(660j) Tuning MOF-Based Metal Oxide Composite Structures for High Performance Energy Storage

Metal-organic frameworks (MOFs) are considered a novel type of crystalline porous structures. These structures are composed of inorganic vertices and organic linkers coupled through the coordination bonds. MOFs have distinct purposes such as high specific surface area, controllable pore size and good thermal stability that makes them good candidates to be used as porous templates.

In this work, the designed synthesis of NiCo₂O₄(Co₃O₄) double shell nanocages (DSNCs) from zeolitic imidazolate framework-67 is studied. The DSNCs are later embedded with graphene to enhance their conductivity and electrochemical performance. The strategy includes the synthesis of zeolite imidazolate framework-67(ZIF-67)/Ni-Co layer doubled hydroxide(LDH) precursor and subsequent transformation to NiCo₂O₄(Co₃O₄) DSNC by thermal annealing. The as-prepared DSNC structure is wrapped with graphene structure through a simple electrostatic self-assembly. Here, we focused on tuning the microstructure of NiCo₂O₄(Co₃O₄) DSNCs by controlling the crystal size of ZIF-67 and Ni-Co LDH formation while etching the initial MOF template.

NiCo₂O₄(Co₃O₄)@rGO composite structure showed a capacitance of 969 F.g^-1 at a discharge current density of 1 A.g^-1 and a remarkable stability, holding 88% of the initial capacitance after 10000 cycles of charge-discharge.

This work shows a universal process for controlled synthesis of different complex spinel structures that can be used for various applications.