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Advanced integrated electrode materials with designed core–shell nanostructure play a crucial role for the application in alternative energy storage system. Herein, hierarchical MoO3@NixCo2x(OH)6x core–shell arrays were equably grown on face of carbon cloth after a series of hydrothermal growth and electrochemical deposition processes. This core–shell arrays structure can not only provide large electroactive surface areas and high speed ion transport paths, but also keep the material structure stable during the process of redox reactions. Thus MoO3@NixCo2x(OH)6x displays excellent electrochemical performance (4.7 F cm−2 at 10 mA cm−2). Moreover, the asymmetric supercapacitor is assembled with MoO3@NixCo2x(OH)6x and carbon nanotubes, which delivers a maximal energy density of 0.50 mWh cm−2 at 4.25 mW cm−2, high specific capacitance and superior cycling stability (94.5% capacitance retention after 5000 cycles). We believe that MoO3@NixCo2x(OH)6x arrays could be a great prospective candidate energy storage materials.

Exploring cost-efficient electrocatalysts for oxygen evolution reaction (OER) is still a huge challenge in the electrochemical energy conversion technology. In this work, Gallium (Ga)-doped Ni3S2 nanosheet arrays grown on Ti3C2-MXene/nickel foam (Ga–Ni3S2/Ti3C2/NF) have been synthesized by a successive hydrothermal and sulfidization process. The Ga doping modulates the electronic structure of Ni3S2, so tuning the adsorption energies of oxygen intermediate (∗OOH). The Ga–Ni3S2/Ti3C2/NF delivers outstanding catalytic activities toward OER with an overpotential of 340 mV at 100 mA cm−2, and exhibits superior electrochemical durability. The excellent OER performance of Ga–Ni3S2/Ti3C2/NF can be ascribed to the 3D sheet arrays morphology and optimized electronic structure. Density functional theory (DFT) calculations also demonstrate that electronic disturbance attributed to Ga doping effectively improves the activity of Ni sites, leading to stronger binding strength of ∗OOH intermediate at Ni sites nearby Ga. This study provides insights into the fabrication of advanced electrocatalysts for application.

In the present work, a phase-field model was developed to investigate the influence of recrystallization on bubble evolution during irradiation. Considering the interaction between bubbles and grain boundary (GB), a set of modified Cahn-Hilliard and Allen-Cahn equations, with field variables and order parameters evolving in space and time, was used in this model. Both the kinetics of recrystallization characterized in experiments and point defects generated during cascade were incorporated in the model. The bubble evolution in recrystallized polycrystalline of U–Mo alloy was also investigated. The simulation results showed that GB with a large area fraction generated by recrystallization accelerates the formation and growth of bubbles. With the formation of new grains, gas atoms are swept and collected by GBs. The simulation results of bubble size and distribution are consistent with the experimental results.

A facile “carbon quantum dots glue” strategy for the fabrication of honeycomb-like carbon quantum dots/nickel sulphide network arrays on Ni foam surface is successfully demonstrated. This design realizes the immobilization of nanosheet arrays and maintains a strong adhesion to the collector, forming a three-dimensional (3D) honeycomb-like architecture. Thanks to the unique structural advantages, the resulting bind-free electrode with high active mass loading of 6.16 mg cm−2 still exhibits a superior specific capacitance of 1130F g−1 at 2 A g−1, and maintains 80% of the initial capacitance even at 10 A g−1 after 3000 cycles. Furthermore, the assembled asymmetrical supercapacitor delivers an energy density of 18.8 Wh kg−1 at a power density of 134 W kg−1, and outstanding cycling stability (100% of initial capacitance retention after 5000 cycles at 5 mA cm−2). These impressive results indicate a new perspective to design various binder-free electrodes for electrochemical energy storage devices.

Heteroatoms doped carbon nanotubes are prepared through a solid-state pyrolytic conversion strategy with low-cost and easy-to-get precursors. The use of inorganic sulfur source makes it possible for sulfur to be effectively introduced, which is found to increase the defective degree in the carbon plane. The defect augment is revealed by systematic physical characterizations to originate from the fact that S atoms get rid of the carbon crystal and diffuse to form bits of sulfides during the heat-treatment process, thus leaving abundant vacant spots and providing access to forming pyridine-N sites. Therefore, more catalytic active sites are exposed and the oxygen reduction reaction (ORR) activity can be improved. Benefiting from the advantages in structure and composition, the resultant catalyst shows a remarkable half-wave potential (0.86 V vs. RHE) and an outstanding durability, superior to that of Pt/C. The zinc-air battery with the resultant catalyst shows high peak power density and excellent rate capability. This work not only develops a facile method to prepare highly active and stable ORR catalyst but also makes deep researches on the activity-enhanced mechanism.

Two-dimensional (2D) electrocatalyst plays an important role in hydrogen production via water splitting. In this work, the first-principles calculation was used to investigate the hydrogen evolution reaction (HER) performance of transition metal (TM) single atom catalysts (SACs) on 2D SnO nanosheets. Among the TM considered (TM = V, Cr, Mn, Fe, Co, Ni, Cu and Pt), V, Fe, Co, Ni, Cu and Pt can effectively improve the catalytic activity of SnO. More importantly, the low-cost Co can exhibit promising HER performance with the Gibbs free energy as low as ~0.015 eV, which is competitive with the precious catalyst Pt. The theoretical exchange current densities of Co SACs can reach ~10−16 A/site. The exciting HER activity is mainly facilitated through the d-d hybridization between the TM and Sn atoms on the SnO surface, which introduces new electron states near the Fermi level. Our work highlights the complexity and diversity of the effect of TM SACs on SnO nanosheets and implies their potential applications as efficient HER electrocatalysts.

Supercapacitors (SCs) are drawing considerable attention because of their remarkable power density, long cycling stability, quick charging/discharging, and environmentally friendly characteristics. They are currently applied in electronic devices and wearable energy storage systems. Recently, the use of asymmetric supercapacitors (ASCs) has been acknowledged as a valid strategy to improve energy density of SCs due to the combination of electric double-layered anodes and redox-schemed cathodes. Here, mesoporous hollow NiCo2S4 sub-microspheres and porous graphene/single-walled carbon nanotubes are synthesized by a simple and elegant method without any use of templates. The as-synthesized products exhibit improved capacitive performance and extraordinary stability. An assembled asymmetric supercapacitor with graphene/single-walled carbon nanotubes and NiCo2S4 as its negative and positive electrodes, respectively, delivers a maximum energy density of 45.3 W h kg−1 (at 800 W kg−1) and an outstanding cycling life (87.5% over 20,000 cycles). This suggests that the obtained products possess huge potential to become the next generation of electrode materials for future energy storage devices.

