Rh1−x Pd x Nanoparticle Composition Dependence in CO Oxidation by NO

Bimetallic 15 nm Pd-core Rh-shell Rh1−x Pd x nanoparticle catalysts have been synthesized and studied in CO oxidation by NO. The catalysts exhibited composition-dependent activity enhancement (synergy) in CO oxidation in high NO pressures. The observed synergetic effect is attributed to the favorable adsorption of CO on Pd in NO-rich conditions. The Pd-rich bimetallic catalysts deactivated after many hours of oxidation of CO by NO. After catalyst deactivation, product formation was proportional to the Rh molar fraction within the bimetallic nanoparticles. The deactivated catalysts were regenerated by heating the sample in UHV. This regeneration suggests that the deactivation was caused by the adsorption of nitrogen atoms on Pd sites. TOF of CO2 as a function of Pd molar fraction for Rh1−x Pd x nanocrystals at 230 °C (before deactivation) and 250 °C (after deactivation) in 80 Torr NO, 8 Torr CO, and 672 Torr He. At 230 °C, prior to deactivation, the Pd-rich catalysts were more active for CO2 production than the Rh-rich catalysts.