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Encapsulation of ultra small metal clusters in silica: Evolution of the concept of nanoreactors and the case of Ag–Pd@SiO2 alloy catalyst

Paper ID Volume ID Publish Year Pages File Format Full-Text
54099 46996 2015 7 PDF Available
Title
Encapsulation of ultra small metal clusters in silica: Evolution of the concept of nanoreactors and the case of Ag–Pd@SiO2 alloy catalyst
Abstract

•Encapsulation in confined space minimises sintering in noble metal nanoparticles.•Thiol protected ultra small clusters of noble metals used as precursors.•Sinter resistant AgPd@SiO2 alloy catalysts synthesised from Ag and Pd clusters.•Catalytic activity is tested by paranitrophenol reduction.

The concept of encapsulation of ultra small clusters within silica evolved as a means to address the sintering of active metal nanoparticles and subsequent deactivation observed in supported noble metal catalysts. It is hypothesised that sintering, which mainly occurs due to mobility of metal species on the support surfaces, can be minimised if the growth and movement of metal nanoparticles are constrained. First, nanoparticles are isolated inside 1D channels in 2D mesoporous compounds and the idea develops to complete encapsulation of thiol protected ultra small nanoclusters in silica spheres. Sintering is better controlled in the latter due to the confined space for growth of nanoparticles. Access of reactant molecules to the active metal surfaces also is ensured by porosity created in the silica matrix forming the basis of the concept of nanoreactors. In this paper, we elaborate on the evolution of this concept from our earlier work on highly sinter resistant silica encapsulated Au, Pd and Au–Pd alloys to the present system of Ag–Pd alloy encapsulated in silica. Silver, with the lowest Tammann temperature among noble metals, is highly prone to sintering which is adequately controlled by alloying with Pd as well as encapsulation in silica. Its enhanced activity in paranitrophenol reduction in comparison with pure metals indicates the advantageous effect of alloying.

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Keywords
Encapsulation; Sintering; Ag–Pd alloy; Ultra small nanoclusters; Sinter-resistant
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Encapsulation of ultra small metal clusters in silica: Evolution of the concept of nanoreactors and the case of Ag–Pd@SiO2 alloy catalyst
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Publisher
Database: Elsevier - ScienceDirect
Journal: Catalysis Today - Volume 251, 1 August 2015, Pages 114–120
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us