RESUMO
For effective supercapacitors, we developed a process involving chemical bath deposition, followed by electrochemical deposition and calcination, to produce WO3/SnO2 nanocomposite electrodes. In aqueous solutions, the hexagonal WO3 microspheres were first chemically deposited on a carbon cloth, and then tin oxides were uniformly electrodeposited. The synthesized WO3/SnO2 nanocomposite was characterized by XRD, XPS, SEM, and EDX techniques. Electrochemical properties of the WO3/SnO2 nanocomposite were analyzed by cyclic voltammetry, galvanostatic charge-discharge tests, and electrochemical impedance spectroscopy in an aqueous solution of Na2SO4 with/without the redox-active electrolyte K3Fe(CN)6. K3Fe(CN)6 exhibited a synergetic effect on the electrochemical performance of the WO3/SnO2 nanocomposite electrode, with a specific capacitance of 640 F/g at a scan rate of 5 mV/s, while that without K3Fe(CN)6 was 530 F/g. The WO3/SnO2 nanocomposite catalyzed the redox reactions of [Fe(CN)6]3/[Fe(CN)6]4- ions, and the [Fe(CN)6]3-/[Fe(CN)6]4- ions also promoted redox reactions of the WO3/SnO2 nanocomposite. A symmetrical configuration of the nanocomposite electrodes provided good cycling stability (coulombic efficiency of 99.6% over 2000 cycles) and satisfied both energy density (60 Whkg-1) and power density (540 Wkg-1) requirements. Thus, the WO3/SnO2 nanocomposite prepared by this simple process is a promising component for a hybrid pseudocapacitor system with a redox-flow battery mechanism.
