Water dissociative adsorption on the precovered Fe (100) surface from DFT computation

The H₂O adsorption and dissociation on two kinds of the precovered Fe surface were studied by density functional theory. On the surface-1, the water molecules prefer to adsorb on the bridge and hollow sites than top sites, but there are no obvious preferred adsorption sites on the surface-2. The impurity energy difference and adsorption energy of the adsorbates are not sensitive to the adsorption orientation and height relative to the surface. Moreover, the Hirshfeld charge and the electronic density of state were analyzed. The rotation and dissociation of H₂O molecules occur on the two kinds of precovered surfaces. Some H₂O molecules are dissociated into OH and H groups. The energy barriers are from 0.4 to 1.0 eV which are consistent with the experimental data. H₂O molecule can be dissociated more easily at the H_a site on boron-precovered surface-1 than those on the phosphorus-precovered surface-1 and boron-precovered surface-2 due to the lower reaction barrier.