NH 3 /Ir(100): Electronic structure and dehydrogenation

Density functional theory was employed to compute the geometric and electronic structures and the stepwise dehydrogenation of NH 3 on Ir(100). The NH 3, NH 2 and NH were found to bind predominately on top, bridge and four-fold hollow sites with adsorption energies to be 0.82 eV, 3.26 eV and 4.85 eV respectively. The mixings of 3a1(NH3)∼5dz2/6s(Ir), 3 a 1 /1 b 1 (NH 2 ) ∼ 5 d yz (Ir) and 3 a 1  + 1 a 2 (NH) ∼ 5 d xz (Ir) and 2a1(NH)∼5dz2(Ir) are responsible for the adsorption of NH 3, NH 2 and NH respectively. The reaction barriers are 0.88 eV, 0.97 eV, 0.94 eV and 0.63 eV for the first, second, third N–H bond breakings and N 2 formation respectively. The competition between decomposition and desorption for NH 3 was demonstrated, NH 2 was found to be the most stable surface species, its accumulation in practice would suppress the first N–H bond scission and thus make it to be the rate-determining step.