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, La1-xSrxMnO3 (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 La0.8Sr0.2MnO3/MF and La0.7Sr0.3MnO3/MF were found to be superior to those of La0.9Sr0.1MnO3/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), La0.8Sr0.2MnO3/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 O22-), 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 La0.8Sr0.2MnO3/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. La0.8Sr0.2MnO3/MF composite can potentially be used in catalytic converters for CO removal of automotive exhaust gases.