Electropumping of Na from or to a Na-beta" alumina solid electrolyte contacted with a thin film porous copper electrode results in fully reversible transport of Na to or from the vacuum-exposed Cu surface. The extent of pumping is controlled by the potential of the catalyst film (V-WR), measured with respect to a reference electrode. The time constants of these spill over and reverse spill over processes are short compared with 1 min. Photoelectron microscopy suggests that the spatial distribution of Na is fairly uniform. Over an extended range of catalyst potential (Delta V-WR similar to 1 V), both the Na coverage (V-Na) and the Cu work function (phi) scale linearly with VWR This is the same regime over which the rate and nitrogen selectivity of the Cu-catalyzed CO+NO reactions are greatly increased. The maximum Na coverage achieved by electro-pumping is similar to 0.06 monolayer, commensurate with the corresponding catalytic response of the system. At sufficiently high positive values of V-WR, this quantity becomes uncoupled from Delta phi, theta(Na), and the catalytic behavior. The possible origin of this uncoupling effect is discussed and a consistent explanation offered for the phenomenon of electrochemical promotion.