MnOx Nanoparticle-Dispersed CeO2 Nanocubes: A Remarkable Heteronanostructured System with Unusual Structural Characteristics and Superior Catalytic Performance

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• 作者：Sudarsanam Putla ; Mohamad Hassan Amin ; Benjaram M. Reddy ; Ayman Nafady ; Khalid A. Al Farhan ; Suresh K. Bhargava
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2015
• 出版时间：August 5, 2015
• 年：2015
• 卷：7
• 期：30
• 页码：16525-16535
• 全文大小：690K
• ISSN：1944-8252

文摘

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 MnO_x 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 MnO_x. This interesting observation is due to conversion of smaller sized Ce⁴⁺ (0.097 nm) to larger sized Ce³⁺ (0.114 nm) in cerium oxide led by the strong interaction between MnO_x 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 MnO_x 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 MnO_x/CeO₂ interface. It was found that MnO_x/CeO₂ heteronanostructures efficiently catalyze soot oxidation at lower temperatures (50% soot conversion, T₅₀ 鈭?60 K) compared with that of bare CeO₂ nanocubes (T₅₀ 鈭?23 K). Importantly, the MnO_x/CeO₂ heteronanostructures exhibit a noticeable steady performance in the oxidation of benzylamine with a high selectivity of the dibenzylimine product (鈭?4鈥?8%) compared with that of CeO₂ nanocubes (鈭?9鈥?1%). The existence of a strong synergistic effect at the interface sites between the CeO₂ and MnO_x components is a key factor for outstanding catalytic efficiency of the MnO_x/CeO₂ heteronanostructures.