A density functional study of atomic oxygen and water molecule adsorption on Ni(1 1 1) and chromium-substituted Ni(1 1 1) surfaces

Density functional theory (DFT) for generalized gradient approximation calculations has been used to study the adsorption of atomic oxygen and water molecules on Ni(1 1 1) and different kind of Ni–Cr(1 1 1) surfaces. The fcc hollow site is energetically the most favorable for atomic oxygen adsorption and on top site is favorable for water adsorption. The Ni–Cr surface has the highest absorption energy for oxygen at 6.86 eV, followed by the hcp site, whereas the absorption energy is 5.56 eV for the Ni surface. The Ni–O bond distance is 1.85 Å for the Ni surface. On the other hand, the result concerning the Ni–Cr surface implies that the bond distances are 1.93–1.95 Å and 1.75 Å for Ni–O and Cr–O, respectively. The surface adsorption energy for water on top site for two Cr atom substituted Ni–Cr surface is 0.85 eV. Oxygen atoms prefer to bond with Cr rather than Ni atoms. Atomic charge analysis demonstrates that charge transfer increases due to the addition of Cr. Moreover, a local density of states (LDOS) study examines the hybridization occurring between the metal d orbital and the oxygen p orbital; the bonding is mainly ionic, and water bonds weakly in both cases.