Magnesium-enhanced redox property and surface acidity-basicity of LaMnO3 perovskites for efficient methane purification

Catalytic combustion has been applied to purify methane emissions from natural gas vehicle exhaust, yet it still requires the development of catalysts with both high activity and robust stability. Herein, non-equivalent promoter-magnesium ions (Mg2+) were introduced into LaMnO3 perovskites via a facile sol-gel method to partially substitute Mn sites and boost the catalytic performance. The incorporation of Mg induced the transition of Mn3+ to Mn4+ and generated oxygen vacancies, which improved the reactivity of lattice oxygen and facilitated the formation of adsorbed oxygen species. Turning the coordination state of Mn and O led to an augmentation of surface acid-basic sites on LaMn1-xMgxO3, which was beneficial for the activation of methane and adsorption of dissociated intermediates. The presence of abundant highly-reducible Mn4+ and surface-adsorbed oxygen species accelerated the complete oxidation of methane. Consequently, LaMn0.7Mg0.3O3 with the optimized surface acidity-basicity and redox property exhibited greatly enhanced catalytic activity, selectivity, water-/sulfur resistance and thermal stability compared to LaMnO3. This study emphasizes the importance of synergistically adjusting surface properties to enhance catalytic purification performance.