Freestanding three-dimensional nitrogen-doped carbon foam with large pores is proposed as a promising electrode configuration for elastic electronics. Although it exhibits excellent mechanical performance, the capacitive performances (especially its rate capability) are still unsatisfactory. By using KMnO4, we demonstrate a smart etching and catalytic process to form highly graphitized and etched nitrogen-doped carbon foam (ENCF) with an exfoliated carbon-shell architecture. These compositional and structural features endow the ENCF electrodes with excellent electron conductivity as well as more ion-accessible electrochemical active sites. Significantly, all-solid-state symmetric supercapacitor devices based on the ENCF electrodes exhibit enhanced specific capacitance and marked high-rate capability. Furthermore, the integrated device has no significant capacity loss under 60% compressive strain.Keywords: compressible electrode; excellent rate capability; KMnO4; nitrogen-doped carbon; symmetric supercapacitor;

We report the discovery of a dramatically enhanced N2 electroreduction reaction (NRR) selectivity under ambient conditions via the Li+ incorporation into poly(N-ethyl-benzene-1,2,4,5-tetracarboxylic diimide) (PEBCD) as a catalyst. The detailed electrochemical evaluation and density functional theory calculations showed that Li+ association with the O atoms in the PEBCD matrix can retard the HER process and can facilitate the adsorption of N2 to afford a high potential scope for the NRR process to proceed in the “[O—Li+]·N2—Hx” alternating hydrogenation mode. This atomic-scale incorporation strategy provides new insight into the rational design of NRR catalysts with higher selectivity.

We demonstrate here a novel strategy to prepare a flexible and free-standing sulfur cathode with improved mechanical strength, the matrix of which is constructed from graphitized nitrogen-doped mesoporous carbon nanofibers (NPCFs). Benefiting from a unique micro/mesoporous structure and highly graphitic carbon, the NPCF film is capable of accommodating more sulfur, and maintains substantially higher mechanical strength and flexibility after sulfur loading as compared with traditional microporous carbon nanofiber films. As a free-standing and flexible cathode for Li–S batteries, the robust composite film exhibits excellent rate capability (540 mA h g−1 at 5C) and cycling stability (76.5% retention after 500 cycles at 5C).

Overcoming the dilemma between hydrogen permeability and stability is critical for realizing the widespread application of mixed protonic–electronic conducting (MPEC) membranes. Herein, fluoride-anion doping is for the first time reported for tuning the separation performance of MPEC membranes. Lanthanum tungstate oxyfluoride membranes, La5.5W0.6Mo0.4O11.25−δFx (x = 0, 0.025, 0.05, 0.10, 0.20, 0.50), exhibit improved hydrogen permeability and enhanced stability compared to their parent oxides, achieving a maximum value of 0.20 mL min−1 cm−2 at x = 0.05. Moreover, the declining hydrogen permeability performance of lanthanum tungstate MPEC membranes during high-temperature operation was systematically analyzed and relative solutions are put forward. The anion-doping and stability-improving strategies might accelerate the development and future practical applications of MPEC membranes.

Designing oxygen cathodes with both high energy density and excellent cycling stability is a great challenge in the development of lithium–oxygen (Li–O2) batteries for energy storage systems. Herein, we design a novel structure of hierarchical NiCo2O4 nanosheets on porous carbon nanofiber films (denoted as NiCo2O4@CNFs) as an oxygen cathode for lithium–oxygen batteries. The NiCo2O4@CNFs cathode delivers a high specific discharge capacity of 4179 mA h g−1, a high energy density of 2110 W h kg−1 and superior cycling stability over 350 cycles. The excellent electrochemical performance of the NiCo2O4@CNFs cathode can be attributed to the rational design and engineering of catalysts and porous conductive electrodes. These results indicate that the NiCo2O4@CNFs electrode is a promising candidate for high energy density and long-life Li–O2 batteries. Additionally, the rational design of the hierarchical catalyst constructed low-dimensional nanostructure and the lightweight porous carbon nanofiber electrode can be also used for other metal–oxygen batteries, such as zinc–oxygen (Zn–O2) batteries, aluminum–oxygen (Al–O2) batteries, and sodium–oxygen (Na–O2) batteries.

We report here a facile and efficient electrodeposition method to modify inexpensive porous stainless-steel nets for use as substrates in the in situ growth of metal–organic framework membranes, such as ZIF-8, ZIF-67 and HKUST-1. Using this method, different metal precursors can be electrodeposited depending on the central metals required in the target metal–organic frameworks. The inorganic modifiers prepared by this approach are sufficiently reactive for the one-step growth of continuous metal–organic framework membranes; their reactivity is comparable with that of organic functional groups. The procedure is also green and cost-effective, which is promising for use in large-scale production.

