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We fabricate a library of binary to quinary element Keplerate clusters stabilized in a medium entropy state. Different ions follow the Irving–Williams series to be incorporated in the clusters.

Neural electrodes have been widely used to monitor neurological disorders and have a major impact on neuroscience, whereas traditional electrodes are limited to their inherent high impedance, which makes them insensitive to weak signals during recording neural signals. Herein, we developed a neural electrode based on the graphene/Ag van der Waals heterostructure for improving the detection sensitivity and signal-to-noise ratio (SNR). The impedance of the graphene/Ag electrode is reduced to 161.4 ± 13.4 MΩ μm

A dual-mechanism energy storage strategy is proposed, involving the electrochemical process of sodium ion battery (SIB) and sodium metal battery (SMB). This strategy is expected to achieve a higher capacity than SIB, and obtain dendrite-free growth of SMB with a well-designed anode. Here, self-constructed bismuth with "sodiophilic" framework and rapid ion transmission characteristics is employed as the sodium host (anode) integrating alloy/de-alloy and plating/stripping process that suppresses the dendrite growth and overcomes the limited capacity of traditional anode. Benefited from this, the capacity (capacity contributed by alloy and plating of sodium in total) of 2000 mAh g

Multi-physics field (MPF) mechanism to Li dendrite has been broadly used in developed routes of protective Li metal anode. It is proved that dendrite can be optimized by adjusting homogeneity of distributions for charge/thermal/structure through chemical reaction field, concentration field, potential field, heat field etc. However, the accurate quantitative for these distributions is still an unsolved problem. Herein, by the natural of entropy (statistics and thermodynamics), we put forwards a quantitative physics field to describe these distributions, named surface distribution entropy (SDE). Subsequently, coupling it into the MPF of electrochemistry, a new finite element analysis model (MPFCS) is developed, which can quantitatively feedback the effect of surface distribution on dendrite growth. Then we re-understand the relationship between nucleation and Li plating within this entropy involved model. In light of this, a dendrite-suppressing route was accomplished through high-density/low-size nucleation with increasing SDE. A step further, an early-warning method for Li anode was realized via the correlation between SDE and extent of dendrite.

Hybridizing carbonous matrix into metal sulfide is confirmed as an effective strategy to enhance electrode conductance and structure stability. However, a comprehensive understanding of the interface reaction mechanism between active materials and carbon substrate is still urgently needed. Based on the band energy theory, a route to enhance the rate ability for electrode is exploited on regulating interfaces of substrates/active heterojunction. Herein, the highly stable Na+-storage performance of GeS2/3DG is delicately designed, where the hierarchical structure is enabled by uniformly overcoating GeS2 nanograins with graphene matrix. Different from the widespread doping route of active materials for fast ion transfer, we focus on the effects of interface regulation on the high-rate Na- ion-storage performance of substrate/active materials. Here, a well-designed interface of the C-Ge bond at the heterointerface induced by hierarchical GeS2/graphene heterojunction is pioneeringly explored, which can result in a fast electron transfer by reducing electron gathering polarization. More importantly, defects in graphene can alleviate the polarization aroused by ion concentration, which not only offers anchoring/doping sites for C-Ge bond but also provides extra ion channels for Na-ion transportation into GeS2. This interface regulation of constructing metal-carbon bonds will shine light on the reaction kinetics and interface stability and contribute to the fundamental understanding of interface reaction mechanisms for metal sulfide anode materials.

The optimized design of size effects and interface effects can enhance the electron/Na-ion migration kinetics for energy-storage materials. Herein, small-size pomegranate-like Bi@C nanospheres (PBCNSs) are synthesized via a simple method and used as the anode of sodium-ion batteries. The composite has a hierarchical structure with ultra-small Bi nanoparticles embedded within carbon spheres which enable fast kinetics and efficient alleviation of stress/strain from the electrodes, and the conductive carbon matrix provides an interconnected electron transportation pathway. Moreover, the hierarchical structure can efficiently prevent the aggregation and pulverization of Bi nanoparticles. The PBCNSs anode delivers excellent sodium-storage performance with an outstanding rate performance (400.3 mA h g−1 at 0.2 A g−1, 372.8 mA h g−1 at 25 A g−1) and long-term cycle stability (340 mA h g−1 after 16 000 cycles at a high current density of 20 A g−1). More importantly, even at a high mass loading of 11.33 mg cm−2, a stable reversible capacity of 327.2 mA h g−1 can be obtained. The mechanism of the high performance was studied by electrochemical measurement and computer simulation.

