DFT/QTAIM Analysis of the Effect of Late Transition Metal Doping on Methane Selectivity in Fischer–Tröpsch Catalysis
Computational and Theoretical Chemistry
The effect of late transition metal substitution into Fe(1 0 0), Ni(1 1 1), and Co(0 0 0 1) surface analogs has been investigated density functional theory (DFT) methods. The surface was modeled using a 7-atom cluster, with perimeter atoms saturated with hydrogen atoms to approximate surface coordination and mitigate dangling bond artifacts. All calculations were performed at the B3PW91 level of theory with the LANL2DZ basis. Eight surface adsorbates were studied: C, CH, CH2, and CH3 represented the hydrogenating steps on surface carbide, while C+CH, CH+CH, C+CH3, and CH2+CH2 represented four competitive coupling pathways. A review of the effect of Cu, Ag, Au, and Pd on the reaction energies and barriers associated with these critical steps is discussed. QTAIM is employed to develop a picture of the electronic environment associated with methane selectivity. Attention is focused on the charge trends for the involved surface atoms and coupling species. Our results suggest that promising candidates for the reduction of FT methane selectivity include Au and Pd on Ni, Au and Ag on Co, and Cu, Ag, and Pd on Fe.
Psarras, P. C.; Ball, D. W. DFT/QTAIM analysis of the effect of late transition metal doping on methane selectivity in Fischer–Tröpsch catalysis. Computational and Theoretical Chemistry 2015, 1063, 1-9.