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Potassium ions batteries (PIBs) have been regarded as a promising choice for electrical energy storage technology due to the wide distribution of potassium resources. However, developing low-cost and robust earth-rich anode materials is still a major challenge for the practical and scalable usage of PIBs. Herein, for the first time, we developed nitrogen doped carbon coating CoS2/CuCo2S4 heterostructure (CoS2/CuCo2S4@NCs) hollow spheres and evaluated as anode for PIBs. The CoS2 and CuCo2S4 heterostructure interface could generate a built-in electric field, which can fasten electrons transportation. The nanostructures could shorten the diffusion length of K+ and provide large surface area to contact with electrolytes. Furthermore, the inner hollow sphere morphology along with the carbon layer could accommodate the volume expansion during cycling. What’s more, the N-doped carbon could increase the conductivity of the anodes. Benefitting from the above features, the CoS2/CuCo2S4@NCs displays an outstanding rate capability (309 mAh g−1 at 500 mA g−1 after 250 cycles) and a long-term cycling life (112 mAh g−1 at 1000 mA g−1 after 1000 cycles) in ether-based electrolyte. Conversion reaction mechanism in CoS2/CuCo2S4@NCs anode is also revealed through ex situ XRD characterizations. This work provides a practical direction for investigating metal sulfides as anode for PIBs.

The recycling technology of photocatalyst powdery has hardly been mature in the photocatalytic oxidation so far. In this work, the hollow TiO2 microspheres with an appropriate thickness are confined in carbon microspheres (CMSs) to form hollow TiO2@CMSs, which are physically integrated with carbon-fiber textile by van der Waals (vdW) interactions to generate separable and recyclable hollow TiO2@CMSs/carbon-fiber vdW heterostructures. Such separable and recyclable heterostructures show remarkable oxidation of 2,4-dinitrophenol. From our detailed characterization and density functional theory (DFT) calculations, we found that carbon fiber can trap electrons exerted from the excitation of hollow TiO2@CMSs and creates holes in hollow TiO2 microspheres, which endow the carbon fiber with photoelectric activity through coherent charge injection. This study indicates that our general strategy for the fabrication of hollow TiO2@CMSs/carbon-fiber vdW heterostructures can be used as separable and recyclable photocatalyst and photoelectrocatalyst with potential industrial applications in environment-related fields.

Spent selective catalytic reduction (SCR) catalysts are defined as hazardous wastes because of the toxicity of V2O5 to the ecological environment. Recycling of V2O5 and TiO2 from the spent SCR catalysts has strikingly social and environmental benefits as well as economic values. In this work, a “NaOH ​+ ​Na2CO3” system was employed to recycle 99.2% of anatase/rutile TiO2 nanospheres with a nanospherical morphology from the spent SCR catalysts by a simple sintering-leaching process. The observed photocatalytic performance of anatase/rutile TiO2 nanospheres was higher than that of the other TiO2 recovered from the spent SCR catalysts, commercial TiO2, and chemosynthetic TiO2, which can be ascribed to the enhanced separation of photo-excited electron/hole in a direct Z-scheme of anatase/rutile TiO2 homostructures. Additionally, high-purity V2O5 microrods with high H2S removal performance were efficiently prepared by a hydrothermal method in the leaching solution, which is superior to the traditional method including NH4VO3 precipitation and solvent extraction as the present method can recycle vanadate from low-grade filtrate with a 99.6% of recovery rate. This study develops an alternative method for controlling pollution of vanadate to soil and water and recycling of valuable metals.

Due to its appropriate bandgap (∼2.4 eV) and efficient light absorption, bismuth vanadate (BiVO4) shows promising photocatalysis activity. However, the charge carrier recombination and poor electron transmission often induce poor photocatalytic performance. Herein, we report a new method to in-situ synthesize non-noble metal Bi decorated mulberry-like BiVO4 by a two-step calcination process. Comprehensive characterizations reveal that non-noble metal Bi nanoparticles grown in-situ on BiVO4 result in the red-shift of the absorbance edge, greatly extending the light absorption from the ultraviolet into the near-infrared region. The surface plasmon resonance excitation of Bi nanoparticles and synergetic effects between Bi and BiVO4 effectively improve the photocatalytic efficiency and promote the separation of photoinduced electron-hole pairs in mulberry-like BiVO4. Density functional theory (DFT) calculation results further verify that the electrons are transferred from Bi to BiVO4 and the formation of OH radical in Bi/BiVO4 is attributed to the lower simulated free energy, which supports our experimental outcomes. This work provides a novel strategy to enhance light absorption and promote efficient solar utilization of photocatalysts for practical applications.

The van der Waals (vdW) integration enables to create heterostructures with intimate contact and bring new opportunities. However, it is not confined to layered materials but can also be generally extended to 3D materials. Multidimensional Bi2O3/BiVO4@graphene oxide (GO) van der Waals heterostructures are synthesized by one-pot wet chemistry method. Bi2O3/BiVO4 composite nanoparticles are self-assembled with GO framework by vdW interaction to form vdW heterostructures, in which GO framework allows short electron transport distance and rapid charge transfer and provides massive reactive sites. Such self-assembled heterostructures show a superior high photoactivity towards oxygen evolution with an enhanced oxygen generation rate of 1828 µmol h−1 g−1, nearly 3 times than that of pure BiVO4, attributed to the accelerated charge separation and transfer processes of Bi2O3/BiVO4@GO vdW heterostructures. This study indicates that our strategy provides a new avenue towards fabricating multi-dimensional vdW heterostructures and inspiring more innovative insights in oxygen evolution field.

Carbon fibers (CFs) show great potential for high-performance supercapacitors in miniature electronics fields, where high energy density and long cycling life are required. However, superior combination of these two attributes in CF-based supercapacitors still presents a long-standing challenge. Herein, straight carbon nanotubes (CNTs) with radial orientation and high chemical/physical stability are served as nanoscale conductive skeletons on CFs for supporting the polyaniline (PANI)/SnS2. The SnS2 with nanoflower-like features significantly increases the specific capacitance and specific surface area (SSA); furthermore, the PANI nanolayers covered on SnS2 petals enable secondary specific capacitance enhancement and inhibition of volume expansion of SnS2 during charging/discharging processes. Benefiting from these structural merits, the resultant PANI/SnS2@CNTs/CFs hybrids exhibit high SSA (2732.5 m2 g−1), high specific capacitance (891 F g−1 at 20 mV s−1) and excellent cycling stability (83.8% after 6000 cycles at 2 A g−1). Moreover, the hybrids deliver a superior energy density of 38.7 W h kg−1 at a power density of 1 kW kg−1 and outstanding performance stability, which should prove to be vastly advantageous as compared to the reported CF-based supercapacitors. Our work puts forward a new thinking of rational construction of high-performance CF-based supercapacitors that can be used in practical energy storage devices.

