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Aqueous zinc ion batteries (ZIBs) are widely researched due to the low-cost and intrinsic safety. However, the rate capability and specific capacity of ZIBs is limited due to the dissolution and structural collapse of cathode materials. It is crucial to construct stable cathode materials to promote rate capability and cycle stability of ZIBs. In this paper, The V3O7 was tightly attached to the surface of graphene oxide (GO) by a hydrothermal reaction and a V3O7/GO heterostructure was successfully achieved. The GO could increase structural stability, enhance electrical conductivity, and expand specific surface area of V3O7. Therefore, the V3O7/GO with a heterostructure exhibits an improved cycle stability and rate capability compared with V3O7. It displayed a specific capacity of 275.6 mA h g−1 at a current density of 1.0 A g−1. The study paves the way for promoting the Zn2+ storage performance of vanadium oxide and developing stable cathode materials of ZIBs.

2D materials is a promising Na+ insertion-type material due to its unique layered structure, however, the long diffusion channels yielded by stacking limited the Na+ storage rate capability. Herein, a 3D MoS2–Ta4C3 heterostructure (M-Ta4C3) composite is designed by supported 2D MoS2 nanosheets on/in the surface/interlayers of 2D Ta4C3 matrix for achieving high rate Na+ storage. The 2D MoS2 nanosheets is confined in the interlayers of Ta4C3 matrix that can avoid the stacking and expand the interlayer spacing of Ta4C3 matrix, which enlarges the contact surface area between electrode and electrolyte, and exposes more electrochemical active sites for Na+ storage. The Ta4C3 matrix improves the conductivity, prevents the aggregation and confines the volume expansion of MoS2 nanosheets which optimizes the structure stability and provides short Na+ diffusion channels. The M-Ta4C3 exhibits a larger interlayer spacing of 1.69 nm, extraordinary electrochemical performance and outstanding rate capability which benefitted from the 3D heterostructure. The M-Ta4C3//AC SIC owns super energy and power densities of 87.6 Wh kg−1 and 3937.3 W kg−1. This work employs Ta4C3 MXene as a Na+ storage material for the first time, and it provides an idea to improve the Na+ storage performance of 2D materials by constructing a 3D heterostructure.

Molybdenum carbide (Mo2C) is an attractive candidate as the electrode active material of supercapacitors (SCs) due to its low cost, outstanding electrical conductivity and superior chemical stability; however, the aggregation of Mo2C nanoparticles impedes its applications. Herein, zero-dimensional (0D) Mo2C nanoparticles are anchored on three-dimensional (3D) octahedral amorphous carbon (3DPO-Mo2C/C) by a mild and effective method with carbonizing and etching the Cu/Mo-based metal–organic framework. The 3DPO-Mo2C/C displays a large specific surface area, abundant mesopores and stable 3D structure, which not only expose more active reaction sites and shorten diffusion paths for electrolyte ions, but also prevent the aggregation and improve the structure stability of Mo2C nanoparticles. It exhibits an outstanding specific capacitances of 110 and 105 F g−1 in the electrolytes of 6 M KOH and 2 M EMIMA/AN. Employing the active carbon (AC) as counter electrode to assemble a SC with 3DPO-Mo2C/C as work electrode, which delivers higher energy and power densities of 12 Wh kg−1 and 1620 W kg−1, and the specific capacitance remains 91.3% after 6000 cycles. This approach not only prevents the aggregation of Mo2C nanoparticles successfully but also provides a possibility for Mo2C to be used in SCs.

A three-dimensional interconnected reticular porous carbon (3D-RPC) with a large surface area of 1535 m2 g–1 by a sol–gel method followed by carbonation as well as a chemical activation process usi...

Lithium-ion capacitors (LICs) can combine the high energy density of battery-type electrode and high power density of capacitor-type electrode, which is considered as one of the most promising electrochemical storage devices. The challenge of developing superior performance LICs is designing suitable electrode materials to overcome the kinetic imbalance between the battery-type anode and the capacitor-type cathode. Herein, defect-rich carbon encapsulated Fe3C nanoparticle (Fe3C@DRC) was obtained via a modified sol-gel method with a calcination process. The defect-rich and microporous structure effectively boosts kinetics and provides additional reaction sites for lithium-ion intercalation/deintercalation process, which leads to an excellent capacity (215 mAh g−1 at 1 A g−1 after 800 cycles) and rate capability (128.8 mAh g−1 even at 10 A g−1). Then a novel Fe3C@DRC//AC LIC was consisted using Fe3C@DRC as anode and activated carbon as cathode. The Fe3C@DRC//AC LIC demonstrates a wide potential window (0–4 V), delivers a high energy density of 187.8 Wh kg−1 at a power density of 200 W kg−1, reached a high power density of 4000 W kg−1 at an energy density of 80 Wh kg−1, and coupled with a reasonable life span (84.8% after 6000 cycles at a current density of 1 A g−1). The study indicates that the introduction of defect-rich strategy may push the practical application of high-rate and high-energy LIC anode materials in energy fields.

