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The heavy rare-earth GdFeO3-type RFeO3 (R = Dy, Ho and Er) orthoferrites (space group Pnma, N 62) show spin reorientation transition characterized by a turning point on the magnetization curves. The basic Arrott plots curves showing positive slopes confirm the second-order nature of the spin reorientation and the transition temperature TSR is estimated to be ∼45 K, ∼53 K and ∼94 K for DyFeO3, HoFeO3 and ErFeO3, respectively. In addition, magnetic entropy change − Δ S M of the three samples is calculated to be 11.4, 9.8 and 7.4 J kg−1 K−1 at 10 K and 50 kOe, respectively. The field sensitive antiferromagnetic state and competitive magnetocaloric performances in RFeO3 have been attracting considerable interest for the possible applications in spintronic devices.

Vibration sensors are essential for signal acquisition, motion measuring, and structural health evaluations in civil and industrial applications. However, the mechanical brittleness and complicated installation process of micro-electromechanical system vibration sensors block their applications in wearable devices and human-machine interaction. The development of flexible vibration sensors satisfying the requirements of good flexibility, high sensitivity, and the ability to attach conformably on curved critical components is highly demanded but still remains a challenge. Here, we demonstrate a highly sensitive and fully flexible vibration sensor with a channel-crack-designed suspended sensing membrane for high dynamic vibration and acceleration monitoring. The flexible sensor is designed as a suspended vibration membrane structure by bonding a channel-crack-sensing membrane on a cavity substrate, of which the suspended sensing membrane can freely vibrate out of plane under external vibration. By inducing the cracks to be generated in the embedded multiwalled carbon nanotube channels and fully cracked across the conducting routes, the suspended vibration membrane shows high sensitivity, good reproducibility, and robust sensing stability. The resultant vibration sensor demonstrates an ultrawide frequency vibration response range from 0.1 to 20,000 Hz and exhibits the ability to respond to acceleration vibration with a broad response of 0.24-100 m/s2. The high sensitivity, wide bandwidth, and fully flexible format of the vibration sensor enable it to be directly attached on human bodies and curvilinear surfaces to conduct in situ vibration sensing, which was demonstrated by motion detection, voice identification, and the vibration monitoring of mechanical equipment.

2D transition metal dichalcogenides such as MoS2 with the unique layered structure have received great attention in the field of lithium-ion batteries (LIBs). However, the low conductivity and poor structural stability adversely affect the rate performance of LIBs. Herein, a flexible and free-standing high-performance lithium-ion battery electrode (MoS2/C@Ti3C2Tx) composed of rice-candy-like MoS2/C intercalated Ti3C2Tx and PVP-derived carbon with a large interlayer distance of MoS2 is designed and demonstrated. Lithium-ion batteries have attracted great attention due to their high energy density. Consequently, as an anode material for lithium-ion batteries, MoS2/C@Ti3C2Tx provides a high discharge capacity of 538.5 mAh g−1 at 0.05 A g−1 and rapid charge/discharge capability of 256.7 mAh g−1 at 2 A g−1, as well as outstanding cycling property (96.7% capacity retention after 150 cycles at 2 A g−1). Density-functional theory (DFT) calculation reveals that the rice-candy-like MoS2/C structure favors adsorption and diffusion of lithium ions and facilitates the redox reactions. The MoS2/C@Ti3C2Tx structure is expected to boost the development of novel 2D materials for high-performance lithium-ion batteries.

Fe3O4 is one of the promising anode materials in Li-ion batteries and a potential alternative to graphite due to the high specific capacity, natural abundance, environmental benignity, non-flammability, and better safety. Nevertheless, the sluggish intrinsic reaction kinetics and huge volume variation severely limit the reversible capacity and cycling life. In order to overcome these hurdles and enhance the cycling life of Fe3O4, a one-dimensional (1D) nanochain structure composed of 2D Ti3C2-encapsulated hollow Fe3O4 nanospheres homogeneously embedded in N-doped carbon nanofibers (Fe3O4@MXene/CNFs) is designed and demonstrated as a high-performance anode in Li-ion batteries. The distinctive 1D nanochain structure not only inherits the high electrochemical activity of Fe3O4, but also exhibits excellent electron and ion conductivity. The Ti3C2 layer on the Fe3O4 hollow nanospheres forms the primary electron transport pathway and the N-doped carbon nanofiber network provides the secondary transport pathway. At the same time, Ti3C2 flakes partially accommodate the large volume change of Fe3O4 during Li+ insertion/extraction. Density functional theory (DFT) calculations demonstrate that the Fe3O4@MXene/CNFs electrode can efficiently enhance the adsorption of Li+ to promote Li+ storage. As a result of the electrospinning process, self-restacking of Ti3C2 flakes and aggregation of Fe3O4 nanospheres can be prevented resulting in a larger surface area and more accessible active sites on the flexible anode. The Fe3O4@MXene/CNFs anode has remarkable electrochemical properties at high current densities. For example, a reversible capacity of 806 mA h g−1 can be achieved at 2 A g−1 even after 500 cycles, corresponding to an area specific capacity of 1.612 mA h cm−2 at 4 mA cm−2 and a capacity as high as 613 mA h g−1 is retained at 5 A g−1, corresponding to an area capacity of 1.226 mA h cm−2 at 10 mA cm−2. The results indicate that the Fe3O4@MXene/CNFs anode has excellent properties for Li-ion storage.

MXenes have received great attention due to their excellent features such as metal-like electronic conductivity, hydrophilic surface groups, and high volumetric capacitance. However, many performances of MXenes are still unsatisfactory due to their low energy density and easy horizontal stacking. In this work, an NiMn2O4@MXene composite with a crumpled surface was fabricated by a hydrothermal method and a developed dip-coating method. The maximum specific capacitance of the electrode is about 1.52 times that of NiMn2O4. Besides, it delivers a retention rate of 93.3% after 4000 cycles due to the increased transport of ions and electrons by the crumpled surface. An asymmetrical device based on the crumpled NiMn2O4@MXene composite and AC was also assembled, which shows an ultra-high energy density. This work provides an effective strategy to solve the vertical stacking problem of MXenes, which can open new avenues for large-scale applications of MXenes in energy storage.

