New Role of Pd Hydride as a Sensor of Surface Pd Distributions in Pd−Au Catalysts

Abstract Isolated or contiguous, the surface distributions of Pd atoms in the Pd?Au bimetallic nanoparticle (NP) catalysts often influence activity and selectivity towards specific reactions. In this study, we used a concomitant Pd hydride formation upon H2 exposure as a probe of presence of contiguous Pd regions in bimetallic NPs. For demonstrating this method, we prepared silica supported monometallic Pd and bimetallic Pd?Au NPs with a Pd/Au ratio of 25/75 (Pd25Au75) and used X-ray absorption spectroscopy, scanning transmission electron microscopy and infrared spectroscopy to detect and quantitatively analyze the Pd hydride regions. This work provides a new approach to characterizing intra-particle heterogeneities within the bimetallic NPs at ambient temperature and pressure.