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Lightweight structures are often used for applications requiring higher strength-to-weight ratios and lower densities, such as in aircraft, vehicles, and various engine components. Three-dimensional (3D) printing technology has been widely used for lightweight polymer structures because of the superior flexibility, personalized design, and ease of operation offered by it. However, synthesis of lightweight polymeric structures that possess both high specific strength and glass transfer temperature (

Low energy density is a fatal disadvantage of electric double-layer capacitor (EDLC). The improvement of the operation voltage of EDLCs is a more effective method to increase the energy density of EDLCs. When the operation voltage of EDLCs is higher than 2.7 V, the oxygen-containing functional groups on the surface of electrode materials (porous carbon) will decompose or chemically react with the electrolyte, causing significant deterioration of EDLC performance. In this paper, porous carbon with low oxygen content is prepared by using the potassium-assisted carbonization of chlorobenzene in Ar/H2 mixed gas to improve withstanding voltage characteristic of porous carbon. By constructing a relatively closed and stable pyrolysis environment (employing the nickel crucible with a lid), using the carbonaceous precursor without oxygen atoms (chlorobenzene) and selecting reasonable carbonization operation atmosphere (Ar/H2), the oxygen content of the as-prepared porous carbon (PC-KC-1000) is only 4.02 wt%. When the PC-KC-1000 sample is used as the electrode material of EDLCs, the operation voltage of EDLCs in the TEABF4/PC and EMIMBF4 electrolytes is respectively 3.3 and 3.5 V, and the maximum energy density is respectively 53.5 and 64.4 Wh kg−1. This strategy provides a new idea for the preparation of porous carbon with low oxygen content.

In general object detection, scale variation is always a big challenge. At present, feature pyramid networks are employed in numerous methods to alleviate the problems caused by large scale range of objects in object detection, which makes use of multi-level features extracted from the backbone for top-down upsampling and fusion to acquire a set of multi-scale depth image features. However, the feature pyramid network proposed by Ghiasi et al. adopts a simple fusion method, which fails to consider the fusion feature context, and therefore, it is difficult to acquire good features. In addition, the fusion of multi-scale features directly by traditional upsampling is prone to feature misalignment and loss of details. In this paper, an adaptive feature pyramid network is proposed based on the feature pyramid network to alleviate the foregoing potential problems, which includes two major designs, i.e., adaptive feature upsampling and adaptive feature fusion. The adaptive feature upsampling aims to predict a group of sampling points of each pixel through some models, and constitute feature representation of the pixel by feature combination of sampling points, while adaptive feature fusion is to construct pixel-level fusion weights between fusion features through attention mechanism. The experimental results verified the effectiveness of the method proposed in this paper. On the public object detection dataset MS-COCO test-dev, Faster R-CNN model achieved performance improvement of 1.2 AP by virtue of the adaptive feature pyramid network, and FCOS model could achieve performance improvement of 1.0 AP. What’s more, the experiments also validated that the adaptive feature pyramid network proposed herein was more accurate for object localization.

Mesocarbon microbeads (MCMBs) have a unique structure consisting of graphite-like carbon crystallites covered by spherical surfaces. Their potential anode performance for sodium-ion batteries is investigated. The carbon crystallites in the MCMBs being prepared at 800 °C have a wider crystallites’ interlayer spacing (d = 0.347 nm) than graphite and are stacked by 5–6 graphene layers with an average crystal width of 3.18 nm. MCMBs present a reversible capacity of ~ 180 mAh g−1 and a coulombic efficiency of ~ 99% during 100 discharge/charge cycles. Their superior electrochemical performance is attributed to their unique structure. We propose that sodium is stored in MCMBs mainly by an intercalation mechanism. After sodium intercalation in carbon crystallites, the carbon atoms of graphene layers stack in an AABAA… type, and the sodium atoms exist between the layers of AA with a detected expanded interlayer spacing of 0.437 nm.

Traditional synthesis methods of mesoporous carbon include hard templates (e.g., metal oxides, metal salts and mesoporous silica) and soft templates (e.g., surfactant and block copolymer). However, complicated and time-consuming procedures, high template costs, and harsh preparation conditions hinder the scale-up of these methods. Here, we report a simple and bottom-up strategy to synthesize mesoporous carbon by using the sodium-assisted carbonization of bromobenzene without additional templates added. Depending on the pyrolysis temperature, the obtained material with nanorod structures has a high surface area of 1902 m2 g−1, a large pore volume of 1.21 cm3 g−1 and a high degree of graphitization. Meanwhile, the pore-forming mechanism of this strategy is explored and attributed to the “in situ templating” effect of NaBr. The resultant material at 800 °C shows considerable rate performance, long lifetime and high power density. Additionally, the versatility and feasibility of the technique are validated via carbonization of six halogenated aromatic hydrocarbons by three alkali metals. Compared with lithium and potassium, sodium has better pore-forming effect and the obtained products possess a high surface area (1450–2100 m2 g−1) and a large pore volume (1.1–1.6 cm3 g−1). Furthermore, these mesoporous carbons show high adsorption capacity on dye macromolecules.

