The Pt-Pd alloy catalyst and enhanced catalytic activity for diesel oxidation

Abstract

By use of a Pt-Pd alloy colloid solution, a Pt(1.0 wt%)-Pd(0.5 wt%) alloy catalyst was prepared on SiO2 support, and the supported Pt-Pd nanoparticles were verified to be highly alloyed and finely dispersed by energy dispersive X-ray spectroscopy (EDS), scanning transmission electron microscope (STEM), and CO adsorption. Under simulated diesel exhaust atmosphere, this Pt-Pd alloy catalyst exhibited a higher catalytic activity than the conventional Pt-Pd catalyst prepared by use of the common Pt and Pd precursors of Pt(NH3)2(NO2)2 and Pd(NO3)2 solutions. The characterization results of X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption of oxygen (TPD-O2) revealed that the Pt and Pd atoms of the Pt-Pd alloy catalyst were apt to be more metallic state, and the O2 adsorption and activation were facilitated significantly. Even at low temperature, there are more activated oxygen species available, and the surface of the Pt-Pd alloy catalyst gets more frequently refreshed for subsequent adsorption and activation for the CO and C3H6 reactants. The above effects resulted from the Pt-Pd alloying together with the high Pt-Pd dispersion of the supported Pt-Pd particles highly promoted the catalytic activity of the Pt-Pd alloy catalyst for diesel oxidation.