Structure-performance relationships of Rh and RhPd alloy supported catalysts using combined EDE/DRIFTS/MS

Energy dispersive extended X-ray absorption fine structure spectroscopy (ED-XAFS), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and mass spectrometry (MS), have been combined for the structure-function study of Rh and RhPd supported catalysts for the reduction of NO by CO. The combined results show that although alloying of Rh with Pd prevents the dissociative oxidation of the Rh by NO, it does not prevent the extensive disruptive oxidation of Rh by CO. The influence of oxidative disruption by molecular CO in such systems may therefore be far more pervasive and catalytically important than has been previously observed. The overall metal particle size observed in the RhPd alloy system during the CO/NO reaction is significantly larger than for the Rh-only system for the entire temperature range employed. The catalytically active sites, however, are likely to be similar, with the overall activity of the alloy system to be reduced due to inactive RhPd alloy nanoparticles.