†Centre for Advanced Materials and Industrial Chemistry (CAMIC), School of Applied Sciences, RMIT University, Melbourne VIC 3001, Australia.
‡Inorganic and Physical Chemistry Division, CSIR-Indian Institute of Chemical Technology, Uppal Road, Hyderabad 500 007, India.
ACS Appl Mater Interfaces. 2015 Aug 5;7(30):16525-35. doi: 10.1021/acsami.5b03988. Epub 2015 Jul 27.
Understanding the interface-induced effects of heteronanostructured catalysts remains a significant challenge due to their structural complexity, but it is crucial for developing novel applied catalytic materials. This work reports a systematic characterization and catalytic evaluation of MnOx nanoparticle-dispersed CeO2 nanocubes for two important industrial applications, namely, diesel soot oxidation and continuous-flow benzylamine oxidation. The X-ray diffraction and Raman studies reveal an unusual lattice expansion in CeO2 after the addition of MnOx. This interesting observation is due to conversion of smaller sized Ce(4+) (0.097 nm) to larger sized Ce(3+) (0.114 nm) in cerium oxide led by the strong interaction between MnOx and CeO2 at their interface. Another striking observation noticed from transmission electron microscopy, high angle annular dark-field scanning transmission electron microscopy, and electron energy loss spectroscopy studies is that the MnOx species are well-dispersed along the edges of the CeO2 nanocubes. This remarkable decoration leads to an enhanced reducible nature of the cerium oxide at the MnOx/CeO2 interface. It was found that MnOx/CeO2 heteronanostructures efficiently catalyze soot oxidation at lower temperatures (50% soot conversion, T50 ∼660 K) compared with that of bare CeO2 nanocubes (T50 ∼723 K). Importantly, the MnOx/CeO2 heteronanostructures exhibit a noticeable steady performance in the oxidation of benzylamine with a high selectivity of the dibenzylimine product (∼94-98%) compared with that of CeO2 nanocubes (∼69-91%). The existence of a strong synergistic effect at the interface sites between the CeO2 and MnOx components is a key factor for outstanding catalytic efficiency of the MnOx/CeO2 heteronanostructures.
理解异质纳米结构催化剂的界面诱导效应仍然是一个重大挑战，因为它们的结构复杂，但对于开发新型应用催化材料至关重要。本工作系统地表征和催化评估了 MnOx 纳米颗粒分散在 CeO2 纳米立方体上用于两个重要的工业应用，即柴油机烟尘氧化和连续流苄胺氧化。X 射线衍射和拉曼研究表明，CeO2 中加入 MnOx 后晶格发生了不寻常的膨胀。这种有趣的观察结果是由于 MnOx 和 CeO2 之间的强相互作用导致较小尺寸的 Ce(4+)（0.097nm）转化为较大尺寸的 Ce(3+)（0.114nm）。从透射电子显微镜、高角度环形暗场扫描透射电子显微镜和电子能量损失谱研究中还注意到另一个引人注目的观察结果，即 MnOx 物种沿着 CeO2 纳米立方体的边缘很好地分散。这种显著的修饰导致 MnOx/CeO2 界面处的氧化铈具有增强的可还原性质。研究发现，与裸 CeO2 纳米立方体（T50 ∼723 K）相比，MnOx/CeO2 异质纳米结构在较低温度下（50%烟尘转化率，T50 ∼660 K）有效地催化烟尘氧化。重要的是，与 CeO2 纳米立方体相比，MnOx/CeO2 异质纳米结构在苄胺氧化中表现出显著的稳定性能，二苄基亚胺产物的选择性高（∼94-98%）。CeO2 和 MnOx 组分界面位置之间存在强烈的协同效应是 MnOx/CeO2 异质纳米结构具有出色催化效率的关键因素。