•A thin and lightweight PI-SiO2 fibrous membrane was successfully synthesized.•The PI-SiO2 membrane possesses high porosity and excellent electrolyte wettability.•The PI-SiO2 membrane shows superior flexibility and thermal stability up to 250 °C.•LiMn2O4/Li cell using the PI-SiO2 separator exhibits excellent rate capability.•LiMn2O4/Li cell using the PI-SiO2 separator displays long cycle life at 55 °C.The commercial polyolefin separators still possess two well-known drawbacks: poor wettability and thermal stability. Herein, a thin and lightweight silica filled in polyimide (PI) nanofibers membrane is prepared by electrospinning. Without any binders, the nano-silica particles are firmly embedded in the PI nanofibers with high structure stability. The PI-SiO2 membrane with high porosity (90%) presents enhanced conductivity due to the excellent electrolyte wettability and large electrolyte uptake (about 2400%). In addition, the PI-SiO2 membrane displays good mechanical flexibility and enhanced thermal stability up to 250 °C, which significantly improve the safety of lithium-ion batteries when used as a separator. The LiMn2O4/Li cell with the PI-SiO2 separator exhibits highly improved rate capability and cycling stability at different temperatures (25 °C and 55 °C), which make PI-SiO2 membrane as a promising secure separator candidate for high-performance and safety lithium-ion batteries.Download high-res image (168KB)Download full-size image

Ultralow Friction MembranesIn their Communication on page 8974 ff., J. Caro et al. report a water purification membrane composed of 2D g-C3N4 nanosheets. Self-supporting spacers and intrinsic and artificial nanopores promote water transport with ultralow friction.

Reibungsarme Membranen In der Zuschrift auf S. 9102 ff. berichten J. Caro et al. über eine Wasseraufbereitungsmembran aus Nanoschichten von graphitischem Kohlenstoffnitrid. Freitragende Abstandhalter sowie intrisische und künstliche Nanoporen bewirken einen reibungsarmen Wassertransport.

AbstractTwo-dimensional (2D) graphitic carbon nitride (g-C3N4) nanosheets show brilliant application potential in numerous fields. Herein, a membrane with artificial nanopores and self-supporting spacers was fabricated by assembly of 2D g-C3N4 nanosheets in a stack with elaborate structures. In water purification the g-C3N4 membrane shows a better separation performance than commercial membranes. The g-C3N4 membrane has a water permeance of 29 L m−2 h−1 bar−1 and a rejection rate of 87 % for 3 nm molecules with a membrane thickness of 160 nm. The artificial nanopores in the g-C3N4 nanosheets and the spacers between the partially exfoliated g-C3N4 nanosheets provide nanochannels for water transport while bigger molecules are retained. The self-supported nanochannels in the g-C3N4 membrane are very stable and rigid enough to resist environmental challenges, such as changes to pH and pressure conditions. Permeation experiments and molecular dynamics simulations indicate that a novel nanofluidics phenomenon takes place, whereby water transport through the g-C3N4 nanosheet membrane occurs with ultralow friction. The findings provide new understanding of fluidics in nanochannels and illuminate a fabrication method by which rigid nanochannels may be obtained for applications in complex or harsh environments.

AbstractTwo-dimensional (2D) graphitic carbon nitride (g-C3N4) nanosheets show brilliant application potential in numerous fields. Herein, a membrane with artificial nanopores and self-supporting spacers was fabricated by assembly of 2D g-C3N4 nanosheets in a stack with elaborate structures. In water purification the g-C3N4 membrane shows a better separation performance than commercial membranes. The g-C3N4 membrane has a water permeance of 29 L m−2 h−1 bar−1 and a rejection rate of 87 % for 3 nm molecules with a membrane thickness of 160 nm. The artificial nanopores in the g-C3N4 nanosheets and the spacers between the partially exfoliated g-C3N4 nanosheets provide nanochannels for water transport while bigger molecules are retained. The self-supported nanochannels in the g-C3N4 membrane are very stable and rigid enough to resist environmental challenges, such as changes to pH and pressure conditions. Permeation experiments and molecular dynamics simulations indicate that a novel nanofluidics phenomenon takes place, whereby water transport through the g-C3N4 nanosheet membrane occurs with ultralow friction. The findings provide new understanding of fluidics in nanochannels and illuminate a fabrication method by which rigid nanochannels may be obtained for applications in complex or harsh environments.