Lithium–sulfur (Li–S) battery is one of the most promising energy storage systems for its ultrahigh theoretical capacity of 2600 Wh kg−1. However, the shuttle effect of soluble lithium polysulfides (LiPSs) leads to severe capacity decay and hinders its practical application. In this work, ultrathin polar MnO2 nanosheets rooting on carbon nanoboxes (C NBs) with high sulfur content have been studied as efficient host for advanced Li–S battery. The carbon nanoboxes confine the active species efficiently and provide large space to relieve the volume expansion during charging/discharging process. The polar MnO2 nanosheets have strong absorption for LiPSs and catalyze the conversion of soluble polysulfides to insoluble Li2S2/Li2S and back to sulfur. As a result, the polysulfide dissolution and shuttle effect are minimized effectively. Li–S battery assembled with S/MnO2@C NBs cathode shows superior electrochemical performance. The discharge capacity of 856 mAh g−1 is attained after 200 cycles at 0.2 C. The capacity can also reach 720 mAh g−1 at 2 C, which is about 2 times higher than the battery assembled with S/C NB electrode.

Electrochemical nitrogen reduction reaction (NRR) is considered as an alternative to the industrial Haber-Bosch process for NH3 production due to both low energy consumption and environment friendliness. However, the major problem of electrochemical NRR is the unsatisfied efficiency and selectivity of electrocatalyst. As one group of the cheapest and most abundant transition metals, iron-group (Fe, Co, Ni and Cu) electrocatalysts show promising potential on cost and performance advantages as ideal substitute for traditional noble-metal catalysts. In this minireview, we summarize recent advances of iron-group-based materials (including their oxides, hydroxides, nitrides, sulfides and phosphides, etc.) as non-noble metal electrocatalysts towards ambient N2-to-NH3 conversion in aqueous media. Strategies to boost NRR performances and perspectives for future developments are discussed to provide guidance for the field of NRR studies.

To develop highly efficient electrochemical catalysts for N2 fixation is important to sustainable ambient NH3 production through the N2 reduction reaction (NRR). Herein, we demonstrate the development of vanadium phosphide nanoparticle on V foil as a high-efficiency and stable catalyst for ambient NH3 production with excellent selectivity. The high Faradaic efficiency of 22% with a large NH3 yield of 8.35 × 10−11 mol·s−1·cm−2 was obtained at 0 V vs. the reversible hydrogen electrode in acid solution, superior to all previously studied V-based NRR catalysts. Density functional theory calculations are also utilized to have an insight into the catalytic mechanism.

Lithium and sodium metal batteries (LMBs, SMBs) with high theoretical capacities and high energy densities have attracted tremendous attention as a new class of energy storage devices. However, these metal batteries usually suffer from uneven metal plating/stripping behavior, continuous side reactions between lithium/sodium metal and electrolyte as well as uncontrollable dendrite growth, seriously hampering their practical applications. To address the abovementioned issues, multi-level strategies have been explored. Studies reveal a few potential solutions: namely, to reduce the local current density of anodes, to form flexible solid-electrolyte interface (SEI) films, to increase the number of metal ion transfer paths, and to improve the shear modulus of electrolytes. This review is aimed to summarize recent advances in rational design of dendrite-free LMBs and SMBs by means of modulation of metal anodes, optimization of electrolytes and modification of separators. The original design concepts, synthesis approaches and their effects on electrochemical performance of metal batteries are discussed. The challenges encountered for future development of dendrite-free LMBs and SMBs are proposed. It is hoped that this review will provide new insights into their technological development and real-world applications.

Various studies suggest that the performances of TMDs are largely thickness dependent. In this paper, we develop a chemical vapor deposition method to synthesis monolayer and bilayer MoS2 flakes with a solution precursor. The MoS2 phototransistors were prepared to investigate their optoelectronic performance. The MoS2 photodetectors exhibit high detectivity of 2.44 × 1011 and a fast response/recovery time of 97 ms/291 ms. The photoresponsivity of bilayer MoS2 flakes was found up to 7160 A W−1. Our research will pave a pathway to control the layer numbers of other TMDs nanostructures, expand the application of high performance 2D materials.

As a carbon-neutral alternative to the Haber-Bosch process, electrochemical N2 reduction enables environment-friendly NH3 synthesis at ambient conditions but needs active electrocatalysts for the N2 reduction reaction. Here, we report that conductive metal—organic framework Co3(hexahydroxytriphenylene)2 (Co3HHTP2) nanoparticles act as an efficient catalyst for ambient electrochemical N2-to-NH3 fixation. When tested in 0.5 M LiClO4, such Co3HHTP2 achieves a large NH3 yield of 22.14 µg·h−1mg−1cat. with a faradaic efficiency of 3.34% at −0.40 V versus the reversible hydrogen electrode. This catalyst also shows high electrochemical stability and excellent selectivity toward NH3 synthesis.

The Haber–Bosch process for industrial-scale NH3 production suffers from hash reaction conditions and serious greenhouse gas emission. Electrochemical N2 reduction is a sustainable and environmentally-benign alternative for ambient NH3 synthesis while demands efficient electrocatalysts to drive the N2 reduction reaction. Herein, we report the ambient electrocatalytic N2-to-NH3 conversion with excellent selectivity enabled by a CoP3 nanoneedle array on carbon cloth (CoP3/CC). When tested in 0.1 M Na2SO4, such CoP3/CC achieves a high faradaic efficiency of 11.94% with an NH3 yield of 3.61 × 10−11 mol s−1 cm−2 at −0.20 V vs. the reversible hydrogen electrode. It also demonstrates high durability.

