Graphenes prepared by three different methods have been investigated as electrode materials in electrochemical supercapacitors. The samples prepared by exfoliation of graphitic oxide and by the transformation of nanodiamond exhibit high specific capacitance in aq. H 2 SO 4 , the value reaching up to 117 F/g. By using an ionic liquid, the operating voltage has been extended to 3⋅5 V (instead of 1 V in the case of aq. H 2 SO 4 ), the specific capacitance and energy density being 75 F/g and 31⋅9 Wh kg -1 respectively. This value of the energy density is one of the highest values reported to date. The performance characteristics of the graphenes which are directly related to the quality, in terms of the number of layers and the surface area, are superior to that of single-walled and multi-walled carbon nanotubes.

With the exploding interest in transition metal chalcogenides, sulfide minerals containing the dianion S2(2-), such as pyrite (FeS2), cattierite (CoS2), and vaesite (NiS2), have recently attracted much attention for potential applications in energy conversion and storage devices. However, the synthesis of the patronite structure (VS4, V(4+)(S2(2-))2) and its applications have not yet been clearly demonstrated because of experimental difficulties and the existence of nonstoichiometric phases. Herein, we report the synthesis of VS4 using a simple, facile hydrothermal method with a graphene oxide (GO) template and the characterization of the resulting material. Tests of various templates such as CNT, pyrene, perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA), and graphite led us to the conclusion that the graphitic layer plays a role in the nucleation during growth of VS4. Furthermore, the VS4/rGO hybrid was proved to be a promising functional material in energy storage devices.

SummaryInteraction with electron -donor and -acceptor molecules such as aniline and nitrobenzene brings about marked changes in the Raman spectrum and the electronic structure of graphene, prepared by the exfoliation of graphitic oxide.

The introduction of ferromagnetic order in ZnO results in a transparent piezoelectric ferromagnet and further expands its already wide range of applications into the emerging field of spintronics. Through an analysis of density functional calculations we determine the nature of magnetic interactions for transition metals doped ZnO and develop a physical picture based on hybridization, superexchange, and double exchange that captures chemical trends. We identify a crucial role of defects in the observed weak and preparation sensitive ferromagnetism in ZnO:Mn and ZnO:Co. We predict and explain co-doping of Li and Zn interstitials to both yield ferromagnetism in ZnO:Co, in contrast with earlier insights, and verify it experimentally.

We report here the synthesis of layer structured WS2/reduced graphene oxide (RGO) hybrids by a facile hydrothermal method for its possible application as supercapacitor materials in energy storage devices. The prepared two-dimensional materials are characterized thoroughly by various analytical techniques to ascertain their structure and to confirm the absence of any impurities. Two-electrode capacitance measurements have been carried out in aqueous 1 M Na2SO4. The WS2/RGO hybrids exhibited enhanced supercapacitor performance with specific capacitance of 350 F/g at a scan rate of 2 mV/s. The obtained capacitance values of WS2/RGO hybrids are about 5 and 2.5 times higher than bare WS2 and RGO sheets. Because of the unique microstructure with combination of two layered materials, WS2/RGO hybrids emerge as a promising supercapacitor electrode material with high specific capacitance, energy density, and excellent cycling stability.