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Multilayer graphene (MLG) prepared via ultrasonic exfoliation has many advantages such as its low-cost and defect-free nature, high electronic conductivity, and large specific surface area, which make it an apt conductive substrate for TiO2 composites. To synthesize graphene/TiO2 hybrids, traditional methods that greatly depend on the chemical bond of oxygen-containing functional groups on graphene with titanium cations are not applicable due to the absence of these functional groups on MLG. In this work, a facile chemical method is developed to directly deposit TiO2 on the MLG surface without the introduction of chemically active groups. With this method, four types of TiO2 materials, that is pure anatase TiO2 nanoparticles, a mixture of anatase TiO2 nanoparticles and rutile TiO2 nanoflowers, pure rutile TiO2 nanoflowers, and pure rutile TiO2 nanorods, are homogeneously anchored on the MLG surface by controlling the amount of HCl in the reactant. Interestingly, the rutile TiO2 nanorods in the TiO2/MLG composite are assembled by many TiO2 nanowires with an ultra-small diameter and ultra-long length, which provides a better synergetic effect for high performances as LIB anodes than other composites. A specific capacity of 631.4 mAh g−1 after 100 cycles at a current density of 100 mA g−1 is delivered, indicating it to be a valuable LIB anode material with low cost and high electrochemical performances. [ABSTRACT FROM AUTHOR]

Supercapacitors have played an important role in electrochemical energy storage. Recently, researchers have found many effective methods to improve electrode materials with more robust performances through the increasing volume of scientific publications in this field. Though nickel cobaltite (NiCo2O4), as a promising electrode material, has substantially demonstrated potential properties for supercapacitors, its composites usually show much better performances than the pristine NiCo2O4. The combination of carbon-based materials and NiCo2O4 has been implemented recently due to the dual mechanisms for energy storage and the unique advantages of carbon materials. In this paper, we review the recent research on the hybrids of NiCo2O4 and carbon nanomaterials for supercapacitors. Typically, we focused on the reports related to the composites containing graphene (or reduced graphene oxide), carbon nanotubes, and amorphous carbon, as well as the major synthesis routes and electrochemical performances. Finally, the prospect for the future work is also discussed. [ABSTRACT FROM AUTHOR]

Abstract We report a simple and general strategy to optimize the composite of reduced graphene oxide (rGO) and polyaniline (PANI) via introducing a small quantity of divalent metal ions M (M = Ni2+, Co2+, Cu2+, Mn2+) as mediators. This simple approach can not only inhibit the aggregation of both the graphene sheets and the PANI nanoparticles, yielding a uniform PANI−rGO morphology with increased specific surface area, but also strengthen the utilization of the good conductivity of rGO, leading to reduced charge transfer resistance. The metal ions modified binary PANI−rGO aerogels (P−GA− M s) exhibit all fairly high specific charges or capacities of 271 (Ni2+), 211(Co2+), 200 (Cu2+) and 181 mA h· g−1(Mn2+), at 1 A g−1 in a three-electrode system, with an average retention of 93% over 10000 cycles of charge-discharge at 3 A g−1. Additionally, as a proof of generality, a ternary system of MoS 2 −PANI−GA with additive Ni2+ showing better electrochemical performance than that without Ni2+ is demonstrated as well. This study provides a rational way on improving the specific charges or capacities of GA-based composites by adopting metal ions as mediators. Graphical abstract The morphology and the interface of the hybrid composite of PANI−rGO can be optimized by introducing of a tiny amount of divalent metal ions M (M = Ni2+, Co2+, Cu2+, Mn2+) as mediators, resulting in the significantly improved supercapacitive performance. Image 1 Highlights • Electrochemical performance of PANI−rGO aerogels can be significantly improved by introducing of divalent metal ions. • The effect of metal ions is mainly to promote the uniform-morphology and homogeneous-composition of PANI-rGO. • The metal ions mediator can strengthen the utilization of the good conductivity of rGO. • The generality to improve the performance of GA-based composites by adopting the facile strategy is verified. [ABSTRACT FROM AUTHOR]

Abstract: We report a one-step synthesis of a nanocomposite of goethite (α-FeOOH) nanorods and reduced graphene oxide (RGO) using a solution method in which ferrous cations serve as a reducing agent of graphite oxide (GO) to graphene and a precursor to grow goethite nanorods. As-prepared goethite nanorods have an average length of 200nm and a diameter of 30nm and are densely attached on both sides of the RGO sheets. The electrochemical properties of the nanocomposite were characterized by cyclic voltammetry (CV) and chronopotentiometry (CP) charge–discharge tests. The results showed that goethite/RGO composites have a high electrochemical capacitance of 165.5Fg−1 with an excellent recycling capability making the material promising for electrochemical capacitors. [Copyright &y& Elsevier]

Ultrasound sonochemical synthesis is a unique synthetic method that can locally create extreme conditions (∼5000 K, ∼1000 bar) at room temperature. By virtue of the effects of acoustic cavitation, a wide range of nanostructured materials with peculiar properties can be fabricated. We innovatively put forward the synthesis of the bimetallic sulfides anchored on graphene nanosheets via ultrasonic treatment for sodium-ion batteries. The as-synthesized nanocomposites exhibit excellent electrochemical properties. Under the conditions of ultrasound irradiation, the two components are in-situ grown and distributed uniformly over the whole graphene; the sodium storage capability and electronic conductivity are greatly boosted by the heterostructures with different band gaps. The strategy proposed herein can promote readers to make new connections between sonochemical synthesis and advanced materials in the field of energy storage. • The synthesis of the bimetallic sulfides anchored on graphene nanosheets via ultrasonic treatment is achieved. • The heterostructured nanocomposites exhibit excellent electrochemical properties. • The strategy helps to make new connections between sonochemical synthesis and advanced materials for energy storage. [ABSTRACT FROM AUTHOR]

Abstract: A microwave-assisted reflux method was used to rapidly synthesize CoAl-layered double hydroxide (CoAl-LDH)/graphene oxide composite. In the synthetic procedure, graphite oxide (GO) was exfoliated to graphene oxide nanosheets in company with the in situ growth of CoAl-LDH. The as-prepared products showed lamellar structures. The aggregation of LDH was effectively prevented by the presence of graphene oxide nanosheets. Electrochemical performances were evaluated by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge–discharge tests. All the composites had higher rate capability than pure CoAl-LDH, maintaining about 80% of discharge capacitance when the current density increased from 1Ag−1 to 20Ag−1. A maximum specific capacitance of 772Fg−1 was obtained at 1Ag−1 in 6M KOH solution for the composite containing 12.9% GO. Moreover, the composite exhibited excellent long cycle life with about 73% specific capacitance retained at 6Ag−1 after 10,000 cycles. [Copyright &y& Elsevier]