In this study, a bismuth ferrite (BiFeO3) nanopowder was synthesized by combining Bi(NO3)3·5H2O, Fe(NO3)3·9H2O, and NaOH raw materials in the presence of polyethylene glycol (PEG) with varying polymerization degrees (i.e. PEG200, PEG400, PEG600, and PEG10000). The synthesis process was carried out by room-temperature solid-state reaction followed by subsequent secondary solid-state reaction at 550 °C. The results suggested a significant influence of PEG polymerization degree on the morphology and size of the as-synthesized products. The grain size decreased after the introduction of PEG but increased with the polymerization degree. The vibrating-sample magnetometry data revealed PEG400 and PEG600 with obvious room-temperature ferromagnetism properties. In UV–Vis spectroscopy, the absorption edge exhibited a blue shift as the polymerization degree of PEG rose. In sum, BiFeO3 nanopowder possessed room-temperature ferromagnetism, thereby suitable photocatalyst for wastewater treatment and environmental purification with convenient recycling and substantial economic value.

Hydrazone organic compounds with a strong conjugation effect have superior characteristics, such as high nonlinear optical sensitivity, short response times, a unique electronic spectrum, and photothermal stability. The conjugated structure of hydrazone compounds leads to its strong dispersion and molecular polarization, and its strong dispersion affects the mutual interference of dispersion wave radiation in a fiber. However, the application of π electron conjugated structures in ultrafast photonics has not been fully studied. Here, nonlinear optical modulation is demonstrated via preparing a set of hydrazone compounds for a mode-locking laser. We applied Hydrazone-1 to an erbium-doped fiber laser, and a 922 fs traditional soliton mode-locked pulse was obtained. Under these conditions, we systematically explained the complex spectral sidebands in which valley sidebands and peak sidebands coexist. Furthermore, a pulse of five bound-state soliton molecules was obtained for the first time. The experiments have proved that hydrazone organic compounds have strong optical properties, which could promote their development as ultrashort pulse light sources upon further research and exploration.

Hierarchical nanosheet-based MoS2–NiS nanotubes coated with N-doped carbon (MNS-HNT@NC) composites were fabricated using a template-assisted hydrothermal and post-sulfidation strategy. The composite, with a tube-like structure, is mainly constructed by ultrathin MoS2–NiS nanosheets. Such hierarchical nanosheet-based nanotubes possess high surface-to-volume ratios, which can release mechanical stress during Na ion insertion/extraction and shorten the pathways for Na ion/electron transport. Furthermore, the internal void space in the nanotube can effectively accommodate the large volume change of the electrode, thereby alleviating structural collapse of the electrode. On the other hand, abundant lattice defects and the internal electric field induced by the heterostructure of MoS2 and NiS boost the Na ion intercalation kinetics. In addition, the MoS2 and NiS nanocrystals uniformly dispersed in the composite can act as mutual spacers, thereby avoiding aggregation during cycling. The MNS-HNT further coated with N-doped carbon can reduce contact resistance and restrict the large volume change, preventing electrode pulverization. Benefiting from these advantages and using an ether-based electrolyte, MNS-HNT@NC, as anode for SIBs, delivers a considerable specific capacity (707 mA h g−1 at 0.1 A g−1), high initial coulombic efficiency of 94%, stable long-term cycling stability (391 mA h g−1 maintained after 700 cycles at 2 A g−1) and superior rate performance (342 mA h g−1 at 10 A g−1).

Gel polymer electrolytes (GPEs) combine the high ionic conductivity of liquid electrolytes and good safety assurance of solid electrolytes. However, the poor interfacial contact between electrode materials and electrolyte is still a big obstacle to the high performance of solid-state batteries. Herein, an integrated cathode/GPE based on continuous composition and preparation technic is obtained by simple UV curing. The improved interfacial contact between cathode and GPE helps to facilitate the fast ions transfer at the interface. Compared with cells assembled with separated cathode and GPE, the cells with integrated cathode-GPE showed much lower interfacial impedance, lower potential polarization and more stable cycling property. This work provided a low-cost natural material gelatin and a simple UV irradiation method to prepare an integrated cathode and gel polymer electrolyte for solid-state lithium batteries. The capacity retention of the cells assembled from integrated structure was 91.4% which was much higher than that of the non-integrated cells (80.9%) after 200 cycles.

In-situ TEM observation and molecular dynamics simulation were used to investigate the evolution of irradiation-induced dislocation loops and their interactions with the pre-existing dislocation lines in molybdenum irradiated by 30 keV He+ at 673 K. The nucleation, annihilation, merging, size change, and types of dislocation loops were investigated in detail, and the hardening effect from dislocation loops was analyzed. With the increase of helium fluence, the volume number density of dislocation loops increased rapidly and then decreased slowly to a saturation value, while the average size of dislocation loops increased continuously until it reached an upper limit. Both 1/2 and loops were formed, with a proportion of 60.2% to 39.8% at 3.95 × 1015 He+.cm−2 (0.07 dpa). The pre-existing dislocation lines would suppress the nucleation and growth of the dislocation loops, while the irradiation-induced dislocation loops had a strong pinning effect on the dislocation lines and impeded their motion. Molecular dynamics simulations were used to clarify the atomistic mechanisms of some major features of the line-loop interactions observed in the in-situ experiment, which showed in a good agreement. The different interaction processes depended on the Burgers vector and plane of the dislocation loop, the motion and reaction kinetics of dislocation segments, and the external loading.

