掺Mn的CeO_2储氧材料对柴油机颗粒氧化活性的影响

Influence of Mn-Doped Ceria on Oxidation Activity of Diesel Engine Particles

由于稀土材料CeO_2本身独特的电子结构而具有良好的储氧/释氧能力及较强的氧化还原性能,故而采用理论计算结合实验研究的方法,探讨了掺杂Mn对CeO2晶体结构、氧空位形成能、电子结构以及对柴油机颗粒催化氧化活性的影响。研究发现:计算得到的纯相CeO_2晶格常数与实验值非常接近,当Mn的质量分数(w(Mn))为50%时,Mn可以较好地进入到CeO_2晶格的内部而形成晶相结构稳定性高的固溶体;在所计算的几种掺杂浓度的Ce_(1-x)Mn_xO_2体系中,氧空位形成能大大降低,且随着w(Mn)的增加而减小,w(Mn)为50%时达到最低,为0.31eV;掺Mn后没有改变CeO_2立方萤石的晶体结构;随着w(Mn)的提高,柴油机颗粒热失重速率整体向低温区域移动,当w(Mn)分别为12.5%、25%和50%时,起燃温度较纯CeO_2分别降低了18、24、42℃,峰值温度分别降低了6、12、32℃;Ce1-xMn_xO_2中的氧空位可能是反应活性位,氧空位越多,越有利于颗粒的氧化。该结果可为汽车尾气净化及其他领域应用提供参考。

Rare earth CeO2 has good oxygen storage/oxygen release ability and strong redox performance due to its special electronic structure. The crystal structure, oxygen vacancy formation energy, electronic structures and the influence on oxidation activity of diesel engine particles with different Mn-doped CeO2 were systematically researched via theoretical calculation and experimental investigation. The results show that the lattice parameters of pure CeO2 are very close to the experimental value. The doped Mn can enter into CeO2 lattice and form solid solution with high structural stability when Mn-doped concentration reaches 50%. With the tow temperature region. When the Mn-doped concentrations reach 12.5%, 25% and 50%, the soot ignition temperature lowers by 18, 24 and 42 ℃ respectively and the peak temperature lowers by 6, 12 and 32℃ respectively compared with pure CeO2. The oxygen vacancies in Ce1-xMnxO2 may be the reactive sites, and more oxygen vacancies are beneficial to the particles oxidation.