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Mixed-Phase Oxide Catalyst Based on Mn-Mullite (Sm, Gd)Mn2O5 for NO Oxidation in Diesel Exhaust

Science  17 Aug 2012:
Vol. 337, Issue 6096, pp. 832-835
DOI: 10.1126/science.1225091

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  1. Fig. 1

    NO conversion versus ramp-up and ramp-down temperatures for MnCe-7:1 (●), SmMn2O5 (□), GdSrCeMn7O14.83 (■), and Pt (○).

  2. Fig. 2

    Microanalysis of catalyst MnCe-7:1. (A) XRD patterns corresponding to (a) mullite [Sm (Ce, Sr)Mn2O5], (b) spinel Mn3O4, and (c) flourite CeO2; (B) SEM image of MnCe-7:1; (C) HRTEM image of MnCe-7:1; (D to E) crystallite orientations, amorphous regions, and interface information; (F) side view of the ideal and stepped mullite (110) surface; (G and H) atomistic models for ideal and stepped (110) SmMn2O5 surfaces, respectively. Red, pink, and light green balls represent O, Mn, and Sm, respectively, while the vertices represent subsurface atoms with the same color scheme.

  3. Fig. 3

    Evolution of DRIFTS spectra at 200°C on MnCe 7:1 during exposure to NO and NO + O2 feed gases with time.

  4. Fig. 4

    Proposed reaction mechanism of NO conversion into NO2 (g) on the stepped mullite (110) surface. TS, transition state.