A unique surface-modified rice-starch-based disordered carbon (SRC) was prepared with the intention of improving the electrochemical properties of anodes for Li-ion batteries. The starch’s surface was altered via an enzymatic hydrolysis process, and these changes were retained following a heat treatment process to create a porous surface. Following surface modification, SRC-based anodes exhibited a higher reversible capacity and coulombic efficiency in the first cycle at the same current density when compared with unmodified rice-starch-based disordered carbon (RC). SRC-based electrodes also displayed improved rate capability behavior and cycling performance. Across the measurements performed during this body of work, the electrodes’ performances were improved when (i) the contact area between the SRC particles and the electrolyte was maximized and (ii) the ordering of the particles on the surface was improved. These results indicate that this is a viable approach for the creation of anodes for Li-ion batteries from modified biomass sources.

Lithium iron phosphate (LiFePO4) is one of the most widely used cathode materials of lithium ion batteries. However, its commercial binder polyvinylidene fluoride (PVDF) is costly, less environmental-friendly and unstable during the long cycling process because of the weak van der Waals forces between the PVDF binder and electrode materials. Herein, an aqueous binder was designed using methacrylate-modified gelatin through UV photo-crosslinking. The crosslinked network and specific functional groups (carboxyl and amino) of the gelatin binder are superior in stabilizing the LiFePO4 electrode structure during long cycles by mitigating the formation of cracks and suppressing the detachment of electrode materials from the Al current collector. The LiFePO4 electrode with gelatin binder displays a high capacity of 140.3 mA h g−1 with 90.1% retention after 300 cycles at 0.5C, which are both superior to that of the PVDF binder (only 114.4 mA h g−1 and 74.8%). This work provides a promising binder to replace the commercial PVDF binder for practical application in energy storage systems.

For realizing two-dimensional (2D) spintronic devices, controllable manipulation of different spin channels is needed. In order to achieve this goal, the materials should have well-separated spin energies induced by spin–orbit coupling (SOC). However, a negligible SOC effect in 2D SnO limits its application in this prospect. Herein, we demonstrate that the stable Janus structure of SnPbO2 can exhibit large spin splitting (67 meV) at the valence band maximum (VBM) due to the breakdown of inverse symmetry. This spin splitting is larger than the thermal fluctuation at room temperature as well as some other 2D systems. In addition, the splitting can be further enhanced by strains (82 meV) or hole doping (147 meV). More importantly, there are no other electronic states except for the Rashba states at the VBM, which make it ideal for practical applications. Our study provides alternative ways to regulate the electronic structure of SnO and the feasibility for spin manipulation in this interesting 2D system.

A novel tri-component hybrid, Pt/pyridine ionic liquid polyoxometalate/reduced graphene oxide denoted as Pt/(epy)3PMo12O40/rGO with well-dispersed, smaller size Pt nanoparticles on rGO is successfully synthesized. The morphology, structure, composition and electrochemical property are characterized by high resolution transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, energy dispersive spectrometer, Raman spectra, thermogravimetric analysis and cyclic voltammetry, respectively. Ionic liquid polyoxometalate (epy)3PMo12O40 availably prevents the aggregations of Pt nanoparticles on the rGO surface, furthermore, effectively improves anti CO poisoning performance and enhances the conductivity of the material. The mass activity of as-prepared Pt/(epy)3PMo12O40/rGO catalyst for methanol oxidation is about 10 times of 20% commercial platinum carbon, 7 times of Pt/rGO, 4 times of Pt/epyBr/rGO, and 2 times of Pt/H3PMo12O40/rGO. This further demonstrates that the ionic liquid polyoxometalate (epy)3PMo12O40 play a very important role in enhancing the eletrocatalytic activity of the tri-component hybrid composite catalyst.

The development of a low-cost and durable non-precious metal-based electrocatalyst for the hydrogen evolution reaction (HER) is important to realize highly efficient overall water splitting. Here, we report the design and fabrication of a binder-free electrocatalyst of three-dimensional macroporous ditungsten carbide (W2C) inverse opal (W2C IO) arrays by a facile thermal carburization process with WO3 IO as a template. The as-fabricated W2C IO exhibits superior electrocatalytic performance in 0.5 M H2SO4 solution in terms of a low overpotential of 146 mV to reach a current density of 10 mA cm−2, a low Tafel slope of 78 mV dec−1 and excellent long-term stability. The superior performance can be attributed to the favorable electronic structure and hydrogen adsorption Gibbs free energy of W2C evidenced by theory calculations and the enhancement of the charge/mass transfer process by the 3D macroporous arrayed electrode design.

The manipulation of valley splitting has potential applications in valleytronics, which lacks in pristine two-dimensional (2D) InSe. Here, we demonstrate that valley physics in InSe can be activated via the magnetic proximity effect exerted by ferromagnetic FeI2 substrate with spin-orbit coupling. The valley splitting energy can reach 48 meV, corresponding to a magnetic exchange field of ~800 T. The system also presents magnetic anisotropy behavior with its easy magnetization axis tunable from in-plane to out-of-plane by the stacking configurations and biaxial tensile strain. The d-orbital-resolved magnetic anisotropic energy contributions indicate that the tensile strain effect arises from the increase of hybridization between minority Fe dxy and dx2&minus, y2 states. Our results reveal that the magnetic proximity effect is an effective approach to stimulate the valley properties in InSe to extend its spintronic applications, which is expected to be feasible in other group-III monochalcogenides.

The exploration of electrocatalysts with high performance of hydrogen evolution reaction (HER) in all media is essential for developing clean energies. Single-atom catalysts (SACs) have attracted wide attentions owing to their maximum atom utilization and excellent catalytic activity. In this work, the HER activities of transition metal (TM) (TM=Fe, Co, Ni and Cu) SACs on two-dimensional SnO monolayer are studied using density functional theory. We found that the low-cost TM SACs can exhibit high HER activity in wide pH-range. Especially, Co SACs show promising catalytic activity with the Gibbs free energy of hydrogen adsorption ( Δ G H ∗ ) as low as ∼0.015 eV, which are also high active in either acidic or alkaline environments. With the experimentally inevitable oxygen vacancies in SnO, the Δ G H ∗ of Co, Ni and Cu SACs are almost zero, which are competitive with the precious catalyst Pt(111) (-0.09 eV). The exceptional HER activity is correlated to the enhanced electron states close to the Fermi level as well as the d-band center positions of the TM. Our work opens new avenues for engineering low-cost TM SACs with pH-universal HER performance, which is of great importance in practical applications.

