Screening the bulk properties and reducibility of Fe-doped Mn2O3 from first principles calculations

Abstract

Manganese oxides, particularly Mn2O3, have demonstrated great potential for oxygen carrier materials in chemical looping applications. The application of these materials in the industrial scale is hindered by thermodynamic restrictions related to the reoxidation process. This disadvantage can be overcome by doping the oxide with a guest cation. Iron is one of the most promising dopants, but the atomic-level understanding of its effects on the properties of α-Mn2O3 is incomplete. Herein, we report a systematic GGA+U study of the bulk properties and reducibility of FexMn2-xO3 (0 ≤ x ≤ 2) as a function of Fe dopant concentration. In particular, we focus on a representative set of 20 models with different Fe content, generated by screening several thousand structures. Our results indicate that substitution of Mn atoms with Fe stabilizes FexMn2-xO3, which is visible through negative values of doping energies, decreasing oxide formation energies, and higher oxygen vacancy formation energies with increasing Fe concentration. Similar to Fe, the presence of an oxygen vacancy increases the band gap in the major spin channel of FexMn2-xO3. Oxygen transport in FexMn2-xO3 is found to depend on Fe content and distribution in the lattice. All in all, our findings provide atomic-level insight into the properties of FexMn2-xO3 and generally agree with experimental observations. Obtained information can be applied to investigate the reactivity of FexMn2-xO3.