NOx storage capacity of yttria-stabilized zirconia-based catalysts

A NOx chemisorption study was performed on yttria-stabilized zirconia (YSZ), an O2− ionically conducting ceramic. NO2 chemisorption on YSZ as well as NO + O2 interactions on Pt/YSZ catalyst were clearly correlated to the presence of surface oxygen vacancies. A remarkable NOx storage capacity was obtained on Pt/YSZ powdered catalysts, by combining nitrates formation and NO2 adsorption on oxygen vacancies. Under cycling conditions (lean phase/rich phase: 3 min/2 min) and using propene as a reductant, powdered Pt-Rh catalyst exhibited overall NOx abatement conversion of around 75% at 250 and 300 °C. Pt/Rh/YSZ catalysts were finely dispersed in the porosity of SiC mini diesel particulate filters (DPFs). Quite reproducible and stable NOx conversions were achieved in cycling conditions with values around 50% between 250 and 400 °C. In addition, YSZ-based catalysts have shown high thermal resistance and sulfur tolerance.

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► Yttria-stabilized zirconia (YSZ) can store NOx on its surface oxygen vacancies.
► NOx conversion of 75% was achieved on Pt-Rh/YSZ powdered catalysts.
► YSZ-based catalysts were deposited in the porosity of mini SiC-DPFs.
► YSZ-based catalysts show high thermal resistance and sulfur tolerance.