CH_4 dissociation on NiCo (111) surface: A first-principles study

摘要

A density-functional theory method has been conducted to investigate the adsorption of CH_x(x=0-4) as well as the dissociation of CH_X (x=1-4) on (111) facets of ordered NiCo alloy. The results have been compared with those obtained on pure Ni (111) surface. It shows that the adsorption energies of C and CH are decreased while it is increased for CH3 on NiCo (111) compared to those on pure Ni (111). Furthermore, on NiCo (111), dissociation of CH_x prefers not to the top of Ni, but to the top of Co. The rate-determining step for CH_4 dissociation is considered as the first step of dehydrogenation on NiCo (111), while it is the fourth step of dehydrogenation on Ni (111). Furthermore, the activation barrier in rate-determining step is slightly higher by 0.07 eV on Ni (111) than that on NiCo (111). From above results, it is important to point out that carbon is easy to form on NiCo (111) although the adsorption energy of C atom is slightly decreased compared to that on Ni (111).