Effect of Charges on the Interaction of a Water Molecule with the Fe2O3(0001) Surface

Electronic charges can play a significant role in interaction between water and oxide surfaces, but not much is known about it. In this work, the interaction of a single water molecule with the Fe2O3(0001) surface was studied by DFT +U calculations. To simulate the charged slabs we have used two different methodologies: directly changing the total number of electrons in the supercell, while using a background charge to keep the whole slab neutral; and including guest atoms that act as donors/acceptors. We find that both approaches give similar qualitative and quantitative results, with the added electron being localized on a single Fe atom, while the hole is delocalized mainly on the surface oxygen layer. In addition, we obtain that a water molecule binds more strongly to the negatively charged surfaces when compared to the neutral case. This reduces the energy barrier and increases the enthalpy gains for water dissociation, while a hole reduces this interaction's strength and also inhibits water dissociation.