[en] ABSTRACT: A nanocomposite for supercapacitor electrode materials was designed and developed by integrating partially disabled Cu_2O (low specific capacity, but high cycling ability) and Ni(OH)_2 (low cyclability and high specific capacity) in the presence of reduced graphene oxide (RGO) nanosheets. Nanocomposite of Cu_2O/RGO/Ni(OH)_2 was directly grown on nickel foam (NF) through a facile one-pot hydrothermal process without any other reductant or oxidant, in which nickel foam acted as both a reductant of GO and Ni source, and a substrate for nanocomposite. The resultant Cu_2O/RGO/Ni(OH)_2 nanocomposites were characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectrometer (XPS), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The electrochemical performance of the as-synthesized Cu_2O/RGO/Ni(OH)_2/NF electrodes were evaluated using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectrometry (EIS) in 6 mol L"−"1 KOH aqueous solution. This Cu_2O/RGO/Ni(OH)_2 nanocomposite exhibits superior capacitive performance: high capability (3969.3 mF cm"−"2 at 30 mA cm"−"2, i.e., 923.1 F g"−"1 at 7.0 A g"−"1), excellent cycling stability (92.4% retention even after 4,000 cycles, for RGO/Ni(OH)_2/NF, 92.3% after 1,000 cycles), and good rate capacitance (50.3% capacity remaining at 200 mA cm"−"2)

[en] Reduced graphene oxide (RGO) on nickel hydroxide (Ni(OH)₂) film was synthesized via a green and facile hydrothermal approach. In this process, graphene oxide (GO) was reduced by nickel foam (NF) while the nickel metal was oxidized to Ni(OH)₂ film simultaneously, which resulted in RGO on Ni(OH)₂ structure. The RGO/Ni(OH)₂ composite film was characterized using by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and field-emission scanning electron microscope (FESEM). The electrochemical performances of the supercapacitor with the as-synthesized RGO/Ni(OH)₂ composite films as electrodes were evaluated using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), electrochemical impedance spectrometry (EIS) in 1 M KOH aqueous solution. Results indicated that the RGO/Ni(OH)₂/NF composite electrodes exhibited superior capacitive performance with high capability (2500 mF cm⁻² at a current density of 5 mA cm⁻², or 1667 F g⁻¹ at 3.3 A g⁻¹), compared with pure Ni(OH)₂/NF (450 mF cm⁻² at 5 mA cm⁻², 409 F g⁻¹ at 3.3 A g⁻¹) prepared under the identical conditions. Our study highlights the importance of anchoring RGO films on Ni(OH)₂ surface for maximizing the optimized utilization of electrochemically active Ni(OH)₂ and graphene for energy storage application in supercapacitors

[en] Graphical abstract: - Highlights: • A uniform 3D nest-like nanostructure of RGO/Ni_3S_2 nanocomposite on Ni foam, in-situ synthesized using a simple, green one-pot hydrothermal approach, exhibits superior capacitive performance (7440 mF cm"−"2 at 10 mA cm"−"2, i.e., 2188.8 F g"−"1 at 2.9 A g"−"1 and 1016 F g"−"1 at 29.0 A g"−"1).< TEMP>Highlights. • RGO/Ni_3S_2/NF composite was in-situ synthesized through a one-step hydrothermal process. • No other reagent except Ni foam, GO and S powder was added. • RGO/Ni_3S_2, RGO/Ni(OH)_2, and RGO/Ni_3S_2/Ni(OH)_2 can be controllably synthesized. • As-prepared RGO/Ni_3S_2/NF nanocomposite exhibits high capability and cyclability. - Abstract: A facile one-step solution-phase route to RGO/Ni_3S_2 on nickel foam (RGO/Ni_3S_2/NF) was presented. The RGO/Ni_3S_2/NF (RNS) nanocomposites were hydrothermal-assisted synthesized, in which nickel foam acted as an auxiliary reductant of GO and S, a Ni source of Ni_3S_2, and a substrate for composite film. RGO/Ni_3S_2/NF composites were characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscope (FESEM), and transmission electron microscopy (TEM). The electrochemical performances of the supercapacitor with as-synthesized RGO/Ni_3S_2/NF (RNS) electrodes are evaluated using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectrometry (EIS) in 2 M KOH aqueous solution. It is found that the RGO/Ni_3S_2/NF electrode exhibits superior supercapacitor performance (7440 mF cm"−"2 at 10 mA cm"−"2, i.e., 2188.8 F g"−"1 at 2.9 A g"−"1), compared with the Ni_3S_2/NF electrode (4360 mF cm"−"2 at 10 mA cm"−"2) and the RGO/Ni(OH)_2/NF electrode (3400 mF cm"−"2 at 10 mA cm"−"2) prepared under identical conditions. Both the temperature and sulfur content play important roles in the controlled synthesis of RNS and its electrochemical performance

