

Density functional calculations have been performed to study the interaction of oxygen with clean and defective pyrite (100) surfaces. Molecular adsorption states are predicted to undergo dissociation because atomic chemisorption is far more favorable thermodynamically for all surfaces. On the defect-free FeS2 surface molecular adsorption takes place on neighboring iron sites in a side-on fashion. S-adatoms react weakly with O2, whereas S-vacancies bind very strongly to molecular oxygen. Dissociative chemisorption on a clean surface prefers the sulfur atoms to iron in sharp contrast to water adsorption. Reaction with atomic oxygen is thermodynamically preferred on the defect sites when they are available. Oxidation can fully eliminate the S-adatom sites by SO2 formation. The most favorable sites for oxidation are sulfur vacancies where O atoms can occupy the missing sulfur sites. The predicted oxidation states and their relative stabilities are in agreement with experiments and expected to assist the inte...