Three-dimensional (3D) microstructured building units have replaced layer-to-layer stacked designs in transparent graphene films to fully exploit the advantages of two-dimensional graphene. However, it is still challenging to precisely control the size and microstructures of these building blocks to develop multifunctional graphene-based materials that satisfy the performance requirements of diverse applications. In this study, we propose a controllable method to regulate the microstructures of building units to form structures ranging from opened bubbles and cubes, while the size decreased from 20 to 3 μm, via an in situ template-modulating technology. NaCl was used as either a liquid or solid template by changing the dc bias. The reduced size and dense arrangement of the building units not only provide an improved mass loading for the transparent films but also build multiple pathways for fast ion/electron transmission, enhancing their promise for various practical applications. Generally, we provide a convenient protocol for finely regulating the microstructure and size of these building units, resulting in multifunctional films with a controllable transmittance, which enables the use of these graphene-based architectures as transparent electrodes in various applications and extends the family of multifunctional materials that will present new possibilities for electronics and other devices.Keywords: graphene opened-bubble; graphene opened-cube; template-modulating; transparent film; tunable microstructure;

To develop a separator with remarkable thermal-resistance for high-safety lithium-ion (Li-ion) batteries, a graphene oxide (GO)-grafted hyper-branched polyether (GO-g-HBPE) macro-porous membrane without any polymer binder was designed and prepared using polystyrene (PS) nanoparticles as hard templates. GO (inorganic part) provides the membrane-formation ability for GO-g-HBPE separator and HBPE (polymer part) imparts excellent affinity with the liquid electrolyte (158% for liquid electrolyte uptake). The GO-g-HBPE membrane, serving as a separator for the batteries, exhibited robust thermal dimensional stability with no dimensional changes at 200 °C for 0.5 h. Moreover, it shows a better electrochemical performance (cycle performance and rate capability) than a commercialized PP separator, implying a promising potential for application in high-safety and high-power Li-ion batteries.

For the development of high-capacity flexible supercapacitors (SCs), a reduced graphene oxide/polyaniline (rGO/PANI) hybrid film with a hierarchical three-dimensional structure, in which PANI nanotubes are sandwiched in rGO nanosheet skeleton, is designed and prepared via vacuum filtration. The rectangular-like PANI nanotubes have a hollow structure with a wall thickness of ca. 100 nm, which can increase the accessible surface area and minimize the ion transfer distance. Additionally, rGO nanosheets act as conductive skeleton to improve the conductivity of active materials and provide some capacitance due to EDLC properties of rGO. As a result, the composite electrode shows a remarkable specific capacitance of 850 F g−1 at 1 A g−1, and superior cycling stability with only 6.8% of the specific capacitance loss after 10000 cycles. The assembled flexible all-solid-state SCs give a high specific capacitance of 208 F g−1 (1 A g−1) and a good rate capacitance, as well as outstanding cycling stability with 87.3% of the initial capacitance retained after 10000 cycles. Furthermore, no structure failure or performance loss at various bending angles is observed. This method may provide a new route for the fabrication of flexible energy storage devices.

In this study, stable water-based heat transfer nanofluid containing a kind of three-dimensional porous graphene (3D PG) has been prepared. For dispersion of 3D PG in water, it is hydrophilic treated by an alkaline method, which is a facile and effective approach in preparing water-soluble graphene by introducing the carboxyl groups (–COOH) as a mild oxidation process using potassium persulfate. The stability and thermal conductive performance of the nanofluid have been investigated with different loading at various temperatures. Experimental results show that the nanofluid can remain highly stability and its enhanced thermal conductivity up to 8–34% can be observed even at lower weight fraction of 0.01–0.07 wt% at room temperature.

•Si/C nanosphere was prepared by using Si-carbon integration method.•Si particles embedded in carbon matrix have ultralow size of 4–10 nm.•Si/C nanosphere presents remarkable lithium ion storage performance.Downsizing the Si particles, creating conductive carbon matrix and constructing porous expansion space are main ways to enhance lithium ion storage performance of Si-based anode. However, up to now, there are few methods can design Si electrodes integrating these structural features. Here we supply novel ultrasmall Si particles embedded in carbon matrix by using a simple Si-carbon integration strategy. The key to this method is the employment of novel organic/inorganic hybrid building block, i.e., octaphenyl polyhedral oligomeric silsesquioxane (Ph-POSS). Ph-POSS has inorganic –Si8O12 core (SiO1.5) and organic phenyl group shell, simultaneously. The Friedel-Crafts crosslinking of phenyl group shell creates continuous polymeric nanospheres and wraps –Si8O12 core in it. After high-temperature heat treatment and magnesiothermic reduction, the crosslinked polymeric nanosphere will be converted into porous carbon matrix with a surface area of 332 m2 g−1, and the –Si8O12 core (ca. 1.0 nm) will be reduced and in-situ grows to ultrasmall Si particle (4–10 nm). This Si/C nanosphere exhibits superior lithium-ion storage performances. The initial discharge and charge capacities can reach 2139 and 1421 mAh g−1, respectively. After 120 cycles, a remarkable capacity of 738 mAh g−1 remains, which is 2.0 times of the theoretical capacity of graphite.Download high-res image (148KB)Download full-size image

Lithium-sulfur (Li-S) battery is considered as the next-generation of cost-efficient rechargeable battery systems to fulfill clean energy transportation systems due to its remarkable high theoretical energy density. Nevertheless, capacity fading and poor cycling stability mostly caused by polysulfide shuttle and active sulfur materials loss play an obstacle role on large-scale viable commercialization. In this paper, a flower-like hierarchical carbon sphere (FHCS) is prepared and coated on commercialized PP separator for polysulfide trapper. This carbon sphere with multi-scale pores strongly absorbs the polysulfide, further tremendously enhances the cycling performances, and the conducted carbon sphere also acts as current collector for improving the conductivity of active materials. The results show the cell demonstrates an initial discharge specific capacity of up to 1427 mAh g−1 at 0.2C, and high reversible capacity of 730 mAh g−1 with degradation rate of only 0.061% per cycle after 500 cycles at 0.5C.

