Effect of Interfacial Structure on Catalytic Properties of Bimetallic Nanoparticles
by
Akhil Tayal(DESY)
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Europe/Berlin
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Description
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.
