Site-specific dissociation of N2 on the stepped Ru(109) surface

The dissociative adsorption of molecular nitrogen on Ru(109) is investigated by temperature-programmed desorption (TPD) and low-energy electron diffraction (LEED). This surface presents double-height steps separated by similar to 9-atom wide Ru(001) terraces. Thermal dissociation of NZ is shown to be site-specific to the steps leaving atomic N on the steps (step-N), while electron-stimulated dissociation of N-2 adsorbed on Ru(109) can also provide atomic N on the terraces (terrace-N) as well as on the steps. The corresponding activation energy for the thermally-activated N-2 dissociation on the steps is measured to be 0.26 +/- 0.05 eV. We postulate that the steps on Ru(109) catalyze not only a unique reaction channel for the N-2 dissociation but also provide active sites during subsequent catalytic reactions by providing more stable adsorption sites for dissociated N atoms. (c) 2005 Elsevier B.V. All rights reserved.