In this work, Mg-10 wt% Ni (M) with higher theoretical hydrogen production is taken as the research object. M − 10C (M = Mg10Ni, C = EG (expandable graphite), SnO2 (stannic oxide), EG-SnO2) composites with various compositions were integrated by high-energy ball milling (HEBM), and their H2 production behavior in simulated seawater were investigated. Not only did X-ray analysis and scanning electron microscopy techniques be used to study the phase composition diffraction pattern and surface morphology of these Mg-based composites in detail, but also the performance and mechanism of hydrogen generation are investigated by initial hydrolysis kinetics. The results demonstrate that the addition of hollow SnO2 nanotubes and lamellar EG to the M alloy make surface loose and porous, and the existing cracks and gaps can increase hydrolysis channels with rapid medium transfer, thereby improving the initial reaction kinetics and the final hydrogen production rates. M − 10C (M = Mg10Ni, C = EG, SnO2, EG-SnO2) composites can produce 98.207, 69.996, 58.235 mL ⋅g−1 H2 within 15 s at 291 K, which are higher than M alloy without any catalyst (38.151 mL⋅g−1 H2). It is worth noting that M-10SnO2 rapidly release 395.4 mL⋅g−1 H2 with 51.35% yield in 2 min at 298 K. The difference between the H2 generation yields is mainly originated from the activity of catalysts on nucleation and growth of Mg(OH)2 in the hydrolysis reaction stage. Moderate initial nucleation rate and the subsequent sufficient growth of Mg(OH)2 nucleus are prerequisites to ensure fast initial hydrogen production rate and high H2 generation yield. Catalysis is an effective means to ameliorate the hydrogen performance of Mg-based alloys, and it is important to choose the appropriate catalyst type. However, the degree of catalysis determined by the content of the catalyst and the manner of addition is also worthy of attention.

Materials with low density, exceptional thermal and corrosion resistance, and ultrahigh mechanical and electromagnetic interference (EMI) shielding performance are urgently demanded for aerospace and military industries. Efficient design of materials' components and microstructures is crucial yet remains highly challenging for achieving the above requirements. Herein, a strengthened reduced graphene oxide (SrGO)-reinforced multi-interfacial carbon-silicon carbide (C-SiC)n matrix (SrGO/(C-SiC)n) composite is reported, which is fabricated by depositing a carbon-strengthening layer into rGO foam followed by alternate filling of pyrocarbon (PyC) and silicon carbide (SiC) via a precursor infiltration pyrolysis (PIP) method. By increasing the number of alternate PIP sequences (n = 1, 3 and 12), the mechanical, electrical, and EMI shielding properties of SrGO/(C-SiC)n composites are significantly increased. The optimal composite exhibits excellent conductivity of 8.52 S·cm-1 and powerful average EMI shielding effectiveness (SE) of 70.2 dB over a broad bandwidth of 32 GHz, covering the entire X-, Ku-, K-, and Ka-bands. The excellent EMI SE benefits from the massive conduction loss in highly conductive SrGO skeletons and polarization relaxation of rich heterogeneous PyC/SiC interfaces. Our composite features low density down to 1.60 g·cm-3 and displays robust compressive properties (up to 163.8 MPa in strength), owing to the uniformly distributed heterogeneous interfaces capable of consuming great fracture energy upon loadings. Moreover, ultrahigh thermostructural stability (up to 2100 °C in Ar) and super corrosion resistance (no strength degradation after long-term acid and alkali immersion) are also discovered. These excellent comprehensive properties, along with ease of low-cost and scalable production, could potentially promote the practical applications of the SrGO/(C-SiC)n composite in the near future.

(Mg-10wt%Ni)-10wt%Ce (Mg10Ni10Ce) was ball-milled with SnO2 nanotubes and Mg10Ni10Ce-xSnO2 (x = 0, 5, 10 and 15 wt%) composites have been prepared. The phase compositions, microstructures, morphologies and hydrolysis H2 generation performance in different aqueous systems (distilled water, tap water and simulated seawater) have been investigated and the corresponding hydrolysis mechanism of Mg10Ni10Ce and Mg10Ni10Ce SnO2 has been proposed. Adding a small amount of SnO2 nanotubes can significantly enhance the hydrolysis reaction of Mg10Ni10Ce, especially the initial hydrolysis kinetics and the final H2 generation yield. Unfortunately, the Mg10Ni10Ce-xSnO2 hardly reacts with distilled water at room temperature. The hydrolysis reaction rate of Mg10Ni10Ce 5SnO2 composite in tap water is still very slow with only 17.3% generation yield after 1 h at 303 K. Fortunately, in simulated seawater (3.5 wt% NaCl solution), the hydrolytic H2 generation behavior of the Mg10Ni10Ce 5SnO2 composite has been greatly improved, which can release as high as 468.6 mL g−1 H2 with about 60.9% generation yield within 30 s at 303 K. The Cl− destroys the passivation layer on Mg Ni Ce alloy surface and the added SnO2 nanotubes accelerate the hydrolysis reaction rate and enhance the H2 generation yield. The Mg10Ni10Ce 5SnO2 composite can rapidly generate a large amount of H2 in simulated seawater in a short time, which is expected to be applied on portable H2 generators in the future.

