Nanocatalysis inspired by Enzymatic Cofactors

Fig. 1 : UHV chamber equipped with standard sample preparation utilities and analysis instrumentation such as a low temperature scanning tunneling microscope, an Auger spectrometer, low energy electron optics and a quadrupole mass spectrometer.

Catalytic reactions are of crucial importance in everyday life. While industrial processes are mostly optimized at high temperatures and pressures, nature provides a variety of catalysts which work under ambient conditions. Inspired by such biological catalytic reactions, our goal is to understand their reaction pathways on an atomic level.

The ammonia synthesis in plants serves as a prominent example of nature efficiency and perfection of catalytic reactions. The active centre (enzymatic cofactor) for this reaction is a metal-sulfide cluster. Recent density functional calculations have shown that, adsorbed on these clusters, nitrogen molecules can be reduced in consecutive steps by protons and electrons from the cell environment without dissociation of the molecule itself.

In order to experimentally study such reactions, we first have to create model catalysts which sufficiently resemble the catalytically active centres in the cells of the plants. Therefore, small metal clusters arranged on a superstructured oxide films yield a promising environment to investigate the catalytic process.

The templates structure will be characterized by low-energy electron diffraction (LEED), Auger electron spectroscopy (AES), and scanning tunnelling microscopy (STM). After adsorption of nitrogen and hydrogen bonding sites, binding energies and intermediate reaction products will be investigated by inelastic tunnelling spectroscopy and thermal desorption spectroscopy.