Lithium–sulfur batteries are a promising next-generation energy storage device owing to their high theoretical capacity and the low cost and abundance of sulfur. However, the low conductivity and loss of active sulfur material during operation greatly limit the rating capabilities and cycling stability of lithium–sulfur batteries. In this work, a unique sulfur host hybrid material comprising nanosized nickel sulfide (NiS) uniformly distributed on 3D carbon hollow spheres (C-HS) is fabricated using an in situ thermal reduction and sulfidation method. In the hybrid material, the nanosized NiS provides a high adsorption capability for polysulfides and the C-HS serves as a physical confinement for polysulfides and also a 3D electron transfer pathway. Moreover, NiS has strong chemical coupling with the C-HS, favoring fast charge transfer and redox kinetics of the sulfur electrode. With a sulfur loading of up to 2.3 mg cm−2, the hybrid material-based lithium–sulfur batteries offer a capacity decay as low as 0.013% per cycle and a capacity of 695 mA h g−1 at 0.5 C after 300 cycles. This unique 3D hybrid material with strong chemical coupling provides a promising sulfur host for high performance lithium–sulfur batteries.

•Universal stability in CO2 of CGO-perovskite dual phase membranes was demonstrated.•Good performance of partial oxidation of methane was achieved in a membrane reactor.•No performance degradation was observed with pure CH4 as reactant in long-term test.To improve the chemical stability of perovskite materials (alkaline earth metal containing) in CO2-containing atmosphere, based on the dual phase structure membranes, we prepared three CO2-stable CGO (Ce0.9Gd0.1O2−δ)-perovskite dual phase membranes, which takes the perovskite oxides as the electrons conducting phase and the fluorite CGO oxide (possesses inherently high chemical stability against CO2) as the oxygen ionic conductor. During the oxygen separation tests, all the membranes exhibit good reversibility when periodically changing the sweep gases from CO2 to Helium and good long-term stability in CO2, which demonstrate these CGO-perovskite dual phase membranes possess universal stability in CO2. Then one of these dual phase membranes (Ce0.9Gd0.1O2−δ-Ba0.5Sr0.5Co0.8Fe0.2O3−δ (CGO-BSCF)) was chosen as a model material to be applied in partial oxidation of methane (POM) to syngas. At 900 °C, the oxygen permeation flux of 14 mL/min cm2, CH4 conversion of 96% and CO selectivity of 97%, and the H2/CO of 2 were achieved. And no performance degradation of the membrane reactor was observed during continuously 230 h operation by using pure CH4 for POM at 900 °C. Due to the good CO2 stability and good performance in POM, the CGO-perovskite dual phase membranes could potentially stimulate their applications in industrial applications.Three type CGO-perovskite dual phase membranes were prepared to demonstrated their universal stability in CO2. Then one model material (Ce0.9Gd0.1O2−δ-Ba0.5Sr0.5Co0.8Fe0.2O3−δ) was chosen as a dual phase membrane reactor to be applied in partial oxidation of methane (POM) to syngas. At 900 °C, the oxygen permeation flux of 14 mL/min cm2, CH4 conversion of 96% and CO selectivity of 97% were achieved. And no performance degradation of the membrane reactor was observed during continuously 230 h operation by using pure CH4 for POM at 900 °C, which indicates that the CGO-perovskite dual phase membranes can be steadily operated in POM process with good performance.Download high-res image (64KB)Download full-size image

•A flexible porous carbon nanofiber film was fabricated by electrospinning.•Ultrafine titanium dioxide and graphene were adopted to modify the nanofibers.•The sulfur cathode film exhibits good flexibility and foldability.•The flexible film cathode shows excellent electrochemical performance.Lithium-sulfur (Li-S) batteries are regarded as a promising next-generation electrical-energy-storage technology due to their low cost and high theoretical energy density. Furthermore, flexible and wearable electronics urgently requires their power sources to be mechanically robust and flexible. However, the effective progress of high-performance, flexible Li-S batteries is still hindered by the poor conductivity of sulfur cathodes and the dissolution of lithium polysulfides as well as the weak mechanical properties of sulfur cathodes. Herein, a new type of flexible porous carbon nanofiber film modified with graphene and ultrafine polar TiO2 nanoparticles is designed as a sulfur host, in which the artful structure enabled the highly efficient dispersion of sulfur for a high capacity and a strong confinement capability of lithium polysulfides, resulting in prolonged cycle life. Thus, the cathode shows an extremely high initial specific discharge capacity of 1501 mA h g−1 at 0.1 C and an excellent rate capability of 668 mA h g−1 at 5 C as well as prolonged cycling stability. The artful design provides a facile method to fabricate high-performance, flexible sulfur cathodes for Li-S batteries.Download high-res image (310KB)Download full-size image

