Modified LaMnO3 perovskite oxide as NOx storage and reduction catalyst for emission control of hydrogen internal combustion engines

As the flagship of zero-carbon emission in transportation, hydrogen internal combustion engine vehicles alleviate global warming pressure but are still restricted by high emission of nitrogen oxides (NOx). A promising approach to reduce NOx emission is the NOx storage and reduction (NSR) technique using on-board H2 as the reductant. As a new generation of NSR catalysts, La-based perovskite oxides are plagued by small specific surface areas and poor reactivity, thus restricting their usability. Here, we proposed to simply fabricate a porous LaMnO3 perovskite oxide via the Pechini method (PC) with the addition of a pore-forming agent, Pluronic 123 (P123). The modified LaMnO3 catalyst (LMO-PC-P) obtained by the PC-P method exhibited a large specific surface area and abundant oxygen vacancies. Such a structural feature not only provided more active sites for NOx storage but also facilitated NO oxidation via forming hyponitrite (N2O22−) rapidly on the defective surface under fuel-lean conditions. As a result, an excellent static NOx storage capability (NSC) was achieved, with a maximum NSC value of 205 μmol/g, which was over two times larger than that of LaMnO3 prepared by the Sol-gel method (LMO-SG). Over the LMO-PC-P sample, meanwhile, desorption of NOx in the fuel-rich mode was promoted, thus benefiting the regeneration of active sites. In the dynamic NSR test, the optimized catalyst achieved 84 % conversion of NOx at 350 °C, while the value for LMO-SG under the same conditions was only 46 %. This study presents a convenient and practical approach for preparing porous and defective NSR perovskite oxide catalysts for NOx emission control in hydrogen internal combustion engine vehicles.