Reactivity of Lattice Oxygen in Ti-Site-Substituted SrTiO Perovskite Catalysts.

An environmental catalyst in which a transition metal (Mn, Fe, or Co) was substituted into the Ti site of the host material, SrTiO, was synthesized, and the reactivity of lattice oxygen was evaluated. For CO oxidation, Mn- and Co-doped SrTiO catalysts, which provided high thermal stabilities, exhibited higher activities than Pt/AlO catalysts despite their low surface areas. Temperature-programmed reduction experiments using X-ray absorption fine structure (XAFS) measurements showed that the lattice oxygen of Co-doped catalyst was released at the lowest temperature. Isotopic experiments with CO and O revealed that the lattice oxygen was involved in CO oxidation on Fe- and Co-doped catalysts; that is, CO oxidation on these catalysts proceeded via the Mars-van Krevelen mechanism. On the other hand, for Mn-doped catalyst, the contribution of lattice oxygen to CO oxidation was relatively negligible, indicating that the reaction proceeded according to the Langmuir-Hinshelwood mechanism. This paper clearly demonstrates that the catalytic mechanism can be adjusted by substituting transition metals into SrTiO.