Designing three-dimensional hierarchical porous chrysanthemum flower-like CoNiFe2O4/carbon spheres as high-performance electrode for supercapacitors and oxygen reduction reaction

Novel three-dimensional electrode materials with high capacitance, long cycle stability and electrocatalytic activity are designed through hydrothermal method. 3D chrysanthemum flower-like morphology of mixed transition metal ferrite (CoNiFe2O4) is fabricated by using carbon spheres (CS) as supporting material and investigated as electrode material for supercapacitor and oxygen reduction reaction. The morphological and structural characterizations of synthesized samples have been examined using scanning electron microscopy, X-ray diffraction, and Brunauer–Emmett–Teller. Cyclic voltammetry, galvanostatic charge discharge and electrochemical impedance spectroscopy are executed for the electrochemical studies. CS-CoNiFe2O4 has illustrated specific area of about 315 m2 g−1, the high specific capacitance of 1542 F g−1 at sweep rate 2 mV s−1, high energy density 63 Wh kg−1 at 0.5 A g−1 current density and capacitance retention (95%) after 1500 cycles in 1.0 M KOH aqueous solution. Furthermore, ORR results reveal a significantly good electrocatalytical activity through high current density and 4-electron transfer process in alkaline medium. The obtained results have suggested that the unusual electrochemical and electrocatalytic activity is raised from synergetic effects between transition metals and carbon materials.