Fish bladder-based activated carbon/Co₃O₄/TiO₂ composite electrodes for supercapacitors

Cobalt oxide/titanium dioxide/activated carbon (Co₃O₄/TiO₂/Ac) composite was synthesized using simple sol-gel method before annealing at 300 °C. Fish bladder derived porous carbon used for the composite was synthesized by pyrolysis followed by chemical activation. Both scanning electron microscopy (SEM) and X-ray diffraction displayed Co₃O₄ and TiO₂ phases well embedded onto the carbon matrices. Cyclic voltammetry in 6 M KOH electrolyte demonstrated that the composite has an excellent specific capacity of 946 Fg^-1 for Co₃O₄/TiO₂/Ac as compared to Co₃O₄/Ac, TiO₂/Ac, and Ac with specific capacitances of 845, 340, and 308 F g⁻¹, respectively at 5 mVs⁻¹. Impedance spectroscopy reveals that the composite has good capacitive behavior with a series resistance of 0.6 Ω. Besides, Co₃O₄/TiO₂/Ac maintains 89.7% of the initial capacitance after 2000 cycles. This study shows that the synergistic effect of the metal oxides and the carbon in the composite can enhance capacitance for practical supercapacitor applications.