DFT Study on the Methane Synthesis from Syngas on a Cerium-Doped Ni(111) Surface

Abstract

The methanation of syngas (CO and H2) on the Ce-doped Ni(111) surface (Ce–Ni(111)) has been investigated by using the density functional method. The doped Ce enhances the adsorption energy of the intermediates on the catalytic surface, except for H2, particularly for O-containing species. On the Ce–Ni(111) surface, the reaction pathway CO + 3H2 → CHO + 5H → CH + O + 5H → CH4 + H2O is the most favorite, in which the energy barrier is 1.18 eV for the rate-determining step. Compared with the pure Ni(111) surface, the doping of Ce improves the catalytic activity both thermodynamically and kinetically. The microkinetic analysis also supports that the methanation of syngas has high reaction rate on the Ce–Ni(111) compared with the pure Ni(111). The temperature has great influence on the reaction rate, while H2/CO ratio shows only slightly impact. Our study also explains the experimental observation that the doped Ce can reduce the reaction temperature from ∼500 °C on the pure Ni(111) to ∼340 °C on the Ce–Ni(111) surface. The coverage of CHO is the largest on the Ce–Ni(111) surface. We expect that the obtained results could be useful for the future experimental study in searching the high efficient catalysts.