Electronic structure of bilayer (Fe, Ni) metallic α-Al 2O3(0001) catalysts towards CH4 adsorption and dissociation

Density functional theory calculations are performed on the monometallic (Fe or Ni) bilayer modified α-Al2O3(0001) surface. Comparison has been made to their structural and electronic behaviors upon CH4 adsorption and dissociation. Local density of states and frontier orbital analysis show that C-H activation proceeds through weak chemical interactions with the metallic 3d electrons. It was found that electron transport within the sp and 3d type orbitals of the catalyst is important for the equilibration of the system. Such electron transport also promotes electron donation to the σ*(C-H) antibonding orbital for C-H bond activation. The calculated adsorption energies showed that the CH+H intermediate is most stable on the Fe/α-Al2O3 catalyst and is suspect to deactivation via carburization. Furthermore, C-H bond activation is most pronounced in cases where the CH4 molecule has one or two H atoms directed towards the catalyst surface.