A Density Functional Theory Modeling Investigation into the Reaction Mechanisms of Ammonia Reduction of Iron Oxide Represented by the Fe2O3 (001) Surface

Abstract

The reaction mechanisms of NH₃ reduction of Fe₂O₃, represented by the Fe₂O₃ (001) surface with a low surface hydrogen coverage, have been studied through density functional theory (DFT) simulation. Various reaction mechanisms are first hypothesized, and then the energy barriers of each of the proposed mechanisms are calculated to determine the most probable reaction pathway. The most likely pathway for NH₃ reduction of Fe₂O₃ to form H₂O involves successive abstraction of H atoms from NH₃ adsorbed on the Fe site, which combine with an O in Fe₂O₃ (001) to form hydroxyl groups, while the H atom in remaining NH reacts with the OH to form H₂O. NH₃ dissociation to H₂ involves the H atom from the remaining NH reacting with the H atom abstracted from NH₃ and adsorbed on the O atom adjacent to the Fe site (H_ad) to form H₂. The N atom adsorbed on the Fe site can also react with the O atom adjacent to the Fe site to form NO. On the Fe₂O₃ (001) surface, the NH₃ reduction of Fe₂O₃ directly plays a dominant role in the reduction process due to the lower energy barrier.