Formation mechanism of synthesizing nanoparticle tungsten carbide (WC) was studied. WC was synthesized by carbothermal hydrogen reduction (CHR) method under various reaction temperatures for holding different post-treatment time in 20% (v/v) CH₄/H₂. The phase transformation mechanism of gaining WC was investigated, by combining CHR with X-ray diffraction (XRD) and temperature programmed reduction mass spectroscopy (TPR-MS). The results show that pure phase of WC has been obtained by CHR after isothermal heat treatment for 24 hours at 750 °C and 12 hours at 950 °C, respectively. These results indicated that two key parameters of higher temperature and longer isothermal heat treatment time are necessary for synthesizing pure phase of WC powder. In order to find out the phase transformation mechanism of tungsten trioxide (WO₃) to WC, the reduction and carburization process among the temperature range from 600 °C to 1000 °C for holding 3 hours at the final temperature were studied. It was shown that at 600 °C, WO₃ was reduced to WO₂, and from 600 °C to 750 °C, WO₂ was reduced to metallic tungsten (W). Moreover, at the temperature range from 750 °C to 900 °C, the mixture phases of tungsten carbide (WC), metallic tungsten (W), or/and tungsten sub-carbide (W₂C) were formed without any oxides species, which indicated that tungsten carbides (WC and W₂C) phases appeared because the oxides phase was thoroughly reduced. However, the occurrence of carburization process was still limited due to the presence of oxygen in the solid. Because of the formed CO and CO₂ there was not enough activated methane reacting with metallic tungsten, so the phase of WC and W₂C were both formed simultaneously, but the reaction of forming WC was the main reaction in the whole carburization process. Moreover, the TPR-MS and XRD results indicated that, WC was formed at lower temperature (750 °C) by the reduced metallic W, which was produced form W₂C in the gas mixture for holding a long time, while at a higher temperature (950 °C), WC was formed form W₂C with the mixture gas directly.

Sodium and potassium-ion batteries are promising for energy storage owing to their source abundance and low cost; however, most active materials still suffer from sluggish kinetics, huge volume variations, and poor conductivity and cycle stability. It remains a great challenge to explore appropriate electrode materials for scaled practical applications. Herein, mesoporous FeCo-incorporated MoS2 nanosheets encapsulated into a porous carbon framework (FeCo@C@MoS2) are smartly designed, artistically fabricated and evaluated for sodium and potassium storage. The FeCo@C@MoS2 electrode displays high reversible capacities of 380 mA h g−1 and 147 mA h g−1 at 500 mA g−1 for sodium and potassium storage, respectively. FeCo derived from a Prussian blue analogue promotes fast reaction kinetics of Na+/K+ transport, introduces the formation of a stable solid electrolyte interphase layer (SEI) in both the interior and exterior of the cube-like porous nanostructure and controls the Na+/K+ fluxes, suppressing the growth of metal dendrites. The porous carbon framework with large interstitial voids can effectively buffer volume variations and mitigate mechanical stress, contributing significantly to alleviate strain intensification on the surface layer between MoS2 and FeCo during repeated plating/stripping processes. Density functional theoretical calculations (DFT) further confirm that the synthesized nanostructure shows an intensified electron state, elevated anti-stress ability, high-quality SEI film and preferable Na+/K+ adsorption energies. This in-depth investigation of the electrochemical performance and the extended energy storage mechanism based on metal alloy/sulfide nanostructures for sodium and potassium storage provides guidance for the smart design of heterojunctions for remarkable energy storage.

The reasonable design of metal compound electrocatalysts is proved to be a good approach to accelerate the sluggish conversion kinetics of polysulfides for high performance lithium–sulfur (Li–S) batteries. Since metal cations usually serve as the active sites to interact with polysulfides, optimizing their electronic and valence states is vital to enhance catalytic activity, especially for electrochemical reactions involving multiple electrons. Herein, the electronic and valence states of metal active sites in hollow carbon-encapsulated Ni3ZnC0.7 (denoted as C/Ni3ZnC0.7) nanospheres are modulated by introducing either donor defects (P dopants) or acceptor defects (Ni vacancies) via P-doping or NaBH4-etching, respectively. Such P dopants and Ni vacancies not only endow P-doped C/Ni3ZnC0.7 (denoted as C/Ni3ZnC0.7-Pm) and NaBH4-etched C/Ni3ZnC0.7 (denoted as C/Ni3ZnC0.7-Bn) nanospheres with abundant defects and distortions, but also modulate the valence states of metal active sites in different ways. P dopants and accompanied Zn vacancies remarkably decrease the electron density of Zn active sites in C/Ni3ZnC0.7-P5 while the Ni vacancies contribute to the dramatic increase of Ni2+ species in C/Ni3ZnC0.7-B1 nanospheres. The modulated Zn sites could anchor polysulfides and serve as reservoirs to regulate the valence of Ni sites. However, the modulated Ni active sites with more Ni2+ species enable fast electron transfer between the Ni2+/Ni(0) pair and polysulfides, playing a more significant role in catalyzing the conversion of polysulfides. As a result, compared with C/Ni3ZnC0.7 and C/Ni3ZnC0.7-P5, C/Ni3ZnC0.7-B1 with more Ni2+ species exhibits stronger chemical adsorption ability toward polysulfides and catalytic ability to accelerate the conversion kinetics of polysulfides. When C/Ni3ZnC0.7-B1 nanospheres are used to modify commonly used PP separators for Li–S batteries, remarkable rate performance up to 4.0C (525.6 mA h g−1) and excellent cycling stability (a decay of 0.0179% over 1400 cycles at 1.0C) are achieved.

Cellulose acetate (CA) is widely used in the preparation of ultrafiltration membranes due to its many excellent characteristics, especially chemical activity and biodegradability. To improve the inherent hydrophobic and antifouling properties of CA membrane, in this work, CA was successfully modified with dopamine (CA-2,3-DA) through selective oxidation and Schiff base reactions, which was confirmed by FTIR and

In this study, cement mortars with different strengths are poured into the large void matrix asphalt macadam material as a semiflexible pavement (SFP) material and the experimental research is carried out. The current research on SFP is mainly focused on the performance of grouting materials and the influence of grouting matrix materials on the overall mechanical properties of SFP and road performance. However, there are some flaws in the study of the influence of grouting material strength on the performance of SFP materials: the difference between the strengths of the selected grouting materials is relatively small, and in some studies, the chosen grouting material strength is low, which leads to insignificant improvements of SFP material performance; besides, the research indicators are also not very comprehensive. In this study, cement grouting asphalt macadam materials are selected as the research object to examine the effect of grouting material strength on the mechanical properties and road performance of SFP materials. Grouting materials with strengths of 19.8 MPa, 30.7 MPa, and 40.2 MPa were poured into the matrix asphalt macadam with a target void ratio of 24% and asphalt content of 2.9% to prepare the corresponding SFP test specimens. The SFP specimens were then subjected to the compressive test, flexural and tensile test, high-temperature stability test, and low-temperature crack resistance test, and the compressive resilient modulus was measured, thereby analyzing the effect of the cement slurry strength on the cement grouting asphalt macadam materials. The results show that when the strength of the cement mortar is 19.8 MPa, 30.7 MPa, and 40.2 MPa, the corresponding SFP material has better mechanical properties. When the strength of the grouting material is 40.2 MPa, the compressive strength of the SFP material is about the same as that of the grouting material. The strength is more than double that of 19.8 MPa and 30.7 MPa, and the flexural tensile strength and elastic modulus also have the above growth laws. The low-temperature crack resistance and high-temperature stability of the SFP material are enhanced with the increase in the strength of the grouting material. When the strength of the grouting material is 40.2 MPa, the mechanical properties and road performance of the SFP material are relatively better. This study provides a reference for strengthening the mechanical properties of SFP materials and boosting the crack resistance of SFP.