Tunable magnetic phase transitions and novel emergent spin phases in two-dimensional materials are fascinating subjects of research. 1T-FeCl2 has been predicted to be a magnetic monolayer. We performed the first-principle calculations based on density functional theory to clarify the electronic structure and magnetic properties of the monolayer 1T-FeCl2 modulated by the uniaxial and biaxial strains. Based on the stable structure confirmed by the phonon calculations, we showed that the geometry and magnetic structures evolved with strain. In combination with the Monte Carlo simulation, we found that the strain could induce a phase transition between the in-plane ferromagnetic order and the out-of-plane anti-ferromagnetic order. Energy bands with the Hubburd U and spin-orbital couplings confirmed the insulator ground state. We identified the strain-magnetism behavior originating from the competition between the direct-exchange interaction and the super-exchange interaction. Meanwhile, the strains regulated the Curie temperatures by selecting the d–p bonding along the x-direction or y-direction. Through strain engineering, the 1T-FeCl2 could be an intriguing platform for the two-dimensional systems and a potential spintronic material.

Due to the serious pollution issue caused by 4-nitrophenol (4-NP), it is of great importance to design effective catalysts for its reduction. Here, a novel and simple strategy was developed for the synthesis of carbon dot-decorated gold nanoparticles (AuNPs/CDs) via the in situ carbonization of organic ligands on AuNPs at room temperature. The enhanced adsorption of 4-NP on CDs via π–π stacking interactions provided a high concentration of 4-NP near AuNPs, leading to a more effective reduction of 4-NP.

As a two-dimensional layered material with a structure analogous to that of graphene, molybdenum disulfide (MoS2) holds great promise in sodium-ion batteries (SIBs). However, recent research findings have revealed some disadvantages in two-dimensional (2D) materials such as poor interlayer conductivity and structural instability, resulting in poor rate performance and short cycle life for SIBs. Herein, we designed MoS2 nanoflowers with an ultra-wide spacing interlayer (W-MoS2/C) anchored on special double carbon tubes to construct three-dimensional (3D) nanostructures. When tested as an anode material in a SIB, the as-prepared CNT@NCT@W-MoS2/C sample achieves high capacities (530 and 230 mA h g−1 at current densities of 0.1 and 2 A g−1, respectively). Density functional theory (DFT) calculations demonstrate that the ultra-wide spacing MoS2/C structure is beneficial for the chemical adsorption of sodium ions and facilitates redox reactions. The wide interlayer spacing and the presence of an intermediate carbon layer provide a rapid diffusion channel for ions and offer a free space for volume expansion of the electrode material.

Lithium-sulfur batteries (LSBs) have gained considerable attention for their desirable energy densities, high theoretical capacities, low cost and environmentally friendly properties. However, the shuttle effect of polysulfides seriously hinders their future practical applications. Herein, a dual-function cathode structure, consisting of 3D porous FeP/rGO microspheres supported on both aluminum foil and a commercial separator, exhibits excellent performance by providing strong adsorption with respect to Li2Sx (x = 1, 2, 4, 6 and 8) and S8. In this rational design, the iron phosphide (FeP) nanoparticles act as a catalyst to accelerate polysulfide conversion and as the designated sites for adsorption. The 3D rGO porous conductive network can provide enough space for sulfur loading and to physically adsorb the polysulfides. More importantly, density functional theory (DFT) calculations also verified the strong interactions (with adsorption energy values of -4.21 to -1.97 eV) between the FeP(111) surface and the sulfur species. The electrochemical results show that the cell using the dual-function cathode structure delivers a capacity of 925.7 mA h g-1, with capacity degradation of 0.05% per cycle after 500 cycles, at a current density of 0.5C. It is also worth mentioning that the cell with sulfur loading of ∼2.2 mg cm-2 maintained a high capacity of 483 mA h g-1 at 0.5C after 500 cycles. In summary, the above results demonstrate the promising application of the dual-function cathode structure for high-performance LSBs.

Industrially, large-scale NH3 production is achieved by the Haber-Bosch process, which operates under harsh reaction conditions with abundant energy consumption and CO2 emission. Electrochemical N2 reduction is an eco-friendly and energy-saving method for artificial N2 to NH3 fixation under ambient reaction conditions. Herein, we demonstrate that ZrS2 nanofibers with a sulfur vacancy (ZrS2 NF-Vs) behave as an efficient electrocatalyst for ambient N2 reduction to NH3 with excellent selectivity. In 0.1 M HCl, this ZrS2 NF-Vs catalyst attains a large NH3 yield of 30.72 μg h-1 mgcat.-1 and a high faradaic efficiency of 10.33% at -0.35 V and -0.30 V vs. reversible hydrogen electrode, respectively. It also shows high electrochemical and structural stability. The density functional theory calculations reveal that the introduction of Vs facilitates the adsorption and activation of N2 molecules.

Industrial-scale synthesis of NH3 mainly relies on the energy-intensive Haber–Bosch technology, which not only needs harsh conditions but also produces a large amount of CO2. Electrochemical N2 reduction is regarded as an environmentally friendly method for artificial N2-to-NH3 conversion, but needs efficient catalysts for the N2 reduction reaction (NRR). Here, we report that Sn dendrites on Sn foil act as a non-noble-metal electrocatalyst for the electrochemical NRR under ambient conditions. This electrocatalyst affords an NH3 yield of 5.66 × 10−11 mol s−1 cm−2 and a Faraday efficiency of 3.67% at −0.60 V versus the reversible hydrogen electrode in 0.1 M PBS (pH = 7.0), with high electrochemical durability.