•BFO, CFO and YIG ferrites nanosheets were prepared by hydrothermal method.•BFO, CFO and YIG ferrites nanosheets were introduced into DSSCs.•BFO, CFO and YIG showed a broad light absorption in the visible light region.•The DSSCs based on P25 TiO2 doped with ferrites showed the enhanced performance.In this article, ferrite materials BiFeO3 (BFO), CoFe2O4 (CFO) and Y3Fe5O12 (YIG) are prepared by hydrothermal method and introduced into dye-sensitized solar cells (DSSCs) for the first time. The properties of ferrite materials were measured by XRD, UV and TEM. The DSSCs, sensitized by N719, were tested under 100 mW cm−2, AM 1.5G simulated sunlight. The power conversion efficiency(PCE)of DSSC based on P25 TiO2 doped with ferrites was increased compared with undoped P25 TiO2. The best doping amount was 0.2% for all the ferrites. The optimized Jsc of 11.7 mA/cm2 and PCE of 5.67% were achieved in the DSSC doped with 0.2% of CFO. The enhanced performance is attributed to its improved optical absorption, light scattering effect and better charge transfer properties induced by the existence of ferrites in P25 TiO2.

•This report describes a tunable upconversion luminescence of monodisperse spherical Y2O3: Yb3+/Tm3+/Er3+ nanoparticles synthesized via homogeneous precipitation method.•Through adjusting the concentrations of Yb3+, Tm3+ and Er3+ ions, red, green and blue emission bands could be tunable to achieve the color of interest.•Near white light emission can be obtained in the tri-doped Y2O3 nanoparticles for a variety of application.Monodisperse Y2O3: Er3+/Yb3+/Tm3+ nanoparticles with various dopant concentrations have been synthesized successfully by a homogeneous precipitation method. Their phase structures and surface morphologies have been characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The diversities of upconversion luminescence spectra and CIE coordinates of prepared samples are investigated in detail at room temperature under 980 nm excitation. Through adjusting the concentrations of Yb3+, Tm3+ and Er3+ ions, three upconversion emission bands in red, green and blue region could be tunable to achieve the color of interest and near white light emission can be obtained in the tri-doped Y2O3 nanoparticles for a variety of application.

Constructing an electrode integrating ultralow SnO2 size, stable carbon barriers and well-developed pore structure are effective to address the issues of crack and pulverization for SnO2-based electrode during lithiation/delithiation process. But until now, it is still a challenge to exploit simple and robust method to fabricate ultrasmall SnO2 particles embedded in a carbon matrix. Herein, we develop a rapid strategy to prepare SnO2/C nanospheres using a simple Friedel–Crafts crosslinking of triphenyltin chloride for only 15 min and subsequent carbonization. The SnO2/C nanospheres (∼500 nm) have ultrasmall SnO2 particles of 4 nm, which were dispersed in carbon continuous phase. Moreover, the pyrolysis of the polymer during carbonization creates considerable micropores inside the carbon phase and leads to a surface area of 463.3 m2 g−1. When used as electrode materials in a lithium-ion battery, the ultrasmall SnO2 particles can prevent the cracking of the electrode, the carbon continuous phase can act as a buffer to protect SnO2 particles from aggregation, and micropores will supply expansive space for volume change. Thus, the SnO2/C nanosphere exhibits superior electrochemical performance, e.g., the first discharge and charge capacities can reach 1453 and 719 mA h g−1 respectively, and 120 cycles later, its capacity remains 629 mA h g−1, indicating a capacity retention of 87.4% (C120th/C2nd).

For the first time, hierarchical S-doped porous carbon was fabricated using sodium lignosulfonate as a carbon and sulfur precursor through a simple template technique. The obtained carbon has a high surface area (1054 m2 g−1), high pore volume (1.73 cm3 g−1), high sulfur content (2.9 wt%), and interconnected open macropores that can provide many storage sites, pseudocapacitance, and short transport paths for ions. The as-obtained S-PC-L-900 exhibits a high specific capacitance (328 F g−1) at 0.2 A g−1, excellent rate performance with 73% capacitance retention after a current density increasing from 0.5 to 20 A g−1 and cycling stability, with 97% capacitance retention after 10 000 cycles. Additionally, a symmetric supercapacitor based on S-PC-L-900 delivers a high energy density (6.9 W h kg−1) at 50 W kg−1.

In present work, Ni/disordered mesoporous carbon (DMC) composites with unique structure have been prepared through a proprietary two-step process combining the sol–gel preparation of DMC and the in situ reduction of Ni from co-precipitated nickel nitrate. Confirmed by scanning electron microscopy, transmission electron microscopy and X-ray diffraction, the Ni nanoparticles were found to be sparsely dispersed in the wormhole-like channel and the mesopores, acting as scattering centres that significantly intensified the electromagnetic (EM) wave multiple reflection and improved the dielectric loss through additional interfacial polarization. Evaluation of the EM absorption properties suggested that the reflection loss (RL) was noticeably reduced from −11.6 dB at 13 GHz to −27 dB at 9 GHz, and the frequency bandwidth corresponding to RL < −10 dB was broadened from about 1 GHz to over 4.5 GHz after incorporation of DMC with Ni. The experimental results show that Ni/DMC composites are superior to neat DMC so that they could be some of the most promising candidates for the new generation of EM absorption materials with improved performance and well-maintained lightweight feature.

•Reduced graphene oxide (RGO) was prepared by the reduction of graphite oxides via microwave irradiation.•The electrochemical performance of the RGO electrodes were measured in different electrolytes.•The effect of oxygen-containing functional groups on the supercapacitor performance was studied.Incompletely reduced graphene (RG) was prepared by reduction of graphite oxides via microwave irradiation at the power of 800 W and 1200 W, respectively. Fourier transform infrared spectra and X-ray photoelectron spectroscopy analyses showed that the RG contains flourish oxygen functional groups such as carboxyl, phenol, carbonyl, and quinone groups. X-ray diffraction, scanning electron microscopy and transmission electron microscopy were employed to investigate the structure, morphology of the RG samples. The electrochemical performance of the RG electrodes were measured in 5 M NaOH, 1 M H2SO4 and 1 M Na2SO4 electrolytes respectively. The supercapacitor performance of oxygen-containing functional group behavior was investigated. The specific pseudocapacitance per unit atomic percentage for either carboxyl or phenol group in 1 M H2SO4 and either carbonyl and quinone group in 5 M NaOH were obtained by galvano-statically charge/discharge measurements

