Band Gap As a Descriptor of Catalytic Activity in Mixed Metal Oxide Oxidation Catalysts

The development of descriptors to relate catalytic performance to material physico-chemical properties is a primary goal of catalysis research. We have found that for a series of mixed metal oxide oxidation catalysts (Bi₃FeMo₂O₁₂, Bi₂Mo_2.5W_0.5O₁₂, and Bi_(1-x/3)V_(1-x)Mo_(x)O₄ for 0 < x < 1), the activation energy for the rate-determining step in the selective oxidation of propene to acrolein can be related to the band gap of the oxide, as measured by diffuse reflectance UV-Visible spectroscopy. That is, band gap is a descriptor for catalytic activity. Detailed theoretical analysis of the mechanism of propene oxidation has enabled the bond-breaking and bond-forming events occurring in the rate-determining transition state to be linked to the electronic excitation taking place in a band gap measurement, which in turn is a function of oxide composition. We further show that the dependence of the band gap on composition can be predicted from knowledge of the energies and sizes of the unoccupied d orbitals on each transition metal center in the oxide. The principles discussed in this talk provide a basis for the rational formulation of superior oxidation catalysts.

Getsoian A.; Zhai Z.; Bell A.T. J. Am. Chem. Soc. 2014, 136 (39), 13684-13697.