[en] Highlights: • The SrHPO_4-coated LiMn_2O_4 is successfully prepared through co-precipitation process. • The SrHPO_4 coating can be effectively stabilizing the structure of prepared spinel. • The cycle performance is significantly enhanced both at room and elevated temperature. • The SrHPO_4-coated LiMn_2O_4 cathodes exhibit lower dissolution of manganese during cycles. - Abstract: The SrHPO_4-coated LiMn_2O_4 composite materials are prepared through co-precipitation method. The phase structures and morphologies of pristine and SrHPO_4 coated LiMn_2O_4 are characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The cycling performances are thoroughly investigated and discussed both at room and elevated temperature. The results indicate that 2.0wt% SrHPO_4 coated LiMn_2O_4 can efficiently improve the cycling performance with capacity retention of 92.3% and 83.6% under room temperature (25 °C) and elevated temperature (55 °C) after 100 cycles at 1 C rate, respectively, which are much better than those of the pristine materials. The CV, EIS and XRF measurements reveal that the enhanced stabilization in the cycling performance can be attributed to the suppression of manganese dissolution into electrolyte with the contribution of SrHPO_4 coating on the surface of LiMn_2O_4

[en] Graphical abstract: Protuberant 3D flower-like network structures of RGO/Co_3O_4/Ni(OH)_2 nanocomposites, in-situ synthesized on nickel foam (NF) using a simple, green one-pot hydrothermal approach, exhibits excellent capacitive performance (10.24 F cm"−"2 at 11 mA cm"−"2, i.e., 2133.3 F g"−"1 at 2.3 A g"−"1). - Abstract: Reduced graphene oxide (RGO)/Co_3O_4/Ni(OH)_2 composites on nickel foam (NF) were hydrothermal-assisted synthesized by using a modified “active metal substrate” route, in which nickel foam acted as both a reductant of GO and Ni source, and a substrate for composite film. As-synthesized samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscope (FESEM), and transmission electron microscopy (TEM). The electrochemical performances of the supercapacitor with the as-synthesized RGO/Co_3O_4/Ni(OH)_2/NF electrodes are evaluated using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectrometry (EIS) in 1 M KOH aqueous solution. It is found that the RGO/Co_3O_4/Ni(OH)_2/NF electrode exhibits superior capacitive performance with high capability (10.24 F cm"−"2 at a current density of 11 mA cm"−"2, i.e., 2133.3 F g"−"1 at 2.3 A g"−"1), compared with the Co_3O_4/Ni(OH)_2/NF electrode (1.71 F cm"−"2) and the RGO/Ni(OH)_2/NF electrode (0.95 F cm"−"2) prepared under identical conditions

[en] A unique MoS₂/RGO/MoS₂ (MRMS) nanostructured composite is prepared on Mo net surface through an in-situ hydrothermal synthesis. During the synthesis process, Mo net serves as not only a support but also Mo source for the lower MoS₂ layer and reductant of GO. MRMS samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Field emission scanning electron microscopy (FESEM) and Transmission electron microscopy (TEM). As-synthesized MoS₂/RGO/MoS₂@Mo directlyacted as super capacitor electrode which exhibited excellent electrochemical performance(*): A high capacity of 1138.5 mF cm⁻² at 20 mA cm⁻² (455.3 F g⁻¹), and a capacity retention of 98.8% after 4000 running times. A symmetric supercapacitor device consisting of two MRMS electrodes was assembled, which exhibited an energy density of 6.22 Wh kg⁻¹ and power density of 1.87 kW kg⁻¹.

[en] A facile one-step hydrothermal process is employed to synthesize a TiO₂/RGO/Ni(OH)₂ (reduced graphene oxide, RGO) composite on nickel foam (NF) by means of an in-situ growth route. In this case, NF acts as support, nickel source of Ni(OH)₂, and supplement reductant of GO. For comparison, RGO nanosheets serve as nano-sized flexible support for connecting TiO₂ and Ni(OH)₂ blocks, which improves the electron transfer and alleviates the volume changes during the repeated charge/discharge process thanks to its high conductivity and mechanical properties. Besides, P25 (commercial TiO₂ consisting of 80% anatase and 20% rutile) serves as TiO₂ source, at different GO/P25 ratio of 1%, 2%, 5%, 10% and 20%. Electrochemical performances of TiO₂/RGO/Ni(OH)₂/NF electrode were evaluated by using cyclic voltammetry (CV), galvanostatic charge/discharge tests (GCD) and electrochemical impedance spectroscopy (EIS) in 1 M KOH electrolyte. The TiO₂/RGO/Ni(OH)₂/NF electrode exhibited significantly enhanced capacitive performance when the weight ratio of GO/P25 was 10%. It delivered high capability of 4342 mF cm⁻² at a current density of 5 mA cm⁻² (374.3 F g⁻¹ at 0.43 A g⁻¹), and excellent charge-discharge cycling stability with 93.75% capacitance retention after 2000 cycles. An asymmetric supercapacitor (ASC) device consisting of this TiO₂/RGO/Ni(OH)₂/NF and an AC negative electrode was assembled.