Batteries and supercapacitors are promising candidates for electrochemical energy storage while the development of their electrode materials is becoming a bottleneck. This limitation necessitates the design of electrode materials with high specific capacity/capacitance and excellent cycling stability, yet at a low cost. Herein, we present the research progress of magnetron sputtering enabled nanostructured materials as electrode materials for electrochemical energy storage. Firstly, magnetron sputtered anode materials (Si-based materials, metal-based materials, metal oxides, etc.) and cathode materials (i.e., transition metal oxides and phosphates) for lithium/sodium ion batteries are systematically reviewed. Secondly, magnetron sputtered electrode materials (metals and metal oxides, metal nitrides, etc.) for electrochemical supercapacitors are discussed. Furthermore, critical insights into the corresponding electrical conductivity and cycling stability of the electrode materials are provided through illustrations of how to rationally design and optimize electrode materials via magnetron sputtering technology. Finally, the emerging challenges and future directions of magnetron sputtered electrode materials for electrochemical energy storage are discussed.

Development of cost-effective electrocatalysts toward the alkaline hydrogen evolution reaction (HER) is crucial for electrolytic hydrogen production applications. In this communication, we report the electrodeposition of cobalt–phosphorus nanoparticles on a polyimide derived N-doped carbon nanosheet array supported on carbon cloth (Co–P@NC/CC) and it is a robust 3D HER electrode. In 1.0 M KOH, this Co–P@NC/CC shows outstanding catalytic activity with the demand of a low overpotential of 75 mV to drive 10 mA cm−2, outperforming most reported Co–P catalysts. Notably, it also demonstrates strong long-term electrochemical durability.

The lithium polysulfide (LiPS) shuttle effect and low redox kinetics are the key problems that hinder performance improvement and prevent achieving the commercial requirements for lithium–sulfur batteries (LSBs), and the reasonable construction of sulfur hosts is one effective strategy to relieve the polysulfide shuttle effect and improve redox kinetics. Herein, N-doped carbon nanocages decorated with homogeneously dispersed TiN nanoparticles (TiN@C NCs) as multifunctional sulfur hosts are designed for superior LSBs. Carbon nanocages provide space to mitigate volume expansion and provide additional physical adsorption to trap the LiPSs. Polar TiN nanoparticles not only exhibit the chemisorption capacity for LiPSs, but also catalyze and promote the conversion of long-chain LiPSs to Li2S2/Li2S in the reduction process as well as the decomposition of Li2S in the oxidation reaction, which significantly boosts electron/ion transport and decreases the potential barrier. Therefore, the S/TiN@C NC cathode has an excellent electrochemical capacity of 1485.7 mA h g−1 at 0.1 C. In particular, the cathode demonstrates high capacity reversibility after 500 cycles at 3 C with a retention of about 73.1%, which is equivalent to a slow capacity decay rate of 0.053% per cycle.

The commercial application of lithium–sulfur (Li–S) batteries is obstructed by the inherent dissolution/shuttling of lithium polysulfides (LiPSs) in a sluggish redox reaction. Here, a heterophase V2O3–VN yolk–shell nanosphere encapsulated by a nitrogen-doped carbon layer has been designed to address the problems of the short cycle life and rapid capacity decay of Li–S batteries synchronously. The structural merits comprise efficient polysulfide anchoring (V2O3), rapid electron transfer (VN) and a reinforced frame (N-doped carbon). The assembled cathode based on the V2O3–VN@NC sulfur host delivered a high initial capacity of 1352 mA h g−1 at 0.1C with excellent rate performance (797 mA h g−1 at 2C) and favorable cycle stability with a low capacity-decay rate of only 0.038% per cycle over 800 cycles at 1C. Even with a high sulfur loading of 3.95 mg cm−2, an initial capacity of 954 mA h g−1 at 0.2C could be achieved, along with a good capacity retention of 75.1% after 150 cycles. Density functional theory computations demonstrated the crucial role of the V2O3–VN@NC heterostructure in the trapping-diffusion-conversion of polysulfides. This multi-functional cathode is very promising in realizing practically usable Li–S batteries owing to the simple process and the prominent rate and cyclic performances.

NH3 is an indispensable chemical with numerous applications; however, its large-scale synthesis highly relies on the industrial Haber–Bosch process, which is performed under harsh conditions (high ...

The rational design and fabrication of promising electrodes with prominent energy storage property and conversion performance is crucial for supercapacitors and electrocatalysis. Herein, potato chip-like cobalt nickel-layered double hydroxide@polypyrrole-cotton pad (CoNi-LDH@PCPs) composite was synthesized by in situ polymerization, which was coupled with facile solution reaction and ion-exchange etching process. An interesting potato chip-like structure can effectively expedite the kinetics of the electrode reactions, while the three-dimensional PCPs texture affords efficient pathways for charge transport, and the voids between adjacent fibers are thoroughly accessible for electrolytes and bubble evolution. When evaluated as a positive electrode for wearable supercapattery, the hierarchical CoNi-LDH@PCPs electrode displayed high specific capacity and excellent flexibility. As an oxygen evolution reaction catalyst, this PCP-based electrode also reveals the lowest overpotential of 350 mV at 10 mA cm-2 and a Tafel slope of ∼58 mV dec-1. In addition, density functional theory calculations suggest that the synthesis strategy for controllable tuning of hollow CoNi-LDH arrays reported here represents a critical step toward high-performance electrodes for energy storage and electrochemical catalysis.

The rational design of the structure is the key to engineering spinel LiNi0.5Mn1.5O4 cathode material to enhance Li+/electron transport and relieve the structural damage during the reduplicative Li+ intercalation/deintercalation, which is closely to the rate and cycling performance. Here, we report hollow microcuboid LiNi0.5Mn1.5O4 composed of interconnected nanoparticles which can simultaneously achieve the easy Li+ diffusion and high structure robustness. The hollow microcuboid has been fabricated by a facile solvothermal reaction followed by a lithiation process. It is found that the morphology and the size can be easily controlled, which depends on the initial nucleation process. The obtained hollow microcuboid LiNi0.5Mn1.5O4 presents excellent rate and cycling performance. It delivers a capacity of 125 mAh g−1 at the discharge rate of 1 C. Even at a high discharge rate of 30 C, the capacity of 109 mAh g−1 and a discharge capacity retention of 94.4% after 900 cycles can be achieved. The excellent performance should be ascribed to its intrinsic hierarchical hollow structure, which not only benefits the diffusion of Li+ but also provides pore spaces to relieve the volume expansion during the high rate charge/discharge process. The result suggests the potential application of hollow microcuboid LiNi0.5Mn1.5O4 cathode material for high-rate and long-life Li ion batteries.