•Introduce pseudocapacitive materials (amorphous FeOOH) in transparent electrodes.•The unique composite structure builds up rapid 3D electron/ion transport pathways.•The composites alleviate the dissolution of active material into electrolyte.•Extend the potential window of FeOOH cathode from −0.8–0 V to −1.2–0 V.Faradaic transition-metal-oxide/hydroxide (TMH) materials are critical for high-performance supercapacitors. However, the preparation of transparent micro-structured TMH electrodes is a great challenge and has become the bottleneck restricting the performance of transparent flexible supercapacitors. Here, Ni(OH)2 nanosheets and amorphous FeOOH nanowires were simply synthesized as micro-structured transparent films through a scalable gas-liquid diffusion method at the air-solution interface. The microstructures are enwrapped in graphene shells (Ni@Gr-TF and Fe@Gr-TF) for increasing rapid 3D electron/ion transport pathways, alleviating the exfoliation and dissolution of active materials into the electrolyte, and extending the potential window of the FeOOH cathode to −1.25–0 V. An asymmetric transparent and flexible supercapacitor (ATFS) based on Ni@Gr-TF//Fe@Gr-TF exhibited a transmittance of 52.3% at 550 nm, a high specific capacity of 17.42 mF cm−2 at 0.2 mA cm−2 (one order higher than the maximum value reported for a transparent graphene membrane), an energy density of 0.67 mWh cm−3 based on the entire device (comparable with nontransparent devices) as well as a high capacity retention (85.1%) after a long cycle life of 20 000 cycles.

•Multicolor tunable yellow-red emission are found in Eu/Er:LiNbO3.•Emission spectra under ultraviolet and blue excitation are discussed.•Color coordinates are calculated to reflect the true color of luminescence.The ability to manipulate the multicolor luminescence will greatly enhance the scope of their applications, ranging from infrared solar cells to volumetric multiplexed bioimaging. Tuning from yellow to red emission was successfully achieved in Eu/Er:LiNbO3 under ultraviolet (UV) and blue excitation. The excitation spectra of Eu/Er:LiNbO3 monitored at 590 nm/618 nm/626 nm were studied. The CIE 1931 color coordinates showed that the emissions fell within the yellow and red region, respectively, under 376 nm and 397 nm excitation. The color coordinates shifted from yellow toward red region upon diode laser excitation of 476 nm.

•Controlled reduced graphene oxide (designed as CRGO) is fabricated.•Dispersion of CRGO at very low particles loading.•Stability, thermal conductivity, and rheological properties of nanofluids are systematically investigated.In this study, controlled reduced graphene oxide (CRGO) was fabricated via modified Hummers’ and chemical reduction methods. CRGO was characterized by power X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. Deionized water based nanofluids with different concentrations were prepared by ultrasonic probe without the use of any surfactants. Furthermore, the stability, zeta potential, thermal conductivity, and rheological properties of the as-prepared nanofluids were systematically investigated using different experimental methods. The experimental results show that the zeta potential for a concentration of 0.2 mg/ml can reach to −50.9 mV at pH = 12.0, and the as-prepared nanofluids also have good dispersion stability with the increase of the nanofluids temperature and additive concentration. All show significant enhancements in thermal conductivity upon increase of the additive concentration and nanofluids temperature, compared with that of base fluids, reaches its maximum enhancement of ∼32.19% at 60 °C for a concentration of 1.0 mg/ml. Moreover, the whole tested nanofluids almost exhibit Newtonian behavior at high shear rates, where all the viscosities decrease approximately linearly with the increase of temperature. Those results demonstrate an outstanding potential for the use of CRGO/water nanofluids as suitable replacements for the conventional fluids in heat exchanger applications.

A composite consisting of well-dispersed and ultrafine hematite quantum-dots (∼2.7 nm) anchored on a three-dimensional ultra-porous graphene-like framework (denoted as Fe2O3-QDs–3D GF) has been designed by a facile and scalable strategy. In the composite, the ultra-porous 3D GF with high conductivity and high surface area was used as a conductive matrix with surface defective sites for the controllable growth of uniformly dispersed, ultra-small Fe2O3-QDs. The graphene framework can tightly hold a great amount of Fe2O3-QDs, thereby ensuring high utilization of active materials and the required conductivity to individual Fe2O3-QDs. The ultra-small-sized Fe2O3-QDs anchored on the 3D GF can endow the composite with a superior high surface area and enough active sites for electrochemical reactions, thus giving the composite a large specific capacitance. As expected, the as-prepared Fe2O3-QDs–3D GF electrode exhibited a high specific capacitance of 945 F g−1 at 1.0 A g−1 in a three-electrode system in 2.0 mol L−1 KOH aqueous solution. In addition, high-performance asymmetric supercapacitors have been fabricated with Fe2O3-QDs–3D GF as the anode and 3D hierarchical porous graphene (HPG) as the cathode, and they showed a very high energy density of 77.7 W h kg−1 at a power density of 0.40 kW kg−1 and maximum power density of 492.3 kW kg−1, as well as excellent cycling stability.

A peculiar nanostructure consisting of nitrogen-doped, carbon-encapsulated (N–C) SnO2@Sn nanoparticles grafted on three-dimensional (3D) graphene-like networks (designated as N–C@SnO2@Sn/3D-GNs) has been fabricated via a low-cost and scalable method, namely an in situ hydrolysis of Sn salts and immobilization of SnO2 nanoparticles on the surface of 3D-GNs, followed by an in situ polymerization of dopamine on the surface of the SnO2/3D-GNs, and finally a carbonization. In the composites, three-layer core–shell N–C@SnO2@Sn nanoparticles were uniformly grafted onto the surfaces of 3D-GNs, which promotes highly efficient insertion/extraction of Li+. In addition, the outermost N–C layer with graphene-like structure of the N–C@SnO2@Sn nanoparticles can effectively buffer the large volume changes, enhance electronic conductivity, and prevent SnO2/Sn aggregation and pulverization during discharge/charge. The middle SnO2 layer can be changed into active Sn and nano-Li2O during discharge, as described by SnO2 + Li+ → Sn + Li2O, whereas the thus-formed nano-Li2O can provide a facile environment for the alloying process and facilitate good cycling behavior, so as to further improve the cycling performance of the composite. The inner Sn layer with large theoretical capacity can guarantee high lithium storage in the composite. The 3D-GNs, with high electrical conductivity (1.50 × 103 S m–1), large surface area (1143 m2 g–1), and high mechanical flexibility, tightly pin the core–shell structure of the N–C@SnO2@Sn nanoparticles and thus lead to remarkably enhanced electrical conductivity and structural integrity of the overall electrode. Consequently, this novel hybrid anode exhibits highly stable capacity of up to 901 mAh g–1, with ∼89.3% capacity retention after 200 cycles at 0.1 A g–1 and superior high rate performance, as well as a long lifetime of 500 cycles with 84.0% retention at 1.0 A g–1. Importantly, this unique hybrid design is expected to be extended to other alloy-type anode materials such as silicon, germanium, etc.Keywords: lithium ion battery; nitrogen-doped carbon; Sn; SnO2; three-dimensional graphene

