Carbon based materials as one promising cathode to accommodate the insoluble and insulating discharge products (Li₂O₂) for lithium oxygen (Li-O₂) batteries have attracted great attention due to their large energy density store ability compared with the other carbon-free cathodes. However, the side reaction occurring at carbon/Li₂O₂ interfaces hinders their large-scale application in Li-O₂ batteries. Herein, a simple and cost-effective strategy is developed for the growth of core-shell-like Co/CoO nanoparticles on 3D graphene-wrapped carbon foam using 3D melamine foam as the initial backbone. This unique 3D hierarchical carbonized melamine foam-graphene-Co/CoO hybrid (CMF-G-Co/CoO) with a continuous conductive network and elastic properties is used as binder-free oxygen electrode for Li-O₂ batteries. Electrochemical and structural measurements show that a synergistic effect is observed between Co/CoO and graphene, where Li₂O₂ grows on the Co/CoO surfaces instead of the carbon surfaces at the initial discharge state (500 mAh ), indicating the reduced carbon/Li₂O₂ interfaces and alleviative side reactions during the electrochemical process. Importantly, the CMF-G-Co/CoO electrode can achieve greatly improved cycle life over the electrode without aid of the Co/CoO. Furthermore, it delivers a large capacity of ≈7800 mAh and outstanding rate capability, exhibiting the great potential for the application in Li-O₂ batteries.

Li-ion hybrid capacitors (LIHCs), consisting of an energy-type redox anode and a power-type double-layer cathode, are attracting significant attention due to the good combination with the advantages of conventional Li-ion batteries and supercapacitors. However, most anodes are battery-like materials with the sluggish kinetics of Li-ion storage, which seriously restrict the energy storage of LIHCs at the high charge/discharge rates. Herein, vanadium nitride (VN) nanowire is demonstated to have obvious pseudocapacitive characteristic of Li-ion storage and can get further gains in energy storage through a 3D porous architecture with the assistance of conductive reduced graphene oxide (RGO). The as-prepared 3D VN–RGO composite exhibits the large Li-ion storage capacity and fast charge/discharge rate within a wide working widow from 0.01–3 V (vs Li/Li⁺), which could potentially boost the operating potential and the energy and power densities of LIHCs. By employing such 3D VN–RGO composite and porous carbon nanorods with a high surface area of 3343 m² g⁻¹ as the anode and cathode, respectively, a novel LIHCs is fabricated with an ultrahigh energy density of 162 Wh kg⁻¹ at 200 W kg⁻¹, which also remains 64 Wh kg⁻¹ even at a high power density of 10 kW kg⁻¹.

Lithium–oxygen (Li–O₂) batteries are receiving intense interest because of their high energy density. A new tubular δ-MnO₂ material prepared by a simple hydrothermal synthesis is an efficient electrocatalyst for Li–O₂ batteries. The synthesized δ-MnO₂ exhibits a unique tubular structure, in which the porous walls are composed of highly dispersed ultrathin δ-MnO₂ nanosheets. Such a unique structure and its intrinsic catalytic activity provide the right electrocatalyst characteristics for high-performance Li–O₂ batteries. As a consequence, suppressed overpotentials—especially the oxygen evolution reaction overpotential—superior rate capability, and desirable cycle life are achieved with these submicron δ-MnO₂ tubes as the electrocatalyst. Remarkably, the discharge product Li₂O₂ of the Li–O₂ battery exhibits a uniform nanosheet-like morphology, which indicates the critical role of the δ-MnO₂ in the electrochemical process, and a mechanism is proposed to analyze the catalysis of δ-MnO₂.

Three-dimensional nitrogen-doped graphene microspheres (3D NGSs) were prepared by using integrated precursor-assisted chemical vapor deposition and the hydrothermal method. The 3D NGSs, with an interconnected network structure, show a high crystallization degree, abundant pore channels, and appropriate nitrogen doping. Electrochemical studies confirm that the glucose oxidase/NGSs electrode shows excellent catalytic activity with a high sensitivity of 15.89 μA mM⁻¹ cm⁻², over a wide linear range of 0.1–3.7 mM, and fast response time of 3.6 s.

Novel 3D hierarchically porous and nitrogen-doped graphene-like microspheres (3D NPGSs) are prepared by precursor-assisted chemical vapor deposition. 3D NPGSs obtained by using Ni microspheres as a structural template exhibit a 3D conductive framework, and have a well-defined porous structure, large surface area and appropriate heteroatom doping, making them suitable for high-performance storage of lithium ions. Consequently, a good rate capability and excellent cycle performance are achieved using the 3D NPGSs as anodes for lithium storage, and a high reversible capacity of 840 mA h g⁻¹ is obtained after 200 cycles. For a further capacitance boost, a thin layer of iron oxide nanoparticles is deposited onto the 3D NPGSs. The resulting 3D FeO_x–NPGS electrode exhibits a stable reversible capacity up to 1343 mA h g⁻¹ after 100 cycles.

