Spinel Interphase Modulation in Ba/Al2O3: A Strategy to Enhance NOx Storage Capacity and Durability of NSR Catalysts

Abstract

NO_x storage reduction (NSR) technology has obvious advantages in NO_x purification of lean-burn gasoline engines, but its application is limited by catalyst deactivation induced by hydrothermal aging. In this work, spinel-structured MeAl₂O₄ (Me = Mg, Ba, Ni) were introduced into the Ba/Al₂O₃ system via an impregnation–calcination method. The composition and structure of spinel-modified Ba/Al₂O₃ samples were characterized by XRF, XRD, SEM, H₂-TPR, and N₂ physical adsorption–desorption techniques. The effect of spinel interphase on the NO_x storage capacity and desorption performance of Ba/Al₂O₃ was investigated by coupling the oxidation function of Pt/Al₂O₃. It was revealed that the spinel interphase as physical barriers and chemical-bonding medium inhibited the solid-phase diffusion of Ba species into the γ-Al₂O₃ lattice, weakened the interaction between Ba species and γ-Al₂O₃, suppressed the formation of BaAl₂O₄ spinel, stabilized the active Ba species, and markedly enhanced hydrothermal stability and NO_x storage capacity of the catalysts. When BaAl₂O₄ was introduced as the interface control layer, the NO_x storage capacity of the aged catalyst was 3.78–13.60 times that of the Ba/Al₂O₃ catalyst at the same temperature. These results provide a novel strategy for designing high-performance NSR catalysts.