Competing routes for charge transfer in co-adsorption of K and O2 on graphite.

Abstract

We have investigated a model co-adsorption system using electron energy loss spectroscopy. When the dispersed phase of K/graphite is exposed to O 2 at 25 K, the charge donated by the alkali is depleted, as evidenced by a reduction of the surface plasmon energy from ∼320 to ∼130 meV. The co-adsorbed O 2 species is molecular, with a vibrational frequency consistent with the 2 Π g ground state of O 2 - . The results demonstrate local transfer of charge from alkali to co-adsorbate, consistent with a simple electrostatic model. By contrast, CO perturbs the K-graphite interaction only weakly