Bismuth has a great potential as an anode for PIBs, due to its layered structure with a large interlayer spacing, long mean free path, high volumetric capacity (3800 mA h L−1) and environmental friendliness. Bismuthene, a 2D-layered structure, can be exfoliated from bismuth by mechanical or chemical methods. The unique structure of bismuthene is beneficial to the diffusion of potassium, penetration of the electrolyte, and buffering of the volume change along the c-axis, which will boost the anode performance of PIBs. An ultrasonication-assisted electrochemical exfoliation method was proposed in this study to prepare ultra-thin few layered bismuthene nanosheets (FBNs) simply and quickly. The as-prepared FBNs were employed in KIBs as an anode and delivered highly stable capacities of 423, 356, 275 and 227 mA h g−1 at the current densities of 2.5, 5, 10, and 15 A g−1, respectively. There was no obvious decay over 2500 cycles with a capacity of over 200 mA h g−1 at 20 A g−1, realizing excellent rate-capability and long-term cycling stability in KIBs. Furthermore, the mechanism of the excellent electrochemical performances was elucidated via in-depth characterization and theoretical calculations. This work provides a new strategy to prepare scalable ultra-thin nanosheets, which act as a promising candidate for the anode in energy storage systems.

Summary Irreversible structure evolution of electrode in the battery always leads to structure collapse and the lost activation of active material. To overcome this technical challenge, synchronous electrochemical reconstruction method is proposed. Herein, as a proof of concept, Bi2Se3 nanosheets are synthesized. It shows an outstanding electrochemical performance as the anode of sodium-ion battery, which is benefitted by structure evolution of Bi2Se3 electrode. More importantly, Cu element deriving from the current collector is detected, which plays a crucial role in this evolution, promoting the electrochemical reconstruction and stabilizing selenium element. The role of Cu is further verified by the Se powder anode. The reconstructed anode from Bi2Se3 nanosheet or pure selenium can not only provide a stable structure but also ensure a faster electronic and ionic diffusion channel, leading to an excellent cyclic and rate performance. Therefore, the reconstruction strategy will be a promising way for the design of electrode with high performance.

As a novel self-healing material, room-temperature liquid metal (LM) composed of Ga and Sn is a promising anode in lithium-ion batteries (LIBs). Although there is no structural pulverization of the anode material with self-healing ability, the volume change during cycling may cause cracks in the supporting structure, such as binders or conductive additives, and thus significantly limits the cycling stability and high capacity for lithium-alloy electrodes. Here, novel self-healing core-shell fibers, with liquid metal nanoparticles as the core coated with a carbon shell (denoted as LMNPs@CS fibers), were synthesized by facile coaxial electrospinning and a carbonization process. The as-prepared fibers, which encapsulated nanosized self-healing LM particles with a well-designed inner void space of the shell, served as free-standing anodes for LIBs. Such anodes offered a reversible capacity of 603.9 mAh g−1 at 1000 mA g−1, excellent rate capability, and a highly stable cycling performance with a discharge capacity of 552 mAh g−1 after 1500 cycles at 1000 mA g−1. The superior electrochemical performance can be attributed to (1) the self-healing ability of the LMNPs, which ensured the superior cycling performance of the electrode, (2) the unique core-shell structure with a well-designed void space, which alleviated the volume changes of LMNPs during the lithiation/delithiation processes, and (3) the self-healing LMNPs, composed of Ga and Sn, possessed high theoretical capacities. These promising strategies and associated opportunities demonstrate great potential for fabricating advanced self-healing anode materials for LIBs.

Three-dimensional graphene-based materials (3D GBMs) not only possess the intrinsic properties of individual 2D graphene sheet but also provide some new collective physicochemical properties such as high porosity, low density, large specific surface area, excellent mechanical properties, unique electrochemical performance and so on. Benefiting from those properties and the unique structure, 3D GBMs are attractive for a broad range of applications. In this review, we will summarize the recent advances in the synthesis of 3D GBMs and their applications in energy conversion/storage and environment fields. The challenges and future outlook are also discussed.

