ABSTRACT
The creation of identical microislands consisting of Ni trimers and multiples thereof on Ru(0001) induced by oxygen adsorption has been observed using scanning tunnelling microscopy. The island formation is caused by an oxygen induced expulsion of Ni atoms or trimers out of the moiré-distorted (densified) Ni monolayer. The exceptional stability of the Ni trimers is attributed to oxygen attachment, forming Ni-oxygen composites, as verified by detailed density functional theory calculations. The high density, identical structure, and notable thermal stability of these islands open up new perspectives for the study of the properties of nanostructured surfaces.
ABSTRACT
We studied simple reaction pathways of molecules interacting with Pt(111) in the presence of water and ions using density functional theory within the generalized gradient approximation. We particularly focus on the dissociation of H2 and O2 on Pt(111) which represent important reaction steps in the hydrogen evolution/ oxidation reaction and the oxygen reduction reaction, respectively. Because of the weak interaction of water with Pt(111), the electronic structure of the Pt electrode is hardly perturbed by the presence of water. Consequently, processes that occur directly at the electrode surface, such as specific adsorption or the dissociation of oxygen from the chemisorbed molecular oxygen state, are only weakly influenced by water. In contrast, processes that occur further away from the electrode, such as the dissociation of H2, can be modified by the water environment through direct molecule-water interaction.
