Solid defect structure and catalytic activity of perovskite-type catalysts La1–xSrxNiO3–λ and La1–1.333xThxNiO3–λ

Abstract

Two series of La_1–xSr_xNiO_3–λ and La_1–1.333xTh_xNiO_3–λ catalysts have been prepared, and the relationships between the solid defect structure and catalytic activity for NH₃ oxidation were measured. The results showed that in the range of x < 0.3, the samples possessed single perovskite-type structure, and as the content of Sr²⁺ decreased and that of Th⁴⁺ increased the catalytic activity increased, which was paralleled with the Ni³⁺ concentration within the catalysts. The active oxygen species (O^– or O^2–₂) were present not only on the surface but also in the bulk of the samples. The synergistic effect of transition metal ions with higher oxidation states and randomly distributed oxygen vacancies was the key factor determining catalytic activity of perovskite-type oxides. A redox mechanism for NH₃ oxidation over ABO₃ is proposed.