The inevitable dissolution, diffusion, and migration of polysulfides cause an irreversible loss of active material, leading to poor cyclic performance in lithium sulfur batteries. Herein, a freestanding tungsten nitride nanorod/carbon cloth (WN/CC) interlayer is prepared by hydrothermal growth to function as both current collector and physicochemical barrier to soluble lithium polysulfides (Li2Sx). The cells containing a dual-functional interlayer deliver a significantly improved initial discharge capacity of 1337 mAh g–1 with a reversible capacity of 814.2 mAh g–1 after 500 cycles at 100 mA g–1. The enhanced electrochemical performance is attributed to the highly adsorptive WN nanorods grown on conductive CC to entrap polysulfides, leading to effective recycling of active materials. The density functional theory (DFT) calculations prove important roles of the WN (200) surface in entrapping polysulfides through their strong adsorption energies (3.21–4.67 eV) with Li2Sx and S8. The potential of the dual-fu...

A unique nanostructure consisting of CNTs as carbon matrix, and were sequentially coated with silicon dioxide, N-doped porous carbon tube (NCT) and MnO2 nanoflowers, the final CNT@NCT@MnO2 composites with large internal voids between CNT and NCT. CNT@NCT@MnO2 combines the nanostructural advantages of internal voids and the N-doped porous carbon, presenting fast diffusion paths for ions and electrons, high conductivity and large surface areas. When used as an anode material in supercapacitors, the CNT@NCT@MnO2 tube-in-tube hierarchical nanostructure exhibite a remarkably excellent electrochemical behavior with a specific capacitance (Csp) of 210 F g−1 at the current density of 0.5 A g−1. Moreover, all-solid-state asymmetrical supercapacitors (ASCs) were fabricated using the CNT@NCT@MnO2 composites as anode and the CNT@NCT as cathode, Na2SO4/PVA gel as the electrolyte and the separator. The all-solid-state ASCs also show the superior performance, such as high energy density of ∼14 Wh kg−1 and a power density of ∼3.6 kW kg−1.

Using low cost, environment-friendly, and sustainable biomass is a unique approach to the preparation carbon-based composites for lithium ion batteries. In our research, hollow, derived microtubes (HMD) were fabricated from graphene/loofah sponge. Each microtube was wrapped with graphene, resulting in conductivity improvement, and facilitated easily controlled growth of ultra-thin MoS2 nanosheets. The method employed a simple process of soaking the HMD in graphene oxide (GO) dispersion liquid, and subsequent carbonization and activation of the HMD/rGO. When ultrathin MoS2 nanosheets were vertically and uniformly grown on the surface of the HMD/rGO, via the hydrothermal method, the HMD/rGO/MoS2 composite was obtained, and exhibited reversible lithium storage capacity of 838.2 mAh g−1 at a current density of 0.2 A g−1 after 200 cycles. This excellent electrochemical performance could be due to the high conductivity of HMD/rGO, a synergistic effect between HMD/rGO and MoS2 nanosheets, a reasonable structural design, and the high theoretical specific capacity of MoS2. Such a structure not only provides a novel, high-quality carbon template/matrix from cheap loofah sponge, but also provides a new way to design sustainable electrodes for electrochemical energy storage, and makes economical, multifunctional, carbon-based hybrids available for other applications.

The low loading and poor cycling performance of sulfur cathodes are among the critical barriers restricting the practical application of lithium–sulfur (Li–S) batteries. The rational design of composites consisting of transition metals and conductive nanocarbon is considered an effective strategy to construct cathode materials for Li–S batteries with excellent cycling stability and rate capability. Herein, we propose a spray drying method to fabricate 3D pomegranate-like titanium nitride (TiN)@graphene composites as hosts for sulfur cathodes. The hollow spheres are coated with graphene layers to form a shell, serving as a highly efficient electrochemical reaction chamber and a reservoir for polysulfides. The TiN@graphene/S electrode exhibits an excellent capacity of 810 mA h g−1 after 200 cycles at 0.5C. The cathodes with high areal sulfur loadings of 2.8 and 3.6 mg cm−2 maintained remarkable capacities of 568 and 515 mA h g−1, respectively, after 500 cycles. The TiN hollow spheres not only accommodate the large volume expansion of sulfur but also improve the conversion of polysulfides during the discharge/charge process. The excellent electrical conductivity of the few-layered graphene shell facilitates electron transport and maintains structural stability. This work offers a strategy to combine inorganic compounds and nanocarbon as sulfur hosts to improve the electrochemical properties of Li–S batteries.

As a promising energy storage device, sodium ion batteries (SIBs) have attracted more and more attention. Nevertheless, the radius of a sodium ion is much larger than that of a lithium ion, and it is still a significant challenge to solve the problem of volume expansion. In order to solve the problem of volume expansion, a rational nanostructure consisting of CNTs as a carbon matrix, and were sequentially coated with mesoporous SnO2 and N-doped porous carbon tube (NCT). Mesoporous SnO2 can alleviate the volume expansion caused by charge and discharge, and the N-doped porous carbon layer can further inhibit the volume expansion of SnO2. When used as an anode material in sodium ion batteries, the CNT@SnO2@NCT heterostructure achieves efficient capabilities (350 and 150 mA h g-1 at current densities of 0.1 and 2 A g-1, respectively).

