Theoretical study of adsorption and dissociation of NH3 on the Ir{110}(1x2) surface

The adsorption and dissociation of NH3 on Ir{110}(1x2) have been investigated using the density-functional calculations at a coverage of 0.25 ML. The adsorption sites, energy, and geometries were obtained for NH3, NH2, and H adsorptions on the surface. The transition state for NH3 dissociation on Ir{110}(1x2) was also identified. It was found that NH3 is adsorbed preferentially at the ridge atop site, while NH2 and H are adsorbed at the ridge bridge site. The activation barrier of NH3 dissociation is 78.4 kJ/mol, which is very close to the NH3 adsorption energy of 90.0 kJ/mol. This indicates that the desorption and dissociation of NH3 on Ir{110}(1x2) are very competitive, which is consistent with the recent experimental results.