Effect of Ni doping on the catalytic properties of nanostructured peony-like CeO2

Abstract

Nanostructured ceria materials have attracted wide attention as catalysts, and the doping of these materials with rare earth elements to modify their catalytic activity has been comprehensively investigated. A novel type of Ni-doped hierarchical nanostructured peony-like ceria (PCO) has been prepared and its catalytic activity is investigated and compared with that of Ni-loaded samples. The prepared Ni-doped ceria have nanoscale grain sizes and open mesopores. This unique morphology endows it with superior catalytic activity for the oxidation of CO and the partial oxidation of methane. It is found that extra oxygen vacancies are generated in the ceria, and the reducibility of the ceria is highly enhanced after Ni-doping. The catalytic activity for CO oxidation is improved after Ni-doping, compared with that of pure ceria and Ni-loaded ceria. In the reaction for the partial oxidation of methane, the 3.8 atm% Ni-loaded PCO sample realizes a higher CH 4 conversion than the Ni-doped ceria. However, it is found that the onset temperature for CH 4 conversion decreases from 400 °C for the pure PCO and 3.8 atm% Ni-loaded PCO sample, to 340 °C for the 5.7 atm% Ni-doped PCO sample. 制备了一种新型 Ni 掺杂多层纳米结构牡丹花状 CeO 2 材料, 研究了其催化性能, 同时与 Ni 负载牡丹花状 CeO 2 样品进行了比较. 结果表明, Ni 掺杂 CeO 2 样品具有纳米晶粒和开放的介孔结构, 特殊的形貌使其在 CO 氧化和甲烷部分氧化反应中具有独特的催化特性. Ni 掺杂后, CeO 2 中产生了多余氧空位, 同时其氧化还原活性也增强, 其在 CO 氧化反应中的催化活性明显高于纯 CeO 2 和 Ni 负载 CeO 2 样品; 在甲烷部分氧化反应中, 牡丹花状 CeO 2 负载 3 atm% Ni 催化剂样品上甲烷转化率高于所有 Ni 掺杂的催化剂样品. 但是在 Ni 负载型催化剂和花状 CeO 2 催化剂上, 甲烷的起始转化温度为 400 o C, 而 5.7 atm%Ni 的掺杂使其降至 340 o C. Oxygen vacancies are generated in bulk ceria after Ni doping, which promotes the reducibility of peony-like CeO2, and hence enhances the catalytic activity for CO oxidation.