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Rational architectural design is the key to improve specific capacitance. Herein, we present a facile one-step hydrothermal process for the fabrication of a TiO2/RGO/MoO2 composite with an unprecedented 3D walnut-shaped hierarchical nanostructure, in which amorphous TiO2 is decorated on the RGO (reduced graphene oxide)/MoO2 surface via a Mo-involved in situ growth route on Mo net (TiO2/RGO/MoO2@Mo). This 3D structure coated with ultrafine arched nanorods is a great breakthrough in electrochemical performances of TiO2– or MoO2-based electrodes as it exhibits an extraordinary areal capacitance of 3927 mF cm−2 at 3 mA cm−2 (i.e. 1636 F g−1 at 1.25 A g−1) with only 3.5% capacitance loss after 5000 cycles. Such an excellent performance is benefitted from the following factors: (i) amorphous TiO2 sculptured MoO2 blocky particles supply more active-site accessibility and facilitate the accommodation of volume expansion. (ii) Arched MoO2 nanorods as well as the walnut-shaped spheres of the composite provide electron transfer paths. (iii) RGO is a soft scaffold, which relieves the volume expansion during the charge/discharge processes. [ABSTRACT FROM AUTHOR]

A roe-shaped ternary nanocomposite, Ni3(PO4)2/RGO/Co3(PO4)2 (NRC), was grown in situ on cobalt foam (CoF). The synthesis and loading of NRC on the CoF was completed through a one-step hydrothermal process by immersing the CoF in an aqueous solution of GO and Ni2+ in the presence of H2PO4−, in which the CoF served as the support, reductant and Co source. Three interfaces of Co3(PO4)2/CoF, RGO/Co3(PO4)2, and Ni3(PO4)2/RGO with strong interactions were constructed based on an in situ conversion reaction of Co to Co3(PO4)2, a redox reaction between GO and the CoF, and the electrostatic attraction force of Ni2+ and GO, respectively. The as-synthesized NRC@CoF had a hierarchically porous structure, and directly acted as a supercapacitor electrode and delivered excellent electrochemical performances: a specific capacitance of 10 237.5 mF cm−2 (1137.5 F g−1) at 5 mA cm−2 (0.56 A g−1) with a capacity retention of 117.8% after 14 000 cycles. Furthermore, NRC@CoF-based asymmetric supercapacitors (ASCs) exhibited a specific capacitance of 4845.9 mF cm−2 (115.4 F g−1) at 5 mA cm−2 (0.12 A g−1), and a high energy density of 44.82 W h kg−1 at a power density of 428.6 W kg−1, as well as good cyclic stability (91.9% after 18 000 cycles). [ABSTRACT FROM AUTHOR]

A novel ultrasensitive nonenzymatic sensor was prepared by in-situ growing layered CuS/RGO/CuS (reduced graphene oxide, RGO) nanostructure on the Cu foam surface through a hydrotherm-assisted process. The CuS/RGO/CuS nanocomposite was characterized with X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectrometer (XPS) and field emission scanning electron microscopy (FESEM). This CuS/RGO/CuS/Cu was directly used as electrochemical sensor of glucose, and its performance was evaluated by cyclic voltammetry and amperometry techniques. The nonenzymatic biosensor exhibited ultrahigh linear sensitivities of 22.67 and 10.54 mA mM − 1 cm − 2 in the concentration ranges of 1–655 μM and 0.655–1.055 mM, respectively. The detection limit was determined to be 0.5 μM with the signal-to-noise of three. Furthermore the sensor showed good long-term stability and good performance in human blood analysis. The present work gives a new insight into facile preparation of metal sulfides/RGO/metal sulfides nanocomposite on its metal substrate and its potential application in nonenzymatic glucose sensor. [ABSTRACT FROM AUTHOR]

A facile one-step hydrothermal process is employed to synthesize a TiO 2 /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 TiO 2 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 TiO 2 consisting of 80% anatase and 20% rutile) serves as TiO 2 source, at different GO/P25 ratio of 1%, 2%, 5%, 10% and 20%. Electrochemical performances of TiO 2 /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 TiO 2 /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 TiO 2 /RGO/Ni(OH) 2 /NF and an AC negative electrode was assembled. [ABSTRACT FROM AUTHOR]

MoS 2 /RGO/Ni 3 S 2 nanocomposite with a unique nanosheet-on-nanosheet structure was prepared through a hydrothermal process by depositing a MoS 2 layer on the upper surface side of reduced graphene oxide (RGO) nanosheets and Ni 3 S 2 layer on the lower surface sides. Furthermore, this, MoS 2 /RGO/Ni 3 S 2 nanocomposite was simultaneously loaded on a Ni foam (NF) substrate. During the synthesis process, nickel foam serves not only as a support but also as the Ni source for the composite and a reductant of GO. When used as an electrochemical electrode, as-prepared MoS 2 /RGO/Ni 3 S 2 @NF, it exhibited excellent electrochemical performance with a high capacity of 8.841 F cm −2 at 50 mA cm −2 , and excellent cyclability, exhibiting capacity retention of 98.4% after 11,000 charge-discharge cycles at the current density of 80 mA cm −2 . [ABSTRACT FROM AUTHOR]

A nanocomposite for supercapacitor electrode materials was designed and developed by integrating partially disabled Cu 2 O (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 2 O/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 2 O/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 2 O/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 2 O/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 ). [ABSTRACT FROM AUTHOR]