Novel composites of Ni-MOF/CNTs and rGO/C₃N₄were synthesized to assemble an asymmetric supercapacitor with high energy and power density.

Graphene/manganese dioxide (MnO₂) composite papers (GMCP) are fabricated via a simple three-step route: preparation of graphene oxide/MnO₂ composite (GOMC) dispersion, subsequent vacuum filtration of GOMC dispersion to achieve graphene oxide/MnO₂ composite paper (GOMCP), and finally thermal reduction of GOMCP to generate GMCP. The morphology and microstructure of the prepared samples are characterized by field-emission scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, Fourier transformation infrared spectroscopy, thermal gravimetric analysis and X-ray photoelectron spectroscopy. Moreover, as a binder-free and flexible electrode material for supercapacitors, the electrochemical properties of the prepared GMCP are evaluated by cyclic voltammetry and galvanostatic charge/discharge tests. As a result, the specific capacitance of the GMCP with the MnO₂ weight ratio of 24% (GMCP-24) reaches 256 F g⁻¹ at a current density of 500 mA g⁻¹ and also shows good cycle stability, indicating a promising potential application as an effective electrode material for supercapacitors.

A new class of multilayer films was constructed by electrostatic layer-by-layer self-assembly, using poly(sodium 4-styrenesulfonate) mediated graphene sheets (PSS-GS), manganese dioxide (MnO₂) sheets, and poly(diallyldimethylammonium) (PDDA) as building blocks. UV-vis spectroscopy, field-emission scanning electron microscopy and X-ray photoelectron spectroscopy were used to characterize the microstructures and morphologies of the multilayer films. Capacitive properties of the synthesized multilayer film electrodes were studied using cyclic voltammetry and galvanostatic charge/discharge in 0.1 M Na₂SO₄ electrolyte. The specific capacitance of the ITO/(PDDA/PSS-GS/PDDA/MnO₂)₁₀electrode reached 263 F g⁻¹ at a discharge current density of 0.283 A g⁻¹; moreover, this film electrode also shows a good cyclic stability and high Coulombic efficiency. Anticipatedly, the synthesized multilayer films will find promising applications as a novel electrode material in supercapacitors and other devices in virtue of their outstanding characteristics of controllable capacitance, good cycle stability, low cost and environmentally benign nature.