Three-dimensional Co3O4/flocculent graphene hybrid on Ni foam for supercapacitor applications

Abstract

A novel Co₃O₄/flocculent graphene (FG) hybrid on commercial Ni foam (NF) has been prepared. The unique flocculent graphene structure is prepared by combining a rapid filtering approach through Ni foam and a template method, in which the thermally expanded graphite is used as precursor and polystyrene (PS) microspheres are used as templates. The PS spheres play an important role in preventing the re-stacking of graphene nanosheets and the formation of flocculent graphene on NF. The PS spheres were first introduced as a guest material and were subsequently removed by calcination. The resulting free-standing FG/NF provides a three-dimensional and high conductivity scaffold for the hydrothermal growth of Co₃O₄ nanoclusters. The obtained Co₃O₄/FG/NF hybrid could be directly used as a binder-free supercapacitor electrode. Moreover, the Co₃O₄ nanoclusters on FG/NF scaffold exhibit improved specific capacitance of 1615 F g⁻¹ compared to that of the bare NF. The 3D active material layer of Co₃O₄/FG/NF hybrid, high conductivity of 3D FG/NF scaffold and functional features of the Co₃O₄ nanocluster morphology synergistically result in an improved electrochemical performance.