Compared with traditional carbonaceous precursors (polymers or natural sources), small molecular organic precursors (SMOPs), such as pyrrole, furan and C6H5X (X = Cl, Br, I), are a class of commercial carbonaceous precursors with strong plasticity, wide accessibility and long-term sustainability. However, it is difficult to directly convert these SMOPs into porous carbon nanomaterials (PCNMs) because of their uncontrolled vaporization under high-temperature pyrolysis. Here, we report a novel and bottom-up strategy to prepare PCNMs by using the potassium-assisted carbonization of pyrrole. Depending on the pyrolysis temperature, the obtained materials possess nanorod microstructures with a high degree of graphitization and a high surface area of 2340 m2 g−1. Additionally, the pore-making mechanism for this strategy is explored and ascribed to the chemical activation of KOH, the intercalation effect and physical activation of potassium. Based on this mechanism, three PCNMs are prepared, with an optimized PCNM electrode for supercapacitors exhibiting excellent rate performance (65% capacitance retention at 80 A g−1) and long-term cyclic stability (86% capacitance retention after 10000 cycles). The device delivers 18.5 Wh kg−1 at a high power density of 62.6 kW kg−1. This simple strategy paves the way for the use of largely unexplored SMOPs in preparing PCNMs for energy storage applications.

Nanostructured integrated electrodes with binder-free design show great potential to solve the ever-growing problems faced by currently commercial lithium-ion batteries such as insufficient power and energy densities. However, there are still many challenging problems that limit the practical application of this emerging technology, in particular complex manufacturing process, high fabrication cost, and low loading mass of active material. Different from those existing fabrication strategies, here using a Co-P alloy foil as precursor we demonstrate a simple neutral salt solution-mediated electrochemical dealloying method to well address the above issues. The resultant freestanding mesoporous np-Co(OH)

Nitrogen-doping can increase the charge density and the wettability of electrode materials, to further reinforce the electrochemical performances of energy storage devices. It is difficult to directly convert small molecular nitrogen-containing organics into N-doped porous carbon materials. Here we demonstrate a bottom-up strategy to prepare N-doped porous carbons by sodium metal-assisted carbonization of pyrrole. Pyrrole is not only a nitrogen source, but also a carbon source. In the process of pyrolysis, sodium assists the formation of the thermally stable polymer structures and catalyzes the graphitization of carbonaceous structures. As the pyrolysis temperature increases, the microstructures of porous carbons become more ordered and the pore structures of porous carbons change from the micropore-dominated structures to the mesopore-dominated structures. The material obtained at 800 °C with the nitrogen content of circa 3.3 wt% displays high-rate performances and long lifetime, when used as the supercapacitor electrodes. The device delivers 14.4 W h kg−1 (8.7 W h L−1) at a high power density of 40.5 kW kg−1 (24.5 kW L−1) and 20.9 W h kg−1 (12.6 W h L−1) at a power density of 13.5 kW kg−1 (8.2 kW L−1). Simultaneously, the technique provides a new idea for the preparation of other heteroatoms-doped porous carbons.

The depolymerization of polycarbonate (PC) into bisphenol A (BPA) is performed by defective xCaO/Ce-SBA-15 nanocomposite assisted by plasma treatment. For such composite catalyst, CaO and CeO2 particles are finely encapsulated into the tubular SBA-15 without leaching or aggregation occurring. Abundant oxygen vacancies are generated from the doping of Ca and Ce atoms into the lattice of SBA-15 composite via the plasma surface engineering, entrusting strong basic sites to such mesoporous composite. The interface interaction between Ca and Ce with defective dimensional support materials predominated to generate maximum basic sites is of critical importance in tailoring the BPA yield. CaO/Ce-SBA-15 with rich oxygen vacancies and rough surface creates rich basic sites to achieve the high efficiency of PC alcoholysis and durable repeated cycles. Meanwhile, the synergistic catalysis between CaO and CeO2 is achieved, while SBA-15 with smaller disordered pores and fine connectivity between adjacent large pore channels enables a good dispersity of such xCaO/Ce-SBA-15 composite and finely prevents the leaching of Ca and Ce particles. Additionally, the high-density defects from the substitution of Ce by Ca and Si atoms as well as the plasma treatment play active basic sites during PC adsorption and activation. Such graft also leads SBA-15 itself becoming a solid base. Hence, the superior of PC depolymerization and superior durability are obtained due to the composition synergistic effects and rich abundant basic sites. It is noted that the abundant Ca on ceria surface provides affluent electrons, which makes decreased Ce valence in CeO2 subsurface and elevation of basic sites. This work explores the generation of tunable basic sites for SBA-15 and is instructive for fabricating desirable multicomponent catalysts composed of bifunctional non-novel catalyst for heterogeneous catalysis with rich surface oxygen vacancies.

