Abstract
• α-MnO 2 nanowires with tailored exposed crystal facets were elaborately synthesized. • Exposed crystal facet of α-MnO 2 is crucial to coordination states of surface O and Mn ions. • α-MnO 2 -310 catalyst exhibited excellent catalytic performance during soot oxidation. • Crystal facet-dependent catalytic activity for soot oxidation is clearly revealed. • Exposed {310} facet of α-MnO 2 can induce formation of surface active sites for activated O 2 . The distribution and coordination states of surface oxygen and metal ions in pure-phase metal oxides are dominated by the exposed crystal facets, which directly affects its physicochemical properties. Herein, we have elaborately constructed three catalysts of single-crystalline α-MnO 2 nanowires with predominantly exposed {310}, {110} and {100} facets, respectively. The α-MnO 2 catalyst exhibits a strong facet-dependent catalytic activity for the three-phase reaction of catalytic soot oxidation. Compared with the low-index {110} and {100} facets, the α-MnO 2 catalyst with exposed high-index {310} facet exhibits the highest catalytic activities (T 50 =333°C, TOF= 1.127 h -1 ), the lowest apparent activation energy (68.4 KJ mol -1 ), and excellent catalytic stability during soot oxidation. Combining the results of characterizations and density functional theory (DFT) calculations, the intrinsic mechanism of crystal facet-dependent catalytic activity for soot oxidation is revealed: The selectively exposed α-MnO 2 {310} facets can induce the formation of coordinative unsaturated atoms and surface defect sites, enhancing the adsorption-activation ability for O 2 and NO. In-depth understanding of the face-dependent catalytic activity of α-MnO 2 catalyst is valuable for the acquisition of high-efficient non-precious metal catalysts during soot oxidation.
Published Version
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