Influence of Sr Substitution on Catalytic Performance of LaMnO3/Ni Metal foam Composite for CO Oxidation

ABSTRACT

A series of Sr-substituted lanthanum manganite perovskites, La_1-xSr_xMnO₃ (LSMO, x = 0, 0.1, 0.2, and 0.3), with mesoporous structures were prepared and coated onto a three-dimensional Ni metal foam (MF) as composite catalysts. The catalytic performances of La_0.8Sr_0.2MnO₃/MF and La_0.7Sr_0.3MnO₃/MF were found to be superior to those of La_0.9Sr_0.1MnO₃/MF, LaMnO₃/MF, and LaMnO₃ powder in terms of catalytic oxidation of carbon monoxide with air. Under the reaction conditions (1.5 vol.% CO and air balance at a weight hourly space velocity of 90,000 hr^–1), La_0.8Sr_0.2MnO₃/MF reached 100% catalytic oxidation of CO, which is 27% higher than that of LaMnO₃ powder. Sr substitution induced an increase of Mn⁴⁺ and adsorbed surface oxygen species (O^–, O₂^–, or O₂^2–), which increased the number of active centers for oxidation and thus enhanced the oxidizing ability of the catalyst. The high activity and excellent stability of La_0.8Sr_0.2MnO₃/MF catalyst can be ascribed to a synergistic effect between the mesoporous structure and the high number of adsorbed oxygen species of the catalyst as well as the interconnected three-dimensional reticular configuration of the nickel metal support, which increases the number of active sites and enhances mass transfer for CO and O₂. La_0.8Sr_0.2MnO₃/MF composite can potentially be used in catalytic converters for CO removal of automotive exhaust gases.