A surface modification method of C/C composites involving a combination of pre-oxidation treatment and in situ growth of CNTs was developed to form a reinforced interfacial structure in Nb-C/C brazed joints. The interfacial structure under different surface conditions of the C/C composites and its effects on the mechanical properties of brazed joints at both room temperature (RT) and elevated temperatures were studied. Through pre-oxidation, annular gaps with an adjustable size were uniformly formed around the carbon fibers, and these gaps acted as artificial channels for the liquid brazing alloy to infiltrate into. The RT shear strength of the Nb-C/C joints increased from 29 MPa to 57 MPa after oxidation of the C/C composites at 800 °C for 5min. The growth of CNTs was able to improve the wettability, since it was beneficial for liquid brazing alloy filling in the annular gaps. Further, a reinforced joint with fine TiC particles was formed by the reaction between Ti and the CNTs. The shear strength of the brazed joints reached 62 MPa after pre-oxidation and CNT growth and remained at 48 MPa at 500 °C. The improvement in the joint shear strength after surface modification of the C/C composites was attributed to the reduced residual stress, increased bonding area, and enhanced pinning effect.

In present work, a novel strategy combining the nitrogen-functionalization and pore structure controlling was developed to prepare nitrogen-doped hierarchical porous carbons (NHPCs) from a bio-decomposited product. This strategy was realized by introducing nitrogen species into the carbon precursor to afford C N forms, which would react with the K-species and thus enhance the carbon etching to improve the pore structure development. The final NHPCs obtained by this strategy not only have a high nitrogen content of 5 at %, but also deliver specific surface area up to 3142 m2 g−1 and total pore volume close to 2.6 m3 g−1. Benefited from the chemical composition and improved pore structure, the NHPCs electrodes exhibit an impressive capacitive performance in ionic liquid electrolyte with high specific capacity (209 F g−1 at 0.05 A g−1 and 148 F g−1 at 20 A g−1), enhanced energy density (up to 88 W h kg−1) and superior cyclic stability (a capacitance loss of 9% after 10000 cycles). The desirable electrochemical performance combined with the green and low-cost precursor and the simple and scalable synthesis route make the NHPCs sample a promising candidate for high-energy supercapacitor.

Two-dimensional (2D) materials with mono or few layers have wide application prospects, including electronic, optoelectronic, and interface functional coatings in addition to energy conversion and storage applications. However, the exfoliation of such materials is still challenging due to their low yield, high cost, and poor ecological safety in preparation. Herein, a safe and efficient solid suspension-improving method was proposed to exfoliate hexagonal boron nitride nanosheets (hBNNSs) in a large yield. The method entails adding a permeation barrier layer in the solvothermal kettle, thus prolonging the contact time between the solvent and hexagonal boron nitride (hBN) nanosheet and improving the stripping efficiency without the need for mechanical agitation. In addition, the proposed method selectively utilizes a matching solvent that can reduce the stripping energy of the material and employs a high-temperature steam shearing process. Compared with other methods, the exfoliating yield of hBNNSs is up to 42.3% at 150 °C for 12 h, and the strategy is applicable to other 2D materials. In application, the ionic conductivity of a PEO/hBNNSs composite electrolytes reached 2.18 × 10−4 S cm−1 at 60 °C. Overall, a versatile and effective method for stripping 2D materials in addition to a new safe energy management strategy were provided.

The photochemistry and sodium storage process have been generally considered as two separated approaches without strong connection. Here, ultraviolet (UV) irradiation was applied to sodium-ion batt...

The morphology, pore structure and chemical composition of materials are key to supercapacitor performances. To design reasonable morphology and optimize pore size distribution of materials, we employ a combination of sol-gel method and chemical activation with an aid of freeze drying to prepare a three dimensional hierarchical porous pitch-based aerogel (3DHPPA). The aerogel owns hierarchical porous structure ranging from 0 to 100 nm, high specific surface area of 2220 m2 g−1 and is made up of carbon onion-like nanospheres of 20–40 nm with enough electric conductivity (103.2 S m−1). In view of the unique architecture, the supercapacitor assembled from 3DHPPA with the area density of 8.9 mg cm−2 exhibits high specific capacitance of 157 F g−1 at 50 mA g−1, excellent rate performance (95 F g−1 at 10 A g−1), considerable energy density of 24.2 Wh kg−1 at 6.75 kW kg−1 (voltage range of 2.7 V) and outstanding cycling life with 81.5% capacitance retention at 2 A g−1 after 8000 cycles in 1 M TEABF4/PC electrolyte. Furthermore, the formation mechanism of the 3DHPCA is elucidated in this work. The simple, feasible and low-cost strategy makes 3DHPPA applicable in other fields of energy storage, hydrogen storage, capacitive deionization and catalysis.

Based on the equation of E = 1/2CV2, increasing voltage can significantly enhance the energy density of electric double-layer capacitors (EDLCs). However, with the voltage above 2.7 V, the lifespan of EDLCs drops rapidly due to the undesired parasitic processes. To operate at voltage above 2.7 V, a frame-filling C/C composite is prepared by constructing relatively perfect carbon network and reducing the oxygen-containing groups. The as-prepared sample F310-800 exhibits high specific surface area (2626 m2 g−1), adequate e-conductivity (142 S m−1), high sp2-bonding carbon content (92.6%) and low oxygen content (4.6 wt%). Although totally free of any carbon black, it demonstrates excellent EDLC performances. It can successfully operate at voltage of 3 V in TEABF4/PC electrolyte and obtain high gravimetric capacitance (Cg) of 140 F g−1 and volumetric capacitance (Cv) of 57.4 F cm−3 at 50 mA g−1 with rate capacity C10/0.05 as high as 66%. Additionally, at voltage of 3.5 V in pure EMIMBF4 electrolyte, it achieves ultrahigh Cg of 156 F g−1 and Cv of 64 F cm−3 at 50 mA g−1. Its energy density can reach up to 66.3 Wh kg−1. Meantime, after 5000 cycles at 2.5 A g−1, it holds 91.9% of its initial capacitance.