•First study on the effect of La/W ratio in lanthanum tungstate on H2 permeability.•H2 flux increases with increasing La/W ratio with little compromise in stability.•La5.5WO11.25-δ is promising with balanced H2 flux and stability.Lanthanum tungstates are the kind of attractive mixed proton-electron conductive (MPEC) oxides, which can be used as the hydrogen permeable membrane with almost infinite hydrogen selectivity in dry hydrogen-containing atmosphere theoretically. A series of lanthanum tungstates with different La/W ratios, La5.3WO11.25-δ (LWO53), La5.4WO11.25-δ (LWO54), La5.5WO11.25-δ (LWO55) and La5.6WO11.25-δ (LWO56), were prepared through a solid-state reaction method and the effect of La/W ratio on the membrane structure, stability and hydrogen permeation properties have been investigated. A pure cubic phase can be formed gradually with the increase in calcination temperature for lanthanum tungstates. The phase formation temperature increases with the increase in the La/W ratio, and a higher oxygen absorption capacity can be achieved in lanthanum tungstate with a higher La/W ratio. The hydrogen permeation flux through the lanthanum tungstate membranes increases slightly with an increase in La/W ratio, while the stability decreases. The lanthanum tungstate membrane with a La/W ratio of 5.5 may be a good candidate for hydrogen separation applications because of its favorable balance between stability and hydrogen permeability.

The performance of a dense ceramic hydrogen-permeable membrane reactor for the nonoxidative methane dehydroaromatization (MDA), according to the equilibrium reaction 6CH4 ⇆ C6H6 + 9H2 with a 6 wt % Mo/HZSM-5 bifunctional catalyst was investigated. A U-shaped ceramic hollow fiber membrane of the composition La5.5W0.6Mo0.4O11.25−δ (LWM0.4) has been used for the in situ removal of H2 to overcome thermodynamic constraints. The yield of aromatics (benzene, toluene, naphthalene) in the MDA could be increased in the beginning of the aromatization reaction by ∼50%–70%, in comparison with the fixed-bed reactor, because 40%–60% of the H2 abstracted have been extracted at 700 °C with a weight hourly space velocity (WHSV) of 840 cm3 gcat–1 h–1. These advantages of the membrane reactor operation decrease with time on stream, since the removal of H2 boosts not only CH4 conversion and yield of aromatics, but also catalyst deactivation by deposition of carbonaceous deposits. However, the catalyst system could be regenerated by burning the coke away with air.Keywords: catalyst regeneration; gas-to-liquids technologies; hollow fiber membrane; hydrogen-permeable ceramic membrane; natural gas conversion; nonoxidative methane dehydroaromatization

Anode materials with capacitive charge storage (CCS) are highly desirable for the development of high-performance sodium-ion batteries (SIBs), because the capacitive process usually shows kinetically high ion diffusion and superior structural stability. Here, we report a new CCS anode material of graphene-based nitrogen-doped carbon sandwich nanosheets (G-NCs). The as-prepared G-NCs show a high capacitive contribution during the discharge/charge processes. As expected, the G-NCs exhibit excellent rate performance with a reversible capacity of 110 mA h g−1, even at a current as high as 10000 mA g−1, and outstanding cycle stability (a retention of 154 mA h g−1 after 10000 cycles at 5000 mA g−1). This represents the best cycle stability among all reported carbon anode materials for SIBs, thereby showing great potential as a commercial anode material for SIBs.

Porous Na3V2(PO4)3@C nanocomposites enwrapped in a 3D graphene network were prepared using a simple freeze-drying-assisted thermal treatment method. The carbon layer and 3D graphene network provide not only a 3D conductive network but also a double restriction on the aggregation of Na3V2(PO4)3 particles that have a high crystallinity under high temperature treatment. Due to the high electrochemical activity of the highly crystalline Na3V2(PO4)3 nanoparticles and 3D conductive network, the novel NVP@C/G material displays a superior rate capability (76 mA h g−1 at 60C) and ultra-long cyclability (82% capacity retention for 1500 cycles at 40C) when used in sodium-ion batteries.

Exploring high-performance negative electrode materials is one of the great challenges in the development of high-energy density asymmetric supercapacitors (ASCs). Herein, a new kind of high-performance nitrogen-doped nanoporous carbon (NPC) electrode with a large surface area and abundant micropores/mesopores was derived from conveniently available fruit waste (shaddock peel) via a facile pyrolysis process. Electrochemical measurements showed that the as-synthesized NPC electrodes possessed a remarkably large capacitance of 321.7 F g−1 with good rate capability and excellent long-term cycling stability. Such excellent electrochemical performance was achieved by shortening the diffusion distance, increasing the electrode–electrolyte contact area and improving the electron conductivity of the NPC electrode arising from its nanoporous architecture and nitrogen doping. As a prototype, an all-solid-state ASC device based on the NPC negative electrode and a MnO2 positive electrode achieved an ultrahigh energy density of 82.1 W h kg−1 at a power density of 899 W kg−1, which is considerably larger than most reported carbon based supercapacitor devices.

