The adsorption and surface reaction of cyanogen on clean and oxygen covered Cu(ll1) have been investigated. From electron energy loss measurements, thermal desorption spectroscopy and electron beam effects in Auger spectroscopy. it is proposed that cyanogen adsorbs dissociatively on Cu(ll1) at 300 K. The activation energy for the desorption was calculated to be 180 kJ/mol. Cyanogen adsorption onto oxygen predosed Cu(ll1) is inferred to produce the NC0 surface species. This interpretation was aided by data of electron energy loss measurements and from HNCO adsorption onto Cu(ll1) at 300 K. A reaction began in the co-adsorbed layer above 400 K. yielding CO2 and NT.

The interaction of HNCO with Pt(ll0) surface has been investigated by different techniques at low and high-temperatures. The adsorption of HNCO on Pt(ll0) caused no reordering of the surface Pt atoms from the (1 X 2) to the (1 X 1) structure. At saturation, an ordered (2 X 2) structure was formed, HNCO was detected in the desorbing gases only after its low temperature (110 K) adsorption; it desorbed in two stages, with peak maxima at 150 and 270 K. In addition, the formation of Hz (Tmax "290 K) and NH3 (Tmax -293 and 390 K) was also observed. When the temperature was raised to above 400 K, Nz and CO evolution was noticed, but neither NC0 nor (NCO)z species were found in the desorbing gases. The adsorption of HNCO at 110 K produced a very intense loss at 10.4 eV and a less intense one at 13.5 eV in the electron energy loss spectra. From the behaviour of these losses at higher temperature it was inferred that the dissociation of adsorbed NC0 species to adsorbed N and CO begins to an appreciable extent above 230 K, and that the dissociation is complete at 310-330 K. It is proposed that NC0 is located in the "trough sites" of the corrugated surface of (1 X 2) structure and that it is multiply bonded to the Pt atoms.

The adsorption and surface dissociation of HNCO on Rh surfaces has been investigated by Auger electron, electron energy loss and thermal desorption spectroscopy.Following the adsorption of HNCO on clean Rh(ll1) and Rh foil at 100 K three adsorbed states can be distinguished by thermal desorption measurements:(i) physisorbed HNCO desorbing at 130 K, (ii) chemisorbed HNCO desorbing at 200 K, and (iii) dissociatively adsorbed HNCO decomposing to various products at higher temperatures. These products are: H, ( Tp = 280 K), CO ( Tp = 450-480 K), N, (Tr = 670 and 790 K) and very small amount of NH, (L$ = 415 K). No desorption of N, was observed from Rh foil up to 900 K. This ws attrrbuted to the boron contamination, which segregated to the surface at higher temperature, and formed a oery stable surface species wrth N. The adsorption of HNCO at 100 K produced a very intense loss at 10.4 eV and a less intense one at 13.5 eV in the electron energy loss spectra in the electronic range. From the behaviour of these losses at higher temperature it was inferred that the dissociation of adsorbed NC0 species to adsorbed N and CO begins to an appreciable extent above 150 K, and that the dissociation is complete at 360-380 K.

No detectable adsorbed species were observed after exposure of HNCO to a clean Cu(ll1) surface at 300 K. The presence of adsorbed oxygen, however, exerted a dramatic influence on the adsorptive properties of this surface and caused the dissociative adsorption of HNCO with concomitant release of water. The adsorption of HNCO at 300 K produced two new strong losses at 10.4 and 13.5 eV in electron energy loss spectra, which were not observed during the adsorption of either CO or atomic N. These loses can be attributed to surface NC0 on Cu( 111). The surface isocyanate was stable up to 400 K. The decomposition in the adsorbed phase began with the evolution of COz. The desorption of nitrogen started at 700 K. Above 800 K, the formation of CzNz was observed. The characteristics of the CO, formation and the ratios of the products sensitively depended on the amount of preadsorbed oxygen. No HNCO was desorbed as such, and neither NC0 nor (NCO)? were detected during the desorption. From the comparison of adsorption and desorption behaviours of HNCO, N, CO and CO2 on copper surfaces it was concluded that NC0 exists as such on a Cu(ll1) surface at 300 K. The interaction of HNCO with oxygen covered Cu(ll1) surface and the reactions of surface NC0 with adsorbed oxygen are discussed in detail.