Thermoelectric (TE) performance of Ca3Co4O9 (CCO) has been investigated extensively via a doping strategy in the past decades. However, the doping sites of different sublayers in CCO and their contributions to the TE performance remain unrevealed because of its strong correlated electronic system. In this work, Sr and Ti are chosen to realize doping at the [Ca2CoO3] and [CoO2] sublayers in CCO. It was found that figure of merit (ZT) at 957 K of Ti-doped CCO was improved 30% than that of undoped CCO whereas 1 at% Sr doping brought about a 150% increase in ZT as compared to undoped CCO. The significant increase in electronic conductivity and the Seebeck coefficient are attributed to the enhanced carrier concentration and spin-entropy of Co4+ originating from the Sr doping effects in [Ca2CoO3] sublayer, which are evidenced by the scanning electron microscope (SEM), Raman, Hall, and X-ray photoelectron spectroscopy (XPS) analysis. Furthermore, the reduced thermal conductivity is attributed to the improved phonon scattering from heavier Sr doped Ca site in [Ca2CoO3] sublayer. Our findings demonstrate that doping at Ca sites of [Ca2CoO3] layer is a feasible pathway to boost TE performance of CCO material through promoting the electronic conductivity and the Seebeck coefficient, and reducing the thermal conductivity simultaneously. This work provides a deep understanding of the current limited ZT enhancement on CCO material and provides an approach to enhance the TE performance of other layered structure materials.

Mg10Ni-MoS2 composites were synthesized, and the amount of molybdenum disulfide (MoS2) and ball milling time was optimized to obtain rapid initial kinetics with high conversion yield at room temperature in simulated seawater. The microstructures and H2 generation thermodynamics were comprehensively investigated to demonstrate the main influential factors on excellent initial hydrolysis performance. Mg10Ni-5 wt%MoS2-15 min can generate 493.3 mL·g-1 H2 at 298 K with 58% yield in 20 s. The H2 generation capabilities of Mg10Ni-5 wt% MoS2-15 min are 569 mL·g-1 H2 and 67%, which are higher than those of Mg10Ni (495 mL·g-1 H2, 56%) in 2 min. The lowest hydrolysis activation energy (18.74 kJ·mol-1) can be achieved by Mg10Ni-5 wt%MoS2, which means low energy consumption. Mg10Ni with higher specific surface area (4.04 m2⋅g-1) than that of Mg10Ni-5wt.%MoS2-15 min (0.78 m2⋅g-1) presents worse H2 generation performance, indicating that higher specific surface area is the secondary determinant for superior initial hydrolysis kinetics and higher conversion yield compared with the added MoS2. The added MoS2 with specific morphologic structure can provide auxiliary mass transfer paths, which shorten the transfer distance and destroy the continuous colloidal layer. Mg-rich alloys optimized for rapid and efficient H2 production performance are expected to be applied large-scale H2 generators.

TiO2 microtubes with tunable wall thickness have been synthesized by a one-step electrospinning method linked with a calcination process. The wall thickness of TiO2 microtubes can be easily tuned by altering the dosage of liquid paraffin. The influence of the thickness on the light-harvesting ability and separation efficiency of the photogenerated carriers was studied using ultraviolet–visible (UV–vis) diffuse reflectance spectroscopy, photoluminescence emission spectroscopy, and photocurrent density measurements. Results show that TiO2 microtubes with an appropriate thickness exhibit enhanced light scattering effect, UV–vis light-harvesting ability, charge separation efficiency, and photocatalytic performance. The degradation rates of rhodamine B and 2,4-dinitrophenol by using TiO2 microtubes synthesized at a dosage of 0.14 g/mL liquid paraffin are 99.9% within 60 min and 97.8% within 40 min, respectively, which are higher than most of the reported values. All these results suggest that our work provides an ideal strategy for adjusting the wall thickness of TiO2 microtubes and new approach to enhance the photocatalytic performance of TiO2.

Increasing attention has been focused on potassium ion batteries (KIBs) as promising energy-storage system (ESS) owing to the abundance and low-cost of potassium resources. Here, SnS2/SnO2 heterostructures were successfully fixed onto stainless steel mesh (SnS2/SnO2/SSM) through a facile two-step hydrothermal method and used as anodes for KIBs. Due to the advantages of SnS2/SnO2 heterostructures and good conductivity of SSM substrate, the SnS2/SnO2/SSM anodes display enhanced electrochemical performance. The SnS2/SnO2/SSM anodes deliver specific capacity of 394 mA h g−1 at 50 mA g−1 over 100 cycles, better than SnO2/SSM. Even at 500 mA g-1 after 250 cycles, high capacity of 155 mA h g−1 can still be obtained.

Potassium-ion batteries (KIBs) have becoming a prospective energy storage technique, due to the abundant potassium resources in the earth crust, approximate redox potential and similar electrochemical behavior of potassium and lithium. However, the insufficient capacity, poor stability and volume expansion of electrode materials during charge and discharge are main factors restricting the further development of KIBs. This work reports an amorphous carbon coated SnO2 nanohseets on hard carbon hollow spheres (AC/SnO2@HCHS) anode with enhanced potassium storage performance. The HCHS acts as a carrier for SnO2 nanosheets, providing high electrical conductivity and stable skeleton. The self-assembled SnO2 nanosheets with high surface area ensures sufficient contact with the electrolyte. Amorphous carbon wrapping can not only relieve SnO2 volume expansion but also provide surface-induced capacitive capacity. As a consequence, the AC/SnO2@HCHS anode presents excellent potassium-ion storage performance with high discharge capacity of 346 mAh g-1 at 0.1 A g-1 over 200 cycles, ultra-long cycling lifetime and outstanding rate capability (236 mAh g-1 at 1 A g-1 over 1000 cycles).

The as-cast magnesium–nickel–cerium (Mg–Ni–Ce) alloys with nominal component (Mg–10 wt% Ni)1−xCex (x = 0, 5, 10, 15 wt%) are optimized by high-energy ball milling (HEBM). Expandable graphite (EG) and molybdenum disulfide (MoS2) have been introduced as surface catalysis to form (Mg10Ni)95Ce5–5 wt% EG–5 wt% MoS2 composite. The synergetic effects of HEBM and catalysts on H2 production of (Mg10Ni)95Ce5 are comprehensively studied. The thermodynamics are studied by H2 generation curves fitting. The HEBM 0Ce, 5Ce, 10Ce and 15Ce alloys at 291 K can generate 530, 747, 720 and 487 mL g−1 H2 with conversion yields of 59%, 87%, 89% and 64% in initial 15 min, respectively. The addition of surface catalysts EG–MoS2 can further enhance the initial hydrogen generation rate and the final conversion yield within short period at room temperature. 773 mL g−1 H2 corresponding to 95% conversion yield can be obtained by HEBM (Mg10Ni)95Ce5–EG–MoS2 within 1 min at 291 K. The synergetic effects of HEBM and EG–MoS2 can promote rapid initial generation rate and high conversion yield of hydrolysis hydrogen generation of (Mg10Ni)95Ce5–EG–MoS2 composite. This work indicates a promising way to synthesize Mg-based alloys with rapid initial hydrolysis H2 generation kinetics and high conversion yield within a short period.