High specific-capacity pseudocapacitive transition-metal-hydroxide (TMH) materials are desirable for future high performance transparent supercapacitors, but have been rarely reported previously. The successful synthesis of TMH materials with desired nanostructures is a key factor for their transparency. Here, Ni(OH)2 nanosheet transparent film (NNS-TF) was developed simply through a gas-liquid diffusion method. The nanostructures were enwrapped in graphene shells (NNS@Gr-TF) for using as transparent electrodes. The unique encapsulation structures build up rapid three-dimensional electron and ion transport pathways together with the underlying ITO layer. The specific areal capacitance (18.9 mF/cm2 at 0.1 mA/cm2) was greatly improved, at least a thousand times higher than the reported value for transparent devices based on planer CVD graphene, and ten times as that for 3D micro-structured graphene membrane.

•The composites film photoanodes were prepared by dip coating method.•The MnTiO3 and MgTiO3 coating layer can effectively promote the dye adsorption.•The MnTiO3/MgTiO3 layer could retard the charge recombination.•The DSSC based on the TiO2/MnTiO3/MgTiO3 photoanode exhibited the highest conversion efficiency.The TiO2/MnTiO3, TiO2/MgTiO3 and TiO2/MnTiO3/MgTiO3 composite photoanodes were prepared by immersing the TiO2 nanosheets film into the mixed solution of titanium tetrachloride and manganese chloride (or magnesium chloride), and followed by calcination treatment. The effects of MnTiO3 and MgTiO3 treatment on the photovoltaic performances of the dye-sensitized solar cells (DSSCs) were investigated. The MnTiO3 and MgTiO3 as coating layer on the surface of TiO2 can effectively promote the dye adsorption adhered to the photoanode film. The photoelectric conversion efficiency of the DSSC based on TiO2/MnTiO3 and TiO2/MgTiO3 photoanodes increased by 25.7% and 15.5% compared with that of pure TiO2-based DSSC, respectively. Furthermore, the DSSC based on the TiO2/MnTiO3/MgTiO3 photoanode exhibited the highest conversion efficiency of 6.39%, exceeding that of pure TiO2-based DSSC by a factor of 1.4. The highest efficiency observed for the DSSC based on this hybrid structure is attributed to the enhanced dye-absorption, fast electron transfer and the energy barrier formed by MnTiO3/MgTiO3 layer, which suppresses the charge recombination and increases the photocurrent. This investigation provides a new way for further improving the photoelectric conversion efficiency of the DSSCs.The MnTiO3/MgTiO3 coating can effectively increase the dye adsorption and suppress the recombination of charges and reduce the dark current loss, and finally enhance the photoelectric conversion efficiency.

•Anodes fabricated by using activated carbon have the highest fracture strength.•SnO2 nanoparticles are mono-dispersed on the surface of rGO sheets and SiO2 spheres.•The hierarchical structure SiO2@SnO2/rGO shows a good electrochemical performance.In order to ease the agglomeration and huge volume change of SnO2 particles, SnO2 nanoparticles were usually anchored on reduced graphene oxide (rGO) and used as anode materials for lithium ion batteries. Unfortunately, graphene sheets tended to overlap with adjacent ones and SnO2 nanoparticles still suffered from agglomeration and huge volume changes to some extent. In this paper, a composite SiO2@SnO2/rGO with coating and hierarchical structure was synthesized by a facile hydrothermal method. SnO2 nanoparticles mono-dispersed on the surface of rGO sheets and SiO2 spheres, while the SiO2@SnO2 spheres were imbedded in the layers of rGO, which was in favor of alleviating the overlapping of graphene sheets and could make large spacious room to accommodate the huge volume changes of SnO2 nanoparticles. SiO2@SnO2/rGO composite also displayed good electrochemical performance. In the first charge/discharge cycle, the SiO2@SnO2/rGO electrode exhibited a large discharge capacity of 1548 mA h g−1 at a current density of 100 mA g−1 and it still retained a discharge capacity of about 600 mA h g−1 after 100 cycles.

•Nickel@carbon/silicone resin (Ni@C/Si-R) flexible absorbing material was prepared.•Ni@C/Si-R shows superior microwave absorption properties in 2–18 GHz.•A deep insight of the difference between calculated RL and measured RL was given.Carbon-encapsulated nickel nanoparticles (Ni@C) with soft magnetic nickel nanoparticle core and dielectric carbon shell were synthesized by a modified arc-discharge method. The calculated reflection loss (RL) of Ni@C/paraffin composites and the measured RL of Ni@C/silicone coatings were studied at thicknesses of 1–3 mm and Ni@C contents of 40–60 wt%. Ni@C nanoparticles show good microwave absorption properties in 2–18 GHz. The minimum calculated RL is −39.82 dB with 60 wt% Ni@C at 3 mm, and the calculated RL <−10 dB can be obtained in the frequency of 5–13.41 GHz. Meanwhile, the minimum measured RL reaches −20.54 dB with 60 wt% Ni@C loading at 2.5 mm and the widest bandwidth of measured RL <−10 dB is 3.64 GHz with 60 wt% Ni@C loading at 1.5 mm.

A sol–gel method has been utilized for synthesizing the wormhole-like mesoporous carbon (WMC), in which the gel skeleton can be regulated by using hydrofluoric acid and sulfuric acid. The electromagnetic characteristics of a series of WMCs with different surface areas embedded in paraffin at 15 wt% loading at 2–18 GHz were investigated. The electric conductivity of WMCs gradually increases with the decrease of surface area, leading to an increase in complex permittivity through dielectric loss. A minimum reflection loss (RL) value of −68.41 dB and a broader absorption band (reach 9.8 GHz) with RL values less than −10 dB are obtained, due to WMC’s well matching the characteristic impedance and dielectric loss, implying its great potential as a microwave absorbing material.

