Versatile superstructures composed of nanoparticles have recently been prepared using various disassembly methods. However, little information is known on how the structural disassembly influences the catalytic performance of the materials. Researchers from the University of New South Wales (UNSW) in Sydney, Australia, and elsewhere have had their research address this issue published in the journal Nature Communications.
Schematic illustration depicting synthesis of the 3D-hm LSMO catalysts. Image credit: Wang et al.
The team, led by UNSW researchers Prof. Rose Amal, Dr. Hamid Arandiyan and Dr. Jason Scott, has developed a novel method that allows them to engineer crystals with a large fraction of reactive facets.
“An ordered mesostructured La0.6Sr0.4MnO3 (LSMO) perovskite catalyst was disassembled using a unique fragmentation strategy, whereby the newly-exposed [001] reactive faces at each fracture were more reactive towards methane oxidation than the regular, i.e. before disassembly,” the authors explained.
“It is of significant interest to use methane as an alternative fuel to coal and oil due to its high hydrogen to carbon ratio which provides comparatively lower greenhouse gas emissions,” they said.
“Catalytic methane oxidation is often employed to stabilize ‘lean’ flames at relatively low temperatures as compared to non-catalytic combustion, thus preventing the formation of noxious nitrogen oxides.”
“Precious metals — for example, Pd and Pt — supported on Al2O3 are well studied and used as commercial catalysts for complete methane oxidation at low temperatures. However, the associated high cost and poor thermal stability of the catalytic elements persist as major challenges.”
“Using perovskite-type catalysts to replace noble metal supported catalysts for methane oxidation has attracted recent attention due to their excellent thermal stability.”
In their Nature Communications paper, the scientists describe a simple fragmentation method to synthesize a novel 3D hexapod mesostructured LSMO perovskite.
“On fragmenting 3D ordered macroporous (3DOM) structures in a controlled manner, via a process that has been likened to retrosynthesis, hexapod-shaped building blocks possessing newly exposed active crystal facets were harvested,” they said.
“Powerful characterization techniques were coupled with theoretical calculations to define the manner by which the improved configuration promotes the methane combustion reaction.”
“The new [110] reactive facets exposed at the weak fracture points of the 3DOM structure provide additional surface area as well as introduce surfaces possessing a reduced energy barrier for hydrogen abstraction from the methane (CH4* -> CH3* + H*) compared to the regular 3DOM [001] nonreactive facets.”
“We believe the design philosophy and the preparation strategy for 3D LSMO provides an original pathway towards engineering high-efficiency catalysts,” they added.
The fragmentation technique can be extended to the controlled preparation and stabilization of other nanomaterials with broad applications, for this reason, it is of great significance.
“The approach demonstrates feasibility, mesoporous material field is eager for more and more researchers from other fields to explore attractive applications,” said study first author Yuan Wang, a PhD student at UNSW.
“There is still ample room for improvement on hierarchically ordered perovskite catalysts designed to reduce atmospheric greenhouse gas concentrations by oxidizing methane emissions and therefore improve cost-effectiveness,” Dr. Arandiyan added.
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Yuan Wang et al. 2017. The controlled disassembly of mesostructured perovskites as an avenue to fabricating high performance nanohybrid catalysts. Nature Communications 8, article number: 15553; doi: 10.1038/ncomms15553
This article is based on text provided by the University of New South Wales.
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