Surface Structure and Reactivity of Ni-Based Binary Intermetallic Catalysts

Intermetallic compounds have attracted considerable interest as heterogeneous catalysts because they often exhibit superior selectivity and enhanced thermal stability compared with their pure metallic counterparts. A detailed understanding of their surface atomic structure and chemistry is therefore essential for explaining and optimising their catalytic behaviour.

This presentation reports a comprehensive investigation of the atomic structure, chemical composition, and reactivity of high-symmetry surfaces of the Ni-based binary intermetallic compounds Ni₂In₃ and Ni₂Ga₃. The study combines several complementary surface-sensitive techniques, including low-energy electron diffraction (LEED), scanning tunnelling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and low-energy ion scattering (LEIS), together with density functional theory (DFT) calculations.

Although the investigated high-symmetry surfaces exhibit subtle differences in both their atomic structure and their reactivity towards hydrogen and oxygen, they all share a common characteristic: the outermost atomic layers contain In (or Ga) atoms bonded to Ni, the catalytically active element. These observations suggest that the surface structures are stabilised by intermetallic bonding. Furthermore, the presence of isolated Ni atoms within the outermost surface layer is expected to provide well-defined active sites while minimising contiguous Ni ensembles, thereby enhancing catalytic performance.

This work was carried out through a collaboration between the University of Liverpool and the CNRS – Université de Lorraine, Nancy research groups within the European Integrated Centre for the Development of New Metallic Alloys and Compounds (ECMetAC).