K Atom Promotion of O2 Chemisorption on Au(111) Surface

Alkali atoms are known to promote or poison surface catalytic chemistry. To explore alkali promotion of catalysis and to characterize discharge species in alkali-oxygen batteries, we examine coadsorption of K and O2 on Au(111) surface at the atomic scale by scanning tunneling microscopy (STM) and density functional theory (DFT). On a clean Au(111) surface, O2 molecules may weakly physisorb, but when Au(111) is decorated with K+ ions, they chemisorb into structures that depend on the adsorbate concentrations and substrate templating. At low K coverages, an ordered quantum lattice of K2O2 complexes forms through intramolecular attractive and intermolecule repulsive interactions. For higher K and O2 coverages, the K2O2 complexes condense first into triangular islands, which further coalesce into rhombohedral islands, and ultimately into incommensurate films. No structures display internal contrast possibly because of high structural mutability. DFT calculations explain the alkali-promoted coadsorption in ter...