To address the issues of low electrical conductivity, sluggish lithiation kinetics and dramatic volume variation in Fe3O4 anodes of lithium ion battery, herein, a double carbon-confined three-dimensional (3D) nanocomposite architecture was synthesized by an electrostatically assisted self-assembly strategy. In the constructed architecture, the ultrafine Fe3O4 subunits (∼10 nm) self-organize to form nanospheres (NSs) that are fully coated by amorphous carbon (AC), formatting core–shell structural Fe3O4/AC NSs. By further encapsulation by reduced graphene oxide (rGO) layers, a constructed 3D architecture was built as dual carbon-confined rGO/Fe3O4/AC. Such structure restrains the adverse reaction of the electrolyte, improves the electronic conductivity and buffers the mechanical stress of the entire electrode, thus performing excellent long-term cycling stability (99.4% capacity retention after 465 cycles relevant to the second cycle at 5 A g–1). Kinetic analysis reveals that a dual lithium storage mechanis...

Although hard carbons have been turned out to be suitable for sodium storage, their high cost and low initial coulombic efficiency (ICE) need to be addressed for the commercial application. Here, we report an effective route including a pyrolysis process and a reductive strategy to synthesize high-performance hard carbons from waste apricot shell. The obtained hard carbons inherit the unique architecture of the apricot shell, delivering a large interlayer spacing and a well-connected structure, which are beneficial for the Na+ intercalation and transport. The anode performance is further enhanced by H2 reduction treatment, which efficiently reduces the defects and thus improves the ICE. The final prepared hard carbons exhibit a promising anode performance with a desirable reversible capacity of ca. 400 mAhg−1, an improved ICE of 79% and an excellent cycling stability. This study should contribute to the better utilization of the biomass waste for the future large-scale application of sodium-ion batteries.

Amorphous carbon-based anode materials are considered as one of the most promising candidates for sodium-ion batteries (SIBs). However, there are two main barriers before large-scale industrialization, i.e. low initial coulombic efficiency (ICE) and high cost caused by low carbon yield of precursors. In this work, we report a novel commercial activated amorphous carbon-based anode synthesized through a facile-tailored strategy consisting of annealing and surface coating. The as-prepared amorphous carbon has a porous internal structure but a very low specific surface area (SSA) with a dense surface carbon layer. As an anode material for SIBs, the obtained amorphous carbon displays an outstanding electrochemical performance including a high reversible capacity of 391 mAh g−1 at a current density of 25 mA g−1 with a high ICE of 80%, and a superior cycling performance with a capacity retention of 97% after 100 cycles. The high ICE is mainly attributed to the denser surface carbon layer which suppresses the penetration of electrolyte and fully utilizes the internal porosity. The commercial availability, and the desirable properties make this novel amorphous carbon-based anode a promising candidate for SIBs.

Commercial lignin, by-product of enzymatic hydrolysis of biomass for bioethanol production, was used to prepare lignin based microsphere by reverse phase polymerization. The reverse phase polymerization had favorable influence on the morphology, size distribution and thermal stability by coordinating solid content and dispersed phase content of lignin emulsion. The carbonization yield at 870 °C of lignin based microsphere reaches to 38.87% by improving 5% from lignin precursor 33.43%, at solid content 0.059 and dispersed phase content 0.050. The mechanism is postulated based on the results from elemental analysis, FT–IR spectroscopy and thermogravimetric analysis. Furthermore, the lignin based microsphere could directly carbonize without pre-oxidization process. Hence, the reverse phase polymerization is a meaningful and possible industrial process. And the gravimetric capacitance of lignin based activated carbon microsphere (LAC-M) is as high as 334 F g −1 , and even after 10,000 cycles at 1 A g −1 a specific capacity of 286 F g −1 remains. Thus, LAC-M is a promising material for high performance SCs.

2D porous carbon nanosheets (PCNs) occupy the foreground in the field of electric double-layer capacitors (EDLCs). However, the mass production of PCNs with ultrathin thicknesses is still a serious challenge. Herein, PCNs constructed of few-layer graphene sheets were synthesized from a sulfonated pitch (SP) carbon precursor and soft-template F127 by a “medium-up” strategy. SP serves as a “medium material”, while F127 acts as a “string” and “spacer”, which plays the leading role of structure directing and prevents the self-restacking of small graphene layers. After activation, sample PCN6 with high carbon yield is constructed with a thickness of only 1.3 nm, sufficient specific surface area of 3006 m2 g−1 and high e-conductivity of 135 S m−1. By virtue of its unique architecture, the PCN6-based EDLC exhibits excellent energy storage properties. In EMIMBF4 electrolyte, it demonstrates an ultrahigh Cg of 157.8 F g−1 (57.4 F cm−3) at 20 A g−1, possessing a top-level rate capacity C20/0.05 of 86.7%. Simultaneously, its energy density can retain up to 67.1 W h kg−1 at a high power density of 17.5 kW kg−1. The ingenious structural design of PCNs can afford inspiration for constructing other 2D architecture carbon materials.

Functionalized graphite oxide films are synthesized by using (NH4)2SO4 during self-assembly process of graphite oxide in water. Instead of stacking layer by layer, graphite oxide films with three-dimensional (3D) structure are obtained due to strong hydration of ions from (NH4)2SO4. After low temperature treatment (400 °C) of the self-assembly films, (NH4)2SO4 decomposes and N-doped films are obtained, the films can be used directly as anodes for lithium ion batteries. According to electrochemical test, the 3D self-assembly films exhibit enhanced lithium ion storage performances such as initial coulombic efficiency and specific capacity due to 3D structure and N atoms. Further studies show that owing to low chemical activities of graphitic structure in air, low temperature treatment (400 °C) under different atmospheres (N2 or air) has little effect on structures and electrochemical performances of 3D self-assembly films, which is meaningful for producing the films on a large scale in the future.

