Abstract The interaction of C 2N 2 with Rh surfaces has been investigated by LEED, Auger electron, electron energy loss (in the electronic range) and thermal desorption spectroscopy. The adsorption of C 2N 2 on a clean Rh(111) surface at 300 K did not give rise to any new LEED pattern. By means of thermal desorption measurements four adsorption states were distinguished at saturation; at 380 K (α), 610 K (β 1), 680 K (β 2) and 740 K (γ). The weakly bound α state is attributed to non-dissociatively adsorbed C 2N 2, while the β and γ states are ascribed to the associative desorption of pairs of CN radicals formed in the surface dissociation of C 2N 2. At the same time, N 2 also desorbed, at T p = 800 and 850 K, indicating that fission of the C− N bond occurred on the Rh(111) surface. In the presence of adsorbed oxygen the rate and the extent of C 2N 2 adsorption are decreased. The oxidation of adsorbed CN groups starts above 360 K, to yield gaseous CO 2 and adsorbed CO and N. From the EELS results it is proposed that the oxidation of cyanide occurs through the formation and further oxidation of an NCO surface intermediate.