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.