DECOMPOSITION OF N2O ON NI(755) AND THE CHARACTER OF THE ATOMIC OXYGEN DEPOSITED AT STEP SITES

Adsorption and reaction of N2O on a stepped Ni(755) surface have been investigated by temperature-programmed desorption (TPD). The decomposi tion of adsorbed N2O occurs exclusively at the step sites on Ni(755) b elow 200 K during TPD ramp, yielding gaseous Nz and leaving atomic oxy gen there. The amount of the atomic oxygen is controlled easily by cha nging the exposure of N2O. The character of the atomic oxygen has been studied by using decomposition of cycloheptane as a probe reaction. A ll the atomic oxygen generated in situ from coadsorbed N2O can react w ith carbon atoms produced from the decomposition of cycloheptane, resu lting in desorption of CO around 600 K upon heating. However, two thir ds of the predeposited atomic oxygen cannot be desorbed as CO upon hea ting up to 723 K. The predeposited atomic oxygen becomes inactive duri ng the predeposition process and probably interacts with the step site s more strongly. (C) 1998 Academic Press.