Here we report the influence of surface composition on the NO_x removal efficiency of lean NO_x trap Pd–La_1-xA_xCoO₃/Al₂O₃-type catalysts. Three catalysts were prepared by the sequential impregnation of 30 wt.% of La_1-xA_xCoO₃-type perovskites and 1.9 wt.% of Pd over alumina. The following perovskite compositions were used: La_0.7Sr_0.3CoO₃, La_0.7Ba_0.3CoO₃ or La_0.5Ba_0.5CoO₃. The results of X-Ray diffraction, N₂ adsorption-desorption at −196 °C, electron microscopy, temperature programmed techniques, and Raman and X-ray photoelectron spectroscopies demonstrated that lanthanum partial substitution by barium promoted the presence of Ba-based phases homogeneously distributed at the surface. This fact together with the higher basicity of Ba than Sr led to an increase of the surface basicity for Ba-doped samples. Likewise, Ba doping also favors the formation of small PdO particles homogenously distributed over the surface in close contact with the perovskite phase. Hence, the interactions between Pd and surface basic sites were also promoted. As a result, 1.9 wt.% Pd–30 wt.% La_0.5Ba_0.5CoO₃/Al₂O₃ catalyst exhibited the highest NO_x adsorption and reduction efficiency. Specifically, the NO global conversion and nitrogen production were as high as 90% and 72% at 350 °C, respectively. The enhancement of NO_x storage capacity during the lean period is mainly assigned to the displacement of gas/solid equilibrium between NO₂ and the available NO_x adsorption sites due to the presence of higher concentration of basic sites at the surface. Meanwhile, the promotion of the NO_x reduction capacity is due to the higher strength of NO_x adsorbed species, which slows down the decomposition rate of NO_x adsorbed species. Furthermore, the high proximity of Pd and perovskite phase favors the intermediate compounds diffusion. These results confirmed the excellent NO_x removal efficiency of the 30 wt.% La_0.5Ba_0.5CoO₃-based catalyst, even above than Pt-based model catalyst.

在这里，我们报告了表面成分对贫NO _x捕集阱Pd–La _1-x A _x CoO ₃ / Al ₂ O ₃型催化剂的NO _x去除效率的影响。通过在氧化铝上依次浸渍30重量％的La _1-x A _x CoO ₃型钙钛矿和1.9重量％的Pd ，制备了三种催化剂。使用以下钙钛矿组合物：La _0.7 Sr _0.3 CoO ₃，La _0.7 Ba _0.3 CoO ₃或La _0.5 Ba _0.5 CoO₃。X射线衍射，-196°C下N ₂吸附-解吸，电子显微镜，程序升温技术以及拉曼光谱和X射线光电子能谱的结果表明，钡部分取代镧可以均匀地促进Ba基相的存在。分布在表面。这一事实以及Ba的碱度高于Sr导致Ba掺杂样品的表面碱度增加。同样，Ba掺杂也有利于形成均匀分布在与钙钛矿相紧密接触的表面上的小PdO颗粒。因此，Pd和表面碱性位点之间的相互作用也得到了促进。结果，1.9 wt。％Pd–30 wt。％La _0.5 Ba _0.5 CoO ₃ / Al₂ O ₃催化剂表现出最高的NO _x吸附和还原效率。具体而言，在350°C下，NO的整体转化率和氮的产生率分别高达90％和72％。NO的增强_X在稀燃期间的存储容量主要被分配给NO之间的气体/固体平衡的位移₂和可用的NO _X吸附位点，由于在表面的碱性位的较高浓度的存在。同时，NO _x还原能力的提高归因于更高的NO _x吸附物质的强度，这减慢了NO _x的分解速率吸附物质。此外，Pd和钙钛矿相的高度接近性有利于中间化合物的扩散。这些结果证实了30重量％的La _0.5 Ba _0.5 CoO ₃基催化剂的优异的NO _x去除效率，甚至高于Pt基模型催化剂。