An ion insertion type in two-dimensional (2D) materials has attracted extensive attention making 2D materials as promising energy storage materials . However, the interlayer spacing plays a key role in the design of 2D materials with fast ions de-intercalation dynamics and high-rate capability. Here, an unprecedented and convenient organic molecular welding approach was proposed to controllably tune different interlayer spacings in Ti 3C2 MXene layers, resulting in pillar and strain- xDA-Ti3C2 structures by a dehydration condensation reaction between diacid molecules (HOOC(CH2)nCOOH) and -NH2 functionalized Ti3C2 layers. The xDA molecules can not only tighten the adjacent layers acting as ropes during the ion insertion process but also pillar the adjacent layers when ion extraction process was used to stabilize the Ti3C2 structure by suppressing the volume change. Furthermore, the interlayer spacing of xDA-Ti3C2 can be controllably tuned from 1.03 to 1.45 nm by choosing xDA with different lengths and controlled interlayer spacings of 1.35 and 1.38 nm can be achieved for the best rate capability of insertion/extraction processes with the superior diffusion coefficient of 4.6 × 10−7/2.8 × 10−8 cm2/s in Li+/Na+ batteries, respectively.

A facile method of chemical welding was proposed to construct the diamine molecules (xDM, x = 2, 3, 4, 6 and 8) pillared- and strained-graphene oxides (GO) with controllable interlayer spacing via the dehydration condensation reaction between GO and xDM. The interlayer spacing of xDM pillared- and strained-GO (GO-xDM) is controllably enlarged by choosing the length of xDM, which determines the pillaring effects. The GO-xDM exhibits a low diffusion barrier and ultrafast Li+ diffusion dynamics due to its enlarged interlayer spacing, which leads the excellent Li+ storage rate capability. The effects of interlayer spacing on Li+ diffusion dynamics are clarified that GO-2DM with the interlayer spacing of 0.911 nm displays the excellent Li+ storage performance and fast Li+ diffusion dynamics (DLi+=2.4 × 10−7 cm2 s−1). The GO-2DM presents a high capacity of 291.8 mAh g−1 at a current density of 0.1 A g−1 and a high-rate capability of 120.8 mAh g−1 at a current density of 5.0 A g−1. The GO-2DM//AC lithium-ion hybrid capacitor delivers a high energy density of 103.6 Wh kg−1 at a power density of 55.8 W kg−1, even reaches 2777.8 W kg−1 at a power density of 61.1 Wh kg−1. The approach of chemical welding provides a novel perspective for controllably enlarging interlayer spacing and designing two-dimensional (2D) energy storage materials with high-rate capability.

Sodium ion capacitors (SICs) have attracted considerable attentions since it is integrating the complementary features of both high energy and power densities. One of the most crucial tasks for develop highly efficient SICs is to increase the faradaic Na+ redox kinetics from the battery-type anode to match the electrical double-layer capacitance-type cathode. In this work, Mo2C nanoparticles uniformly anchored into cross-linked hierarchical porous carbon (HPC-Mo2C) have been produced by a water-soluble NaCl template strategy. The as-obtained HPC-Mo2C composite shows a large specific surface area of 385.6 m2 g−1 with well distributed micro–meso–macropores structure, delivering a superior rate capability (108.2 mAh g−1 at 5 A g−1) and robust long-term cycling of 190.6 mAh g−1 at 1 A g−1 after 2500 cycles. Electrochemical measurements illustrate that the Mo2C nanoparticles uniformly anchored into cross-linked hierarchical porous structure can accelerate fast Na+ diffusion kinetics toward excellent rate capacity and increase the pseudocapacitive behavior for the redox reaction. The SIC composed of HPC-Mo2C as anode and activated carbon (AC) as cathode delivers an impressive energy density of 130.2 Wh kg−1 and ultra-high power density of 30,000.0 W kg−1, as well as an unprecedented cycling stability of 88.9% retention after 10,000 cycles with a potential range of 0–4.0 V. This work may cater to the requirements for rationale kinetic matching electrode for the advanced SICs.

