Solvothermal Synthesis of Fe2O3 Loaded Activated Carbon as Electrode Materials for High-performance Electrochemical Capacitors

This article describes a facile solvothermal synthesis method to prepare Fe2O3/AC composites for electrochemical capacitors from Iron (III) chloride hexahydrate (FeCl3·6H2O), activated carbon (AC, from petroleum coke), and four different precipitants (i.e., NaOH, CH3COONa, HMT, CO(NH2)2). X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS) and Thermogravimetric (TG) analysis show that the products consisted of nanosized α-Fe2O3 (weight ratios: 48.1, 47.9, 44.2, 44.3%) loaded onto AC particles (∼ 20 μm). Significantly, both kind and dosage of precipitants exhibit effects on the specific capacitances of Fe2O3/AC composites. The highest specific capacitance reaches up to 240 F g−1 (at a current density of 1 A g−1 in 6 M KOH aqueous electrolyte) when the molar ratio of CH3COONa: FeCl3 is 9. On the other hand, the sample prepared with NaOH: FeCl3 molar ratio being 1.5 exhibits excellent rate capability with specific capacitance of 215 F g−1 at 1 A g−1, and 89.3, 82.3, 78.1, 72.6 and 65.1% capacity retention at 2, 5, 10, 20, and 40 A g−1, respectively. These electrochemical performances are superior to other materials consisted of Fe2O3/carbon nanotube (CNT), graphene oxide (GO) or reduced graphene oxide (rGO) composites, demonstrating the great potential of Fe2O3/AC composites in the development of high-performance electrode materials for electrochemical capacitors.