Polyvinylpyrrolidone (PVP) assisted in-situ construction of vertical metal-organic frameworks nanoplate arrays with enhanced electrochemical performance for hybrid supercapacitors

Construction of two-dimensional (2D) metal-organic frameworks (MOFs) for energy storage and conversion has attracted great attention due to the synergistic advantages of 2D nanostructures and MOFs. Herein, a Co-MOF material with different 2D morphologies of vertical nanoplate arrays and faveolate nanosheets are in-situ fabricated on Ni foam with and without using polyvinylpyrrolidone (PVP) as a regulator. Toward the application in energy storage, both of two morphologies of the Co-MOF exhibit good electrochemical properties. In particular, the vertical Co-MOF nanoplate arrays deliver a high areal capacity of 8.56 C/cm2 at the current density of 5 mA/cm2, which is much higher than that of faveolate Co-MOF nanosheets (2.39 C/cm2 at 5 mA/cm2). Moreover, a hybrid supercapacitor (HSC) device using the Co-MOF nanoplate arrays positive electrode and activated carbon (AC) negative electrode is assembled, which delivers a volumetric capacitance of 17.9 F/cm3 at 10 mA/cm2, a high energy density of 7.2 mW h cm−3 and a good cyclic stability (retaining over 88.0% of initial capacitance after 3000 cycles). These findings demonstrate that the as-fabricated 2D Co-MOFs possess a huge potential in energy storage.