MnO_<i>x</i> Nanoparticle-Dispersed CeO₂ Nanocubes: A Remarkable Heteronanostructured System with Unusual Structural Characteristics and Superior Catalytic Performance

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_<i>x</i> 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_<i>x</i>. 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_<i>x</i> 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_<i>x</i> 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_<i>x</i>/CeO₂ interface. It was found that MnO_<i>x</i>/CeO₂ heteronanostructures efficiently catalyze soot oxidation at lower temperatures (50% soot conversion, <i>T</i>₅₀ ∼660 K) compared with that of bare CeO₂ nanocubes (<i>T</i>₅₀ ∼723 K). Importantly, the MnO_<i>x</i>/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 MnO_<i>x</i> components is a key factor for outstanding catalytic efficiency of the MnO_<i>x</i>/CeO₂ heteronanostructures