Catalytic properties of nanocrystalline WO3−x, Pt/WO3−x, and Pd/WO3−x particles

Abstract

The gas-condensation technique is used to produce the nanocrystalline (NC) WO3−x, Pt/WO3−x, and Pd/WO3−x powders under different atmosphere and pressure. HRTEM images show that a coherently bonded interface exists between Pt or Pd and WO3−x. The nanocrystal WO3−x, Pt/WO3−x, and Pd/WO3−x grow into a needle shape with a plate inside when these as-evaporated powders are compacted and sintered at 900 °C for 2 h. The plate grows preferentially in {220} plane along the 〈0011〉 direction. However, the mean particle size of nanophase Pt and Pd increases only from <10 nm to 30 nm and 50 nm, respectively. The results of CO oxidation show that nanophase Pt/WO3−x powders have better catalytic effects on converting CO to CO2 than nanophase WO3−x and Pd/WO3−x powders.