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A three-dimensional reduced graphene oxide/nickel-cobalt sulfide (RGO/NiCo2S4) aerogel was fabricated by an efficient and facile one-step hydrothermal approach. The NiCo2S4 needle-like structure consisted of many small nanoparticles well attached to the surface of the RGO sheet. The prepared aerogel had high porosity and conductivity. As an active electrode material for supercapacitors, the RGO/NiCo2S4 aerogel exhibited a large capacitance of 813 F g−1 at 1.5 A g−1. Besides, the asymmetric supercapacitor (RGO/NiCo2S4 aerogel//RGO) showed a Cs of 45.3 F g−1 at 1.0 A g−1 and a suitable remaining capacitance of over 84.3 % after 2000 cycles. The asymmetric supercapacitor had a high energy density of 40.3 Wh kg−1 at 375.0 W kg−1 and a power density of 26.2 kW kg−1 at 3.7 kWh kg−1, which suggests this device has great potential applications in energy storage.

Transition metal chalcogenides have wide studied as active electrode materials for electrochemical storage devices. In this study, we successfully fabricated a binder-free electrode of hierarchical Co-Mo-S nanosheets on nickel foam (CMS/NF) by a facile hydrothermal method under microwave irradiation. The CMS layer, with a thickness of a few nanometers, was decorated on the NF's surface. Taking advantage of the large specific surface area of NF and the high capacitance and porosity of CMS, the prepared electrode is believed to have a rapid electron and ion transport, large electroactive sites, and excellent cycle stability. The specific capacitance of 1080 F g−1 at 1 A g−1 and excellent cycling stability (90.4% retention in specific capacitance after 5000 cycles) were obtained. For further practical applications, an asymmetric supercapacitor was assembled using the CMS/NF as the cathode and the activated carbon as anode material. The prepared device exhibited a high capacitance of 47 F g−1 at 1 A g−1 and a high energy density of 42.6 Wh kg−1 at a power density of 850.3 W kg−1 at a wide operating voltage of 1.6 V. This current method could provide a rapid one-step process for other 3D porous electrodes for high-performance supercapacitors.

Dye and heavy metal contaminants are mainly aquatic pollutants. Although many materials and methods have been developed to remove these pollutants from water, effective and cheap materials and methods are still challenging. In this study, highly porous hydroxyapatite/graphene oxide/chitosan beads (HGC) were prepared by a facile one-step method and investigated as efficient adsorbents. The prepared beads showed a high porosity and low bulk density. SEM images indicated that the hydroxyapatite (HA) nanoparticles and graphene oxide (GO) nanosheets were well dispersed on the CTS matrix. FT-IR spectra confirmed good incorporation of the three components. The adsorption behavior of the obtained beads to methylene blue (MB) and copper ions was investigated, including the effect of the contact time, pH medium, dye/metal ion initial concentration, and recycle ability. The HGC beads showed rapid adsorption, high capacity, and easy separation and reused due to the porous characteristics of GO sheets and HA nanoparticles as well as the rich negative charges of the chitosan (CTS) matrix. The maximum sorption capacities of the HGC beads were 99.00 and 256.41 mg g−1 for MB and copper ions removal, respectively.

A binder-free 3D electrode of MnO 2 arrays on graphene@nickel foam was successfully prepared via a two-step method. The nickel foam was first coated with a graphene sheet by chemical vapor deposition (CVD) and then decorated with MnO 2 of different morphologies, ultrathin MnO 2 nanosheets and ultralong MnO 2 nanowires, by facile hydrothermal method. Due to the large specific surface area, high electronic conductivity and good capacitance of electrode materials, the obtained electrode exhibited rapid electron and ion transport, large electroactive surface area, and excellent structural stability. The electrode showed a high specific capacitance of 723 F cm −2 at a high current density of 30 mA cm −2 and a good cycling stability (with a negligible 2.4% decay in specific capacitances after 2300 cycles), promising its applications to high-performance supercapacitors.

This study presents a high porous nanocomposite composed of reduced graphene oxide and NiMoS4 (RGO/NiMoS4) for supercapacitor electrode materials. The different morphologies of NiMoS4 growth on RGO sheets were obtained via a facile one-step microwave-assisted method. The obtained material comprised NiMoS4 nanoneedles of several nanometers in diameter, which are well attached to the surface of RGO nanosheets. The RGO/NiMoS4 nanocomposite had a mesoporous structure, high specific surface area, and high electric conductivity. These excellent characteristics yield a fast electron and ion transport, and a large number of electroactive sites. The RGO/NiMoS4 composite delivered a specific capacitance of 1273 F g−1 at a current density of 1.0 A g−1, high-rate capability of 71.3% retention from 1 to 6.5 A g−1. Besides, an asymmetric supercapacitor device had a capacitance of 80 F g−1 at a current density of 1.0 A g−1 and an energy density of 82.5 Wh kg−1 at a power density of 1000 W kg−1 with an operating voltage of 1.6 V. Thus, the current RGO/NiMoS4 nanocomposite has a great potential for energy storage application.