Three-way catalytic properties and microstructures of metallic glass driven composite catalysts

Abstract

Pd-dispersed composite catalysts were derived from Zr2Pd-based metallic glasses; Zr65Pd35, Zr65Pd30Pt5 and Zr50Pd35Ce15 by heat treatment at 600 °C in air, and their catalytic properties were evaluated. The results of the X-ray diffraction (XRD) analysis indicated that the PdO phase mainly formed in Zr65Pd35 catalyst and the metallic Pd phase formed in Zr65Pd30Pt5 and Zr50Pd35Ce15 catalysts. The scanning electron microscopic (SEM) images showed that the size of the Pd (PdO) particles increases with addition of Pt and Ce into Zr2Pd metallic glass. The three-way catalytic (TWC) activity of Zr50Pd35Ce15 catalyst was lower than that of the others. The differences of catalytic activity between Zr65Pd35 catalyst and Zr65Pd30Pt5 catalyst were very slight, although the former had smaller Pd particles than that of the latter. The XRD and XAFS results showed that the PdO phase of Zr65Pd30Pt5 catalyst transformed to the metallic Pd phase after catalytic activity test. The redox potential of Pd2+/Pd0 was important for the catalytic activity. The catalytic properties were influenced by the morphology and chemical state of Pd phase in these catalysts. Since these properties were controlled in these catalysts, new type materials derived from metallic glass was proposed toward the property of TWC in this work.