Controlled thermolysis of MIL-101(Fe, Cr) for synthesis of FexOy/porous carbon as negative electrode and Cr2O3/porous carbon as positive electrode of supercapacitor

Abstract In the present study, two kinds of metal oxide/carbon nanocomposite were prepared through calcination of MIL-101(Fe, Cr). The morphological and structural properties of the specimens were investigated using X-ray diffraction, Fourier-transform infrared spectroscopy, Brunauer, Emmett, and Teller analysis, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy. The electrode materials were also electrochemically investigated using cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy techniques in 6 M KOH electrolyte. Because of synergistic effect of metal oxides and carbon, the obtained samples showed excellent performance; in a way that Cr2O3/C and FexOy/C showed high specific capacitance of 420 F g−1 and 114 F g−1 at current density of 2 A g−1, respectively. The Cr2O3/C electrode also displayed high rate capability even at scan rate of 1500 mV s−1. Moreover, we successfully developed an asymmetric supercapacitor in which Cr2O3/C served as positive electrode and FexOy/C served as negative electrode. The asymmetric device can deliver an energy density of 9.6 W h kg−1 and power density of 8000 W kg−1, with 93% capacitance retention after 3000 charge–discharge cycles. These outcomes show that the MOF-derived metal oxide/carbon composite can be regarded as a promising development for advanced electrode materials for applying in supercapacitors.