The effect of the structure and oxygen defects on the simultaneous removal of NOx and soot by La2−xBaxCuO4

Abstract

La_2−xBa_xCuO₄ (x = 0–0.6) perovskite-like oxides were prepared by the citric acid sol–gel method. Their structures and physico-chemical properties were characterized by XRD, BET, FT-IR, SEM, XPS, H₂-TPR, O₂-TPD, NO-TPD and soot-TPR experiments. The catalytic performances in the simultaneous removal of NO_x and soot were investigated by the temperature-programmed reaction. The XRD and FT-IR results show that the substitution of Ba²⁺ for La³⁺ results in the crystal structure transformation from orthogonal La₂CuO₄ to tetragonal La_2−xBa_xCuO₄ accompanied by the disappearance of the Jahn–Teller effect. Doping of Ba²⁺ will mainly affect two aspects: the transition of Cu²⁺ to Cu³⁺ in the orthorhombic system and the increase of the oxygen vacancy concentration in the tetragonal system. The substitution of Ba²⁺ in La_2−xBa_xCuO₄ catalysts produces more active oxygen species, more Cu³⁺ content and better redox ability, which determines their better catalytic performance in the simultaneous removal of NO_x and diesel soot particles. The La_1.8Ba_0.2CuO₄ catalyst shows the best catalytic activity with 360 °C T_i, 510 °C T_m and 81.4% NO conversion.