Ultrahigh-molecular-weight polyethylene (UHMWPE) and UHMWPE composites reinforced with graphene oxide (GO) were successfully fabricated through a new step of liquid-phase ultrasonic dispersion, high-speed ball-mill mixing, and hot-pressing molding technology. When the GO/UHMWPE composites were lubricated with deionized water (DW) and normal saline (NS) solution, their friction and wear properties were investigated through sliding against ZrO₂. The worn surface and wear volume losses of these composites were studied with scanning electron microscopy, X-ray photoelectron spectroscopy, and a Micro-XAM 3D non-contact surface profiler. The results show that the microhardness of the GO/UHMWPE composites was improved by 13.80% and the wear rates were decreased by 19.86 and 21.13%, whereas the depths of the scratches were decreased by 22.93 and 23.77% in DW and NS lubricating conditions, respectively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39640.

Porous chitosan (CS)/graphene oxide (GO) composite xerogels were prepared through a simple and “green” freeze-drying method. Scanning electron microscopy, Fourier transform infrared spectrometry, powder X-ray diffraction, and compressive strength measurements were performed to characterize the microstructures and mechanical properties of as-prepared composite xerogels. The results show that the incorporation of GO resulted in an observable change in the porous structure and an obvious increase in the compressive strength. The abilities of the composite xerogels to absorb and slowly release an anticancer drug, doxorubicin hydrochloride (DOX), in particular, the influence of different GO contents, were investigated systematically. The porous CS/GO composite xerogels exhibited efficient DOX-delivery ability, and both the adsorption and slow-release abilities increased obviously with increasing GO content. Additionally, the best adsorption concentration of DOX was 0.2 mg/mL, and the cumulative release percentage of DOX from the xerogels at pH4 much higher than that at pH 7.4. Therefore, such porous CS/GO composite xerogels could be promising materials as postoperation implanting stents for the design of new anticancer drug-release carriers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014, 131, 40006.

Graphene sheet (GS)–ionic liquid (IL) supercapacitors are receiving intense interest because their specific energy density far exceeds that of GS–aqueous electrolytes supercapacitors. The electrochemical properties of ILs mainly depend on their diverse ions, especially anions. Therefore, identifying suitable IL electrolytes for GSs is currently one of the most important tasks. The electrochemical behavior of GSs in a series of ILs composed of 1-ethyl-3-methylimidazolium cation (EMIM⁺) with different anions is systematically studied. Combined with the formula derivation and building models, it is shown that the viscosity, ion size, and molecular weight of ILs affect the electrical conductivity of ILs, and thus, determine the electrochemical performances of GSs. Because the EMIM–dicyanamide IL has the lowest viscosity, ion size, and molecular weight, GSs in it exhibit the highest specific capacitance, smallest resistance, and best rate capability. In addition, because the tetrafluoroborate anion (BF₄⁻) has the best electrochemical stability, the GS–[EMIM][BF₄] supercapacitor has the widest potential window, and thus, displays the largest energy density. These results may provide valuable information for selecting appropriate ILs and designing high-performance GS–IL supercapacitors to meet different needs.

Graphene quantum dots (GQDs) have attracted tremendous research interest due to the unique properties associated with both graphene and quantum dots. Here, a new application of GQDs as ideal electrode materials for supercapacitors is reported. To this end, a GQDs//GQDs symmetric micro-supercapacitor is prepared using a simple electro-deposition approach, and its electrochemical properties in aqueous electrolyte and ionic liquid electrolyte are systematically investigated. The results show that the as-made GQDs micro-supercapacitor has superior rate capability up to 1000 V s⁻¹, excellent power response with very short relaxation time constant (τ₀ = 103.6 μs in aqueous electrolyte and τ₀ = 53.8 μs in ionic liquid electrolyte), and excellent cycle stability. Additionally, another GQDs//MnO₂ asymmetric supercapacitor is also built using MnO₂ nanoneedles as the positive electrode and GQDs as the negative electrode in aqueous electrolyte. Its specific capacitance and energy density are both two times higher than those of GQDs//GQDs symmetric micro-supercapacitor in the same electrolyte. The results presented here may pave the way for a new promising application of GQDs in micropower suppliers and microenergy storage devices.

Nanofibrous biocomposite scaffolds of poly(vinyl alcohol) (PVA) and graphene oxide (GO) were prepared by using electrospinning method. The microstructure, crystallinity, and morphology of the scaffolds were characterized through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The mechanical properties were investigated by tensile testing. Moreover, Mouse Osteoblastic Cells (MC3T3-E1) attachment and proliferation on the nanofibrous scaffolds were investigated by MTT [3-(4,5-dimeth-ylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay, SEM observation and fluorescence staining. XRD and FTIR results verify the presence of GO in the scaffolds. SEM images show the three-dimensional porous fibrous morphology, and the average diameter of the composite fibers decreases with increasing the content of GO. The mechanical properties of the scaffolds are altered by changing the content of GO as well. The tensile strength and elasticity modulus increase when the content of GO is lower than 1 wt %, but decrease when GO is up to 3 and 5 wt %. MC3T3-E1 cells attach and grow on the surfaces of the scaffolds, and the adding of GO do not affect the cells' viability. Also, MC3T3-E1 cells are likely to spread on the PVA/GO composite scaffolds. Above all, these unique features of the PVA/GO nanofibrous scaffolds prepared by electrospinning would open up a wide variety of future applications in bone tissue engineering and drug delivery systems. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013