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Abstract

Thermal desorption spectroscopy (TDS) was mainly used to study the chemisorption of nitrogen on specially prepared Pd-rich surfaces of the PdCu(1 1 0) single-crystal alloy. The TD spectra showed two desorption maxima below 500 K; the α state and the β state with desorption maxima at 130 and 445 K, respectively. The β state is characteristic for the alloy surface and was not observed on pure constituent metals. With higher doses the TD spectra display an unexpected behaviour. Although the top layer consists entirely of Pd (∼100% Pd), the presence of Cu atoms as impurities in the subsurface region (5–15% Cu) was found to influence the interaction of the Pd atoms in the top layer with adsorbed nitrogen leading to the formation of strongly adsorbed nitrogen species with desorption rate maxima at 445, 580 and 680 K, respectively. The enhanced formation of these species was attributed to the electronic interaction of surface Pd with Cu atoms present in subsurface region.