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Keywords:

  • alumina;
  • green chemistry;
  • nitrogen oxides;
  • rare earths;
  • structure–activity relationships

Abstract

Rare-earth-doped Pt/Ba/RO-CZA (RO=La2O3, Nd2O3 and Y2O3; CZA=Ce0.6Zr0.4O2-Al2O3) were synthesized and characterized by XRD, N2 physisorption, Raman spectroscopy, H2 temperature-programmed reduction, extended X-ray absorption fine structure analysis, scanning transmission electron microscopy, and X-ray photoelectron spectroscopy. The effect of the addition of rare earths on Pt/Ba/RO-CZA was explored, and the relationship between their structures and properties was disclosed. In comparison with Pt/Ba/CZA, La and Nd addition, especially La addition, resulted in an apparent increment of oxygen vacancies and the improvement of the reductive capacity of Ce4+, which are favorable for NOx reduction. However, the presence of Y induced a negative effect on NOx storage and reduction (NSR). The NSR performances of Pt/Ba/RO-CZA were initially evaluated by using NO-to-NO2 conversion, NOx storage capacity, and NOx conversion. The NOx conversion in Pt/Ba/La-CZA and Pt/Ba/Nd-CZA at 350 °C is up to 98 and 94 %, respectively. Interestingly, the addition of rare earths contributes to the enhancement of the thermal stability, a slight decrement of NOx conversion was observed after Pt/Ba/RO-CZA were maintained at 350 °C for 100 h, whereas an obvious loss of catalytic activity was found in Pt/Ba/CZA under the same conditions. TEM analysis showed that the presence of La inhibits the agglomeration of Pt and the sintering of particles.