Bimetallic core-shell catalysts, combining a core of one metal and a one-atom thick layer of another, can be more effective than either metal alone. However, rationally designing new catalysts of this class requires a better understanding of their mode of action.

Dionisios G. Vlachos and Wei Guo, University of Delaware, Newark, DE, USA, have used density functional theory calculations and Monte Carlo simulations to elucidate the mechanism of ammonia decomposition using nickel monolayers on a platinum (111) host surface. The results of the study indicate that a presumably “defective” patched distribution of nickel on the surface performed better as a catalyst than a “perfect” closed nickel surface.

The team explained this phenomenon by the characteristics of the active sites: patches on the surface provide both nickel terraces and edges, which show different catalytic activity. While the terraces catalyze N−H bond breaking, the edges of the nickel patches facilitate the formation of N₂. The results provide new oppurtunities for catalyst design, and the researchers are planning to investigate both other bimetallic materials and different reactions.

• Patched bimetallic surfaces are active catalysts for ammonia decomposition,
  Wei Guo, Dionisios G. Vlachos,
  Nature Commun. 2015, 6, 8619.
  DOI: 10.1038/ncomms9619