Hybridizing carbonous matrix into metal sulfide is confirmed as an effective strategy to enhance electrode conductance and structure stability. However, a comprehensive understanding of the interface reaction mechanism between active materials and carbon substrate is still urgently needed. Based on the band energy theory, a route to enhance the rate ability for electrode is exploited on regulating interfaces of substrates/active heterojunction. Herein, the highly stable Na

Benefiting from the reversible conversion reaction upon delithiation, nanosized SnO2, with its theoretical capacity of 1494 mA h g–1, has gained special attention as a promising anode material. Here, we report a self-assembled SnO2/Sn-reduced graphene oxide (rGO) sandwich nanocomposite developed by organometallic precursor coating and in situ transformation. Ultrafine SnO2 nanoparticles with an average diameter of 5 nm are sandwiched within the rGO/carbonaceous network, which not only greatly alleviates the volume changes upon lithiation and aggregation of SnO2 nanoparticles but also facilitates the charge transfer and reaction kinetics of SnO2 upon lithiation/delithiation. As a result, the SnO2/Sn-rGO nanocomposite exhibited a superior lithium storage capacity with a reversible capacity of 1307 mA h g–1 at a current density of 80 mA g–1 in the potential window of 0.01–2.5 V versus Li+/Li and showed a reversible capacity of 767 mA h g–1 over 200 cycles at a current density of 400 mA g–1. When cycling at a...

Si is among the highest theoretical capacity anodes for lithium-ion batteries, but it suffers from huge volume expansion during lithiation. Here we report a new approach to alleviating the volume change-induced degradation of Si anodes by mixing Si with a room-temperature liquid metal (LM), namely, Ga–Sn alloy. The Ga–Sn alloy is fluid with self-healing ability, acting as the liquid buffer for the Si upon lithiation and delithiation and healing the cracks caused by the volume expansion and contraction. The resulting Si/LM composite exhibits a high capacity and excellent cyclicability. The composite anode delivers a reversible capacity of ∼670 mAh/g after 1000 cycles, with an outstanding rate capability.

A HF-free approach was designed for synthesizing Si@C@void@C as an anode for Li-ion batteries, in which two layers of polymers with various C yield upon calcination were chemically grown on Si particles, followed by carbonization to remove the inner polymer, leaving void spaces and coating a thin inner layer of C, while forming an exterior C shell from the outer polymer layer.

The core-shell SnSe@TiO2/C heterostructure composite with high reactivity, small size, and superior electrochemical performance for sodium-ion batteries (SIBs) was synthesized for the first time using a controllable arc-discharge technique. The electrochemical measurements demonstrate that the outstanding mechanical stability of the TiO2 shell can improve the cycling stability, rate capability, and high specific capacity of SnSe. The as-prepared core-shell SnSe@TiO2/C composite combines the benefits of SnSe and TiO2, with SnSe nanoparticles improving ion diffusion kinetics and specific capacity while TiO2 maintains excellent cycling stability. Furthermore, the core-shell heterostructure approach can synergistically reduce volume fluctuation and aggregation of active materials during cycling. At a current density of 1 A/g, the capacity can reach 318 mAh/g, with a steady cycling performance of 1100 cycles. The novel core-shell heterostructure composite is expected to be a promising candidate as an anode material for next-generation high-performance SIBs due to its outstanding electrochemical performance and ease of synthesis for large-scale production.

Benefiting from fluidity and surface tension, materials in a liquid form are one of the best candidates for self-healing applications. This feature is highly desirable for improving the life cycle of lithium-ion batteries (LIBs) because the volume expansion/contraction during the cycles of high-capacity anodes such as Si and Sn can result in mechanical fracture and lead to inferior cycle performance. Here, we report a novel room-temperature liquid metal (LM) as the anode to improve the cycle life of LIBs. The LM anode comprises an alloy of Sn and Ga, a liquid at room temperature with inherent self-healing properties, as confirmed by the in situ and ex situ analyses. Because both Ga and Sn have high theoretical capacities (769 and 990 mA h g−1, respectively), the resulting LM anode delivers a high capacity of 775, 690, and 613 mA h g−1 at the rate of 200, 500, and 1000 mA g−1, respectively. There was no obvious decay in more than 4000 cycles with a capacity of ∼400 mA h g−1 at 4000 mA g−1, realizing the best cycle performance among all metal anodes.

A 3D graphitic foam vertically aligned graphitic structure and a low density of defects is derived through chloroaluminate anion intercalation of graphite followed by thermal expansion and electrochemical hydrogen evolution. Such aligned graphitic structure affords excellent Al-ion battery characteristics with a discharge capacity of ≈60 mA h g-1 under a high charge and discharge current density of 12 000 mA g-1 over ≈4000 cycles.