Shuttle effect of lithium polysulfides (LiPSs) is among the critical obstacles hampering development of lithium-sulfur batteries. Herein, we present a porous Mo2C-Mo3N2 heterostructure/rGO host and the Mo2C-Mo3N2 heterostructure combines the merits of high adsorption Mo2C and high catalytic Mo3N2 so as to achieve rapid anchoring-diffusion-conversion of LiPSs across the Mo2C-Mo3N2 heterointerface. The Mo2C-Mo3N2 heterointerface boosts the trapping efficiency and conversion to Li2S of LiPSs. rGO provides fast paths for electron transport as well as serves as a protective layer to prevent the structure from being damaged during cycling. Density functional theory (DFT) calculation shows that Mo2C has stronger adsorption ability for Li2S4 than Mo3N2 and Mo3N2 has better reaction kinetic characteristics. Experimentally, Mo2C-Mo3N2/rGO@S electrode respectively shows outstanding rate capability. At high sulfur loadings (3.4 and 5.0 mg cm−2), the capacity retention values are 78%, and 70% at 0.5C after 300 cycles. Mo2C-Mo3N2/rGO sulfur electrodes shows high Li+ diffusion coefficient of 4.56 × 10-7 cm2 s−1, which benefits from the accelerated conversion of LiPSs at interface. Our results reveal the critical role of anchoring-diffusion-conversion of LiPSs in terms of inhibiting the shuttle effect.

Renewable‐electricity‐driven N2 reduction is an attractive approach for ambient NH3 synthesis, but active electrocatalysts are needed to enable the N2 reduction reaction. Monolithic electrodes with active components anchored on conductive supports provide many advantages like structural stability, large surface area, and low electrical resistance. Here, a novel “oxidation‐etching” strategy is proposed to carve the surface of Cu foam into structures of particles, cubes, and sheets for N2 reduction electrocatalysis. The optimal catalyst achieves a Faradic efficiency as high as 18% at −0.35 V vs reversible hydrogen electrode (RHE) and a large NH3 yield of 2.45 × 10−10 mol s−1 cm−1 at −0.40 V vs RHE in 0.1 M HCl. Notably, it also shows superior long‐term electrochemical durability, with the preservation of electro‐activity for at least 20 hours.

The rational design of the nano structure is crucial for overcoming the inherent defect and engineering high performance of Li2MnSiO4 cathode material. In the present study, uniform coaxial carbon nanotube CNT@Li2MnSiO4@C has been designed and synthesized by an efficient step-by-step strategy and applied as high-performance cathode for lithium ion battery. It is demonstrated that the product has a uniform coaxial structure, the thickness of Li2MnSiO4 shell and outermost carbon layer is about 20 nm and 4.5 nm, respectively. This properly design can effectively improve the electric conductivity, shorten the Li ion diffusion length, relax volume change upon charge/discharge and relieve the manganese dissolution. Benefit from its unique structural features, the CNT@Li2MnSiO4@C electrode material overcomes the intrinsic disadvantage of Li2MnSiO4 of poor electronic/ionic conductivity and fast capacity fading rate, and hence exhibiting promising improvement on reversible capacity and cycling properties.

Spherical N-doped mesoporous TiO2/C (MTC) composite micro-particles are produced by spray drying (SD) and carbonization process. The particle size of MTC microsphere is between 2 and 3.4 µm, and the N-doped amorphous C around TiO2 could provide a conductive matrix, and buffer the volume change. When evaluated as electrodes for Li-ion batteries (LIBs) and Li-S batteries (LSBs), the MTC microsphere exhibits relatively high discharge-voltage plateau, excellent capacity retention and rate capability. As anode for LIBs, after 200 cycles, a reversible capacity more than 230 mA h g−1 can achieved at 1 C. And for LSBs, a specific capacity of 1317.7 mA h g−1 at 1 C and the capacity retention of 73.8% after 500 cycles. The superior electrochemical performance is ascribed to robust scaffolding architecture and conductive N-doped carbon matrix. The excellent electrochemical performance and process ability of the MTC microspheres make them very attractive as electrode materials for use in high rate battery application.

Manganese dioxide (MnO2) is an ideal electrode material for supercapacitors due to its low cost and large theoretical specific capacity. We reported the hydrothermal synthesis MnO2 nanostructures with different morphologies through the variation of hydrothermal temperature and dwell time. It was found that cauliflower-like δ-MnO2 particles are prepared at a lower temperature while the needle-like α-MnO2 nanorods are formed at a higher temperature. The morphologies of MnO2 were also affected by the hydrothermal dwell time. The needle-like α-MnO2 nanorods have the higher specific surface (114 m2 g−1) than that of the cauliflower-like δ-MnO2 particles. Electrochemical properties were evaluated using cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS). The hierarchical multidimensional MnO2 architecture nanostructured surface with particles and nanorods, shows a maximum specific capacity (311.52 F g-1 at 0.3 A g−1). These results provided a generic guideline in developing different nanostructured electrode materials for electrochemical energy storage.

A series of CuCo2O4 nanostructures with different morphologies were prepared by a hydrothermal method in combination with thermal treatment. The morphology, structure and composition were investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. As the electrode materials for supercapacitors, CuCo2O4 nanoneedles delivered the highest specific capacitance compared with other CuCo2O4 nanostructures. Electrochemical performance measurements demonstrate that the carbon layer can improve the electrochemical stability of CuCo2O4 nanoneedles. The CuCo2O4@C electrode exhibits a high specific capacitance of 1432.4 F g−1 at a current density of 1 A g−1, with capacitance retention of 98.2% after 3000 circles. These characteristics of CuCo2O4@C composite are mainly due to the unique one dimensional needle-liked architecture and the conducting carbon, which provide a faster ion/electron transfer rate. These excellent performances of the CuCo2O4@C electrode confirmed the material as a positive electrode for hybrid supercapacitor application.

