Static adsorption of MOFs nanosheets on 3D nanocubes for supercapacitor electrode materials

Abstract

Metal-organic frameworks (MOFs) are of interest because of their excellent specific surface areas and pore structures. Two-dimensional (2D) nanosheets suffer from the disadvantages of random growth and easy agglomeration, which greatly limit their applications. This study combines nanosheets with structurally unique materials to improve their performance. Iron cobalt Prussian blue (FeCo-PBA) nanocubes of uniform size are synthesized at room temperature (25 ℃). Subsequently, the Prussian blue (PBA) surface is modified using sodium dodecyl sulfate to load Co-Ni-MOF nanosheets. This method enhances the adhesion of the nanosheets on the FeCo-PBA surface and improves the stability of the material. The PBA@Co-Ni-MOF is then vulcanized to fully activate the MOF metal species and obtain more active sites, and the sample PBA@CoS2/NiS2 is obtained. The obtained samples (PBA@CoS2/NiS2) are found to have good electrochemical performance. They exhibit an excellent specific capacitance of 1261 F g−1 (694 C g−1) at 1 A g−1. A hybrid supercapacitor consisting of activated carbon (AC) and PBA@CoS2/NiS2 composites as the cathode and anode, provide an energy density of 63 W h kg−1 at a power density of 837 W kg−1. The device exhibits outstanding cycle stability of 87% after 5000 cycles. The study demonstrates a flexible way to activate MOF to boost the performance of supercapacitor electrode materials. The static adsorption method maintains the stacking structure of clearly defined nanosheets while also enriching the active sites, which has potential for designing of MOF derivatives for energy storage devices.