MIL-101(Fe)-Attached Graphene Oxide for High-Performance Supercapacitors with Sound Stability in Acid Electrolyte

Metal-organic frameworks (MOFs) have shown their unique potential in energy storage devices due to their large surface area, porous structure, and abundant active redox sites. However, in the field of MOFs-based supercapacitor electrodes, advantages of aqueous acid electrolyte are largely overlooked due to the instability of MOFs in an acid environment. To investigate potentials of aqueous acid electrolyte in MOFs-based supercapacitors, we chose MIL-101(Fe), a MOF with sound stability in acidic solution, and attached graphene oxide (GO) on it as a composite material (GO@MIL-101) to enhance its electrochemical performance and stability. As a result, it showed an excellent areal capacitance of 309.66 mF cm(-2) at 2 mA cm(-2) and a specific capacitance of 302.47 F g-1 at 1 A g(-1) with a potential window of 0.9 V with a good rate capacity (with 70.6% of initial capacitance (2 mA cm(-2)) at 8 mA cm(-2)) and good cycling stability of 80.01% capacitance retention after 9000 cycles in a three-electrode system in 3 M H2SO4 electrolyte. Furthermore, an asymmetric supercapacitor (ASC) was constructed as GO@MIL-101//Ti3C2Tx, and it showed a high energy density of 20.68 Wh kg(-1) at 315 W kg(-1) and 25.59 mu Wh cm(-2) at 1412.75 mu W cm(-2) with excellent cycling stability (89.6%) after 4000 cycles. This work puts forward an idea of constructing a MOFs-based electrode with sound stability in acidic solution and provides a promising path taking advantage of aqueous acid electrolyte in MOFs-based supercapacitors.