Water Adsorption on Na/Cu(111): State-Specific Coupling with Quantum Well States

The adsorption of water molecules on sodium-covered Cu(111) surfaces have been studied using first-principles calculations. Water molecules interact predominantly with the quantum well states of the Na overlayers, leading to charge transfer and reduction of the dissociation barrier. This interaction is state specific. At one monolayer Na coverage, the water molecule shows a maximum ratio between the adsorption energy and dissociation barrier, favoring the catalytic water splitting reaction. This conclusion is in accord with experimental observation and suggests the possibility for state-selective control of water–surface interactions.