Site-specific dissociation of N2 on the stepped Ru(1Â 0Â 9) surface

The dissociative adsorption of molecular nitrogen on Ru(1 0 9) is investigated by temperature-programmed desorption (TPD) and low-energy electron diffraction (LEED). This surface presents double-height steps separated by ∼9-atom wide Ru(0 0 1) terraces. Thermal dissociation of N2 is shown to be site-specific to the steps leaving atomic N on the steps (step-N), while electron-stimulated dissociation of N2 adsorbed on Ru(1 0 9) can also provide atomic N on the terraces (terrace-N) as well as on the steps. The corresponding activation energy for the thermally-activated N2 dissociation on the steps is measured to be 0.26 ± 0.05 eV. We postulate that the steps on Ru(1 0 9) catalyze not only a unique reaction channel for the N2 dissociation but also provide active sites during subsequent catalytic reactions by providing more stable adsorption sites for dissociated N atoms.