Pd@Rh core-shell nanocrystals with well-defined facets and their enhanced catalytic performance towards CO oxidationf

摘要

Here we report a facile synthesis of Pd@Rh core-shell nanocrystals with octahedral and cubic shapes.Under optimized conditions,Rh atoms can be deposited on Pd octahedral or cubic seeds in a layer-by-layer fashion to generate core-shell nanocrystals with a well-controlled shape.We then use CO oxidation as a probe to evaluate the catalytic performance of the core-shell nanocrystals with reference to a number of commercial catalysts.When supported on mesoporous silica,both the octahedral and cubic Pd@Rh nanocrystals show CO to CO2 conversion levels similar to that of a commercial Pt/Al2O3 catalyst while the two catalysts based on pure Rh(commercial Rh/C and Rh nanocubes/silica)needed much higher temperatures to reach the same level of conversion.In terms of ignition temperature,the Rh nanocubes show a value of 260 °C while those of the octahedral and cubic Pd@Rh nanocrystals are as low as 140 and 150 °C,respectively.Our results suggest that there is no significant difference between the octahedral and cubic PdcaRh nanocrystals in terms of performance towards CO oxidation while both of them are advantageous over Rh nanocubes or Rh/C.