Effect of atomic ordering on hydrogen dissociation on Ni3 Fe surfaces

The dissociation of molecular to atomic hydrogen on clean surfaces of Ni3 Fe with either an ordered or disordered structure has been directly investigated by thermal desorption studies. Results show that when exposed to an ordered Ni3 Fe surface, molecular hydrogen dissociates to produce atomic hydrogen, which desorbs from the surface around 350 K. On the other hand, hydrogen does not dissociate on a disordered Ni3 Fe surface. These results indicate that atomic ordering has a marked effect on surface chemical reactivity. Furthermore, our study provides a mechanistic basis to explain the hydrogen-induced embrittlement in ordered Ni3 Fe but not in disordered Ni3 Fe. © 2009 American Institute of Physics.