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Auger electron spectroscopy, high-resolution electron energy loss spectroscopy and temperature programmed desorption methods have been used in order to investigate the adsorption properties and reactions of acetaldehyde on gold decorated rhodium and BN/Rh(111) surfaces. Scanning tunneling microscopy and X-ray photoelectron spectroscopy measurements were carried out to characterize the gold nanoparticles on clean and hexagonal boron nitride (h-BN) covered Rh(111). The adsorption of acetaldehyde was not completely hindered by gold atoms; however, depending on the structure of the outermost bimetallic layer (surface alloy) the dissociation of the parent molecule was suppressed, namely the production of carbon monoxide was inhibited by the gold domains. Our measurements with acetaldehyde on Au/h-BN/Rh(111) confirmed the observation that the lack of suitable adsorption sites eliminates the formation of CO. Nevertheless, increased coverage of gold enhanced the amount of adsorbed aldehyde at low temperature. We may predict that the low reactivity of acetaldehyde on Au/h-BN/Rh(111) significantly determine the ethanol decomposition mechanism on this surface.

Adsorption properties of azobenzene, the prototypical molecular switch, were investigated on a hexagonal boron nitride (h-BN) monolayer (“nanomesh”) prepared on Rh(111). The h-BN layer was produced by decomposing borazine (B 3 N 3 H 6 ) at 1000–1050 K. Temperature-programmed desorption (TPD) studies revealed that azobenzene molecules adsorbed on the “wire” and “pore” regions desorb at slightly different temperatures. Angle-resolved high-resolution electron energy loss spectroscopy (HREELS) measurements demonstrated that the first molecular layer is characterized predominantly by an adsorption geometry with the molecular plane parallel to the surface. Scanning tunneling microscopy (STM) indicated a clear preference for adsorption in the pores, manifesting a templating effect, but in some cases one-dimensional molecular stripes also form, implying attractive molecule–molecule interaction. Density functional theory (DFT) calculations provided further details regarding the adsorption energetics and bonding and confirmed the experimental findings that the molecules adsorb with the phenyl rings parallel to the surface, preferentially in the pores, and indicated also the presence of an attractive molecule–molecule interaction.

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