H_2在Ni,Pd与Cu表面的解离吸附

H2 DISSOCIATIVE ADSORPTION ON SURFACES OF Ni, Pd and Cu

用EAM方法(embeded-atom method)研究H_2在Ni,Pd与Cu的(100),(110)与(111)面上的解离吸附.首先通过拟合单个H原子在Ni,Pd与Cu不同表面上的吸附能和吸附键长,得到H与这些金属表面相互作用的EAM势,然后计算H_2在这些表面上以不同方式进行解离吸附时的活化势垒E_a,吸附热q_(ad)与吸附键长R.并给出H_2在(110)面上解离吸附的势能曲线.计算结果表明H_2的解离吸附与衬底种类、衬底表面取向及解离方式有关.H_2在Ni表面上解离时活化势垒很低,而在Cu表面解离时活化势垒较高.H_2在开放的(110)面较易解离,而在密堆积的(111)面较难解离.在各种可能的解离途径中,H_2最倾向于沿着从桥位到相邻心位解离.

The dissociative adsorption of hydrogen molecule on (100), (110) and (111) surfaces of Ni, Pd and Cu are investigated using the embeded-atom method (EAM). First, the EAM potentials for H-metal surfaces are obtained by fitting the adsorption energies and the length of adsorption bond for single H atom on different surfaces of Ni, Pd and Cu. Then, the activation barriers Ea, adsorption heat q2d and corresponding H-metal bond length R for dissociation of H2 through various pathways are calculated. The potential energy contours for H2 dissociation on (110) surfaces of different metals are presented. The calculated results show that the dissociative adsorption of a hydrogen molecule depend on the species of substrate, the surface orientation and the dissociative pathways. The activation barrier for H2 dissociation on Nisurface is very low, while it is higher for H2 dissociation on Cu surface. The dissociative adsorption of H2 is easier on open (110) surface than that on close-packed(111) surfaces. Among the discussed dissociation pathways, it appears that the most favourable pathway for H2 is that from bridge site to the adjacent centre sites.