Metal sulfide materials have been investigated extensively as anodes for alkali metal ion batteries. In this work, the N-doped graphene/bismuth sulfide (NGBS) composites are prepared for potassium-ion batteries (PIBs) anode and deliver an excellent electrochemical performance in K-ion storage. The N-doped graphene armor can accommodate the large volume variation and the weak electrical conductivity of the bismuth sulfide electrode, but also provides more active sites for K-ion storage which obviously enhances the specific capacity. Moreover, the active sites of the graphene play a crucial role in restricting the “shuttle effect” of polysulfide by forming C–S bonds reversibly during electrochemical redox process and achieve the stable electrochemical cycles as a hybrid anode for PIBs. The K-ion insertion/deinsertion and the reversible C–S bonds formation of the NGBS electrode during the electrochemical cyclic process are revealed by the in-situ X-ray diffraction, in-situ Raman spectroscopy, cyclic voltammetry and X-ray photoelectron spectroscopy in detailed.

Bilayer-Bi12O17Cl2 nanosheets (BBNs), a kind of unusual stoichiometric bismuth oxychloride, with abundant oxygen vacancies (OVs) were synthesized by a simple but efficient hydrothermal method, and acted as the generalist material for Potassium-ion battery (PIB) anode and CO2 reduction reaction. The BBNs with a thickness of ~1.5 nm offer a large electrode-electrolyte contact interface and a short path for K+ diffusion. Importantly, the abundant OVs not only provide more active sites but also promote ionic transmission and electrical conductivity. As an anode for PIB, it provides a high initial discharge capacity (627.5 mA h g−1 at 500 mA g−1), high rate performance (420 mA h g−1 at 10 A g−1) and outstanding cycle performance (198 mA h g−1 after 1500 cycles at 10 A g−1). When evaluated as the electrocatalyst for CO2 reduction, the BBNs exhibited an impressive activity, selectivity and stability (JHCOO- = 11.5 mA/cm2 at −0.89 V, Faradaic efficiency >92%, and durability for >12 h). Considering the easy preparation, low cost, and fast-kinetics, this promising strategy and associated opportunities demonstrate great potential for energy storage or electrocatalysts.

Summary Flexible electronics have been rapidly developed in recent years. However, there are still some concerns about the degradation and short life caused by mechanical damage during their operation. Here, we present a self-healing electret nanogenerator (SENG) that can restore its structure and function after mechanical damage, benefiting from a healable polymer with reversible imine bond and the instantaneous healing ability of liquid metal. After destructive testing comprising four cutting-healing cycles the output current of the SENG autonomously recovers to the original values before damage. Finally, as a practical device, the SENG is demonstrated to work in both energy harvesting and human physiology-monitoring applications. This research offers a feasible route for improving reliability and lifetime of electret generators or other flexible electronics that suffer from mechanical damage.

Li metal anode is one of the most promising anodes for next-generation high-energy-density batteries. However, some lethal challenges, such as Li dendrite, inferior coulombic efficiency, and infinite volume change during repeated Li plating/stripping restrict its practical application. Although carbon-based materials are ideal hosts for Li deposition, unsatisfied lithiophilic property and vulnerable solid electrolyte interphase (SEI) film still remain unsolved. Herein, we report the fluorinated mesoporous carbon (FMC) nanosheets derived from spent cathodic carbon of aluminum electrolysis as a versatile dendrite-free current collector. Two types of C–F bonds are discovered in FMC. One is C(sp2)-F, which serves as lithiophilic site for Li nucleation with reduced barrier. The other is C(sp3)-F, which breaks to produce extra LiF during Li deposition, facilitating the formation of stable LiF-rich SEI film. The synergistically designed Li@FMC|LiFePO4 full cells demonstrate improved cycling performance with high coulombic efficiency. This work provides possibility for direct utilization of waste electro-carbon in energy storage application.

