One-pot synthesis of CoFe(2)O(4)/rGO hybrid hydrogels with 3D networks for high capacity electrochemical energy storage devices

CoFe(2)O(4)/reduced graphene oxide (CoFe(2)O(4)/rGO) hydrogel was synthesized in situ via a facile one-pot solvothermal approach. The three-dimensional (3D) network structure consists of well-dispersed CoFe(2)O(4) nanoparticles on the surfaces of graphene sheets. As a binder-free electrode material for supercapacitors, the electrochemical properties of the CoFe(2)O(4)/rGO hybrid hydrogel can be easily adjusted by changing the concentration of the graphene oxide (GO) precursor solution. The results indicate that the hybrid material made using 3.5 mg mL(−1) GO solution exhibits an outstanding specific capacitance of 356 F g(−1) at 0.5 A g(−1), 68% higher than the pure CoFe(2)O(4) counterpart (111 F g(−1) at 0.5 A g(−1)), owing to the large specific surface area and good electric conductivity. Additionally, an electrochemical energy storage device based on CoFe(2)O(4)/rGO and rGO was assembled, which exhibits a high energy density of 17.84 W h kg(−1) at a power density of 650 W kg(−1) and an excellent cycling stability with 87% capacitance retention at 5 A g(−1) after 4000 cycles. This work takes one step further towards the development of 3D hybrid hydrogel supercapacitors and highlights their potential application in energy storage devices.