A NiS-MoS2@N-doped carbon (HH-NMS@NC) composite is fabricated by sacrificial template, self-assembly, and post-sulfidation strategy. The NiS nanoparticles are uniformly anchored on MoS2/NC nanosheets to construct a hierarchical hollow structure, which can shorten the electrons/ions transport pathway, facilitate electrolyte infiltration, and thus enhance the electrochemical kinetics. Furthermore, the N-doped carbon coating can significantly improve the electrical conductivity and prevent the electrode pulverization during cycling due to effectively restricting the large volume change of metal sulfides. In addition, mixed metal sulfides show an intrinsic synergistic effect for enhancing sodium storage compared to single-component metal sulfides. Given these advantages, HH-NMS@NC as anode for Na-ion batteries exhibits enhanced electrochemical performance. Specifically, HH-NMS@NC can deliver an initial discharge of 488 mAh g−1 and 311 mAh g−1 retained after 700 cycles at 1 A g−1, corresponding to 0.064% capacity decay per cycle. Furthermore, it shows a superior rate capability of 377 mAh g−1 at 8 A g−1.

Two-dimensional ferromagnetic semiconductors hold great promise for next-generation spintronic applications. However, candidates with high Curie temperature (Tc) are still lacking. Using the first-principles calculations, the PtBr3 monolayer is found to exhibit ferromagnetic order above the room temperature. The formation of PtBr3/WSe2 van der Waals heterostructures can increase the Tc to ∼ 410 K by additional super-exchange path of Pt-Se-Pt. The spin-exchange interactions for this path is as strong as ∼ 22 meV, which is superior to most other magnetic system. The out-of-plane compression further boosts the Tc to ∼ 636 K. The interlayer magnetic coupling is highly tunable depending on the stacking alignment, which closes or weakens some super-exchange channels. In addition, the interlayer interaction leads to a phase transition from half-metal to semiconductor, which greatly promotes its potential in spintronic applications. The strong stacking dependent feature is feasible to manipulate the magnetic orders by external strain or mechanical motion.

A facile strategy has been developed to realize the controllable synthesis of two dimensional (2D) single crystalline ZnCo2O4 nanosheet arrays (h-ZCO NSs) on the Ni foam surface. According to the SEM, TEM and BET analysis, it was found that the h-ZCO NSs have a hexagonal structure with a thickness of ca. 84 nm, and display a high specific surface area of 94.1 m2 g–1 with the pore size distribution of ca. 8 nm. As electrochemical capacitor electrode, h-ZCO NSs show large specific capacitance (1004.9 F g−1 at 3.3 A g–1), good rate capability and excellent cycling stability (93.5% capacitance retention after 2000 cycles at 10.0 A g–1), indicating better electrochemical performance. Additionally, serving as a gas sensor, h-ZCO NSs also exhibit remarkable sensitivity and selectivity towards methanol gas. All these impressive performances suggest that the h-ZCO NSs are a promising electrode material for electrochemical capacitors and gas sensors.

This work focuses on mechanism of heat generation in an agitating drum with dense gas-solid flow where particles move at high velocity (30 m/s). Numerical simulations and experiments are used to study the influence of granular flow characteristics, design parameters, process parameters and particle properties in heat generation and energy-conversion coefficient. Heat generates from sliding friction, rolling friction, viscous force of liquid-bridge or the modeled particle deformation. The variable goes to liquid volume due to high temperature (533 K) in wet particle flows. Concerning the velocity and particle motion several thermal transfer models are modified to match particle/particle and particle-wall/blade collisions, which are integrated to DEM-CFD numerical simulation. Experiments detected the temperature of external drum wall, the effect of temperature on liquid phase and the granular motion by visualization tests. The numerical results are verified by experimental data with good agreements. The effects of agitating speed and initial filling degree on temperature increase are not always in positive correlation, which are more significant in wet particles flow. Numerical simulations predicted the dynamic particles characteristic, the heat resources and the thermal conduction to reveal the heat generating mechanisms. Besides, the improved blades design to enhance heat generation is analyzed qualitatively and deduced.

The composites of N-doped ordered mesoporous carbon (N-CMK-3) anchored with tin disulfide (SnS2) nanosheets (NSs) have been synthesized via a maneuverable hot bath method at low temperature. The as-synthesized SnS2@N-CMK-3 composites exhibit a hierarchical structure with two dimensional (2D) SnS2 nanosheets uniformly grown on N-CMK-3, leading to a large specific area (126.7 m2 g−1) with mesoscale porosity. As anode material for lithium ion batteries (LIBs), SnS2@N-CMK-3 composite exhibits a high initial capacity of 1438.9 mA h g−1 (200 mA g−1). Moreover, the electrochemical performance remained at 618.9 mA h g−1 after 200 cycles, which are significantly higher than that of the pristine SnS2. The outstanding electrochemical properties might be due to the 2D nanosheet-morphology feature of SnS2 and the addition of N-CMK-3 that could availably inhibit the agglomeration of active substances and raise the conductivity of the composite electrode.

Structural failure of polyaniline (PANI) stemmed from repeated swelling-shrinkage during Faradic process represents an imminent issue hindering the real application of this material for advanced energy storage. Herein, we explore a clean and facile hydrogel-mediated layer-by-layer strategy to conformally coat a layer of oriented PANI nanofibers on multi-walled carbon nanotubes (MWCNTs) where a layer of UV-polymerized poly(acrylic acid) (PAA) hydrogel is first formed in between as electrodes for supercapacitors. Such an intriguing core-shell tri-component structure perfectly alleviates the drawbacks of PANI as well as combines the advantages of MWCNTs. Especially, the hydrogel used increases the adhesion between PANI and MWCNTs, buffers the structural variation of PANI during cycling, and provide extra driving force accelerating electrolyte penetration throughout active materials. Therefore, the well-intergrown hybrids (PANI/P-MWCNT) display high electrochemical performance as compared to PANI and PANI/MWCNT, i.e., an improved capacitance of 612.5 F g–1 at 0.5 A g–1, and excellent cycling behavior of 81.5% capacitance retention at 5 A g–1 over 1500 cycles. Also, the maximum energy density of the PANI/P-MWCNT based symmetric configuration reaches 8.2 Wh kg–1. Significantly, such a hydrogel-bridged design concept may find the important application for the synthesis of competitive candidates for energy storage.