Thermal conductivity is one of key parameters of adsorbents, which will affect the overall system performance of adsorption chiller. To improve adsorbent’s thermal conductivity is always one of research focuses in chemisorption field. A new chemical composite adsorbent is fabricated by adding carbon coated metal(Aluminum and Nickel) nanoparticles with three different addition amounts into the mixture of chloride salts and natural expanded graphite aiming to improve the thermal conductivity. The preparation processes and its thermal conductivity of this novel composite adsorbent are reported and summarized. Experimental results indicate that the nanoparticles are homogenously dispersed in the composite adsorbent by applying the reported preparation processes. The thermal conductivity of the composite adsorbent can averagely enlarge by 20% when the weight ratio of the added nanoparticles is 10 wt%. Moreover, carbon coated aluminum nanoparticles exhibit more effective enlargement in thermal conductivity than nickel nanoparticles. As for the composite adsorbent of CaCl2-NEG, there is a big reinforcement from 30% to 50% for Al@C nanoparticles, however only 10% in maximum caused by Ni@C nanoparticles. The proposed research provides a methodology to design and prepare thermal conductive chemical composite adsorbent.

In this study, composites consisting of well-dispersed TiO2 nanoparticles deposited on the surface of reduced graphene oxide (designed as TiO2-G) were fabricated via a facile synthesis method, namely in situ hydrolysis of TiCl4 and subsequently immobilization on the surface of reduced graphene oxide. TiO2-G/water nanofluids with the nanoparticles loading of 0.02, 0.03, 0.05, 0.07, and 0.1 wt% were prepared by ultrasonic probe in the condition without the addition of surfactants. Furthermore, the stability, zeta potential, and thermal conductivity of the TiO2-G/water nanofluids were analyzed by using different experimental methods. With the nanoparticles loading of 0.02 wt% (0.015 vol%) and 0.05 wt% (0.038 vol%), the zeta potential value of TiO2-G/water nanofluids can reach up to −46.49 and −37.44 mV, respectively, exhibiting great stability. Compared to that of the base fluid, the thermal conductivity of TiO2-G/water nanofluids increased with the increase of the loading of TiO2-G composite and the temperature of the nanofluids, and reached a maximum enhancement of ~33 % at a composite concentration of 0.1 wt% (0.078 vol%). Therefore, TiO2-G/water nanofluids can be applied to heat exchanger systems, as they provide a good long-time dispersion stability and a significant thermal conductivity enhancement.

Graphene-based nanocomposites have been one of the most attractive electrode materials of supercapacitors. But in most cases, graphene-based nanocomposites always use single nanoparticle as active material, which cannot meet the increasing demand for next generation of energy storage devices. In the present paper, we prepared Fe2O3–Ni(OH)2/graphene nanocomposite by simple one-step hydrothermal method. The dual-particle system reveals a synergistic effect between Fe2O3 and Ni(OH)2, i.e., Ni(OH)2 can enhance the electrical conductivity of Fe2O3, and then Fe2O3 can act as electrical conductivity bridges between Ni(OH)2 nanoparticles and RG. As a result, the Fe2O3–Ni(OH)2/graphene nanocomposite presents impressing electrochemical performance, including high specific capacitance (~857 F/g), good rate capability, and outstanding cycling stability (after 5000 cycles, 100 % retention).

Meso-/macropore structure and graphite microcrystallite are two critical impacts on high-rate supercapacitive energy storage performance of nanoporous carbon. In the present paper, we prepared a novel graphitic carbon with three-dimensional interconnected meso-/macroporous nanonetwork by a simple one-step Friedel–Crafts crosslinking reaction. A metal-containing aromatic molecule, ferrocene, is selected as started building units. The crosslinking reaction of aromatic rings leads to the formation of meso-/macroporous nanonetworks, and the Fe element can act as a catalyst to accelerate the formation of graphite microcrystallite during carbonization. The experimental results show that the crystal sizes along the c-axis direction (Lc) of the as-obtained graphitic porous carbons are 0.92–1.49 nm and the graphitization do not damage nanopore structure, so that their surface areas are higher than 500 m2 g−1. Owing to their unique structural features, i.e., meso-/macroporous network can shorten the ion transport distance and accelerate ion transport rate, and the moderate graphite microcrystalline is beneficial for electron transfer, this graphitic porous carbon shows high-rate supercapacitive energy storage. For example, the capacitance retention of the as-prepared samples can reach 88 % when the scan rate was raised from 10 to 300 mV s−1.

•Nd doped Li3V2(PO4)3/C samples were synthesized via simple sol–gel routine.•Magnetic properties of Li3V2(PO4)3/C were significantly changed by Nd doping.•Li3V1.95Nd0.05(PO4)3/C showed better electrochemical properties than undoped one.A series of neodymium doped Li3V2−xNdx(PO4)3/C cathode materials have been successfully synthesized by a citric acid assisted sol–gel method. Nd doped samples (x ≤ 0.10) have well developed monoclinic structure of Li3V2(PO4)3 with enlarged unit cell volume. All samples present typical characteristics of paramagnetism in 4 < T ≤ 300 K, but the magnetic susceptibilities of Nd doped samples increase with Nd content (except for x = 0.15). Nd doped composites show better electrochemical property than that of the undoped one. Among them, the Li3V1.95Nd0.05(PO4)3/C displays the highest capacity and best cycle stability. The Li3V1.95Nd0.05(PO4)3/C presents the first discharge capacity of 129.2 mAh g−1 at 1 C rate in the voltage range of 3.0–4.3 V, 21.7% higher than that of Li3V2(PO4)3/C. And no capacity loss occurs after 100 cycles. The high structural stability, low charge-transfer resistance and rapid Li+ diffusion due to the presence of Nd3+ are mainly responsible for the superior electrochemical performance of Nd doped Li3V2(PO4)3/C cathode materials.

•G/NiO was synthesized by using alcohols-reduced graphene as substrate.•G/NiO presents a globule-on-sheet structure and reveals a synergistic effect.•G/NiO displays high specific capacitance and superior cycling stability.Graphene/nickel oxide composite (G/NiO) was synthesized through a facile hydrothermal method and subsequently microwave thermal treatment by using alcohols-reduced graphene as substrate. The as-prepared G/NiO was characterized by X-ray diffraction, Raman spectra, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscope and transmission electron microscope. The results indicate that the graphene oxide has been successfully reduced to graphene, and NiO nanoparticles are homogeneous anchored on the surface of graphene, forming a globule-on-sheet structure. The loading content of NiO nanoparticles anchoring on the surface of graphene nanosheets can be controlled by adjusting the hydrothermal temperature. The G/NiO displays superior electrochemical performance with a specific capacitance of 530 F g−1 at 1 A g−1 in 2 M of NaOH. After 5000 cycles, the supercapacitor still maintains a specific capacitance of 490 F g−1 (92% retention of the initial capacity), exhibiting excellent cycling stability.