[en] A reduced graphene oxide (RGO)-based nanocomposite of redox counterpart of the oxides of Cu(I)-Cu(II) pair for Faradaic reaction, Cu_2O/CuO/RGO, was controllably synthesized through a facile, eco-friendly one-step hydrothermal-assisted redox reaction of elemental Cu and graphene oxide (GO) without the addition of any other reagents. The resultant Cu_2O/CuO/RGO nanocomposites were characterized by X-ray diffraction (XRD), Raman spectroscopy, Thermogravimetric analysis (TG), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). It is found that, when dealloyed nanoporous Cu was used as a Cu source, the uniform spherical Cu_2O/CuO nanoparticles with double size scales (∼25 nm and ∼5 nm) were anchored on RGO sheets. This Cu_2O/CuO/RGO nanocomposite redox counterpart exhibits improved rate capability and excellent cycling stability, i.e., only ca. 21.4% of the capacity was lost when the discharge current density increases from 1 A g"−"1 (173.4 F g"−"1) to 10 A g"−"1 (136.3 F g"−"1). Especially, the capacity remains almost unchanged (98.2%) after 100,000 cycles at 10 A g"−"1. The good electrochemical performance and simple accessibility prove that this Cu_2O/CuO/RGO composite consisting of a pair of redox counterparts is a promising material for supercapacitor applications

[en] A nanocomposite consisting of CuO, reduced graphene oxide (rGO) and Cu₂O nanoparticles was hydrothermally and in-situ deposited on a copper foil. The composite contains 3 kinds of interfaces, namely CuO/rGO, rGO/Cu₂O and Cu₂O/Cu. This facilitates redox reactions to occur between graphene oxide and the copper foil, and also leads to electrostatic attraction between the positively charged copper ions and negatively charged rGO. This, in turn, leads to improved electron and ion transfer. The modified foil is shown to directly act as a sensor for amperometric detection of both glucose (at 0.65 V vs SCE) and hydrogen peroxide (at −0.3 V). Figures of merit for sensing glucose (in 0.1 M NaOH) include (a) an ultrahigh sensitivity of 3401 µA·mM^-1·cm^-2, (b) a limit of detection as low as 0.10 μM, (c) a linear detection range extends from 0.5 μM to 8.3 mM, and (d) a response time of <0.5 s. As for sensing hydrogen peroxide (at pH 7), the sensitivity is 366.2 µA·mM^-1·cm^-2, the limit of detection is 0.05 μM, the linear range extends from 0.5 μM to 9.7 mM, and the response time is 0.8 s. < Image>.

[en] The reconstruction of segmental bone defects remains an urgent problem in the orthopaedic field, and bone morphogenetic protein-2 (BMP-2) is known for its potent osteoinductive properties in bone regeneration. In this study, chitosan microspheres (CMs) were prepared and combined with absorbable collagen sponge to maintain controlled-release recombinant human bone morphogenetic protein-2 (rhBMP-2). The rhBMP-2-loaded composite scaffolds were implanted into 15 mm radius defects of rabbits and the bone-repair ability was evaluated systematically. CMs were spherical in shape and had a polyporous surface, according to SEM images. The complex scaffold exhibited an ideal releasing profile in vitro. The micro-computed tomographic analysis revealed that the rhBMP-2-loaded composite scaffold not only bridged the defects as early as 4 weeks, but also healed the defects and presented recanalization of the bone-marrow cavity at 12 weeks. These results were confirmed by x-ray. When compared with other control groups, the composite scaffold group remarkably enhanced new bone formation and mechanical properties, as evidenced by bone mineral content evaluation, histological observations and biomechanical testing. Moreover, the biocompatibility and appropriate degradation of the composite scaffold could be obtained. All of these results clearly demonstrated that the composite scaffold is a promising carrier of BMP-2 for the treatment of segmental bone defects. (paper)