Summary The creation of Li metal anodes while minimizing dendrite growth is an important challenge for developing high-energy density batteries. Dendrites can originate from an inhomogeneous charge distribution or an irregular substrate, and often, the way to suppress dendrite growth is to avoid their formation altogether (ion-uniform mechanism over a shelf time). Herein, we propose a different route to eliminate dendrite formation, called an asymmetrical bidirectional current mode (ABCM) of charging, leading to a healable Li metal anode and resulting in a positive feedback cycle. This mode allows for a stable cyclic performance and suppresses dendrite formation effectively (while holding the polarization ∼27 mV for over 1,000 h), and provides a better result than suppressing Li dendrites via weakening of the Li dendrite (ion-uniform mechanism). These results indicate that ABCM may be a promising way to stabilize the Li anode of Li metal batteries, without any chemical/physical modification of the anode., Graphical Abstract, Highlights • A healable Li metal anode via anti-direction current to correct dendrite timely • Suppressed dendrite growth, very low and stable polarization after long cycling • Technology for stable Li metal battery without any chemical/physical modification, Electrochemical Energy Storage; Electrical Engineering; Energy Materials

The rising H2 economy demands active and durable electrocatalysts based on low-cost, earth-abundant materials for water electrolysis/photolysis. Here we report nanoscale Ni metal cores over-coated by a Cr2 O3 -blended NiO layer synthesized on metallic foam substrates. The Ni@NiO/Cr2 O3 triphase material exhibits superior activity and stability similar to Pt for the hydrogen-evolution reaction in basic solutions. The chemically stable Cr2 O3 is crucial for preventing oxidation of the Ni core, maintaining abundant NiO/Ni interfaces as catalytically active sites in the heterostructure and thus imparting high stability to the hydrogen-evolution catalyst. The highly active and stable electrocatalyst enables an alkaline electrolyzer operating at 20 mA cm(-2) at a voltage lower than 1.5 V, lasting longer than 3 weeks without decay. The non-precious metal catalysts afford a high efficiency of about 15 % for light-driven water splitting using GaAs solar cells.

It has been a great challenge to achieve the direct light manipulation of matter on a bulk scale. In this work the direct light propulsion of matter is observed on a macroscopic scale using a bulk graphene-based material. The unique structure and properties of graphene, and the novel morphology of the bulk three-dimensional linked graphene material make it capable not only of absorbing light at various wavelengths but also of emitting energetic electrons efficiently enough to drive the bulk material, following Newtonian mechanics. Thus, the unique photonic and electronic properties of individual graphene sheets are manifested in the response of the bulk state. These results offer an exciting opportunity to bring about bulkscale light manipulation with the potential to realize long-sought applications in areas such as the solar sail and space transportation driven directly by sunlight.

Hydrogen evolution reaction (HER) from water through electrocatalysis using cost-effective materials to replace precious Pt catalysts holds great promise for clean energy technologies. In this work we developed a highly active and stable catalyst containing Co doped earth abundant iron pyrite FeS(2) nanosheets hybridized with carbon nanotubes (Fe(1-x)CoxS(2)/CNT hybrid catalysts) for HER in acidic solutions. The pyrite phase of Fe(1-x)CoxS(2)/CNT was characterized by powder X-ray diffraction and absorption spectroscopy. Electrochemical measurements showed a low overpotential of ∼0.12 V at 20 mA/cm(2), small Tafel slope of ∼46 mV/decade, and long-term durability over 40 h of HER operation using bulk quantities of Fe(0.9)Co(0.1)S(2)/CNT hybrid catalysts at high loadings (∼7 mg/cm(2)). Density functional theory calculation revealed that the origin of high catalytic activity stemmed from a large reduction of the kinetic energy barrier of H atom adsorption on FeS(2) surface upon Co doping in the iron pyrite structure. It is also found that the high HER catalytic activity of Fe(0.9)Co(0.1)S(2) hinges on the hybridization with CNTs to impart strong heteroatomic interactions between CNT and Fe(0.9)Co(0.1)S(2). This work produces the most active HER catalyst based on iron pyrite, suggesting a scalable, low cost, and highly efficient catalyst for hydrogen generation.

Recently, interest in aluminium ion batteries with aluminium anodes, graphite cathodes and ionic liquid electrolytes has increased; however, much remains to be done to increase the cathode capacity and to understand details of the anion–graphite intercalation mechanism. Here, an aluminium ion battery cell made using pristine natural graphite flakes achieves a specific capacity of ∼110 mAh g−1 with Coulombic efficiency ∼98%, at a current density of 99 mA g−1 (0.9 C) with clear discharge voltage plateaus (2.25–2.0 V and 1.9–1.5 V). The cell has a capacity of 60 mAh g−1 at 6 C, over 6,000 cycles with Coulombic efficiency ∼ 99%. Raman spectroscopy shows two different intercalation processes involving chloroaluminate anions at the two discharging plateaus, while C–Cl bonding on the surface, or edges of natural graphite, is found using X-ray absorption spectroscopy. Finally, theoretical calculations are employed to investigate the intercalation behaviour of choloraluminate anions in the graphite electrode., Rechargeable aluminium ion batteries are an emerging class of energy storage device. Here the authors reveal high-quality natural graphite as a promising cathode for Al-ion batteries, also identifying chloroaluminate anion intercalation in graphite by Raman spectroscopy.