•The LFP–CNT–G composite was successfully prepared by solid station method.•The interlaced CNTs reduced the crumple of graphene and improved tap density of the composite.•The LFP–CNT–G electrode exhibited superior electrochemical performance.A three-dimensional lithium iron phosphate (LiFePO4)/carbon nanotubes (CNTs)/graphene composite was successfully synthesized via solid-state reaction. The LiFePO4/carbon nanotubes/graphene (LFP–CNT–G) composite used as Li-ions battery cathode material exhibits superior high-rate capability and favorable charge–discharge cycle performance under relative high current density compared with that of LiFePO4/carbon nanotubes (LFP–CNT) composite and LiFePO4/graphene (LFP–G) composite. Graphene nanosheets and CNTs construct 3D conducting networks are favor for faster electron transfer, higher Li-ions diffusion coefficient and lower resistance during the Li-ions reversible reaction. The synergistic effect of graphene nanosheets and CNTs improves the rate capability and cycling stability of LiFePO4-based cathodes. The LFP–CNT–G electrode shows reversible capacity of 168.9 mA h g−1 at 0.2 C and 115.8 mA h g−1 at 20 C. The electrochemical impedance spectroscopy demonstrate that the LFP–CNT–G electrode has the smallest charge-transfer resistance, indicating that the fast electron transfer from the electrolyte to the LFP–CNT–G active materials in the Li-ions intercalation/deintercalation reactions owing to the three-dimensional networks of graphene and carbon nanotubes.The excellent electrochemical performances can be attributed to the synergistic effect of CNTs and graphene.

Reduced graphene oxide/Mn3O4 (GM) composites were prepared by a simple and convenient strategy, that is, microwave irradiation of the hydrothermal product of reduced graphene oxide–Mn(NO3)2 mixtures. Mn3O4 nanoparticles with sizes of 20–50 nm were uniformly distributed on the surface of reduced graphene oxides. The GM composites exhibited good electrochemical performance with a specific capacitance of 344.8 F g−1 at the discharge current density of 1 A g−1 using 5 M NaOH as the electrolyte. The energy density of the GM composites was as high as 47.8 W h kg−1 with a power density of 1000 W kg−1. After 5000 cycles of charge/discharge experiments, a high level retaining specific capacitance of 342.1 F g−1 was obtained with 99.2% retention of the initial capacitance at 1 A g−1 and the equivalent series resistance of the GM composites system was much lower than that of pure Mn3O4. Therefore, the GM composites with large capacitance, good cycling performance and reversibility can be used as a promising electrode material for supercapacitor applications.

TiO2-reduced graphene oxide nanocomposite has been synthesized by a facile hydrothermal process. The structure and morphology have been characterized by X-ray diffraction and scanning electron microscopy. The result shows that a unique nanocomposite has been obtained with the TiO2 nanoparticle homogenously dispersed onto the reduced graphene oxide sheets. The electrochemistry performance has been tested through cyclic voltammetry, constant current discharge/charge tests, and electrochemical impedance techniques. The initial lithium ion storage capacity is 368 mAhg−1 at the rate of 10 mAg−1, which exceeds the theoretical capacity value of the anatase TiO2 (335 mAhg−1). The nanocomposite exhibits good high-rate capacity of 136.1 mAhg−1 at rate of 1,000 mAg−1, and, after 100 cycles, the coulombic efficiency is still maintained as high as 98.6 %. The high specific capacity and good stability can be attributed to the unique structures and make the nanocomposite a promising substitute of the current commercial graphite anode in high-power, high-rate application of lithium ion batteries.

•Near-stoichiometric Er:LiNbO3 crystal was grown by Czochralski technique.•The strongest 1.54 μm emission is observed for Er:NSLN crystal.•Judd–Ofelt parameters based on UV–vis-infrared absorption spectra are discussed.•Absorption/emission cross-section and fluorescence lifetimes are reported.•Gain cross-section spectra in the eye-safe regime of 1450–1650 nm are studied.Near-stoichiometric LiNbO3 crystal heavily doped with Er3+ ions (Er:NSLN) was grown by Czochralski technique. An enhancement of 1.54 μm emission and a lengthening lifetime of 4I13/2→4I15/2 transition observed in Er:NSLN crystal would meet the requirement of the greatly shortening optical diffusion route for Er-doped waveguide amplifiers (EDWAs). Inductively coupled plasma mass spectrometry (ICP-MS) was used to determine the concentration of Er3+ ion in the crystal. Based on Judd–Ofelt theory, the spectroscopic properties of Er:NSLN crystal were discussed, and the obtained intensity parameters Ωt implied that the increased [Li]/[Nb] ratio had a large influence on the value of Ω2. The emission cross-sections of 1.54 μm emission were calculated by Füchtbauer–Ladenburg and reciprocity methods. Studies on the gain cross-section, estimated as a function of the population inversion ratio, suggested that Er:NSLN crystal could be considered as a potential material in the application of the tunable lasers around 1.54 μm wavelength.

LiFePO4 is very good potential cathode materials for the power lithium-ion batteries because of its high theoretical capacity and high voltage, but its electrochemical performance suffers from the low electronic conductivity. In this paper, the multi-walled carbon nanotubes (MWCNTs)/LiFePO4 composites cathode materials are prepared by ball milling. With high conductivity and the network structure existing in the LiFePO4 electrode, carbon nanotubes can reduce internal resistance and increase practical capacity and cycle stability of LiFePO4. As electrodes of lithium battery, the charge–discharge capacity, cyclic voltammetry, cycle life, alternating current impedance, and discharge temperatures characteristic of LiFePO4/MWCNTs (the loading of MWCNTs from 0 to 20 %) are investigated. The resistances of LiFePO4/MWCNTs decrease with the increase of MWCNTs loading and reach a minimal value of 56 Ω in the 10 % loading of MWCNTs, and result in the improvement of electrochemical performance. It is found that the composite electrode with 10 % loading of MWCNTs exhibits a best charge–discharge performance, and has initial charge capacities of 148 mAhg−1 and discharge capacities of 145 mAhg−1, respectively at 0.1 °C rate and the capacity retention is 98 %. The result of the pure LiFePO4 shows that the discharge capacity is 131 mAhg−1 at the rate of 0.5 °C, which means the increase in capacity of the LiFePO4/MWCNTs electrode achieves 16 %. The LiFePO4/MWCNTs composites also have perfectly high temperature performance due to the excellent thermal stability of the MWCNTs, and the discharge capacity of the composite electrode is 164 mAhg−1 at 0.1 °C rate in the temperature of 60 °C. After 30 cycles, the capacity still maintains as 163 mAhg−1 and the capacity retention is 99 %. The excellent cycle performance of the LiFePO4/MWCNTs electrode may attribute to the netlike-structure mechanical and electrical performance of MWCNTs.