The Si/hard-carbon/graphene (Si/HC/G) composite material used as lithium ion battery (LIB) anode was synthesized by emulsion polymerization of the mixture of resorcinol and formaldehyde in the suspension of silicon nanoparticles, followed by loading on the graphene sheets and annealing treatment of 800 °C. The as-prepared three-dimensional Si/HC/G composite is composed of the Si/HC microspheres on the graphene network. In the portion about Si/HC, some of the Si nanoparticles are embedded into the hard carbon, which can provide the great strength alleviating the volume expansion and shrinkage of Si. The graphene portion can connect Si/HC microspheres preventing the electrode cracks and can provide the pathway to improve the transport of electrons and diffusion of lithium ions. Hence, the Si/HC/G composite could not only avoid the pulverization of the Si-based material but also enhance the electronic conductivity, displaying excellent electrochemical performances. Compared with the HC and Si/HC samples, the Si/HC/G composite possesses the specific charge capacity of 514.8 mA h g−1 at the high current density of 2 A g−1 and has the high charge capacity of 818 mA h g−1 at the current density of 100 mA g−1 after 100 charge and discharge cycles. Resultantly, the Si/HC/G composite shows great potential for the application of lithium ion battery anode material in the future.

A low-cost and sustainable anode material is essential for the future commercialization of sodium-ion batteries (SIBs). Among all proposed anode materials for SIBs, hard carbons are considered to hold the most promise. However, high cost and low carbon yield of precursors limit its industrialization process. Here the synthesis of a biomass-derived hard carbon from leonardite humic acid (LHA) through a facile process was reported. The obtained hard carbons with an amazing high carbon yield of 60.73% were evaluated as anode for SIBs. The LHA-based hard carbons exhibit a promising anode performance with a sodium storage capacity of 345 mAh g −1 , an initial coulombic efficiency up to 73% and superior cyclic stability. Combined with the facile synthesis process and abundant resource, the LHA-based hard carbons may hold a promising future as anode materials for SIBs.

Cloud applications provides users with services that can be accessed on demand through the Internet. Fertile service frameworks are considered one of the most critical ingredients for the envisaged benefits so as to further interactions among cloud computing resources and application components. Such foundations should lead to the proliferation of new innovative services and applications. The research community has been exploring the Open Service Gateway initiative's (OSGi) potential as a top candidate for cloud application platforms. Although the current OSGi specification provides some level of support for dynamic service discovery, tracking, and composition, more should be done to be able to adequately address the need for diverse interaction patterns for cloud applications. This paper introduces a novel service framework built upon OSGi platforms that supports a directed-acyclic-graph style composition of constituent services. Given a declarative blueprint of service interconnections and interactions, the framework can find and assemble corresponding component services to form a real application. Our proposal can enable a realistic topology of service component interlinkings beyond linear chaining interactions as supported by the status quo. The design, implementation details, and validation results of our workflow-based service composition framework architecture are discussed in the paper.

NaOH-etched mesocarbon microbeads (MCMBs) are prepared by carbonizing a mixture of green MCMBs and NaOH at 650 °C, and are used as the anode material for sodium-ion batteries (SIBs). Comparing with pristine MCMBs, NaOH-etched MCMBs have more surface fissures, more bigger pores with a mean diameter of ~5.0 nm, and graphite-like crystallites with wider interlayer space (356 pm). The etched MCMBs anode displays better rate capability and cyclability. It keeps a capacity of >218 mAh g−1 at a current of 15 mA g−1 with a coulombic efficiency of >97% during 60 cycles. We consider that the etched MCMBs’ structure facilitate the sodium transfer and make them being potential as the anode material for SIBs.

Among all of the requirements for carbon materials used in electric double-layer capacitors (EDLCs), specific surface area (SSA) and electrical conductivity is a pair of mutual competing demands. In this paper, a series of frame-filling structural nanoporous carbons were prepared using an amphiphilic mixture of graphite oxide and a coal tar pitch-based carbonaceous material as precursor ensuring a high carbon yield. In the final porous composites, the few-layer graphene microsheets derived from graphite oxide contribute to the conductive frame construction by randomly cross-stacking during exfoliation and thermal reduction, while nanoparticles derived from coal tar pitch-based carbonaceous material fill into the frame and chemically bind on the surface of graphene microsheets of about 2 nm in thickness. The SSA is up to 2441 m2 g−1 and the electrical conductivity is 179 S/m. It has energy storage superiorities over an ordinary nanoporous carbon, rendering a shortened relaxation time constant (5.34 s), improved gravimetric capacitance (115.4 F/g) as well as cyclic stability in 10,000 cycles with 87.8% capacity retention in 1 M TEABF4/PC electrolyte. The frame-filling structural nanoporous carbon shows great potential for blocks or high-capacity energy storage system by complex serial-parallel.

The electrochemical performance of low-cost, pitch-based hard carbon anodes in lithium-ion batteries is reported. Pitch-based hard carbon anodes were prepared, stabilized in air at 290 °C for 1 h after different temperature programming, and then carbonized in N2 at 1000 °C. The optimal anode with temperature programming of 24 h had abundant oxygenic functional groups, a large interlayer space, and a stable morphology. When used as anodes in lithium-ion batteries after 100 cycles at a current density of 100 mA g−1, the capacity was 258.6 mAh g−1 with a capacity retention ratio of 90.6 %. This large capacity combined with the superior cycling performance indicates that prolonged oxidative stabilization is an effective strategy in improving electrochemical performances of lithium-ion batteries.

Magnetic Fe 3 O 4 @TiO 2 core-shell microspheres are ideally applied in several specific fields due to their unique properties. A facile liquid phase deposition route for the fabrication of Fe 3 O 4 @TiO 2 core-shell microspheres was developed. The core-shell structure was obtained by direct deposition of TiO 2 on the surface of Fe 3 O 4 microspheres. The prepared products were characterized by using Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM). The waxberry-like microspheres were nearly spherical with diameters of about 500 nm and average shell thickness of 80 nm. The shell layer was composed of smaller primary TiO 2 nanoparticles with sizes from 10 to 20 nm. A possible growth mechanism of the core-shell structure was proposed. The photo-catalytic decomposition of methylene blue and the recycling of prepared core-shell microspheres were also investigated.