Transition metal sulfide compounds with carbon materials are promising for high-performance supercapacitors. Carbon nanofibers (CNFs) wrapped with NiS nanoparticles were herein obtained through electrospinning and calcination. NiS nanoparticles in composite nanofibers are covered by a layer of graphitic carbon, which not only increase the conductivity but also provide active regions for nanoparticle growth to prevent aggregation. The CNFs-NiS electrode has high specific capacity of 177.1 mAh g −1 at 1 A g −1 (0.41 mAh cm −2 at a current density of 2.3 mA cm −2 ) and long-term cycling stability, with 88.7% capacitance retention after 5000 cycles. The excellent electrochemical activity may be attributed to the accessible specific surface, unique porous structure of CNFs and high specific capacitance of NiS. In addition, the asymmetric supercapacitor has an enhanced volumetric energy density of 13.32 mWh cm −3 at a volumetric power density of 180 mW cm −3 and high cycling stability, with 89.5% capacitance retention after 5000 cycles. It also successfully lights up a light-emitting diode. The CNFs-NiS composite has significant potential applications in supercapacitor.

Hollow and core–shell particles are currently attracting global attention because of their special properties. We herein proposed a facile self-sacrificial template strategy for the synthesis of cobalt tetraoxide (Co3O4) with hollow and core–shell nanostructures. Starting with metal formate framework (MFF) template [CH3NH3][Co(HCOO)3], a series of core–shell nanostructure MFF@Co(OH)2 microboxes and hollow Co(OH)2-H were successfully obtained through a reaction between the MFF template and sodium hydroxide (NaOH) combined with different washing processes. Finally, hollow and core–shell nanostructure Co3O4 products were obtained after calcination, which inherited the structures from corresponding precursors. In addition, the formation processes of hollow and core–shell nanostructures were studied. Moreover, the catalytic activity of the as-obtained Co3O4 for carbon monoxide (CO) oxidation was investigated. Such hollow and core–shell nanostructures gave different physiochemical properties. Hollow structure C...

Coal-based multiscale porous carbon materials (CPCs) have been successfully fabricated through a friendly method with NaCl, Na2CO3, and Na2SiO3 as structural templates, instead of alkali activation...

Lithium-sulfur batteries have several disadvantages, such as intrinsic insulation of sulfur and Li 2 S, large volume expansion, and inevitable shuttle effect, which lead to low utilization of active materials and rapid capacity decay. Herein, leaf-like interconnected network structure of MWCNT/Co 9 S 8 was synthesized by a simple hydrothermal method. The MWCNT/Co 9 S 8 /S delivers a high specific capacity and good cycling stability. The initial discharge capacity of MWCNT/Co 9 S 8 /S is 1124 mAh g −1 and retains at 503 mAh g −1 after 100 cycles at 0.1 C. The improved electrochemical performance of MWCNT/Co 9 S 8 /S could be attributed to the interconnected network MWCNT and polar Co 9 S 8 . As conductive skeletons, the interconnected network structure of MWCNT midribs provide fast conduction paths for electron and additional space for volume expansion of sulfur. Furthermore, sulfur particles well-distributed on the MWCNT/Co 9 S 8 scaffold facilitate Li + ions storage and release for energy delivery, which is beneficial to excellent activation of sulfur and high rate capacity. In addition, the polar Co 9 S 8 leaves provide strong binding sites to trap polar polysulfide intermediates, which can suppress the shuttle effect effectively.

Cobalt-based, nitrogen-doped porous carbon materials with in situ grown carbon nanotubes (CNTs) were synthesized by the facile carbonization of porous 3D Bio-MOF-11 [Co2(ad)2(CH3COO)2]·2DMF·0.5H2O (ad = adenine). Co-N/PC@CNT-Ts inherit the octahedral shape from the precursor, and have a porous structure with in situ grown CNTs catalyzed by Co particles. Co-N/PC@CNT-T materials have excellent activities as bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in 0.1 M KOH electrolyte. Among the Co-N/PC@CNT-Ts, Co-N/PC@CNT-700 has the highest electrocatalytic activity. For ORR, Co-N/PC@CNT-700 has a higher onset potential of 0.92 V vs. reversible hydrogen electrode (RHE), high stability and methanol tolerance, which are even better than that of Pt/C. For OER, it has a low potential of 1.63 V at a current density of 10 mA cm-2. In addition, Co-N/PC@CNT-700 affords a low reversible overvoltage (bifunctional performance parameter) of 0.862 V between ORR and OER compared to the current advancing bifunctional catalysts. The superb bifunctional activity can be attributed to uniform CoNx active sites embedded in graphitized carbon, unique in situ grown CNT structure and ordered mesoporous structure. The synergistic effect enlarged the contact surface, exposed more active centers and provided many pathways, thereby boosting the electrocatalytic performance. In conclusion, this study provides a novel avenue for the application of stable transition metal-based, nitrogen-doped carbon materials as extremely efficient electrocatalysts for ORR and OER.

Hierarchical mesoporous LiNi1/3Co1/3Mn1/3O2 spheres have been synthesized by urea-assisted solvothermal method with adding Triton X-100. The structure and morphology of the as-prepared materials were analyzed by X-ray diffraction and electron microscope. The results show that the as-prepared samples can be indexed as hexagonal layered structure with hierarchical architecture, and the possible formation mechanism is speculated. When evaluated as cathode material, the hierarchical mesoporous LiNi1/3Co1/3Mn1/3O2 spheres show good electrochemical properties with high initial discharge capacity of 129.9 mAh g−1, and remain the discharge capacity of 95.5 mAh g−1 after 160 cycles at 10C. The excellent electrochemical performance of the as-prepared sample can be attributed to its stable hierarchical mesoporous framework in conjunction with large specific surface, low cation mixing and small particle size. They not only provide a large number of reaction sites for surface or interface reaction, but also shorten the diffusion length of Li+ ions. Meanwhile, the mesoporous spheres composed of nanoparticles can contribute to high rate ability and buffer volume changes during charge/discharge process.