Single-walled carbon nanotubes are promising nanoelectronic materials but face long-standing challenges including production of pure semiconducting SWNTs and integration into ordered structures. Here, highly pure semiconducting single-walled carbon nanotubes are separated from bulk materials and self-assembled into densely aligned rafts driven by depletion attraction forces. Microscopy and spectroscopy revealed a high degree of alignment and a high packing density of ~100 tubes/micron within SWNT rafts. Field-effect transistors made from aligned SWNT rafts afforded short channel (~150 nm long) devices comprised of tens of purely semiconducting SWNTs derived from chemical separation within a < 1 micron channel width, achieving unprecedented high on-currents (up to ~120 microamperes per device) with high on/off ratios. The average on-current was ~ 3-4 microamperes per tube. The results demonstrated densely aligned high quality semiconducting SWNTs for integration into high performance nanoelectronics., This paper was published in Small. File contains SI and article

Coal, which is abundant and has an incompact structure, is a good candidate to replace graphite as the raw material for the production of graphene. Here, a new solution phase technique for the preparation of graphene from coal has been developed. The precursor: graphene oxide got from coal was examined by atomic force microscopy, dynamic light scattering and X-ray diffraction, the results showed the GO was a small and single layer sheet. The graphene was examined by X-ray photoelectron spectroscopy, and Raman spectroscopy. Furthermore, graphene films have been prepared using direct solution process and the electrical conductivity and Hall effect have been studied. The results showed the conductivity of the films could reach as high as 2.5 x 10(5) Sm(-1) and exhibited an n-type behavior.

Aiming to the synthesis of graphene/single-walled carbon nanotube (SWNT) hybrid materials, an arcing-discharge method for an efficient and large-scale production has been developed. Furthermore, the performance of supercapacitors using this graphene/SWNT hybrid has been studied, which gives a remarkable result with the specific capacitance of ∼350 F/g at 2.7 V and an energy density of ∼68 Wh/kg in the standard industry organic electrolyte system.

A feasible and scalable CO2-assisted arc discharge method was developed to directly synthesize single-walled carbon nanotubes (SWCNTs) with largely semiconducting species. Not only was electronic-type selectivity achieved on a large scale, with a semiconducting SWCNT (s-SWCNT) content of >90%, but also diameter selectivity was obtained, with a majority having diameters of >1.5 nm. The photo-catalytic water splitting performance of these SWCNTs with different ratios of s-SWCNTs to metallic single-walled carbon nanotubes (m-SWCNTs) was examined. The results show that, compared with m-SWCNTs, s-SWCNTs demonstrate a much better photocatalytic effect when used together with the common photo-catalyst TiO2.

The current progress on the production of aligned single-walled carbon nanotubes (SWCNTs), particularly the horizontally aligned ones, is reviewed. There are two main categories for the alignment of SWCNTs: the post synthesis assembly and the in situ growth approaches. The post synthesis assembly approach mainly involves dispersing SWCNTs in solutions and aligning SWCNTs using spin-coating, Langmuir–Blodgett assembly, mechanical shearing, or blown bubble film techniques. The in situ growth approach produces aligned SWCNTs directly during their growth using controlled chemical vapor deposition and arc discharge techniques. The latter approach has the advantage of avoiding the defects generated during the post treatment methods, and may also be combined with other growth controls such as structure selectivity of SWCNTs and direct device patterning for scale up applications.

Aiming at preventing restacking of individual graphene sheets by using a simple green hydrothermal route, we have introduced carbon nanotubes to act as the spacer in fabricating a three-dimensional (3-D) hierarchical structure with graphene sheets. These 3-D hierarchical structure materials have been used to fabricate supercapacitor devices, and a high specific capacitance of 318 F/g for graphene with an energy density of 11.1 (W h)/kg has been achieved.