An Atomic-Scale Mechanism of Potassium-Oxygen Redox Chemistry.

The interaction between K atoms and oxygen molecules on solid surfaces is of topical interest to oxidation-reduction processes in K-O₂ batteries. Alkali metals have one ns electron in their valence shell, making them highly chemically reactive toward oxidizing reactants. Mechanistic information on the oxygen reduction by K at the atomic level is scarce despite its key role in defining the alkali metal-O₂ battery performance. Here, we use scanning tunneling microscopy and density functional theory to investigate the reduction of a single oxygen molecule by K atoms codeposited on the Ag(111) surface. Our study provides fundamental chemical information on the binary and collective interactions between the O₂ and K atoms on metal surfaces.