A hydrothermal strategy is developed to realize the controllable synthesis of hexagonal bipyramid α-Fe2O3 microcrystals (HB-α-Fe2O3 MCs) using FeOOH nanorods as precursor. Based on the SEM, TEM and BET analysis, such HB-α-Fe2O3 MCs have a perfect hexagonal bi-pyramid structure with the specific surface area of 78.2 m2 g–1. Formation mechanism of HB-α-Fe2O3 MCs is tentatively proposed by comparative structure-evolution investigations. By virtue of their structural advantages, HB-α-Fe2O3 MCs served as a gas sensor exhibit remarkable sensor response, selectivity, and response/recovery towards ethanol gas. All these impressive performances indicate their appealing application in advanced gas sensors. This well-controllable hexagonal bipyramid microcrystals are opening up an unusual way to fabricate advanced electrodes for sensor, catalyst, and energy-related applications.

In this Letter, we present the excellent negative differential resistance (NDR) characteristics of AlN/GaN double-barrier resonant tunneling diodes (RTDs) in which the active layers are grown by molecular beam epitaxy on thick GaN-on-sapphire templates manufactured by metal-organic chemical vapor deposition. Here, indium flux is introduced as surfactant to reduce the interface roughness and improve the sharpness of heterointerface during epitaxial growth of AlN/GaN/AlN quantum well. The processed device with a top collector diameter of 1 μm size demonstrates a record peak current density of 1039 kA/cm2 while simultaneously featuring a peak-to-valley current ratio of 1.23 at room temperature, excellent achievements among all the reported GaN-based RTDs on any substrates. In addition, no degradation of device performance together with free of hysteresis is observed for the 1000 times consecutive up-to-down voltage sweeps under forward bias. These remarkable achievements are attributed to the marked improvement in heterointerface quality of AlN/GaN/AlN double-barrier quantum well by adopting indium as surfactant during epitaxial growth as clarified by transmission electron microscopy analysis, which dramatically suppresses the interface roughness scattering and elements interdiffusion, thus significantly improving the NDR signatures in current–voltage curves. The obtained results in this work illustrate that indium-surfactant added epitaxy technique turns out to be a promising approach for the modulation of vertical electron resonant tunneling in III-nitride heterostructures and realization of highly reproducible and reliable AlN/GaN double-barrier RTDs, in favor of implementation for future high-power solid-state electronics operating in terahertz spectra.

It is of prime importance to develop anode electrocatalysts for direct methanol fuel cells (DMFCs) with good performance, which is critical for their commercial applications. Metal-organic framework (MOF)-derived carbon materials are extensively developed as supports of catalysts. Herein, Co embedded nitrogen-doped carbon nanotube hollow porous carbon (Co-NCNT-HPC) derived from MOFs have been fabricated, which were synthesized by pyrolyzing at an optimized temperature of 800 °C using ZIF-8@ZIF-67 as a precursor. The presence of ZIF-8@ZIF-67 ensures the doping of nitrogen and the large specific surface area of the support materials at high temperatures. A Pt/Co-NCNT-HPC800 sample, which was synthesized using Co-NCNT-HPC800 as a support, showed an enhanced mass activity of 416.2 mA mg−1Pt for methanol oxidation reaction (MOR), and the onset potential of COad oxidation of 0.51 V, which shifted negatively about 0.13 V compared with Pt/C (20%). Moreover, the Pt/Co-NCNT-HPC800 sample exhibits high stability. This work provides a facile strategy for MOF-derived carbon materials to construct advanced electrocatalysts for MOR.

Two series of the ferrite-based materials have been synthesized for an oxygen evolution reaction (OER) activity screening. Series 1 includes different types of the ferrites: S-type (BaFe2O4), R-type (BaFe4Ti2O11), M-type (BaFe12O19) and tetravalent substituted M-type (BaFe11TiO19, BaFe10Ti2O19). Series 2 consists of a divalent substituted M-type ferrites (BaFe11·9Co0·1O18.95, BaFe11·9Ni0·1O18.95, BaFe11·9Zn0·1O18.96). The thermodynamic and electrokinetic approaches have been used to evaluate the best catalyst from both series of samples. According to the thermodynamics BaFe11·9Ni0·1O18.95 is the most preferable, while according to the kinetics BaFe10Ti2O19 has the best Tafel slope.

Appropriate material is the key to improve the energy and power density of sodium ion batteries. Herein, monoclinic Cu2Se is acquired by a facile one-pot solid method using Cu foil and Se power as the raw materials without use of expensive reagents and sophisticated instruments. Cu2Se exhibits preeminent cycling and rate properties. Concretely, Cu2Se represents reversible capacity of 264 and 241 mAh g−1 at 0.1 and 10 A g−1, as well as high capacity retention of ≈100% over 1000 cycles at 1 A g−1. When Cu2Se is applied as anode to assemble full battery with Na3V2(PO4)2F3@rGO, this battery exhibits a largest energy density of 97 Wh kg−1 (with a power density of 117 W kg−1) and a biggest power density of 1180 W kg−1 (with energy density of 59 Wh kg−1) based on the gross mass of cathode and anode active materials. A combination of ex-situ X-ray diffraction, transition electron microscopy tests and first-principle calculations demonstrate a reversible transformation between Cu2Se and Cu exists in the discharge-charge process. Stable solid-electrolyte interface film, highly infiltrative electrode and capacitive Na + storage behaviours are in favor of the excellent property. The preeminent electrochemical performance indicates that Cu2Se is a highly desirable anode material for high-performance sodium ion batteries.

A series of smulti-heteroatom doped Cu1.8Se/C composites are synthesized through a one-step direct selenization of Cu-based MOF containing hexa(4-carboxyl-phenoxy)-cyclotriphosphazene (HCTP-COOH) ligand. The MOF-derived Cu1.8Se/C composites with nanosheet structures are characterized to be Cu1.8Se nanoparticles embedded in carbon matrix doped with N, P and O atoms. The superior sodium-storage performance of Cu1.8Se/C-450 composite is proven to be resulted from the high specific surface area, the unique structure and the multi-heteroatom doping. The Na-ion half-cells from Cu1.8Se/C-450 electrodes exhibit a maximum capacity of 372.9 mA h g−1 at 50 mA g−1, an satisfactory rate capacity (133.3 mA h g−1 at 5 A g−1) and modest cycling stability. A sodium-ion hybrid capacitor (SHIC) device Cu1.8Se/C-450//AC assembled with Cu1.8Se/C-450 and AC shows desirable energy-storage properties. It delivers a maximum energy density of 65.8 W h kg−1 at 81.4 kW kg−1, and a capacity retention of 75.3% with 3000 testing cycles at 2 A g−1 with the operation voltage window of 0–4.0 V. The prospects of stated materials synthesis strategy and application of the as-prepared material Cu1.8Se/C-450 in SHIC device are presented.