The electrode materials with structure stability and binder-free are urgently required for improving the electrochemical performance of lithium-ion batteries. In this work, interconnected α-Fe2O3 nanosheet arrays directly grown on Ti foil were fabricated via a facile galvanostatic electrodeposition method followed by thermal treatment. The as-prepared α-Fe2O3 has an open network structure constituted of interconnected nanosheets and can be directly used as integrated electrodes for lithium-ion batteries. The α-Fe2O3 nanosheet arrays exhibit a high reversible capacity of 986.3 mAh g−1 at a current density of 100 mA g−1. Moreover, a reversible capacity of ca. 425.9 mAh g−1 is achieved even at a superhigh current density of 10 A g−1, which is higher than the theoretical capacity of commercially used graphite. The excellent performance could be attributed to the efficient electron transport, the large electrode/electrolyte interfaces and the good accommodations for volume expansion from the interconnected nanosheet arrays structure.

•Co3O4@PPynanowirearraysaresynthesizedbyatwo-stepmethod(*).•Co3O4@PPy NWAs exhibit improved rate capability and long cycle life.•The enhanced performance is attributed to the conductive PPy coating layer.Coaxial Co3O4@polypyrrole (Co3O4@PPy) nanowire arrays have been successfully synthesized via a simple hydrothermal method and further a polymerization process. According to the composition and morphology characterization, it is found that a thin layer of amorphous PPy is uniformly coated on the surface of the Co3O4 nanowire. When directly used as an anode material for lithium-ion batteries, the Co3O4@PPy nanowire arrays electrode exhibits high reversible capacity, good rate capability, and improved cycling stability. A reversible capacity of 700 mAh g−1 is sustained at the current of 3 A g−1 after 500 cycles, showing better cycling stability than the bare Co3O4 nanowire arrays (only 150 mAh g−1 at the current of 3 A g−1after 100 cycles). Even at a high current of 20 A g−1, the Co3O4@PPy nanowire arrays can still maintain a capacity of 470 mAh g−1, which is much higher than that of the bare Co3O4 nanowire arrays (158 mAh g−1). The synergetic effect of the arrays structure and the PPy buffer layer contributes to the enhanced electrochemical performance of the Co3O4@PPy nanoarrys. As a result, the introduction of conductive polymer coating layer is an effective strategy to enhance the electrochemical performance of nanoarrays structure for advanced energy storage.

•TiN-coated micron-sized Ta-doped Li4Ti5O12 was synthesized via a facile method.•Both TiN coating and Ta doping of Li4Ti5O12 improved the electronic conductivities.•LTOTaN30 anode showed better anodic performance than the bare and mono doped LTO.Micron-sized Li4Ti5O12 with both surface modification (TiN) and inner Ta5+ doping has been synthesized via a combination of solid-state reaction and surface thermal nitridation. The physical and chemical properties of all samples are tested systematically. The results demonstrate that tantalum is successfully doped in the lattice of Li4Ti5O12 and a thin amorphous TiN coated on the surface of the Li4Ti5O12 particles. The TiN coating layer enhances surface electronic conductivity and electrical contact between particles, while Ta5+ bulk doping in the lattice improves the intrinsic ionic conductivity and electronic conductivity inside particles. Being used as anode materials for lithium-ion batteries, the co-doped Li4Ti5O12 electrode shows much better electrochemical performance (144.5 mAh g−1 at 5 C after 500 cycles with a capacity retention of 91.63%) than that of pristine Li4Ti5O12 and mono tantalum doped or TiN coated Li4Ti5O12, only Ta-doped Li4Ti5O12 delivers 112.1 mAh g−1 at 5 C after 500 cycles and the TiN-coated Li4Ti5O12 electrode only retains 122.6 mAh g−1 at 5 C after 500 cycles. This design by exploring both surface modification and bulk doping is highly attractive for high performance Li4Ti5O12 manufacturing and may be applicative to other micron-sized electrode materials with inferior conductivity.

Nanostructured Pt-metal alloys have shown impressive catalytic properties for the oxygen reduction reaction (ORR) in acidic medium, but their long-term stability has not been satisfactory. Herein, we look beyond the traditional Pt-metal alloys and have developed a new kind of Pt-nonmetal alloy electrocatalyst for the ORR. Specifically, the novel catalyst is composed of interconnected platinum monophosphide (PtP) alloy nanocrystals (∼3–4 nm) and featured supportless nanotube array morphologies. Due to the unique combination of composition and structure, the obtained PtP alloy nanotube arrays not only exhibited remarkable ORR activity, but also showed almost no degradation of the half-wave potential after accelerated durability tests. The result suggests that alloying Pt with a nonmetallic element (such as P) is indeed an effective approach to address the poor stability of Pt-based catalysts in acidic medium.