Lignin as second most abundant natural polymer after cellulose is the main by-product of conventional pulp and paper industry and mostly consumed as a low-grade fuel in industrial burner or boiler. It is necessary to explore the possibility for high value-added application of lignin. Lignin-based activated carbon (LAC) is prepared through a two-step pre-pyrolysis and activation or directly activation method for high-performance supercapacitors (SCs). This paper is devoted to examining the role of pre-pyrolysis treatment in the preparation of LAC. Pre-pyrolysis treatment is expected to alter the pore size distribution, maintain the morphology and improve the graphitization degree of lignin. Multiple characterization methods are used to measure the pore structure, morphology and graphitization degree of LAC. Consequently, LAC with pre-pyrolysis exhibits high V micro / V total ratio, uniform morphology and relatively high graphitization degree in comparison with directly-activated LAC. In detail, The V micro /V total ratio of LAC with pre-pyrolysis at 600 °C has increased from 22% to 66%. What’s more, the gravimetric capacitance reaches to as high as 312 F g −1 by improving 100 F g −1 , the specific capacitance is 14.0 μF cm −2 , and even after 10,000 cycles at 1 A g −1 a specific capacity of 261 F g −1 (about 95% retention ratio) remains while directly-activated LAC is only 218 F g −1 . Hence, LAC with pre-pyrolysis is a promising material for high performance SCs.

Using the facile method of solvent evaporation, the leonardite fulvic acids (LFA)-based porous carbon microbeads (PCM) have been successfully prepared at ambient pressure, followed by carbonization and KOH activation (a low mass ratio alkali/LFA = 1.5) in an inert atmosphere. The effects of KOH treatment on pore structures and the formation mechanism of the PCM were discussed. The results showed that the sample exhibited remarkable improvement in textural properties. The activated carbon microbeads had high surface area (2269 m2 g−1), large pore volume (1.97 cm3 g−1), and displayed excellent capacitive performances, compared with carbon powder. The porous carbon material electrodes with the “porous core structure” behaved superiorly at a specific capacitance of 320 F g−1 at a current density of 0.05 A g−1 in 6 M KOH electrolyte, which could still remain 193 F g−1 when the current density increased to 100 A g−1. Remarkably, in the 1 M TEABF4/PC electrolyte, the PCM samples could reach 156 F g−1 at 0.05 A g−1, possess an outstanding energy density of 39.50 Wh kg−1, and maintain at 22.05 Wh kg−1 even when the power density rose up to 5880 W kg−1. The balance of structural characteristic and high performance makes the porous carbon microbeads a competitive and promising supercapacitor electrode material.

Lignin as the second most abundant natural polymer was applied to prepare a hierarchical porous carbon (HPC) for supercapacitors (SCs). Direct activation with various KOH dosages was applied to obtain HPC. Both pore size distribution and electrochemical performance were evaluated and compared to optimize the KOH dosages. Field emission scanning electron microscope (FESEM), high-resolution transmission electron microscope (HRTEM), Fourier transform infrared spectrometry (FT-IR), and Raman spectroscopy were also applied to better understand the structure change of HPC with KOH dosages. High gravimetric capacities (C g) of 268 and 162 F g−1 were obtained in aqueous and organic solutions, respectively. Excellent rate and cycle performance demonstrated the stable structure of HPC. Energy density could reach as high as 40.89 W h kg−1 in organic solution. Besides, it was also concluded that a high C g can be obtained with low KOH dosage in aqueous solution while high KOH dosage was needed in organic solution. In a word, lignin was indeed a suitable precursor for the preparation of HPC in SCs.

The anode performance of mesocarbon microbeads (MCMBs) is tested as they are used in sodium-ion batteries. The MCMBs carbonized at 700 °C consist of graphite-like crystallites with an interlayer distance of 357 pm, and with a crystal stack height of 1.61 nm. They deliver an initial charge capacity of 232 mAh g −1 at a current density of 25 mA g −1 , and keep a reversible capacity of 161 mAh g −1 after 60 cycles. The MCMB anodes exhibit good reversible sodium insertion/extraction behavior, which results from their internal crystallites and their unique external spherical surface layers. XRD and Raman analyses indicate that the MCMB anode stores energy by the electrochemical intercalation of sodium into the graphene sheets.

A novel room temperature gas sensor based on 3D hierarchical flower-like TiO2 microstructures was fabricated and applied to detect ethanol vapor at room temperature. This flower-like TiO2 microstructures composed of thin nanosheets were synthesized using a hydrothermal process and following calcination method. The sensor exhibited good sensing properties such as high selectivity, good stability, quick response/recovery characteristics and good reproducibility to ethanol vapor at room temperature, showing great potential for ethanol detection, which is desirable and promising for applications in variety of fields.

A new kind of soft carbon and hard carbon composite nanofibers were fabricated from isotropic pitch and polyacrylonitrile via simple electrospinning followed by stabilization and carbonization. The obtained fibrous mat was directly used as anodes of lithium-ion batteries without binder added and current collector. The composite nanofibers electrodes display a large reversible capacity of 452 mA h g−1 at a current density of 20 mA g−1 and a capacity of 255 mA h g−1 at 200 mA g−1 after 200 cycles. The improved electrochemical performance can be attributed to the unique fibrous structure which will facilitate electrons and ions transfer and the porous structure which will accommodate quantities of lithium ions.

The LiMn0.5Fe0.5PO4/C nanocrystallites with a uniform size (∼50 nm) are successfully prepared by employing a facile solvothermal method at 180 °C. Amphiphilic carbonaceous material (ACM) is chosen as the carbon precursor and forms a homogeneous carbon layer covering the LiMn0.5Fe0.5PO4 particles. The as-prepared LiMn0.5Fe0.5PO4/C sample, with a high Brunauer-Emmett-Teller (BET) surface area of 69.3 m2 g−1, is used as the cathode material for lithium-ion batteries (LIBs) and delivers a reversible capacity of 158 mAh g−1 at 0.05 C. It shows remarkable rate capability with discharge capacities of 130 mAh g−1 at 1 C, 105 mAh g−1 at 10 C and 99 mAh g−1 at 30 C. Meanwhile, the material maintains 121 mAh g−1 at 1 C after 150 cycles with 93 % capacity retention. The kinetic behaviors of LiMn0.5Fe0.5PO4/C sample are investigated by high throughout cyclic voltammetry. The small particle size, partial Fe substitution, and homogeneous carbon coating make a synergetic effect on enhancing the sample’s electrochemical properties.