Few-layer black phosphorus (FLBP) nanosheets feature high charge storage capacity, large surface area, considerable mechanical flexibility, high carrier mobility and adjustable intrinsic band gap, allowing wide applications in electrochemical storage and conversion. This article presents a review on the preparation of FLBP materials and their applications in rechargeable batteries, including alkali metal batteries. Top-down and bottom-up synthetic strategies of FLBP are overviewed with examples of mechanical, liquid-phase and electrochemical exfoliation routes and chemical vapour and pulsed laser deposition. The electrochemical properties, structure-performance relationship and electrode mechanisms of FLBP are demonstrated as anode materials for storage of lithium, sodium and potassium ions. Issues including huge volume expansion and structural instability are discussed, along with solving strategies such as composing with nanostructured carbon, MXene, conductive polymer and transition metal oxides. Furthermore, the remaining challenges and future perspectives for the electrochemical use of FLBP are highlighted.

The inhibitory effect of two heterocyclic porphyrin compounds, specifically 5,10,15,20-tetrakis(pentafluorophenyl)-21H,23H-porphyrin palladium(II) (PF-1) and 4,4′,4″,4‴-(porphyrin-5,10,15,20-tetrayl)tetrakis(benzoic acid) (PF-2), was studied in a sweet corrosion environment (3.5 wt % NaCl + CO2) on J55 steel by means of weight loss and electrochemical methods. Surface changes were studied using contact angle, scanning electrochemical microscopy (SECM), and atomic force microscopy (AFM) techniques. It was established that PF-2 showed the superlative inhibition efficiency of average of about 93% at 400 ppm concentration. The inductive behavior of the J55 steel surface in the presence of inhibitors was confirmed by SECM. The AFM further confirmed that the surface roughness was considerably decreased in the presence of porphyrins. The surface wettability of the steel was also investigated, and the results established the formation of a water-repellant layer on the surface when porphyrins are absorbed and layer became more hydrophobic with PF-2. Thermodynamics studies showed that the inhibition efficiencies of two compounds evaluated by all measurements follow the Langmuir adsorption isotherm.

By 60 Co-γ irradiation method, the Chitosan-oligosaccharide (COS) was grafted onto the inner surface of the polystyrene (PS) microtiter, which was soaked with COS solution before the irradiation. To evaluated the effect of COS concentration on the properties of the PS microtiter, FTIR, XPS, AFM, Contact angle tester and enzyme-linked analyser was used to measure the surface properties and BSA adsorption of PS-COS plates. The results shows that, with the increase of COS concentration, the contact angle clearly decreased at the dose of 12 kGy. The absorbance variances of the COS modified plate is less than 5% while the BSA adsorption is higher than the PS plates. The COS-modified microtiter has the potential applications in biochemical analysis.

A poor performance of the ternary cathode material, LiNi 1/3 Co 1/3 Mn 1/3 O 2 , at rate capability and low temperature, limits its further application, in electronic markets. Some of the previous research works report that surface modification of cathode materials can enhance their cycle stability. In the current work, (42.5-x) Li 2 O: 57.5B 2 O 3 : xLi 2 SO 4 modified LiNi 1/3 Co 1/3 Mn 1/3 O 2 cathode materials are prepared via the solution method followed by heat-treatment at 500 °C. The lithium fast ion conductors (42.5-x) Li 2 O: 57.5B 2 O 3 : xLi 2 SO 4 provide a stable surface protection for LiNi 1/3 Co 1/3 Mn 1/3 O 2 . The results indicate that (42.5-x) Li 2 O: 57.5B 2 O 3 : xLi 2 SO 4 modified LiNi 1/3 Co 1/3 Mn 1/3 O 2 exhibits enhanced electrochemical performance at high rates and low temperatures. (42.5-x) Li 2 O: 57.5B 2 O 3 : xLi 2 SO 4 (x = 10) modified LiNi 1/3 Co 1/3 Mn 1/3 O 2 samples increase the discharge capacity retention of LiNi 1/3 Co 1/3 Mn 1/3 O 2 from 33.4% to 85.3% at the rate of 1C and from 48.6% to 70.0% at −20 °C. The high resolution transmission electron microscopy and scanning electron microscopy confirm the existence of a thin Li 2 O-B 2 O 3 -Li 2 SO 4 coating layer (about 10 nm) on the original structure of LiNi 1/3 Co 1/3 Mn 1/3 O 2 . The cyclic voltammetry and electrochemical impedance spectroscopy test results demonstrate that the presence of LBO-S coating reduces the interfacial resistance towards lithium ion migration.

In this work, NiCo 2 O 4 nanowalls composed of ultrathin nanosheets are fabricated successfully on Ni foam by a facile one-pot solvothermal method followed by thermolysis of the precursors. The as-prepared NiCo 2 O 4 products are evaluated as electrode materials for supercapacitors and lithium ion batteries. The results show high discharge capacitance of 925 mF/cm 2 at a current density of 5 mA/cm 2 , with remarkable cycling stability (about 24.2% loss after 6000 cycles) and excellent rate performance (71.5% capacitance retention with current density range from 1 mA/cm 2 to 20 mA/cm 2 ). In addition, Ni foam supported NiCo 2 O 4 nanowalls possess excellent discharge capacity of 1100 mAh/g as lithium ion battery anode at a current density of 100 mA/g. The excellent electrochemical performance of NiCo 2 O 4 nanowalls could be ascribed to the unique spatial structure composed of interconnected ultrathin nanosheets, which facilitates ion penetration and electron transportation, demonstrating their potential applications as electrode materials for high performance supercapacitors and lithium ion batteries.