An asymmetrical supercapacitor (ASC), comprising reduced graphene oxide (rGO)-encapsulated nickel phosphite hollow microspheres (NPOH-0.5@rGO) as positive electrode, and porous nitrogen/sulfur co-doped rGO aerogel (NS-3D rGO) as negative electrode has been prepared. The NPOH-0.5@rGO electrode combines the advantages of the NPOH hollow microspheres and the conductive rGO layers giving rise to a large specific capacitance, high cycling reversibility, and excellent rate performance. The NS-3D rGO electrode with abundant porosity and active sites promotes electrolyte infiltration and broadens the working voltage range. The ASC (NPOH-0.5@rGO//NS-3D rGO) shows a maximum voltage of up to 1.4 V, outstanding cycling ability (capacitance retention of 95.5% after 10,000 cycles), and excellent rate capability (capacitance retention of 77% as the current density is increased ten times). The ASC can light up an light-emitting diodes (LED) for more than 20 min after charging for 20 s. The fabrication technique and device architecture can be extended to other active oxide and carbon-based materials for next-generation high-performance electrochemical storage devices.

Two-dimensional carbon nanomaterials have attracted much attention in the last decade because of their promising applications. Recently, the discovery of N-doped holey graphene (NhG) with plentiful in-plane holes and high N contents as the anode material has opened up exciting opportunities to improved electrochemical performance for the li-ion Battery applications. In this paper, we provide a bottom-up and economic solution-combustion synthesis route for the simple preparation of NhG. The nitrogen content, specific surface area (SSA) and pore size of the as-obtained NhG all increase with the increasing ratio between the oxidizer and fuel. With the increased nitrogen content and SSA, the prepared NhG exhibits higher capacity performance for lithium ion storage, especially for the prepared NhG4, gives rise to the highest initial reversible capacity 1354 mAh g−1 at 0.2 A g−1 as the carbon anode material. The detailed explanation of this “Bottom-up” route to prepare NhG is also provided for its extensive applications.

Crack-based flexible strain sensor have advantages of high sensitivity and high detection resolution, which have shown high promise for applications in human–machine interface, biological health detection, and electronic skin. However, the conductive layer in the commonly used crack-based strain sensors tends to lift off after repeatedly stressing/releasing because of the weak interface bonding property, limiting the robustness of flexible sensors. Moreover, the cracks induced by the flat membrane structure are concentrated on the two-dimensional (2D) surface, which limits the further improvement of the sensor's sensitivity. In this study, a new type of flexible strain sensor was fabricated by embedding the 3D annular cracks in the elastomer. By optimizing the fiber weaving structure, the maximum gage factor of the device could reach 45 within strain range of 0–15%, and the minimum detection accuracy reached 0.1%. The sensor maintains good linearity within 15% and good hysteresis characteristics within 5%. Besides, the interpenetrating structure formed between the elastomer material and the conductive material resulted in the increase in the stability of the interface, endowing the device with highly stable sensing performance and high mechanical robustness (anti-scratch). Experiments show that the device can be cycled 10,000 times under a strain of 10%. Finally, the proposed sensor was able to detect even small vibrations and human motion characteristics, exhibiting great potential for broad range of practical applications.

Molybdenum phosphide (MoP) is considered one of the promising electro-active materials for lithium-ion batteries (LIBs) owing to the high theoretical capacity but development of MoP anodes faces challenges such as the poor cycle stability. Herein, we propose a facile strategy to synthesize MoP/CNTs microspheres from a spray drying method followed by a phosphating process. The carbon nanotubes (CNTs) are inlaid throughout the MoP/CNTs microspheres, which not only promotes the electrical conductivity of the composite, but also relieves volume change during cycling. Benefit from the synergistic effect by coupling the MoP nanoparticles with CNTs and the nano/micro structure, the anode material of porous MoP/CNTs microspheres shows excellent cycling stability and specific capacity, for example, a capacity of 1568 mAh g−1 for 300 cycles at 200 mA g−1. Quantitative kinetics analysis reveals that the charge storage mechanism of MoP/CNTs mainly relies on pseudocapacitance behavior, especially at high scan rates (86.6% at 0.5 mV s−1), which improves the lithium storage performance at high scan rates. Our results provide insights into the design and synthesis of the functional materials with nano-micro structure for high-performance LIBs.

We have developed an effective chemical-vapor-deposition method to fabricate large-scale cerium hexaboride nanowire arrays on flexible carbon substates. The nanowires show diameters of 80–200 nm and lengths of 5–30 μm. The high resolution transmission electron microcopy (HRTEM) indicates that the nanowire is of high crystalline with the growth orientation of [001]. The field emission of these nanowires shows favorable electron emission properties, including the turn-on fields of 1.76 V μm −1 , threshold fields of 3.60 V μm −1 and high field emission enhancement factors of 2203 ± 27, respectively. The field emission properties depending on the gap between the anode and cathode are also investigated. The results show that the turn-on fields and threshold fields decrease from 1.76 and 3.60 V μm −1 to 1.28 and 2.77 V μm −1 , respectively; whereas the field emission enhancement factors increase from 2203 ± 27 to 4012 ± 66 with the anode-cathode distance increasing from 500 to 700 μm. The excellent field emission performances indicate the promising application prospects of this material in flexible electronics and optoelectronics, such as high light electron sources, flat panel displays and thermal electrical power converters.

Due to the high specific capacities and environmental benignity, lithium-sulfur (Li-S) batteries have shown fascinating potential to replace the currently dominant Li-ion batteries to power portable electronics and electric vehicles. However, the shuttling effect caused by the dissolution of polysulfides seriously degrades their electrochemical performance. In this paper, Mn2O3 microcubes are fabricated to serve as the sulfur host, on top of which Al2O3 layers of 2 nm in thickness are deposited via atomic layer deposition (ALD) to form Mn2O3/S (MOS) @Al2O3 composite electrodes. The MOS@Al2O3 electrode delivers an excellent initial capacity of 1012.1 mAh g−1 and a capacity retention of 78.6% after 200 cycles at 0.5 C, and its coulombic efficiency reaches nearly 99%, giving rise to much better performance than the neat MOS electrode. These findings demonstrate the double confinement effect of the composite electrode in that both the porous Mn2O3 structure and the atomic Al2O3 layer serve as the spacious host and the protection layer of sulfur active materials, respectively, for significantly improved electrochemical performance of the Li-S battery.

