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

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 (Had) 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.