Nitrogen-doped Li4Ti5O12 (LTO) is first synthesized by thermal decomposition of LTO and melamine. As indicated by TG, XPS and TEM analysis, nitrogen is successfully doped in LTO and the generated TiN layer is deposited on the surface of the LTO particle. The LTO with certain nitrogen modification (LTON12) on the surface exhibits enhanced electronic conductivity and Li ion diffusivity. The LTON12 electrode exhibits much better rate capability and cycling performance than the pristine LTO. The LTON12 electrode delivers a capacity of 124.2 mA h g−1 after 500 cycles at 5 C with a high capacity retention of 89.1% while the capacity retention of the pristine LTO is only 43.7%. In addition, the LTON12 exhibits a capacity of 74.3 mA h g−1 at even 100 C with a fixed discharge rate of 1 C. The excellent electrochemical performance of N-doped LTO is attributed to the improved electronic and ion conductivities provided by the thin TiN coating layer on the particle surface.

Structure stability and fast charge–discharge capacity are highly desirable for electrode materials applied in lithium ion batteries (LIBs). In this report, binder-free Co–CoOx nanowire arrays (NWAs) were obtained by a simple H2 reduction of Co3O4 NWAs. The resulting Co–CoOx NWAs were grown directly on the current collector with enough open space between each nanowire, which provides fast charge transfer channels and large accessible surface area to the electrolyte. More importantly, the introduction of electrochemically inactive Co without volume change during cycling for LIBs could improve the structural stability of the Co–CoOx NWA electrode and the high electronic conductivity of metallic Co in the array structure greatly enhances the electron transfer ability of Co–CoOx nanowires. Benefitting from those designed structural features, the binder-free Co–CoOx NWAs achieved remarkable electrochemical performances with excellent cycle stability at high rates and high rate capacity. The Co–CoOx NWA electrode maintains highly stable capacities of 990 and 740 mA h g−1 after 1000 cycles at 10 and 20 A g−1, respectively. At an ultrahigh rate of 50 A g−1, a high reversible capacity of 413 mA h g−1 is achieved. The result demonstrates that such a novel Co–CoOx nanowire array structure is a new strategy to design high performance anode materials for LIBs.

A-site deficient (Pr0.9La0.1)1.9Ni0.74Cu0.21Ga0.05O4+δ ((PL)1.9NCG), with the K2NiF4 structure, is found to exhibit higher oxygen transport rates compared with its cation-stoichiometric parent phase. A stable oxygen permeation flux of 4.6 × 10−7 mol cm−2 s−1 at 900 °C at a membrane thickness of 0.6 mm is measured, using either helium or pure CO2 as sweep gas at a flow rate of 30 mL min−1. The oxygen flux is more than two times higher than that observed through A-site stoichiometric (PL)2.0NCG membranes operated under similar conditions. The high oxygen transport rates found for (PL)1.9NCG are attributed to highly mobile oxygen vacancies, compensating A-site deficiency. The high stability against carbonation gives (PL)1.9NCG potential for use, e.g., as a membrane in oxy-fuel combustion processes with CO2 capture.

Supercapacitors and Li-ion batteries are two types of electrical energy storage devices. To satisfy the increasing demand for high-performance energy storage devices, traditional electrode materials, such as transition metal oxides, conducting polymers and carbon-based materials, have been widely explored. However, the results obtained to date remain unsatisfactory, and the development of inexpensive electrode materials (especially for commercial manufacturing) with superior electrochemical performance for use in supercapacitors and in Li-ion batteries is still needed. The as-prepared NiMoO4 nanosheets (NSs) with interconnecting nanoscale pore channels and an ultrathin structure provide a large electrochemical active area, which facilitates electrolyte immersion and ion transport and provides effective pathways for electron transport. Therefore, the as-prepared NiMoO4 NS electrode exhibits a high specific capacity and an excellent rate capability and cycling stability in supercapacitors and in Li-ion batteries. Moreover, a high energy density (43.5 W h kg−1 at 500 W kg−1) was obtained for the symmetric supercapacitor (SSC) composed of two sections of NiMoO4 NSs.

Perovskites show excellent specific catalytic activity toward both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline solutions; however, small surface areas of the perovskites synthesized by traditional sol–gel methods lead to low utilization of catalytic sites, which gives rise to poor Li–O2 batteries performance and restricts their application. Herein, a hierarchical mesporous/macroporous perovskite La0.5Sr0.5CoO3-x (HPN-LSC) nanotube is developed to promote its application in Li–O2 batteries. The HPN-LSC nanotubes were synthesized via electrospinning technique followed by postannealing. The as-prepared HPN-LSC catalyst exhibits outstanding intrinsic ORR and OER catalytic activity. The HPN-LSC/KB electrode displays excellent performance toward both discharge and charge processes for Li–O2 batteries, which enhances the reversibility, the round-trip efficiency, and the capacity of resultant batteries. The synergy of high catalytic activity and hierarchical mesoporous/macroporous nanotubular structure results in the Li–O2 batteries with good rate capability and excellent cycle stability of sustaining 50 cycles at a current density of 0.1 mA cm–2 with an upper-limit capacity of 500 mAh g–1. The results will benefit for the future development of high-performance Li–O2 batteries using hierarchical mesoporous/macroporous nanostructured perovskite-type catalysts.Keywords: bifunctional catalysts; electrospinning; hierarchical mesoporous/macroporous nanotubes; lithium−oxygen batteries; perovskites

