Hydrogen and Ammonia Co-Adsorption on (1 1 1) and Pd(1 1 1) ( = Pd, Ru, Ag, Au, Cu) Surfaces.

Ammonia (NH) represents a promising zero-emission fuel in hydrogen fuel cells. Membrane reactors for NH decomposition based on Pd-alloys have demonstrated high NH conversion, high hydrogen diffusivity, and high hydrogen selectivity, which allows for the production of high-purity H without the need for gas separation or purification. However, it is observed that Pd-alloy membranes are to a various degree prone to H flux inhibition in the presence of NH. Hence, finding proper means to tailor the surface adsorption properties through, e.g., alloying is imperative to further improve the technology. In the current work, hydrogen and ammonia co-adsorption phenomena on (1 1 1) and Pd(1 1 1) ( = Pd, Ru, Ag, Au, Cu) surfaces are studied using density functional theory calculations. It is shown that the surface adsorption properties are strongly dependent on the surface composition, which can be linked to the corresponding electronic structure at the membrane surface.