A three-dimensional hierarchical porous carbon loaded ultrafine Mo2C (3DHPC-Mo2C) nanomaterial was synthesized by an effective approach that combines NaCl template and K2CO3 in-situ activation together. The 3D hierarchical porous carbon with macro-meso-micropores interlacing structure acts as a skeleton provides a large surface area (409 m2 g−1) and effectively prevents the agglomeration of Mo2C during the carbonization process, which not only conducive to expose more active sites and shorten the transmission path of electrolyte ions but also helps to give full play to the features of Mo2C, such as high conductivity. Because of the outstanding microstructure, the 3DHPC-Mo2C shows a superior electrochemical performance that delivers a high specific capacitance of 206 F g−1 at 0.5 A g−1 and superior cycling stability of 96.6% through 7000 cycles. Meanwhile, an asymmetric supercapacitor (3DHPC-Mo2C//AC) was assembled in ionic liquid electrolyte (EMIMAC/AN) and achieves a high specific energy of 20 Wh Kg−1 at the specific power of 224 W Kg−1, which is higher than most reported carbide-based asymmetric supercapacitors and provide a promising strategy for the preparation of Mo2C and its application in energy storage.

The development of low-cost, high-purity and high-performance porous carbon is of great significance for promoting the commercial application of supercapacitors. In this paper, porous carbon spheres (PCSs) with excellent electrochemical performance were obtained by carbonization and activation of starch gel spheres as precursor which is prepared by microemulsion process. The obtained PCSs exhibit both microporous and mesoporous structure, showing a large specific surface area of 1117.0 m2 g[Formula: see text] and exhibiting a high specific capacitance of 221.3 F g[Formula: see text]at a current density of 0.5 A g[Formula: see text] in aqueous electrolyte (and still displays capacity of 146.0 F g[Formula: see text] in ion liquid electrolyte). The PCSs//PCSs symmetric supercapacitor (SSC) based on aqueous electrolyte exhibits an energy density of 10.9 Wh kg[Formula: see text] at a power density of 300.0 W kg[Formula: see text], whereas that based on ion liquid electrolyte achieves a high energy density of 29.0 Wh kg[Formula: see text] at 650.0 W kg[Formula: see text]. The study provides a new idea to develop low-cost, high-purity and high-performance porous carbon materials for supercapacitors.

MXenes are a new class of two-dimensional (2D) materials and have been considered as promising energy storage materials due to their high conductivity and unique layered structure. To improve the charge storage performance of these materials, it is crucial to prevent self-stacking and expand the interlayer spacing of MXenes since this will increase the transfer channels and accessible active sites for electrolyte ions and improve the dynamics of charge storage. This paper presents an effective approach to preventing self-stacking and expanding the interlayer spacing of Ti3C2 using electrostatic reassembly between lanthanum ions and exfoliated Ti3C2 sheets to obtain a secondary-formed multilayer-structured Ti3C2 (La/e-Ti3C2). An increased interlayer spacing and greater specific surface area were achieved and capacitive performance was improved compared with that of pure multilayer Ti3C2. The specific capacitance of La/e-Ti3C2 was found to be 233.3 F g−1 at a current density of 0.5 A g−1 and the capacitance retention under 2 A g−1 was as high as 94.3% after 10,000 cycles. An interesting result is presented, namely that a large interlayer spacing is beneficial for improving the rate capability of Ti3C2 at different current densities. The study paves the way for controllable tuning of the interlayer spacing, specific surface area, and pseudocapacitive performance of two-dimensional materials.

