Ce. Lyman et al., X-RAY-EMISSION SPECTROMETRY OF PHASE-SEPARATION IN PT-RH NANOPARTICLES FOR NITRIC-OXIDE REDUCTION, Ultramicroscopy, 58(1), 1995, pp. 25-34
Composition determinations of individual sub-10 nm metal particles in
Pt-Rh/alumina by analytical electron microscopy are consistent with a
low-temperature miscibility gap below about 750 degrees C in this syst
em. Pt-rich alloy particles are more active than pure Pt for the reduc
tion of nitric oxide with hydrogen at temperatures less than or equal
to 300 degrees C. Rh-rich particles appear to have low activity for th
is reaction. Catalysts which contain a bimodal distribution of Pt-rich
and Rh-rich particles are not as active as pure Pt. Composition versu
s size plots of small metal particles appear to comprise a new charact
erization method for supported metal catalysts.