It was shown that the steady-state diffusion rate of potassium atoms into a graphite surface at 1100 to 1500K increased strongly if the electric field outside the surface was directed so that no positive ions could leave the surface. This means that the thermal process of removing K atoms from a basal graphite surface was changed by the direction of the external electric field. If ions were allowed to leave the surface, most K atoms leave in the form of ions or easily ionizable Rydberg species, but if the electric field was reversed the K atoms disappeared from the surface by diffusion into the material, not by desorption. The mechanism was not yet understood in its details, but the thermal barrier for this process was the same as that required to form a Rydberg state, as shown in recent kinetic studies. It was speculated that the rate of diffusion into a metal surface could be increased by a graphite layer, which could greatly increase the hydrogen diffusion in metals used for hydrogen storage.

Electric Field Control of the Rapid Diffusion of K Atoms into a Graphite Surface. Holmlid, L., Wang, J.: Chemical Physics Letters, 1997, 268[3-4], 285-90