Nitrogen-doped bamboo-like carbon nanotubes (N-BCNTs) were synthesised using a facile one-step pyrolysis process. Due to their unique one-dimensional hollow structure and intrinsic high nitrogen content, N-BCNTs exhibit high capacity, superior rate capability, and excellent cycle stability and are, thus, promising anode materials for sodium-ion batteries.

A mixed protonic and electronic conductor material BaCe0.85Tb0.05Zr0.1O3−δ (BCTZ) is prepared and a Ni-BCTZ cermet membrane is synthesized for hydrogen separation. Stable hydrogen permeation fluxes can be obtained for over 100 h through the Ni-BCTZ membrane in both dry and humid conditions, which exhibits an excellent stability compared with Ni-BaCe0.95Tb0.05O3−δ membrane due to the Zr doping.

•Ta doping in Li4Ti5O12 would enlarge the lattice parameter of Li4Ti5O12.•The ionic conductivity and electronic conductivity of Li4Ti5O12 are improved by Ta doping.•The Li4Ti5O12 with only 0.1 at% Ta doping exhibits superior electrochemical performance.A series of Tantalum-doped lithium titanate (Ta-doped Li4Ti5O12) samples have been successfully synthesized by one step solid-state method using TiO2, Li2CO3, and Ta2O5 as raw materials. The Li4Ti5O12 with only 0.1 at% Ta doping (Li4Ti4.995Ta0.005O12) exhibits higher rate capability and better cyclic stability than the pristine Li4Ti5O12. Li4Ti4.995Ta0.005O12 could deliver 95.1 mAh g−1 at 10C with much lower overpotential (216.1 mV) while the pristine Li4Ti5O12 delivers only 50.4 mAh g−1 at 10C with higher overpotential of 392.2 mV. As indicated by XRD, HRTEM and electrochemical characterizations, Ta doping in Li4Ti5O12 would enlarge the lattice parameter of the Li4Ti5O12, and facilitate the Li+ diffusion during the charge/discharge process. In addition, the higher charge compensation of the stoichiometric reduction of Ti4+ to Ti3+ by introducing Ta increases the electronic conductivity of Li4Ti5O12. The improved ionic conductivity and electronic conductivity are beneficial to the electrochemical performance of Li4Ti5O12. As a result, Ta doping is a new strategy for enhancing the electrochemical performance of Li4Ti5O12.

The carbon material is regarded as the most promising anode candidate for sodium ion battery. In this paper, we found that the porous structure is a critical factor for the improving of carbon anode material. Porous structure is successfully fabricated in nitrogen doped carbon sphere (N-CS) via the mature template-assisted method and the sodium storage property of the porous nitrogen doped carbon sphere (P-N-CS) and N-CS is investigated. The results show that the P-N-CS possesses super rate capability of 155 mAh g−1 at 1 A g−1, which is much higher than that of N-CS (18 mAh g−1). In addition, the P-N-CS exhibits outstanding cycle stability with 206 mAh g−1 after 600 cycles at 0.2 A g−1 and the capacity of N-CS is only 96 mAh g−1 at the same condition. The super electrochemical performance of P-N-CS could be attributed to the high content of pores. Moreover, the high content of pyridinic and graphitic N could facilitate the transfer of sodium ion and electron.

•BaCe0.85Tb0.05Zr0.1O3−δ (BCTZ) was developed by Zr-doping for the first time.•BCTZ membranes with asymmetric structure have been prepared successfully.•BCTZ membrane can be steadily operated for hydrogen separation for over 370 h.•BCTZ exhibits remarkably enhanced phase structure stability.A mixed proton and electron conductor BaCe0.85Tb0.05Zr0.1O3−δ (BCTZ) has been developed by the partial substitution of Ce with Zr in BaCe0.95Tb0.05O3−δ (BCT) to improve the phase structure stability of BCT. The BCTZ membranes with asymmetric structure have been successfully prepared and evaluated for hydrogen separation. A stable hydrogen permeation flux has been found over 370 h operation. The improved stability recommends BCTZ for a potential application in the hydrogen separation.