A TiO2 film photoanode with gradient structure in nanosheet/nanoparticle concentration on the fluorine-doped tin oxide glass from substrate to surface was prepared by a screen printing method. The as-prepared dye-sensitized solar cell (DSSC) based on the gradient film electrode exhibited an enhanced photoelectric conversion efficiency of 6.48%, exceeding that of a pure nanoparticle-based DSSC with the same film thickness by a factor of 2.6. The enhanced photovoltaic performance of the gradient film-based DSSC was attributed to the superior light scattering ability of TiO2 nanosheets within the gradient structure, which was beneficial to light harvesting. Furthermore, the TiO2 nanosheets with exposed {001} facets facilitated the electron transport from dye molecules to the conduction band of TiO2 and further to the conductive glass. Meanwhile, the high specific surface area of TiO2 nanosheets helped the adsorption of dye molecules, and the TiO2 nanoparticle underlayer ensured good electronic contact between the TiO2 film and the fluorine-doped tin oxide glass substrate. The electrochemical impedance spectroscopy measurements further confirmed the electron transport differences between DSSCs based on nanosheet/nanoparticle gradient film electrodes and DSSCs based on nanosheet/nanoparticle homogeneous mixtures, pure TiO2 nanoparticles and pure TiO2 nanosheets with the same film thickness.

•Li4Ti5O12/carbon nanotubes (CNTs) composite is prepared by mixing powders.•Li4Ti5O12/CNTs composite show large capacity, good cycling performance.•Li4Ti5O12/CNTs composite electrodes of low resistance are obtained.•The Li4Ti5O12/CNTs composite electrodes have steady discharge platform.Li4Ti5O12 sub-micro crystallites are synthesized by ball-milling and one-step sintering under different heat treatment temperature from 700 °C to 900 °C. The composite electrode of Li4Ti5O12/carbon nanotubes (CNTs) is prepared by mixing powders of Li4Ti5O12 and CNTs in different weight ratios. Before mixing, in order to disperse CNTs in Li4Ti5O12 particles preferably, the CNTs are cut and dispersed by hyperacoustic shear method and the composite electrodes of low resistance of about 20–30 Ω are obtained. The composite electrodes have steady discharge platform of 1.54 V and large specific capacity, initial discharge capacities are 168, 200, 196, 176 mAh g−1 in different Li4Ti5O12:CNTs weight ratios of 94:1, 92:3, 90:5, 88:7 respectively at 0.1 C discharge rate for the Li4Ti5O12 synthesized in an optimized heat treatment temperature of 800 °C. In our experimental range, the composite electrode in a CNTs weight ratio of 3:92 shows the best performance under different discharge rate such as the initial capacity is 200 mAh g−1 with discharge capacities retention rate of nearly 100%. Its capacity is about 151 mAh g−1 under 20 C rate discharge condition with excellent high-rate performance. There is almost no decline after 20th cycles under 10 C rate discharging condition.

•Self-healable PVA hydrogels were prepared by the cyclic freezing/thawing method.•The self-healability depends on the PVA content and its crystalline structure.•The hydrogels show two transition points at the PVA contents of 6 wt% and 12 wt%.•The PVA content shows significantly high water stability.The self-healable polyvinyl alcohol (PVA) hydrogels were prepared by the cyclic freezing/thawing method. Effect of PVA content on the crystalline structure, self-healability and water stability of PVA were explored. Results show that the self-healability of PVA hydrogels depends on the PVA content and emerges at the PVA content of 25 wt%. The PVA content induces the crystal structure of PVA to change. The change shows two transition points at the PVA contents of 6 wt% and 12 wt%. The crystal structure of PVA significantly affects the tensile strength and water stability of PVA hydrogels. The high water stability of PVA hydrogels results from an increase in crystallite size or crystallinity of PVA.

•By one-step anodization of Ti foil together with an adjacent Ti strip, we fabricate the regionally distributed TNTAs.•By manipulating the anodization time, the tube density of the TNTAs grown in the specific region can be controlled over a wide range while keeping no tube in the other regions.•We find that the region-specific growth of TNTAs may be due to the narrow gap formed between the Ti foil and the adjacent Ti strip.In this work, we report the growth of regionally distributed TiO2 nanotube arrays (TNTAs) by one-step anodization of Ti foil together with an adjacent Ti strip. Under our anodization condition, the TNTAs in the specific region covered by the Ti strip grow earlier and quicker than that in the other regions. The tube density could be controlled over a wide range in the specific region while keeping no tube in the other regions. The mechanism of such region-specific growth of TNTAs is discussed. Our findings might be manipulated to fabricate various TNTAs defined patterns for many functional applications.

•Quantitatively and synchronously characterized the stability of MWNT suspensions.•The lowest normalized transmission variation corresponds to the highest stability.•The sedimentation velocity is influenced significantly by the initial dispersibility.•Disperbyk-2012 and Disperbyk-198 surfactants effectively stabilize suspensions.Multi walled carbon nanotubes (MWNTs) suspensions were prepared by using propylene glycol n-propyl ether (PnP), ethylene glycol monobutyl ether (EB) and propylene glycol monomethyl ether (PM) as solvents, copolymer Disperbyk-2012 (D-2012) and Disperbyk-198 (D-198) as surfactants associated with ultrasonication. The de-dispersion and sedimentation behaviors of suspensions were characterized by a step view centrifugation methodology which allows accelerating and quantifying the stability of dispersions in a direct way. During 1000 rpm accelerated centrifugation for 5600 s, PnP, EB and PM suspensions showed severe de-dispersion and sedimentation behaviors compared with that of surfactant suspensions, the sedimentation velocities of PnP, EB and PM dispersions were far more than that of surfactant suspensions. Both real time and statistic instability index analysis were performed and the results showed that PnP/D-198 and EB/D-198 were superior mediums for MWNTs suspensions, a plausible dispersing and stabilizing mechanism of the used surfactants and solvents for MWNTs was proposed.