It is highly desired to develop high efficient non-precious metal catalysts for urea oxidation and energy-saving electrolytic hydrogen production. In this communication, we report that bimetallic NiCoP nanosheets array on carbon cloth acts as a superb and stable catalyst for urea oxidation reaction (UOR) with the need of potential of 0.455 V to achieve 50 mA cm−2 in 1.0 M KOH and 0.33 M urea. The excellent catalytic activity for hydrogen evolution reaction (HER) enables this electrode as a bifunctional UOR and HER catalyst and its two-electrode system affords 20 mA cm−2 at a cell voltage of only 1.25 V, 360 mV smaller than that of pure water splitting, with strong long-term electrochemical stability.

MnMoO4 nanotubes of diameter about 120 nm were successfully synthesized by a single-spinneret electrospinning technique followed by calcination in air, and their structural, morphological, and electrochemical properties were studied with the aim to fabricate high-performance supercapacitor devices. The obtained MnMoO4 nanotubes display a 1D architecture with a porous structure and hollow interiors. Benefiting from intriguing structural features, the unique MnMoO4 nanotube electrodes exhibit a high specific capacitance, excellent rate capability, and cycling stability. As an example, the tube-like MnMoO4 delivers a specific capacitance of 620 F g−1 at a current density of 1 A g−1, and 460 F g−1 even at a very high current density of 60 A g−1. Remarkably, almost no decay in specific capacitance is found after continuous charge/discharge cycling for 10,000 cycles at 1 A g−1. An asymmetric supercapacitor fabricated from this MnMoO4 nanotubes and activated carbon displayed a maximum high energy density of 31.7 Wh kg−1 and a power density of 797 W kg−1, demonstrating a good prospect for practical applications in energy storage electronics.

Development of carbon electrodes with high volumetric electrochemical performance is challenging for high-performance energy storage devices. In this work, we demonstrate a novel sucrose-derived porous carbon monolith (NPC-m) constructed by holey carbon nanosheets for super-high volumetric energy storages. NPC-m, derived from sucrose via a facile yet scalable and economic “bottom-up” synthesis route, exhibits a high specific surface area of 1376 m2 g−1, a narrow hole size distribution, and a high N content (∼6.65 at. %). Most importantly, a self-stacking density as high as 1.26 g cm−3 can be achieved via simple drying processes. The electrodes based on NPC-m in carbon electrodes deliver super-high volumetric capacities of 1385 mAh cm−3 (0.1 A g−1) for Li-ion batteries and 380 F cm−3 (0.5 A g−1) for supercapcacitors, highlighting their great potentials for high-performance energy storages.

In this paper, a highly ordered three-dimensional ZnFe2O4@MnO2 core/shell nanosheet arrays (ZnFe2O4@MnO2 NSAs) on three-dimensional (3D) Nickel foam (Ni foam) have been prepared via a facile, stepwise hydrothermal approach and further investigated as a battery-type electrode material. It is found that the honeycomb-like ZnFe2O4@MnO2 NSAs have outstanding electrochemical performances using cyclic voltammetry (CV), galvanostatic charge-discharge (CD), and electrochemical impedance spectroscopy (EIS) in a three-electrode system. Based on the unique nanostructure, the ZnFe2O4@MnO2 NSAs exhibit an exceptional capacity of 1084 C g−1 at current density of 2 A g−1 and long-term capacity retention of 96.1% after 5000 cycles at current density of 4 A g−1. Moreover, the ZnFe2O4 nanosheet arrays (ZnFe2O4 NSAs) also have 714 C g−1 at a current density of 2 A g−1 exhilaratingly and the capacity value is proven to be the highest when compared with other structures of ZnFe2O4 taken from the other literatures. Some synergistic effects are identified to be responsible for the observations: Firstly, high crystalline quality of the ZnFe2O4 NSAs core which is directly grown on 3D Nickel foam (a conductive current collector), allowing fast electron transport; secondly, the unique structure of honeycomb-like MnO2 shell that has an ultralarge surface area for electrochemical reaction; thirdly, smart combination of ZnFe2O4 and MnO2 effectively utilizes their different virtues and also compensate their defects; finally, highly conductive 3D Ni foam substrate, which fully eliminate conductive additives and binders.

Composites consisting of selenium/carbon (Se/C) encapsulated by ultra-thin Ni(OH)2 nanosheet shell are synthesized as cathode for high-performance lithium-selenium batteries. The Se/C-Ni(OH)2 cathode presents excellent discharge capacities and cyclic stability with almost 100% Coulombic efficiencies. It delivers a reversible capacity of 323 mAh g−1 after 300 cycles with almost negligible capacity degradation after 100 cycles at a high current density of 1 C. Several unique functional features of the composite electrodes are responsible for the findings. The uniform mixture of Se and carbon black in the composite promotes the utilization of the active materials with enhanced ion/electron transfer. The Ni(OH)2 nanosheets maintain the integrity of Se/C core during cycles, reducing the shuttling effect reactions of polyselenides. These results demonstrate that the Se/C-Ni(OH)2 composite cathode is a promising candidate for application in rechargeable lithium-selenium batteries.

In this work, photoelectric responses of nanocrystalline WO3 film to humidity under UV light irradiation were investigated. Nanocrystalline WO3 film with porous structure was prepared on Al2O3 substrate by the technology of screen printing and the subsequent heat treatment. The as-prepared nanocrystalline WO3 film was characterized with X-ray diffraction (XRD) and field-emission gun scanning electron microscopy (FE-SEM). The time-dependent photoelectric responses of nanocrystalline WO3 film were studied by exposing it to a wide humidity range of 20–80% relative humidity (RH) at room temperature under UV light irradiation. High performance photoelectric responses of nanocrystalline WO3 film to humidity were observed. To illustrate it, a possible explanation for the photoelectric responses to humidity was proposed. On the basis of the results, the high performance photoelectric responses of WO3 to humidity will provides a new insight into the design and fabrication of advanced photo-activated humidity sensors.