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.