First-Principles Modeling of Direct versus Oxygen-Assisted Water Dissociation on Fe(100) Surfaces

The O–H bond breaking in H2O molecules on metal surfaces covered with pre-adsorbed oxygen atoms is an important topic in heterogeneous catalysis. The adsorption configurations of H2O and relevant dissociation species on clean and O-pre-adsorbed Fe(100) surfaces were investigated by density functional theory (DFT). The preferential sites for H2O, HO, O, and H were investigated on both surfaces. Both the first H abstraction from adsorbed H2O and the subsequent OH dissociation are exothermic on the O-pre-adsorbed Fe(100) surface. However, the pre-adsorbed O significantly reduces the kinetics energy barriers for both reactions. Our results confirmed that the presence of pre-adsorbed oxygen species could significantly promote H2O dissociation.