摘要
Density functional theory (DFT) was employed to predict the most stable structure of Pd-doped Ni(111), Ni(100), and Ni(211) surfaces, and the activity for CH4 dissociation on pure and Pd-doped Ni surfaces. We predict that the thermodynamically most stable structures are the surface-doped Pd/Ni surfaces, where a surface Ni atom is replaced by a Pd atom; subsurface-doped Pd/Ni surfaces are thermodynamically unstable. Of the surface-adsorbed Pd/Ni surfaces, only the Pd/Ni(211) surface is thermodynamically stable. From the calculated adsorption energies of CH4 dissociation intermediates (CH4, CH3, CH, C and H) on surface-doped Pd/Ni surfaces, we find Pd-doping to reduce the adsorption energy for all species except for CH4. In addition, from the calculated activation barriers for CH4 and CH dissociations, we predict CH4 and CH to dissociate predominately on Ni(211) and Pd/Ni(211) step surfaces, followed by the broad Ni(100) and Pd/Ni(100) surfaces. Pd-doping raises the activation barriers for CH4 and CH dissociations. For the most active Ni(211) surface, Pd-doping causes the CH dissociation step to have a higher activation barrier than the CH4 dissociation step, which changes the rate limiting step, and helps reduce carbon deposition. (C) 2013, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.
