Effect of Interfacial Structure on Catalytic Properties of Bimetallic Nanoparticles

by Akhil Tayal (DESY)



Nanoparticles (NPs) of platinum group elements such as Ru and Pd show remarkable catalytic properties and are widely used for the chemical storage of hydrogen. Numerous recent investigations reveal that the mono-metallic NPs of Ru suffers from one critical drawback of poor thermal stability. It was observed that the Ru NPs used for the three-way catalytic process gets oxidized to form volatile RuO4 and evaporates at moderate temperatures, thus deteriorating catalytic performance. Similarly, NPs of Pd possess a wide range of applications for fuel cell electrodes, automobile exhaust-gas purification, hydrogen storage, etc. However, it suffers from surface poisoning by CO, and it is less economically viable for the hydrogen storage application. Recently, various investigations on the bimetallic NPs, such as Pd-Ru, Ru-Cu, Pt-Ru, Au-Pt, and Ag-Ru, show a substantial improvement in the catalytic properties, hydrogen storage capacity, and stability relative to the individual NPs. Interestingly it was found that many bimetallic systems show catalytic properties that are not observed in the mono-metallic NPs. Moreover, many of the above bimetallic systems are immiscible in bulk but can only be formed in the solid-solution alloy phase in the NPs. It suggests that the new form of NPs solid-solution alloys shows distinct behavior from the individual NPs. Therefore, to explore the novel catalytic properties of these bimetallic systems, a systematic investigation is required to understand their local structure. The local structure in the proximity of alloy mixing sites strongly correlates with the electronic structure that gives rise to the novel catalytic properties. In this talk, I will present the XAFS investigation of various bimetallic systems such as Pd-Ru for the three-way catalytic applications. Pd-Pt and Ag-Rh NPs alloys for the chemical storage of hydrogen. The finding reveals that the local structure around the interfacial region actively governs the catalytic properties in these systems.