Effect of atomic ordering on hydrogen dissociation on Ni₃Fe surfaces

Abstract

The dissociation of molecular to atomic hydrogen on clean surfaces of Ni₃Fe with either an ordered or disordered structure has been directly investigated by thermal desorption studies. Results show that when exposed to an ordered Ni₃Fe 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 Ni₃Fe 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 Ni₃Fe but not in disordered Ni₃Fe.