Enhanced Performance of WO3/SnO2 Nanocomposite Electrodes with Redox-Active Electrolytes for Supercapacitors

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.