Transition metal dichalcogenides (TMDs) caused widespread concern because of their possess graphite-like two-dimensional structure, which allows Na+ reversible de-intercalation between the interlayers and contributes high theoretical capacity. However, the poor conductivity and structural instability greatly limited their application to sodium ion batteries (SIBs). Herein, three-dimensional (3D) honeycomb MoSe2/rGO nanocomposites with outstanding sodium ion storage performance were prepared. The MoSe2/rGO combined the advantages of MoSe2 and rGO. The typical layered structure of MoSe2 provide Na+ diffusion pathways and sufficient active sites, while the rGO increase conductivity and alleviate structural change during Na+ insertion/extraction process. The stable discharge capacity of MoSe2/rGO reaches 300 mAh g−1 at 0.1 A g−1 and retains 247 mAh g−1 after 100 times. It retains a high capacity of 214.7 mAh g−1 at 1 A g−1 and shows outstanding rate capability. The MoSe2/rGO//AC hybrid sodium-ion capacitors (HSIC) achieves a high capacitance of 56.7 F g−1 at 0.1 A g−1, it exhibits an energy density of 87.7 W kg−1 at a power density of 208.8 W h kg−1 and retains 50.5 W h kg−1 when it increases to 1051.4 W kg−1. The article brings up a novel opinion for designing porous TMDs based composites as ideal energy storage materials.

This paper introduces new seawater flocculants. Ferric sulfate solution and polysilicic acid were mixed. After standing and curing, polymeric ferric silicate sulfate was obtained. The optimum preparation process was explored. When Fe/Si=10:20, curing pH in the range of 1.0 to 3.0, flocculants had best flocculating activity. The polymeric ferric silicate sulfate solution and 200 μg/L chitosan solution were mixed to make composite flocculants. Flocculating activity assessments were studied. When pH in the range of 6.0 to 10.0, temperature in the range of 10 °Cto 40 °C, flocculating activity could be stable. Total phosphorus (TP) and total organic carbon (TOC) removal rates of new flocculants were higher than 80% while algae and bacteria removal rates of new flocculants were all higher than 90%. These flocculants were multi-effect seawater flocculants.

Magnesium borate (Mg2B2O5) whisker was successfully synthesized by high temperature flux method using Magnesium chloride, boric acid, sodium hydroxide and sodium chloride as raw materials.The as-prepared product was characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy(SEM), Transmission Electron Microscope (TEM) and X-Ray Photoelectron Spectrometry (XPS). The results showed that the as-prepared sample had triclinic structure and consisted of whisker-like particles with an average diameter about 1.25 μm and length up to 40μm. XPS results confirmed that the molar ratio of each atom agreed with the stoichiometric composition of Mg2B2O5. The growth mechanism was briefly discussed.

In this paper, several types of PVDF hollow fiber membranes used in the gas membrane separation process for extracting bromine from simulated seawater or concentrated seawater were studied. The micropore, hydrophobic property, mechanical strength and material chemistry of the PVDF membranes soaked in seawater or concentrated seawater were characterized by SEM-EDX, IR, contact angle testing instrument and electronic fabric strength tester, which were compared with those of origin membranes. At last, the mass transfer coefficient and flux during a long time were gained by operating a permeation experiment with a chosen type of PVDF membrane module.

A single inlet and multi-inlet hollow fiber modules (HFMs) were designed in order to investigate the fluid hydrodynamics of the shell side. Residence time distribution (RTD) curves was measured under different packing density and inlet. Mean residence time ( ), variance( ) and the number of tanks (N) were also calculated to reflect the degree of backmixing. The experimental results indicated that the random packing of fiber caused the non-ideal flow in shell side. With the increasing of the packing density, the non-ideal flow was more serious. Contrasting to the traditional one, multi-inlet hollow fiber modules could weaken the trailing of the RTD curves and control the backmixing. With the quantity and the site of the inlets changed, non-ideal flow can be further improved. The hydraulic characterization of the shell side flow were related with not only the quantity but also the site of inlets. The results indicated that the muti-inlets design is superior to that of a single inlet.

Magnesium borate ( Mg 2 B 2 O 5) nanorods were synthesized by a two-step process, including solution-chemical technology and a ternary-flux method, using concentrated seawater and H 3 BO 3 as raw materials. X-ray diffraction (XRD) showed that the sample had triclinic structure. Scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HR-TEM) indicated that it consisted of rod-like particles with an average diameter of 100–150 nm and length over 5 μm. Differential thermal analysis (DTA) confirmed that the melting point of the ternary-flux and the formation temperature of Mg 2 B 2 O 5 were lower than single-flux process. The formation of Mg 2 B 2 O 5 nanorods was more efficient by ternary-flux than single-flux. Mechanical property of Mg 2 B 2 O 5 nanorods reinforced Nylon-6 composites showed that KH550 was the optimal coupling agent and made the strength of the composites to be improved to different degrees.