The role of oxidation states in the hydroxylation reaction on manganese oxide thin films

Abstract

Water interaction with material surfaces is known to be fundamental for countless technological applications. To explore the initial and fundamental steps on water/oxides interfaces, the hydroxylation reaction was investigated on wellordered MnO(001) and Mn3O4(001) surface model systems. These manganese oxide surfaces exhibit cations with distinct oxidation states that play a role in the hydroxylation reaction. Based on X-ray photoelectron spectroscopy at near-ambient pressure, hydroxyl and water molecules are identified on both surfaces. Applying a fitting model considering the different multiplets of the Mn 2p, it was shown that the Mn2+ cation on the MnO(001) surface is an active site whose associated satellite intensity is affected after the hydroxylation reaction. Nevertheless, on Mn3O4(001), the Mn2+ and Mn3+ cations have their component intensities affected only under water pressure.