Abstract The catalytic efficiency of CeO2 carriers and the catalytic properties of palladium (Pd) nanocrystals loaded on different morphology CeO2 carrier were studied for lean methane (CH4) combustion. The catalytic activity of simple CeO2 carriers was ranked in the order of rod-CeO2(r-CeO2) > cube-CeO2(c-CeO2) > octahedral-CeO2(o-CeO2). After the Pd species was loaded on CeO2, 90% of CH4 was converted at 348 °C catalyzed by Pd/octahedral-CeO2 (Pd/o-CeO2) with (1 1 1) crystal faces, which had much higher catalytic activity comparing with Pd loaded on c-CeO2 with (1 0 0) crystal faces and r-CeO2 with (1 1 0) and (1 0 0) crystal faces. The results of XRD, HRTEM, EDS, H2-TPR, XPS and elemental mapping showed that the Pd species in the form of Pd0 and PdO were highly dispersed on surface of all CeO2 carriers. Most importantly, quasi In-situ XPS results convinced that Ce3+/Ce4+ ion pairs played an important role in the catalytic combustion of low-concentration methane by adsorbing or releasing oxygen. Compared with r-CeO2 and c-CeO2, the concentration of Ce3+ on the surface of o-CeO2 carrier was greatly increased when the Pd species were present, which indirectly reflected that the concentration of oxygen vacancies on the carrier surface also increased. Consequently, the high catalytic activity of Pd/o-CeO2 is not only related to the high dispersion of Pd0 and PdO species on the surface of the catalyst, but also closely related to the synergistic interaction between Pd species and (1 1 1) specific faces of o-CeO2 exposing.

中文翻译：

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不同形态氧化铈的典型晶面对贫甲烷燃烧Pd/CeO 2 催化剂活性的影响

摘要 研究了CeO2 载体的催化效率和负载在不同形态CeO2 载体上的钯(Pd) 纳米晶对贫甲烷(CH4) 燃烧的催化性能。简单CeO2载体的催化活性按棒状-CeO2(r-CeO2)>立方-CeO2(c-CeO2)>八面体-CeO2(o-CeO2)的顺序排列。将 Pd 物质负载在 CeO2 上后，90% 的 CH4 在 348°C 被具有 (1 1 1) 晶面的 Pd/八面体-CeO2 (Pd/o-CeO2) 催化转化，与Pd 负载在具有 (1 0 0) 晶面的 c-CeO2 和具有 (1 1 0) 和 (1 0 0) 晶面的 r-CeO2 上。XRD、HRTEM、EDS、H2-TPR、XPS 和元素映射的结果表明，Pd0 和 PdO 形式的 Pd 物种高度分散在所有 CeO2 载体的表面。最重要的是，准原位XPS结果确信Ce3+/Ce4+离子对通过吸附或释放氧气在低浓度甲烷的催化燃烧中起重要作用。与r-CeO2和c-CeO2相比，当Pd物种存在时，o-CeO2载体表面Ce3+的浓度大大增加，这间接反映了载体表面氧空位的浓度也增加了。因此，Pd/o-CeO2 的高催化活性不仅与 Pd0 和 PdO 物种在催化剂表面的高度分散有关，还与 Pd 物种与 (1 1 1) 特异性相互作用密切相关。 o-CeO2 表面暴露。