In-situ construction of metal organic frameworks derived Co/Zn–S sandwiched graphene film as free-standing electrodes for ultra-high energy density supercapacitors

Metal organic frameworks (MOFs) with in situ porous nanostructures and high specific surface area have been widely used in supercapacitors , and the reduced graphene oxide (rGO) nanosheets is an excellent electronic conductor and support in loading other materials. Herein, for the first time, we report the unique Co/Zn-MOF derived Co/Zn–S polyhedron homogeneously embedded between the rGO sheets film as a binder-free electrode for high performance hybrid supercapacitor . Using a mild in situ synthesis method and vulcanization process, a 3D nano-electrode material Co/Zn–S@rGO is prepared by combining Zn 0.76 Co 0.24 S nanoparticles with rGO film. Among them, Co/Zn–S@rGO-7 samples with optimizing ratio deliver a high capacitance of 1640 F g −1 at the current density of 1 A g −1 in 6 M KOH alkaline aqueous electrolyte . The asymmetric supercapacitor (Co/Zn–S@rGO-7//AC) using Co/Zn–S@rGO as the positive electrode and activated carbon as the negative electrode shows an ultra-high energy density of 91.8 W h kg −1 , when the power density is 800 W kg −1 . Moreover, the device also shows a high cycle stability under high current density (90.3% capacity retention after 8000 cycles). It shows that the electrode materials prepared by this method has a good application prospect in electrochemical energy storage .