Lithium-rich layered oxide Li[Li0.23Ni0.15Mn0.62]O2, which also can be written as 0.6Li2MnO3·0.4LiNi0.5Mn0.5O2 or 0.9Li[Li1/3Mn2/3]O2·0.4LiNi0.5Mn0.5O2, is synthesized using a solid-state reaction method. Its crystal structure and electrochemical behavior as the cathode material in lithium-ion batteries are studied. A reaction mechanism is proposed to interpret its unique electrochemical behavior shown in the first charge–discharge cycle. It includes four reactions: (1) LiNi0.5Mn0.5O2 → Li+ + Ni0.5Mn0.5O2 + e−, (2) Li[Li1/3Mn2/3]O2 → Li+ + [Li1/3Mn2/3]O2 + e−, (3) [Li1/3Mn2/3]O2 → 1/3 Li+ + 2/3 MnO2 + 2/3 O· + e−, and (4) Li+ + Ni0.2Mn0.8O2 + e− → LiNi0.2Mn0.8O2. The extraction of oxygen atoms (O·) in the reaction (3) results in the crystal structure rearrangement. Based on this hypothesis, it is found that the expected capacity of activated lithium-rich layered oxide xLi2MnO3·(1 − x)LiNi0.5Mn0.5O2 (0 ≤ x ≤ 1) increases from 230 to 280 mAh g−1 with increasing x value. Li[Li0.23Ni0.15Mn0.62]O2 has an expected total first charge capacity of 396 mAh g−1, but its expected capacity is only 247 mAh g−1 due to an initial capacity loss caused by the oxygen loss. Experimentally, within a charge–discharge voltage window from 2.0 to 4.8 V, Li[Li0.23Ni0.15Mn0.62]O2 delivers a charge capacity of 310 mAh g−1 and a discharge capacity of 215 mAh g−1, respectively, at 40 mA g−1 during the first cycle. The electrochemical kinetic behavior of Li[Li0.23Ni0.15Mn0.62]O2 is controlled by the charge-transfer process rather than by Li+ diffusion or blockage of solid-electrolyte interphase (SEI) layers at the end of Li+ extraction in the first charge.

Activated carbon is heat-treated in a H2 atmosphere at 600, 800, and 1000 °C for 1 h, respectively, to be used as electrode material for electrical double layer capacitors (EDLCs). After heat treatment, the surface morphology has no obvious change as compared with the raw material. The specific surface area and pore volume of sample treated at 600 °C have a slightly increase while those of samples treated at higher temperature decrease. XPS and elemental analysis indicate that oxygen containing functional groups on the sample are significantly reduced after treatment. The electrochemical performance of samples was evaluated using cyclic voltammetry and galvanostatic charge–discharge tests in 1 M TEABF4/PC electrolyte. The sample treated at 600 °C shows the optimized electrochemical performance with increase capacitance, enhanced stability, and improved energy density. Its initial specific capacitance is near 127 F/g, and initial coulombic efficiency is about 52 %. At 3.0 V, its energy density reaches 32 Wh/kg and specific capacitance is about 70 F/g at 1 A/g even after 10,000 charge–discharge cycles. Thus, heat treatment at 600 °C under H2 atmosphere is an effective method to improve electrochemical properties of EDLCs based on activated carbon material.

Novel hierarchical porous carbon aerogels (PCAs) derived from amphiphilic carbonaceous material (ACM) have been mass-prepared via a facile solvent exchange induced self-assembly process and subsequent carbonization and KOH activation. The resulting products are stacked up by highly interconnected carbon nanoparticles with a certain amount of micropores and mesopores, which aggregate to build a three-dimensional macroporous architecture. The hierarchical porous structure facilitates fast ion transportation inside the electrode simultaneously preserving efficient ion surface electrochemical reactions. Capacitive and rate performances were evaluated by fabricating symmetric capacitors with both aqueous and organic electrolytes. The PCA-0.5 and PCA-1.0 electrodes exhibit superior specific capacitances of 261.2 and 227.9 F g−1 at a current density of 0.05 A g−1 in 6 M KOH electrolyte, and still remain 145.5 and 175.4 F g−1 as the current density increases to 100 A g−1, respectively. Remarkably, the PCA-0.5 and PCA-1.0 electrodes show stable cycle durability with a slight capacitance loss of 8.2 and 11.2 % after 5000 cycles at 1 A g−1, respectively. Furthermore, in organic electrolyte system, the PCA-1.0 electrode manifests an outstanding capacitance of 155.4 F g−1 at a current density of 0.05 A g−1. The encouraging results demonstrate that PCAs are a sort of promising and competitive supercapacitors electrode materials.

Nanosized C/LiFePO 4 /MWCNTs secondary particles were synthesized by a combination of hydrothermal progress and a facile electro-polymerization polyaniline process with simultaneous calcinations. In combination with the continuous three-dimensional (3D) networks and high electronic conduction facilitating the kinetics of both electron transport and lithium ion diffusion within the particles, the optimized electrodes exhibit an ultrahigh rate capacity with a tap density of 1.78 g cm − 3 , stable charge/discharge cycle ability. The synthesized LiFePO 4 composite demonstrated an increased reversible capacity and better cycling ability compared to the bare LiFePO 4 , offering a discharge capacity of 169.9 mAh g − 1 (nearly to its the theoretical capability 170 mAh g − 1 ) at the C/10 rate and delivering a good rate performance with a capacity of 143.4 mAh g − 1 at a high rate of 20 C, and stable charge/discharge cycle ability (> 95% capacity retention after 200 charge/discharge cycles).This non-organic facile synthesize avenue can be highly desirable to prepare next-generation high-power lithium ion batteries.