Suitable anode materials for potassium ion batteries (KIBs) with high capacity, good reversibility and stable cycling performances are still in large demand. Here, flexible N doped carbon/bubble-like MoS2 core/sheath framework (MoS2/NCS) is prepared as an anode material for potassium ion batteries. The N doped carbon sponge (NCS) skeleton with good conductivity and high surface area guarantees superior rate capability and high stability of MoS2/NCS anode. The chemical bonds (C Mo) firmly bridge MoS2 and NCS together, which further ensures MoS2/NCS stable cycling performance. More importantly, volume expansion is greatly buffered during cycling by this unique structure: the voids between bubble-like MoS2 sheath and NCS core can effectively buffer volume expansion generated during potassium intercalation/deintercalation; the enlarged interlayer spacing contribute more space to buffer volume change; the ultrathin nanosheets can shorten the charge diffusion distance and buffer volume change. As a consequence, MoS2/NCS delivers a capacity of 374 mAh g−1 over 200 cycles at 50 mA g−1. Even at 1000 mA g−1, a capacity of 212 mAh g−1 can still be obtained over 1000 cycles. We believe this MoS2/NCS structure will highlight the potential of MoS2 in practical KIBs applications.

In order to suppress the overpressure and flame damage caused by the explosion of premixed methane-air, a self-built duct with a 10 × 10 × 100 cm was used to conduct an experimental study on the ex...

The extraordinary mechanical and physical properties of carbon nanotubes (CNTs) have provided the impetus in developing a new promising CNT/carbon (CNT/C) composite, which may effectively alleviate the shortcomings of sharp-angle and thin-walled C/C components in mechanical performance. Present researches on preparing CNT/C composites focus on infiltrating pyrocarbon into CNT assemblies such as array, block, sheet, film, and buckypaper using complicated and time-consuming methods. Here, we report a facile and efficient strategy for preparing CNT fiber/C composites via electrified preform heating chemical vapor infiltration. Densification process is identified as continual deposition of pyrocarbon around CNTs (called coaxial structure) and further deposition among them, which can be accomplished in short time. Small-diameter (below 500 nm) coaxial structures give composites high deformability; larger ones coupled with bridging action of pyrocarbon among them result in better load transfer and more conductive pathways. Optimized CNT fiber/C composites demonstrate impressive tensile strength (205 MPa) and excellent conductivity (431 S/cm), which are comparable to the previously reported C/C and CNT/C composites. Moreover, such composites exhibit lightweight (1.21 g/cm3), good deformability and high fracture strain. Our work could open up a general strategy for efficiently fabricating various high-performance CNT/C composites that could be used in high-temperature aerospace fields.

High-energy sodium-ion batteries have a significant prospective application as a next-generation energy storage technology. However, this technology is severely hindered by the lack of large-scale production of battery materials. Herein, a self-standing film, assembled with SnS-Sn/multiwalled carbon nanotubes encapsulated in carbon fibers (SnS-Sn/MCNTs@CFs), is prepared using ball milling and electrospinning techniques and used as sodium-ion battery anodes. To compensate the poor internal conductivity of SnS-Sn nanoparticles, MCNTs are used to interweave SnS-Sn nanoparticles to improve the conductivity. Moreover, the designed three-dimensional carbon fiber conductive network can effectively shorten the diffusion path of electron/Na+, accelerate the reaction kinetics, and provide abundant active sites for sodium absorption. Benefiting from these unique features, the self-standing film offers a high reversible capacity of 568 mA h g-1 at 0.1 A g-1 and excellent cycling stability at 1 A g-1 with a reversible capacity of 359.3 mA h g-1 after 1000 cycles. In the sodium-ion full cell device, the capacity is stable at 283.7 mA h g-1 after 100 cycles at a current of 100 mA g-1. This work provides a new strategy for electrode design and facilitates the large-scale application of the sodium-ion battery.

Constructing a hierarchical structure with tunable pore size is a practical method to improve the capacity of photocatalytic hydrogen production of catalysts. In this work, titanium dioxide/graphitic carbon nitride (TiO2/g-C3N4) nanofibers with hierarchical meso/macro-porous structure are fabricated by combining a one-step electrospinning method and calcination process, in which the hierarchical meso/macro-porous structure is developed by introducing polyvinylpyrrolidone and liquid paraffin into the electrospinning solution. Comprehensive characterizations reveal that the hierarchical meso/macro-porous TiO2/g-C3N4 nanofibers have improved ultraviolet-visible light absorption, the separation efficiency of carriers, and photocatalytic performance. The photocatalytic H2 evolution is up to 1202 μmol g−1 in 7 h, which is better than those of corresponding TiO2/g-C3N4 photocatalysts previously reported. This work provides a new strategy to build a hierarchical meso/macro-porous nanofiber and an ideal solution to improve the hydrogen production of TiO2/g-C3N4.

Potassium-ion batteries (KIBs) hold great promise as an electrochemical energy storage system owing to the abundance of potassium resource in the earth's crust, close redox potential to lithium, and similar electrochemical behavior to lithium system. In this work, the defect and hollow size of the hollow porous KxCoF3 (KCF) open framework are tuned using a micro-emulsion method. The optimized metallic K0.66CoF3 (K0.66CF) is used for the first time as an advanced anode material for KIBs, which exhibits a high capacity of 167 mAh g−1 at a current density of 50 mA g−1 over 200 cycles. A high-rate performance with a capacity of 139 mAh g−1 at 1000 mA g−1 and an impressively ultra-long cycle life over 3000 cycles are achieved. Density functional theory (DFT) calculations show that the K defects together with the enlarged interlayer space in this open framework can boost the electronic and ionic diffusion, stabilize the crystal structure and accommodate more K ions during cycling. In addition, the unique hollow porous structure increases the contact area of K0.66CF with electrolyte and provides shortened ion diffusion paths for K+. This work provides the basic understanding of tuning defects and hollow size for boosting electrochemical behavior in energy storage fields.

