High-Performance Energy Storage and Conversion Materials\nDerived from a Single Metal–Organic Framework/Graphene Aerogel\nComposite

Abstract

Metal\noxides and carbon-based materials are the most promising\nelectrode materials for a wide range of low-cost and highly efficient\nenergy storage and conversion devices. Creating unique nanostructures\nof metal oxides and carbon materials is imperative to the development\nof a new generation of electrodes with high energy and power density.\nHere we report our findings in the development of a novel graphene\naerogel assisted method for preparation of metal oxide nanoparticles\n(NPs) derived from bulk MOFs (Co-based MOF, Co­(mIM)₂ (mIM\n= 2-methylimidazole). The presence of cobalt oxide (CoO_<i>x</i>) hollow NPs with a uniform size of 35 nm monodispersed\nin N-doped graphene aerogels (NG-A) was confirmed by microscopic analyses.\nThe evolved structure (denoted as CoO_<i>x</i>/NG-A) served as a robust Pt-free electrocatalyst with excellent\nactivity for the oxygen reduction reaction (ORR) in an alkaline electrolyte\nsolution. In addition, when Co was removed, the resulting nitrogen-rich\nporous carbon–graphene composite electrode (denoted as C/NG-A)\ndisplayed exceptional capacitance and rate capability in a supercapacitor.\nFurther, this method is readily applicable to creation of functional\nmetal oxide hollow nanoparticles on the surface of other carbon materials\nsuch as graphene and carbon nanotubes, providing a good opportunity\nto tune their physical or chemical activities.