Mechanistic Insights into the Effect of Ca on the Oxidation Behavior of Fe₃O₄: A Combined DFT and AIMD Study

With the increasing adoption of traveling grate machines, increasing the proportion of pellets in blast furnace burdens has become a key strategy for reducing carbon emissions in ironmaking. Magnetite (Fe₃O₄) is not only the core raw material for pellet production but also serves as an important transition metal oxide catalyst, widely used in various fields due to its unique electronic structure and surface activity. This study employed density functional theory (DFT) and ab initio molecular dynamics (AIMD) to simulate the oxidation process of a Ca-doped Fe₃O₄ (110) surface at 1073 K, revealing the inhibition mechanism of the gangue element Ca and its impact on surface catalytic activity at the atomic scale. The results demonstrate that Ca segregates on the Fe₃O₄ surface, where it adsorbs and activates O₂ molecules, thereby delaying O₂ migration to active iron bridge sites and subsequent dissociation, which ultimately inhibits the oxidation kinetics. Electronic structure analysis indicates that the breakage of the O-O bond is accompanied by a sharp decrease in system energy (stabilizing at approximately −509 eV); it also clearly elucidates the charge transfer process and the mechanism of Fe-O bond formation during this exothermic reaction. This research provides a theoretical foundation for the development of fluxed pellets and high-temperature-resistant catalysts.