In this study, we developed as-cast (Mg10Ni)1-xCex (x = 0, 5, 10, 15 wt%) ternary alloys by using a flux protection melting method and investigated their hydrolysis hydrogen generation behaviour in simulate seawater. The phase compositions and microstructures of as-cast (Mg10Ni)1-xCex ternary alloys are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) equipped with electron energy dispersion spectrum (EDS) and transition electron microscope (TEM). Their kinetics, thermodynamics, rate-limiting steps and apparent activation energies are investigated by fitting the hydrogen generation curves at different temperatures. With increasing Ce content, the (Mg10Ni)1-xCex ternary alloys show increased electrochemical activities and decreased eutectic. When 10 wt% and 15 wt% Ce added, the active intermediate phase of Mg12Ce has been observed. The hydrogen generation capacity of (Mg10Ni)95Ce5 is as high as 887 mLg−1 with a hydrolysis conversion yield of 92%, which is higher than that of Mg10Ni alloys (678 mLg−1) with a yield only 75% at 291 K. The initial hydrolysis reaction kinetics of Mg–Ni–Ce alloys is mainly controlled by the electrochemical activity and the mass transfer channels formed in the alloys. Such a structure-property relationship will provide a possible strategy to prepare Mg-based alloys with high hydrogen conversion yield and controlled hydrolysis kinetics/thermodynamics.

Sodium-ion batteries (SIBs) are promising alternatives to lithium-ion batteries (LIBs) in view of the natural abundance and low cost of sodium resource. Constructing high-performance anode is essential and challenging for the futuristic SIBs development. Transition metal sulfides have been proved as promising anode materials for SIBs due to their large specific capacities. Here, in situ assembly of cobalt sulfide nanosheets on stainless steel mesh (SSM/CoS) as a binder-free anode for SIBs is carried out through a facile electrochemical deposition procedure. The SSM/CoS products are directly used as anode electrodes without addition of binder and conductive additives. As a result, a high capacity of 313 mAh g−1 is obtained at a current density of 50 mA g−1 over 100 cycles.

Achieving high-stability, long span-life, and fast sodiation reaction kinetics in sodium ion battery (SIB) can significantly promote its practical application. Here, we use freeze-drying and carbonization to prepare a flexible N-doped silk wadding-derived carbon/SnOx@reduced graphene oxide (N-SWC/SnOx@rGO) film as an ultra-stable anode for a half/full SIB. A superior capacity of 572.2 mA h g−1 at 0.1 A g−1 and long span-life over 1000 cycles are obtained in the N-SWC/SnOx@rGO film anodes. Moreover, a super-stable capacity of 245.7 mA h g−1 can be secured in the assembled SIB full cell, outperforming the current studies. After the detailed structural and performance characterization, we attribute these superior capacities to the following unique structural characteristics: 1) SnOx nanoparticles (

The as-cast Mg-Ni alloy with nominal component Mg-10 wt%Ni (Mg10Ni) is successively modified based on the internal refinement by melt-spinning and external decoration through surface catalysis. The isothermal hydrogenation kinetics, absorption/desorption thermodynamics, hysteresis and non-isothermal desorption of modified Mg-rich alloys are investigated in this work. The results of modification indicate that the alloying and refinement microstructure are the foundation for high capacity and rapid kinetics. The active surface is the precondition to achieve the above-mentioned process. MWCNTs especially MWCNTs coupling with TiF3 can easily activate the Mg-10 wt%Ni alloy and promote rapid absorption/desorption kinetics by H2 dissociation and H-atoms auxiliary diffusion. Mg-rich Mg-Ni alloy after internal refinement and external decoration with MWCNTs and TiF3 possesses superior thermodynamics and hysteresis. As high as 5.5 wt% hydrogen can be rapidly absorbed within 60 s and the endothermic peak is around 374 °C, which shifts toward low temperature as high as ∼75 °C than that of Mg-10 wt%Ni alloy without any catalysts. It is the synergistic catalytic effect originated from the assisted diffusion of MWCNTs and the surface spillover special effects of TiF3 that promote the outstanding thermodynamics and hysteresis for Mg10Ni-MWCNTs-TiF3.

In this work, La-doped Mg-Ni multiphase alloys were prepared by resistance melting furnace (RMF) and then modified by high-energy ball milling (HEBM). The hydrolysis H2 generation kinetics/thermodynamics of prepared alloys in NaCl solutions have been investigated with the help of nonlinear and linear fitting by Avrami-Erofeev and Arrhenius equations. Combining the microstructure information before and after hydrolysis and thermodynamics fitting results, the hydrolysis H2 generation mechanism based on nucleation & growth has been elaborated. The final H2 generation capacities of 0La, 5La, 10La and 15 La alloys are 677, 653, 641 and 770 mL·g − 1 H2 in 240 min at 291 K, respectively. While, the final H2 generation capacities of HEBM 0La, 5La, 10La and 15 La alloys are 632, 824, 611 and 653 mL·g − 1 H2 in 20 min at 291 K, respectively. The as-cast 15La alloy and HEMB 5La alloy present the best H2 production rates and final H2 production capacities, especially the HEBM 5La can rapidly achieve high H2 generation capacity (670 and 824 mL·g − 1 H2) at low temperature (291 K) within short time (5 and 20 min). The difference between the H2 generation capacities is mainly originated from the initial nucleation rate of Mg(OH)2 and the subsequent processes affected by the microstructures and phase compositions of the hydrolysis alloys. Relative low initial nucleation rate and fully growth of Mg(OH)2 nucleus are the premise of high H2 generation capacity due to the hydrolysis H2 generation process consisted by the nucleation, growth and contacting of Mg(OH)2 nucleus. To utilization H2 by designing solid state H2 generators using optimized Mg-based alloys is expected to be a feasible H2 generation strategy at the moment.

Mg alloys hydrolysis is considered as an environmentally friendly and efficient hydrogen production method. In this work, residuary industrial Mg alloy waste (IMAW) employed in hydrolysis process is creative and meaningful to promote ‘Green hydrogen’ strategy. To explore proper hydrolysis systems and effective modification ways, various IMAW and the short-term ball-milling effect are systematically investigated. To achieve rapid initial kinetic and high hydrogen capacity, (Mg10Ni90)Ce10 (MNC) is firstly introduced to further modify AZ91D and ZK60. The microstructure evolution, thermodynamic behavior and modified mechanism are investigated to analyze the role of MNC in hydrolysis process. AZ91D and ZK60 attle after activated by MNC obtain 0.81 and 0.56 H2 yield in initial 2 min, higher than samples without MNC (0.56 and 0.04). Meanwhile, the maximum hydrogen generation rates can reach 340.9 and 262.8 mL·g−1·min−1. The hydrolysate morphologies of IMAW before and after activation are confirmed to change from dense and continuous to loose and granular, and the Ea are greatly reduced. The modified mechanism based on the micro-local temperature acceleration is proposed and elaborated. IMAW modified by MNC achieves a green and effective H2 generation process, which can pave way for portable hydrogen generators and industrial hydrogen generation system.