LiFePO4·xLi3V2(PO4)3 (LFP·xLVP, x = 0, 0.05, 0.1, 0.15, 0.2) composites were prepared by the two-step solid-state method. The structure, morphology and electrochemical properties were characterized by X-ray diffraction, scanning electron microscope, cyclic voltammetry, charge-discharge performance test and electrochemical impedance spectroscopy. It was indicated that composites were presented rough in surface of ball-like particles. Two phase of LFP and LVP combination improved electrochemical properties of LFP. The LFP·0.1LVP has the highest discharge capacity of 154 mAh/g at 0.2 C. Compared with LFP, the rate performance of the LFP·0.1LVP increased 13% and 8% at 1 C and 10 C after five cycles. It possessed excellent cycle life of 99.8% after 100 cycles at 1 C especially. The all preparation process without any solvent addition was easy operation, energy saving and environmentally friendly.

Pomelo peel extract (PPE) has been evaluated as a corrosion inhibitor for N80 steel in 3.5% NaCl saturated with CO2 solution using weight loss measurements, Fourier transform infrared spectroscopy, potentiodynamic polarization, electrochemical impedance spectroscopy, scanning electron microscopy (SEM), scanning electrochemical microscopy (SECM) and quantum chemical calculations. The inhibition efficiency was found to increase with increasing PPE concentration. Potentiodynamic polarization measurements indicated that the PPE was a mixed type inhibitor. The adsorption of PPE obeyed the Langmuir adsorption isotherm and mainly the physical adsorption. The SECM and SEM studies were used to investigate adsorbed film on the N80 steel surface. Quantum chemical calculation indicated that the major component of the PPE has more tendencies for adsorption.

Porous carbon nanotubes (PCNTs) containing sulfur were successfully fabricated through a simple approach, which is the simultaneous activation and carbonization of sulfonated polydivinylbenzene nanotubes with KOH. The PCNTs take on hierarchical porous structure composed of well interconnected mesopores and numerous micropores. Chemical analysis shows that the PCNTs contain sulfide and sulfone groups. When assessed as electrodes by a three-electrode system in 6 M KOH aqueous solution, the PCNTs displayed the excellent electrochemical performance. An optimal sample of PCNTs activated at 650 °C for 3 h not only exhibits a high specific capacitance of 331 F g−1 at 1 A g−1, but also shows considerable rate capability with the retention of 80.4% at 20 A g−1. Additionally, it has the good cycling performance with 84% capacitance retention, while a high capability of about 243 F g−1 still reaches over 5000 cycles at 5 A g−1. We presented a promising route to scale-up synthesize porous carbon nanotube electrode materials for high-performance supercapacitors.

A LiNi1/3Co1/3Mn1/3O2 (NCM) cathode material is coated with fluoroborate glass (xLi(2)O-yB(2)O(3)-zLiF) to improve the electro-chemical performance of lithium-ion batteries. An xLi(2)O-yB(2)O(3)zLiF layer was successfully coated onto the surface of NCM by using a solution-phase method. The resulting materials are characterized by using X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The xLi(2)OyB(2)O(3)- zLiF-coated NCM exhibits a superior discharge capacity, rate capability, and cycling stability than those of the uncoated material. Notably, the initial discharge capacity of bare and 2Li(2) O-B2O3-LiF-coated NCM were 182.1 and 207.5 mAhg(-1), respectively, in the voltage range from 2.5 to 4.5 V. At a rate of 5C, the discharge capacity of Li2O-B2O3-LiF-coated NCM is 144.4 mAhg(-1), whereas that of bare NCM is 76.7 mAhg(-1). After 50 cycles at a rate of 0.2C, the capacity retentions of Li2O-B2O3LiF-, 2Li(2)O-B2O3-LiF-, Li2O-2B(2)O(3)-LiF-, and Li2O-B2O3-2LiF-coated NCM are 96.8, 97.2, 95.6, and 95.2%, respectively, whereas the capacity retention of bare NCM is 81.4%. Cyclic voltammetry and electrochemical impedance spectroscopy results indicate that the xLi(2)O-yB(2)O(3)-zLiF coating reduces electrode polarization and decreases charge-transfer resistance at the electrolyte-electrode interface, further improving the electrochemical activity of the NCM cathode material.

Hierarchically porous carbons offer great benefits for constructing advanced electrodes for energy-related applications. Herein, we reported facile synthesis of cross-linked carbon networks (HPCNs) made from N-doped nanosheets. By using MgO as self-sacrificial templates, the polyethylene glycol and melamine precursors were first uniformly coated on the template, and then annealed at the elevated temperature in inert atmosphere before removing the templates by mild acid etching. Interestingly, the capacitance performance of HPCNs could be easily modulated by adjusting the mass ratio of the precursors and templates, as well as the carbonization temperature. The optimized HPCNs showed specific capacitances of 192.6 F g −1 at 1.0 A g −1 and 156.2 F g −1 even at 20 A g −1 in 6.0 M KOH solution, and long-term cyclability with 85.5% capacitance retention at high current load of 10 A g −1 after 8000 successive cycles, which were attributed to structural merits of these continuous networks including high surface area of 370.8 m 2 g −1 , high pore volume of 1.65 cm 3 g −1 , as well as high nitrogen content of 9.920 wt.%. Owing to simplicity of the synthesis method and superior performance, such HPCNs may promise great potential in energy storage fields.

In this study, a highly active oxygen reduction reaction (ORR) electrocatalyst (MG-15) of Mn3O4 nanoparticles (NPs) supported by reduced graphene oxide (rGO) has been fabricated through one-step microwave-assisted synthetic route. Upon microwave-assisted synthesis, the formation of Mn3O4 NPs and the reduction of GO occurs simultaneously. Transmission electron microscope (TEM) profile reveals that Mn3O4 NPs are uniformly distributed evenly on the winkled rGO sheets. The MG-15 hybrid materials show enhanced electrocatalytic activity compared to rGO, Mn3O4 NPs and the mixture of rGO and Mn3O4 NPs, which indicates that the synergistic effect of Mn3O4 and rGO enhances the overall performance. Additional, the oxygen reduction peak of the MG-15 catalyst in a 0.1M KOH solution is tested at -0.15V, which is more positive than Pt/C (-0.154V). The onset potential of the MG-15 is close to Pt/C. Most importantly, the mechanism analysis shows that it favors the 4e- pathway for ORR. Furthermore, the MG-15 also exhibit excellent durability and methanol.