Thermally exfoliated graphite oxide (GO) has been prepared at a low temperature and ambient pressure usually contains flourish oxygen functional groups. We find that complete oxidized graphite can be successfully expanded, as well as partially exfoliated and reduced at a very low temperature about 200 °C and ambient pressure without any supplementary conditions such as high vacuum or under hydrogen environment. The electrochemical properties of supercapacitor electrodes are studied by cyclic voltammetry (CV) and galvanostatic charge/discharge (DC) methods. Supercapacitors are constructed with as-prepared functionalized graphene have good electrochemical performance, with a maximum specific capacitance of 315 F g−1 at the charge/discharge current density of 100 mA g−1 using 1 M KOH electrolyte and a high charge/discharge efficiency of about 97%.Highlights► We report graphite oxide (GO) expansion at 200 °C and ambient pressure. ► The as-prepared graphene contains flourish oxygen functional groups. ► The maximum specific capacitance was 315 F g−1, higher than prepared at vacuum. ► The charge/discharge efficiency was about 97% at a current density of 100 mA g−1. ► This simple method shows great potential application of graphene supercapacitors.

The multi-walled carbon nanotubes (MWNTs) were added to the nickel hydrogen battery negative electrode to prepare high-power CNTs compound nickel hydrogen battery. Their capacity, large-current discharging performance of high-power battery and the cycle life were investigated. It's found that adding carbon nanotubes was greatly advantageous for enhancing the electrochemical performance of the battery as a whole, especially the large-current discharge performance and cycle life. When the weight ratio of the MWNTs in the compound electrode was 0.8%, the overall performance of the battery was the best, which has a highest capacity of 3369 mAh under the condition of 3000 mA charge current and 6000 mA discharge current (2C-rate discharge), and the cycle life surpassed 600 times (97% discharge depth). Especially under the 10C-rate large-current discharge condition (3000 mA charge current and 30000 mA discharge current), its cycle life still surpassed 100 times (75% discharge depth). In 600th cycle, the inner electric resistance of battery without MWNTs is 5 times more than adding 8% MWNTs. The adding of MWNTs can prevent inner resistance from rising, and therefore improve the cycle life of the Ni–MH batteries.

We have synthesized multi-wall carbon nanotubes by catalytic chemical vapour deposition (CCVD) method using an AB5 hydrogen storage alloy with diameter ranging from 38 to 150 μm as a catalyst. The H2 uptake capacity of the carbon nanotubes prepared using an AB5 alloy as a catalyst is about 4 wt.% through to the pressure of 8 MPa at room temperature. Differential thermal analysis–thermogravimetric analysis (DTA–TGA) technique has been applied to investigate the effect of the diameters of the AB5 alloy catalyst of micrometer magnitude and the technique conditions in the CCVD process on the thermal properties of carbon nanotubes. As the catalyst diameter increases from 38 to 150 μm, the average diameter of the prepared carbon nanotubes increases and the diameter distribution also enlarges. Electron microscope, Raman spectrum and thermal analysis all indicated that the catalyst sizes affect the diameter and the thermal properties of the carbon nanotubes. When the catalyst diameter increases, the initial weight loss temperature and the differential thermal peak temperature of the carbon nanotubes increases, which shows that the lager the diameter of the carbon nanotubes is, the higher the oxidation temperature, and the better the anti-oxidizablity. However, if the diameter of the catalyst is larger than 100 μm, the anti-oxidizablity does not rise anymore but tend to be invariableness. In the CCVD preparation process, the anti-oxidizability of the carbon nanotubes increases, when raising the ratio of the hydrogen gas in the reaction gas in our experimental range (4:1, 3:1, and 2:1, respectively).

The nanotubes were prepared by the dc arc-discharge method in helium and argon gas ambient under controlled pressure, and subsequently purified by oxidation in air. The room temperature electron spin resonance (ESR) spectra of purified carbon nanotubes prepared under different inert gases and their pressure were measured. The dependence of the ESR line shape, linewidth, g-value of the nanotubes on the inert gases and their pressures is found and discussed.

•C/SiO1.5 nanospheres were fabricated by emulsion polymerization of twin monomer.•C/SiO1.5 nanospheres show molecular-scale bi-continuous structure.•The diameter of C/SiO1.5 nanospheres can be tailored from 27 to 53 nm.•C/SiO1.5 nanospheres show a high reversible capacity of 444 mAh/g.Novel C/SiO1.5 nanospheres were fabricated by simple emulsion polymerization of twin monomer, i.e., methacryloxypropyltriethoxysilane (MP/TES). MP/TES contains organic component MP and inorganic component TES, which can be converted into carbon and SiO1.5via sequential emulsion polymerization and condensation, resulting in the formation of molecular-scale bi-continuous C/SiO1.5 structure. The SiO1.5 content is as high as 90%, and the size of SiO1.5 phase is ca. 1.3 nm. In addition, the diameter of C/SiO1.5 nanospheres can be well tailored from 27 to 53 nm by changing the emulsifier concentrations. When used as electrode in lithium ion battery, carbon phase can improve the electrical conductivity and protect the electrode from crack; low spherical diameter can reduce the ion transfer distance and high SiO1.5 content will supply enough active sites for lithium ion storage, and thus, C/SiO1.5 nanospheres present remarkable lithium ion storage performance. The initial discharge and reversible capacities of C/SiO1.5 nanospheres can reach 752 and 328 mAh g−1. After 100 cycles, a remarkable capacity of 444 mAh g−1 remains, which is 1.2 times of the theoretical capacity of graphite.

A composite consisting of well-dispersed and ultrafine hematite quantum-dots (∼2.7 nm) anchored on a three-dimensional ultra-porous graphene-like framework (denoted as Fe2O3-QDs–3D GF) has been designed by a facile and scalable strategy. In the composite, the ultra-porous 3D GF with high conductivity and high surface area was used as a conductive matrix with surface defective sites for the controllable growth of uniformly dispersed, ultra-small Fe2O3-QDs. The graphene framework can tightly hold a great amount of Fe2O3-QDs, thereby ensuring high utilization of active materials and the required conductivity to individual Fe2O3-QDs. The ultra-small-sized Fe2O3-QDs anchored on the 3D GF can endow the composite with a superior high surface area and enough active sites for electrochemical reactions, thus giving the composite a large specific capacitance. As expected, the as-prepared Fe2O3-QDs–3D GF electrode exhibited a high specific capacitance of 945 F g−1 at 1.0 A g−1 in a three-electrode system in 2.0 mol L−1 KOH aqueous solution. In addition, high-performance asymmetric supercapacitors have been fabricated with Fe2O3-QDs–3D GF as the anode and 3D hierarchical porous graphene (HPG) as the cathode, and they showed a very high energy density of 77.7 W h kg−1 at a power density of 0.40 kW kg−1 and maximum power density of 492.3 kW kg−1, as well as excellent cycling stability.