Graphene with antidots shows great potential in wearable devices and highly sensitive sensors. In this paper, we fabricated the patterned graphenes of circle, square, and triangle by ultrafast laser processing. The given patterned graphene can precisely detect one specific gas from the CO/NO/H2O-mixed gases. The sensing performance results demonstrated that the circle patterned graphene (cir-graphene) was most sensitive to CO with the highest sensitivity with the gauge factor (GF) of 3.9 × 104. For NO sensing, the triangle patterned graphene (tri-graphene) conducted the best results. The square patterned graphene (squ-graphene) was the most sensitive to H2O. The DFT calculations revealed that CO was chemical adsorbed on cir-graphene with the most negative adsorption energy (−3.638 eV). For NO sensing, tri-graphene performed best. While, the patterned graphene was not available to H2O sensing. This work offers a novel solution to next-generation wearable multifunctional sensors, and a new insight for the selective sensing mechanism.

In this work, we prepared flexible carbon-fiber/semimetal Bi nanosheet arrays from solvothermal-synthesized carbon-fiber/Bi2O2CO3 nanosheet arrays via a reductive calcination process. The flexible carbon-fiber/semimetal Bi nanosheet arrays can function as photocatalysts and photoelectrocatalysts for 2,4-dinitorphenol oxidation. Compared with carbon-fiber/Bi2O2CO3 nanosheet arrays, the newly designed flexible carbon-fiber/semimetal Bi nanosheet arrays show enhanced ultraviolet-visible (UV-vis) light absorption efficiency and photocurrent, photocatalytic, and photoelectrocatalytic activities. Photocatalytic analyses indicate that the surface plasmon resonance (SPR) of semimetal Bi occurs under solar-simulated light irradiation during the photocatalytic process. The carbon-fiber traps the hot electrons exerted from the SPR of semimetal Bi and creates holes in the semimetal Bi nanosheets, which boosts the photocatalytic activity of the carbon fiber through plasmonic sensitization. Both photocatalytic experiments and density functional theory (DFT) calculations indicate that the electrons transferred to the carbon fiber and the holes created in semimetal Bi contribute to the formation of •O2- and •OH, respectively. The synergistic effect between electrocatalysis and photocatalysis under the solar-simulated light results in almost complete degradation of 2,4-dinitorphenol during the photoelectrocatalytic process. This work realizes a non-noble-metal plasmonic catalyst and provides a new avenue for the commercialization of photocatalysis and photoelectrocatalysis using the separable and recyclable carbon-fiber/semimetal Bi nanosheet arrays in the environment-related field.

Adding fiber can improve the brittleness of plain concrete. Compared with plain concrete, basalt fiber-reinforced concrete has the advantages of strengthening, toughening, and crack resistance. Compared with steel fiber-reinforced concrete, basalt fiber-reinforced concrete has better construction performance. Basalt fiber concrete is a type of inorganic material with environmental protection and high mechanical properties, which has an important mechanical advantage for controlling the deformation of the soft surrounding rock tunnel. Through the indoor model test of mechanical behavior of reinforced concrete and basalt fiber-reinforced concrete lining, the bearing characteristics of basalt fiber-reinforced concrete lining was studied. The results show that, compared with reinforced concrete, the initial crack load of basalt fiber-reinforced concrete is increased by 20%; the toughness of lining structure is enhanced by adding basalt fiber, and the lining can still bear large bending moment and deformation after the initial crack appears; after the initial crack appears, the bearing characteristic curve of reinforced concrete lining rises slowly and converges rapidly; the bearing characteristic curve of basalt fiber-reinforced concrete lining rises slowly, and there is no sign of convergence when it reaches 2 times of initial crack load. For the soft surrounding rock tunnel, it is necessary to seal the rock surface as early as possible, provide support as soon as possible, and have a certain deformation capacity. Basalt fiber-reinforced concrete can better meet these needs.

Sn-based materials show great potentials as sodium-ion battery (SIB) anodes. However, limited to the preparation process and expensive raw materials, it is a great challenge to large-scale produce self-standing Sn-based materials. Herein, we develop a cost-effective and large-scale production method to fabricate flexible B4C/Sn/acetylene black@reduced graphene oxide (B4C/Sn/AB@rGO) films as self-standing SIB anodes by using high energy ball milling technology and self-standing process. In the film, the coated B4C acts as a conductor to enhance the internal conductivity and AB is used as a shell of B4C/Sn to accelerate the absorption of electrolyte solution, while rGO plays a role as a tie to connect B4C/Sn/AB units to accelerate the electronic transmission and simultaneously alleviate the volume expansion during the charge/discharge process. Finally, the B4C/Sn/AB@rGO films as the SIB anodes deliver a high reversible capacity of 393.4 mA h g−1 at 0.1 A g−1 and excellent cycling stability at 1 A g−1 with the reversible capacity of 155.5 mA h g−1 over 500 cycles. Moreover, the assembled sodium-ion full cell shows a stable capacity at 201.5 mA h g−1 for 50 cycles at 0.1 A g−1. This study indicates that our synthetic B4C/Sn/AB@rGO film has a great potential as the self-standing SIB anode.

