Palladium-platinum powder catalysts manufactured by colloid synthesis

Palladium, platinum and PdPt bimetallic colloidal particles were prepared in atomic ratios of 4:1, 1:1 and 1:4 by the reduction of K2PdCl4 and/or K2PtCl4 in the presence of cationic surfactant, tetradecyltrimethylammonium bromide (C14TABr). The nanoparticles in the “as prepared” state were characterized by TEM, EDS and XPS, UPS, permitting to determine their mean particle size, bulk and surface composition. The bulk composition of the bimetallic samples determined by EDS was close to their nominal value, while XPS indicated Pt enrichment near to the surface. All samples in the “as received” state contained surface oxide impurity and contained carbon impurities. The monometallic samples contained considerably more C as the bimetallic ones. A quasi-in situ H2 treatment at 473 K in the electron spectrometer resulted in cleaner metals, containing less carbon and oxygen, as shown by XPS and UPS.