Local structure and short-range ordering of MnO2–Ce(1 − x)ZrxO2/TiO2

• Amorphous CeO2 was characterized in terms of structural analysis.
• CeO2 aggregation in the MnOx–CeO2/TiO2 is suppressed with addition of Zr.
• Short range ordering among the catalytic materials was identified.
• High catalytic activity was achieved by improvement of dispersion.

ABSTRACTThe mechanism of the dispersion improvement in Zr-added MnOx–CeO2/TiO2 is investigated. Through crystallographic analyses of the catalyst powder synthesized by the sol–gel method, it was observed that the MnOx–CeZrO2 (catalytic materials) formed on TiO2 was in amorphous phase. The aggregation of Ce occurs in MnOx–CeO2/TiO2, while all catalytic materials are well-dispersed with the Zr addition, which is attributed to the formation of Zr–Mn bonding. The result from X-ray absorption fine structure (EXAFS) analysis at Ce L3-edge revealed that the amorphous phase formed on a TiO2 particle was arranged in order of Ce, Zr and Mn. The Mn4 +/Mn3 + ratio increased from 0.84 to 2.36 with increasing addition of Zr, supporting the result obtained from Differential Scanning Calorimetry (DSC) analysis. Catalytic activity was evaluated to identify the effect of dispersion and the improvement of the de-NOx efficiency was approximately 50% at 150 °C, which can be explained by large contact area between Mn and Ce.

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