Hybrid Mg/Li-ion Batteries (MLIBs) combine both the advantages of fast alkali metal ions intercalation cathode and dendrite-free Mg anode that exhibits satisfactory electrochemical performance. However, achieving superior comprehensive battery performance is still a main challenge for MLIBs. Novel hollow opening nanoflower MoS2-CuS-EG (HONF-MoS2-CuS-EG) cathode with unique structure as MLIBs cathode was firstly fabricated via a facile hydrothermal method and superior comprehensive electrochemical performances are presented. Constructed by increased interlayer distance MoS2, metallic-like conductivity CuS and superior electrical conductivity EG, high discharge capacity and superior rate performance are demonstrated by HONF-MoS2-CuS-EG electrode. The volume expansion/contraction during charge-discharge cycles can be effectively buffered by EG and superior cycle stability. The discharge capacity at 10th cycle is as high as 240.6 mAh·g−1, which increases over the 1st cycle by 8.6% at 50 mA·g−1. The discharge capacities at 200 and 1000 mA·g−1 are 201.4 and 117.5 mAh·g−1. The capacity retention rates after 100 cycles (172.4 mAh·g−1) and 200 cycles (73.5 mAh·g−1) for HONF-MoS2-CuS-EG electrode at 50 mA·g−1 are 47.43% and 22.22%, which are much higher than those of hollow close nanoflower MoS2 (HCNF-MoS2) cathode (2.81% and 1.95%). As high as 262.5 mAh·g−1 discharge capacity with 91.6% capacity retention of HONF-MoS2-CuS-EG at 500 mA·g−1 and 150 cycles is presented, indicating that increasing current density is favor to cycle performance of HONF-MoS2-CuS-EG cathode. The electrochemical mechanism of HONF-MoS2-CuS-EG electrode in MLIBs is also elaborated. This work provides a practical approach to construct advanced MoS2-based cathode materials for MLIBs.

MgH2-M (M = MWCNTs or TiF3 or both of them) composites prepared by high-energy ball milling (HEBM) are used in this work to illustrate the effect of catalysts on isothermal activation, thermodynamic and hysteresis of MgH2 hydrides. The phase compositions, microstructures, particle morphologies and distributions of MgH2 with catalysts have been evaluated. The isothermal synergetic catalytic-activation and dehydrogenation effect of MWCNTs and TiF3 evaluated by P-C-T give the evidences that the addition of catalysts is an effective strategy to destabilize MgH2 and reduce the dehydrogenation temperatures. The isothermal activation process can be remarkly accelerated by adding MWCNTs or TiF3. It's worthnoting that fast initial absorption rate and high hydrogenation capacity are obtained for modified MgH2 when adding MWCNTs coupling with TiF3 and no special activation treatment is needed. The activation effect is mainly attributed to the large contraction/expansion stresses caused by accelerated catalytic desorption/absorption cycles. The catalytic effect on thermodynamic is mainly attributed to electronic exchange reactions with hydrogen molecules during the dissociation-absorption or recombination-desorption process. The thermodynamic hysteresis of catalyzed MgH2 is also investigated to evaluate the energy consumption and estimate the efficiency of the isothermal hydrogen absorption/desorption process. A probable synergetic catalytic-activation mechanism is probed.

Porous media has a significant effect on flame and overpressure of methane explosion. In this paper, the pore diameter and thickness of porous media are studied. Nine experimental combinations of different pore diameter and thickness on the propagation of flame and overpressure of methane explosion in a tube are analyzed. The results show that the porous media not only can suppress the explosive flame propagation, but the porous media with large pore diameter can cause deflagration and accelerate the transition of flame from laminar to turbulent. The pore diameter of the porous media mainly determines the quenching of the flame. Simply increasing the thickness of porous media may cause the flame to temporarily stop propagating, but the flame is not completely extinguished for larger pore diameter. However, the deflagration propagation speed of flame is affected by the thickness. The attenuation of overpressure by porous media is mainly reflected in reducing the duration of overpressure and the peak value of overpressure. The smaller the pore diameter, the greater the thickness, and the more remarkable the reduction in overpressure duration and peak value. Suitable pore diameter and thickness of porous media can effectively suppress flame propagation and reduce the maximum value and duration of overpressure.

Ultrathin SnS2 layers with high theoretical specific capacity displays promising advantages as an anode in sodium storage systems. However, their poor conductivity and large capacity loss during charging/discharging process are urgently needed to be addressed. Herein, an exotic hierarchical SnS2/carbon nanotube@reduced graphene oxide (SnS2/CNT@rGO) composite has been designed and developed to be an anode for sodium-ion batteries. Functionally, the CNT penetrates into the petals of SnS2 micro-flowers to increase the conductivity of SnS2, while the three-dimensional rGO wraps around the SnS2/CNT composite to relieve the volume expansion of SnS2 during the charging/discharging process and construct “rGO conductive bridge” to accelerate electrode reaction kinetics. Benefiting from these exotic functionalization, the SnS2/CNT@rGO anode possesses excellent reversible capacity and superior cycling stability with a high reversible capacity of 528 mA h g−1 at 50 mA g−1 and a retained capacity of 301 mA h g−1 after 1000 cycles at 1 A g−1, which are better than most of the previously reported Sn-based and carbon-based anode materials. This study offers a promising strategy for significantly improving the cycling stability in the ultra-stable electrode materials in sodium-ion batteries.

In this study, a metastable microstructure composed of the single B2 phase was produced in Ti-40Al-8Nb (at. %) alloys by water quenching from 1400 °C. After annealing the fully-B2 microstructure at 1000 °C for 600 min, a refined microstructure composed of α2, γ and B2 phases was obtained. Detailed analysis demonstrated that both the lath-liked coherent α2 phase and equiaxed incoherent α2 phase formed in the B2 matrix within a short time. During the subsequent tempering process, nanoscale γ lamellar precipitated from the coherent α2 phase. Due to the large stored energy in the ultra-thin lamellar structures, the recrystallization of the γ phase happened, resulting in the globalization of the lamellar structures. Besides, γ twins also formed in the B2 matrix by following the Kurdjumov-Sachs (K-S) orientation relationships. With the increase of isothermal holding time, the coarsening of the α2 and γ phases occurred, leading to a refined microstructure with the average grain size of 2 μm.

In the present paper, we have investigated the tribological properties and microstructure of the used gear oil theoretically and experimentally. The deterioration process of the in-service gear lubricant oils was also discussed. The viscosity and microstructure of oils running different mileages were analyzed by viscometer and Fourier Transform Infrared Spectroscopy (FTIR), respectively. In addition, the friction and wear behaviors of the friction pair of the GCr15 steel ball and disc were investigated using a ball on disc tribometer under different mileages’ gear oils lubrication conditions. These techniques give reproducible and reliable data with which to evaluate the severity of deterioration process of oils. The objective of this work is to understand the deterioration process of gear oil and analyze the influence of deterioration on the performance and microstructure of lubricant oils used in gear box. Possible explanations of deterioration process as well as its influence on friction and wear behaviors are also discussed. The results reveals the tribological properties of used oils depended on strongly the microstructure and its deterioration process of oil.

