Sol-gel synthesis, characterization, and supercapacitor applications of MCo2O4 (M = Ni, Mn, Cu, Zn) cobaltite spinels

High performance MCo2O4spinels (M = Ni, Mn, Cu, Zn) were synthesized by the sol gel method (citrate) and their capacitive behavior was investigated in alkaline electrolyte. Their structural, morphological, functional groups and textural properties were characterized by TG/DSC, XRD, SEM, FTIR, EDS and BET. The capacitive properties of spinel MCo2O4 samples were thoroughly investigated in 1 M KOH aqueous electrolyte using cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The results revealed high stability of the samples and excellent electrochemical reversibility, and exhibited specific capacity depending on the nature of the transition metal ion M. A high specific capacitance of 285 F g−1 was measured for CuCo2O4 and a low capacitance of 158 F g−1 for ZnCo2O4.In addition, MCo2O4 spinels displayed good stability during long-term cycles with a cycling efficiency which exceeds75% after 1000 cycles. The obtained results classified MCo2O4 cobaltite spinels as most promising materials for their application in super capacitors.