Decomposition of methyl species on a Ni(211) surface: investigations of the electric field influence

Abstract

Density functional theory calculations are performed to examine how an external electric field can alter the reaction pathways on a stepped Ni(211) surface with regard to the decomposition of methyl species. We compare our results to those previously obtained on a close-packed Ni(111) surface and a bimetallic Au/Ni surface. The structures, adsorption energies, and reaction energy barriers of all methyl species on the Ni(211) surface are identified. The calculated results indicate that the presence of an external electric field not only alters the site preferences for the adsorbates on Ni(211), but also significantly changes the adsorption energies of the CH_x species. By comparison with our previous results, this electric field effect is smaller than that on Ni(111). The local electric field value is also found to differ at the various adsorption sites for the CH₃ group on Ni(211). From the results, a correlation between the calculated local electric fields, the adsorption energies and effective dipole moments values is investigated. The calculations also show that the stepped surfaces are more reactive for the elementary dissociation reactions of the CH_x species as compared to the Ni(111) surface. The final conclusion is that a positive electric field strengthens the adsorption energy of reactant CH₃, increases the energy barriers of the decomposition of CH_x species and weakens the adsorption energies of C and H. This suggests that the formation of pure C atoms deposits will be impeded by an external positive electric field.