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Graphene Nanocomposites Templated from Cage-Containing Metal-Organic Frameworks for Oxygen Reduction in Li-O2 Batteries
Here, in an effort to develop high-performance ORR catalysts, we have been interested in investigating the templating effect of cage-containing metal-organic frameworks (MOFs) on the formation of novel nanocarbon composites and on the resulting ORR activity in Li-O2 batteries. Due to the accessibility of metal-cation centers, the variety of building blocks, and the high micropore surface area, MOF is able to offer unique opportunities in synthesizing efficient ORR catalysts.(12) However, to date, the studied MOFs as precursors for catalyst synthesis are limited to commercially available microporous ones. The use of specially designed MOFs with unique structures for preparing high-performance ORR catalysts remains unexplored.
In this work, we report the first demonstration of a newly-developed Co containing MOF material with giant polyhedral cages (cage size ~1.8 nm) as a template in preparation of transition metal-nitrogen-carbon ORR catalysts, especially for nonaqueous Li-O2 battery cathodes. As a result, a Fe-based catalyst dominant by nitrogen-doped graphene/graphene tube (tubular graphene) nanocomposites was prepared through heat-treating a novel nitrogen/carbon precursor dicyandiamide (DCDA) in the presence of iron species. The in situ formation of nitrogen-doped graphene/graphene tube templated by the MOF may provide a new route for preparation of carbon nanocomposites for electrochemical energy applications.
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