Spinel Interphase Modulation in Ba/Al2O3: A Strategy to Enhance NO x Storage Capacity and Durability of NSR Catalysts

Abstract NOx storage reduction (NSR) technology has obvious advantages in NOx 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 NOx 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 NOx storage capacity of the catalysts. When BaAl2O4 was introduced as the interface control layer, the NOx 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.