Role of oxygen vacancies and porosity in enhancing the electrochemical properties of Microwave synthesized hematite (α-Fe2O3) nanostructures for supercapacitor application

Abstract

Herein, we report a green and cost-effective microwave-assisted synthesis of oxygen vacancy-rich porous α-Fe2O3 nanorods and α-Fe2O3 nanospheres for supercapacitor applications. The synthesized samples were characterized using Field emission scanning electron microscopy (FESEM) coupled with Energy Dispersive X-Ray (EDX), X-ray diffraction (XRD), Raman Spectroscopy, X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET) analysis. The synthesized α-Fe2O3 nanorods have a high specific surface area of 133.6 m2g-1 and a pore size of around 15.2 nm. With the use of cyclic voltammetry (CV), galvanostatic charge-discharge experiments, and electrochemical impedance spectroscopy, the electrochemical characteristics of α-Fe2O3 nanorod and nanosphere-based electrodes were studied and compared. In contrast to hematite nanospheres, which displayed a specific capacitance of only 715.05 Fg-1, hematite nanorods exhibited the highest specific capacitance of 1253.02 Fg-1 and excellent capacitance retention of 93% after a long life of 3000 cycles in 3 M KOH electrolyte with a potential window of −0.2 to 0.55 V. The enhancement in electrochemical properties could be attributed to its porous nature and the presence of oxygen vacancies which provided more active sites for redox reactions and high electrical conductivity. The results demonstrate that oxygen vacancy-rich and porous α-Fe2O3 nanorods synthesized via the green approach can serve as an ideal electrode material for supercapacitors.