The mechanism of graphene growth under rapid growth is yet unknown, limiting the industrialization proceeding of graphene application. In this paper, the heat conduction and solute migration are researched by the real-time observation and theorical calculation for further understand the mechanism of rapid growth of graphene by high-power laser fabrication. The highest temperature is 1832 K recorded by infrared thermography and 1905 K calculated by Fourier’s second law. The carbon source is delivered in the liquid state with high diffusion rate. It only takes 3.065 s to complete the growth of graphene. This work will offer an engineering solution to fabricate high-quality and large-area graphene.

Potassium-ion batteries (KIBs) have been considered as a promising alternative to lithium-ion batteries (LIBs) due to the diffusely distributed and low-cost potassium resources and high operating voltage. However, achieving satisfactory battery performance is still a main challenge for KIBs development. Here, ultrathin metallic cobalt selenide (CoSe2) nanosheets are successfully assembled onto three-dimensional nitrogen doped carbon foam (CSNS/NCF) bridged by Co-C and Co-N-C bonds as a flexible core/sheath framework for potassium storage. The CSNS/NCF not only features with large surface area for sufficient contact with electrolyte with fast electrons and K ions diffusion but also provides a robust network with strong chemical bonds for stable potassium storage. Density functional theory (DFT) calculations show that the barrier for K atom migration in ultrathin CoSe2 nanosheets is lower than that in bulk CoSe2. Benefiting from the above advantages, the optimized CSNS/NCF displays a high specific capacity of 335 mAh g−1 after 200 cycles at 50 mA g−1. This work provides a practical approach to construct advanced anode materials for KIBs systems.

Carbon nanotube/graphene foam/silicon carbide (CNT/GF/SiC) composites are prepared by in-situ growth of CNT in GF and followed by infiltration and pyrolysis of CNT-dispersed polycarbosilane. Results show that the CNT/GF/SiC composites exhibit outstanding electromagnetic interface (EMI) shielding effectiveness (SE) of 32.1 dB in X-band, especially the specific SE reaches up to 33.8 dB cm3/g with a low density of 0.95 g/cm3. The interconnected conductive graphene network improves the conductivity and sharply increases electric loss; meanwhile, the rich structural defects and multiscale interfaces including GF-CNT interface and CNT-SiC interface offer additional polarization loss, both of which endow composites with outstanding EMI shielding performance.

As-cast (Mg-10Ni)1-x-Lax (x = 0, 5, 10, 15 wt%) ternary Mg-rich alloys with different La contents are successfully prepared by the flux protection melting method. The mechanism of hydrolysis hydrogen generation is investigated in combination with the phase compositions, microstructures, electrochemical properties and hydrolysis hydrogen generation properties. The results show that with the increase of La, the electrochemical activity increase, while the eutectic microstructure decreases. When adding 10 wt% and 15 wt% La, the Mg17La2 active intermediate phase is observed. In corrosive weak acid medium, the (Mg-10Ni)90La10 (10La) alloy presents the best hydrogen generation performance, while in the neutral distilled water medium, the (Mg-10Ni)85La15 (15La) alloy performs well. The initial hydrolysis reaction kinetics of Mg-Ni-La alloys in distilled water is mainly controlled by the electrochemical activity of the alloy. While, it is mainly determined by the mass transfer channels formed in the microstructures when in weak acid medium. The mechanism of hydrolysis hydrogen generation and the controlled hydrolytic hydrogen generation strategy of Mg-Ni-La alloys proposed in this work provide possible technical guidance to prepare Mg-based hydrogen generation alloys with high reaction activity, high hydrogen generation yield and controlled hydrolysis kinetics.

Owing to the rich abundance and low-cost of K resources, potassium-ion batteries (KIBs) have been a promising alternative to lithium-ion batteries (LIBs). The exploration of suitable anode materials is challenging but of great importance for KIBs development. Alloying anodes such as Sn, Sb and their oxides have been proved as promising anode materials for KIBs due to their high specific capacities. Here, Sn nanoparticles uniformly anchored on N doped porous carbon (Sn/NPC) are prepared using simple sol-gel method and heat treatment. As support skeleton, NPC endows Sn/NPC good conductivity and prevent agglomeration of Sn nanoparticles, which can be beneficial for high capability and rate performance. When evaluated as anode of KIBs, enhanced capacity of 198 mAh g−1 is achieved at a current density of 50 mA g−1 after 200 cycles.

By cutting electro-deposited nickel plates at different angles between the rolling planes and the growth plane, we obtained bulk samples with different initial textures. We investigated the microstructures, macrotextures, and microhardness of such samples before and after cold rolling. The results showed that the samples cut at different angles have different initial textures before the cold rolling, and their microstructures changed from isotropic crystals to columnar ones as the cutting angle increased. After cold rolling, the deformed microstructures textures were the same. However, the microhardness of the material was closely related to the cutting angle. As the cutting angle increased, the microhardness decreased significantly. This phenomenon is associated with the dimensional differences between the axial and horizontal directions of the columnar crystal grains of the electro-deposited materials.

Recycle and reuse of the nanosized photocatalysts is a common challenge in the catalyst field. To address this issue, we rationally load meso‑carbon@TiO2 core-shell microspheres on carbon fiber felt to synthesize macro-sized meso‑carbon@TiO2/carbon fiber composites by an in-situ adsorption method. From the detailed microstructural and spectroscopic characterization, it has been found that the absorption edge of meso‑carbon@TiO2 core-shell microspheres is extended to the visible light region, and the recombination of photon-excited electrons and holes can be significantly suppressed when compared with P25 TiO2 powder. The experiment results of meso‑carbon@TiO2/carbon fiber composites indicates that the photocatalytic degradation rate under UV–vis light is much higher than that under visible light irradiation due to the higher charge carrier separation efficiency and the higher electron consumption of the direct Z-scheme. Moreover, the photocurrent density and the separation of photon-excited electrons from holes can be effectively promoted in the photoelectrocatalysis of meso‑carbon@TiO2/carbon fiber composites under visible light. The synergistic effect between electrocatalytic and photocatalytic oxidation under visible light results in almost complete degradation of Rhodamine B. Our study provides an avenue to recycle and reuse nanosized photocatalysts and open a possibility for practical industrial application of photocatalysis and photoelectrocatalysis using separable and recyclable meso‑carbon@TiO2/carbon fiber composites.