Decomposition of NH3 on Ir(110): A first-principle study

The adsorption and dehydrogenation of NH3 on Ir(110) have been investigated using periodic density functional calculations. The adsorption sites, the adsorption energies, the predominant adsorption configurations and the transition states of the stepwise dehydrogenation of NH3 were identified. The results show that the NH3 prefers the top site with inclining 68.6° of N―Ir bond relative to the surface, while NH2, NH, N and H favor the short bridge position. The NH decomposition to N and H or recombination with H to form NH2 shares the similar and relatively high reaction energy barrier, implying that NH will be the main surface species in the NH3 dehydrogenation processes. N―N bond formation possesses the highest energy barrier of 1.75 eV, indicating that it is the rate-limiting step for NH3 decomposition. Barrier decomposition analysis reveals that the deformation and the binding to the surface of the reactants and the interaction among binding species in transition states will increase the activation energy while the bonding to the surface of the species in transition state will decrease the energy barrier.