Facile Hydrothermal Synthesis and First Principle Computational Studies of NiSb2O4 and Its Electrochemical Properties with Ni3(Fe(CN)6)2(H2O) for Hybrid Supercapacitors

To realize the ideal electrode material for supercapacitors, the scientific community has been prompted to investigate a variety of materials. This study deals with the hydrothermal synthesis of NiSb2O4 for the first time for application to hybrid supercapacitors. First-principles density functional theory (DFT) calculations are employed to study the electronic structure of synthesized NiSb2O4. The single phase tetragonal structure NiSb2O4 is revealed from X-ray diffraction (XRD) analysis. Rod-like micron-sized structures are revealed through field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analysis. Structural parameters and unit cell dimensions are deduced from Rietveld refinement analysis. The comparative effects of various K+ electrolytes (1 M KOH, 1 M KCl, 1 M KNO3 and 0.5 K2SO4) on the NiSb2O4 negative electrode material are studied. Cyclic voltammogram (CV) showed greatest specific capacitance of 758 F g−1 at 2 mV s−1 in 1 M KOH. Galvanostatic charge-discharge analysis (GCD) exhibited capacitance of 382 F g−1 at 1 A g−1. The asymmetric supercapacitor is assembled with synthesized Ni3(Fe(CN)6)2(H2O) as positive electrode and the device exhibits a specific capacitance of 344 F g−1 at 1 mV s−1 in 1 M KOH in the wider potential window of 1.6 V, suggesting its potential application as an energy storage device.