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.

Flexible graphene sheet (GS)/polyaniline (PANi) nanofibers composite paper was prepared via a facile and fast two-step route composed of electrostatic adsorption between negatively-charged poly(sodium 4-styrenesulfonate) (PSS) mediated GS (coded as PSS-GS) and positively-charged PANi nanofibers and the follow-up vacuum filtration of the as-prepared PSS-GS/PANi nanofibers suspension. By observations of field emission scanning electron microscopy (FE-SEM) and high resolution transmission electron microscopy (HR-TEM), it is clearly seen that representative and highly ordered layered PSS-GS/PANi composite papers have been achieved and PANi nanofibers are coated by PSS-GS. In addition, the synthesized PSS-GS/PANi composite papers are also characterized by Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy, and the results further confirm the successful synthesis of PSS-GS/PANi composites and the existence of strong interaction between PSS-GS and PANi nanofibers. The most interesting thing is the effective synergy can remarkably improve electrochemical properties of GS by introducing PANi nanofibers, which can ascribe to high surface area of GS and good combination between PSS-GS and PANi nanofibers. The highest specific capacitance of the composites reaches 301 F/g. Thermogravimetry analysis (TGA) indicates that the thermal stability of the PSS-GS/PANi composites is obviously improved compared to the pure PSS-GS and PANi.

NixCo_1−x(OH)₂ composite microspheres are successfully synthesized with the assistance of alkali solution by employing a bimetallic Co–Ni–MOF as both the precursor and the self-sacrificing template, demonstrating excellent electrochemical performance.