•The V2O5 nanotubes are prepared by eletrospinning with using low-cost inorganic vanadium source.•The as-prepared V2O5 has porous, hollow and interconnected nanostructures.•By controlling the annealing time, a small amount of carbon can be retained in V2O5 nanotubes.•The V2O5 nanotubes with carbon exhibit excellent high rate performance and cycling stability.In this work, porous vanadium pentoxide (V2O5) nanotubes have been synthesized by a simple electrospinning technique followed by an annealing process with using low-cost inorganic vanadium precursor. By controlling the annealing time at 400 °C, a small amount of polymer pyrolysis carbon can be retained which improves the conductivity of the porous V2O5 nanotubes. When evaluated as a cathode material for lithium ion batteries, the porous V2O5 nanotubes delivered capacities of 114.9, 99.7 and 79.6 mAh g−1 at 10, 20 and 50C in the voltage range of 2.5-4.0 V, respectively. Moreover, the porous V2O5 nanotubes display good cycling performance, the capacity retention is 97.4% after 200 cycles at 50C. The results indicate that fabricating nanostructured V2O5 with a porous interconnected morphology is an effective way to improve the electrochemical performance of V2O5.

We report a novel CO2-stable reduction-tolerant dual-phase oxygen transport membrane 40 wt% Nd0.6Sr0.4FeO3−δ–60 wt% Ce0.9Nd0.1O2−δ (40NSFO–60CNO), which was successfully developed by a facile one-pot EDTA–citric sol–gel method. The microstructure of the crystalline 40NSFO–60CNO phase was investigated by combined in situ X-ray diffraction (XRD), scanning electron microscopy (SEM), back scattered SEM (BSEM), and energy dispersive X-ray spectroscopy (EDXS) analyses. Oxygen permeation and long-time stability under CO2 and CH4 atmospheres were investigated. A stable oxygen flux of 0.21 cm3 min−1 cm−2 at 950 °C with undiluted CO2 as sweep gas is found which is increased to 0.48 cm3 min−1 cm−2 if the air side is coated with a porous La0.6Sr0.4CoO3−δ (LSC) layer. All the experimental results demonstrate that the 40NSFO–60CNO not only shows good reversibility of the oxygen permeation fluxes upon temperature cycling, but also good phase stability in a CO2 atmosphere and under the harsh conditions of partial oxidation of methane to synthesis gas up to 950 °C.

Ultrathin and highly-ordered 2D CoO nanosheet arrays (NSAs) composed of nanocrystals were fabricated via a facile galvanostatic electrodeposition technique. The as-prepared CoO NSAs exhibit excellent cyclability (retain 1000 mA h g−1 after 100 cycles at 1 A g−1) and rate capability (520 mA h g−1 at 10 A g−1) when they are directly used as an anode for LIBs.

•A novel facile synthesis of graphene nanosheets involving freeze-drying technology.•The as-prepared materials exhibit superior cycle stability and rate performance.•The freeze-drying helps to enlarge the interlayer distance and specific surface area.Graphene nanosheets are synthesized by a novel facile method involving freeze-drying technology and thermal reduction. The microstructure and morphologies are characterized by X-ray diffraction, Brunauer–Emmett–Teller measurements, Fourier transform infrared spectroscopy, and high resolution transmission electron microscope. The results indicate that graphene nanosheets with high specific surface area (358.3 m2 g−1) and increased interlayer distance (0.385 nm) are successfully obtained through the freeze-drying process. The electrochemical performances are evaluated by using coin-type cells versus lithium. A high initial reversible capacity of 1132.9 mAh g−1 is obtained at a current density of 100 mA g−1. More importantly, even after 300 cycles at a high current density of 1000 mA g−1, a stable specific capacity of 556.9 mAh g−1 can be achieved, suggesting the graphene nanosheets exhibit superior cycle stability. The fascinating electrochemical performance could be ascribed to the high specific surface area and the increased layer distance between the graphene nanosheets.

•Ultrathin-shell graphene hollow spheres were synthesized by a simple template assisted method without surfactant.•The thickness of the shell is uniform and only 5 nm.•The graphene hollow spheres show excellent electrochemical performance.In this work, ultrathin-shell graphene hollow spheres have been designed and synthesized from the graphene oxide nanosheets by a simple template assisted method without surfactant. It is found that the obtained graphene hollow spheres have a high surface area (248.3 m2 g−1), ultrathin porous shells (5 nm) and an interconnected structure. More strikingly, the as-prepared graphene hollow spheres exhibit outstanding electrochemical performance as an anode material for lithium-ion batteries. Even at a high current density of 5000 mA g−1, a high reversible specific capacity of 249.3 mAh g−1 can be achieved. Furthermore, after 100 cycles, about 97.1% of the specific capacity is maintained at a high current density of 1000 mA g−1. The excellent electrochemical properties could be attributed to the attractive structure advantages of the graphene hollow spheres including the high surface area, ultrathin porous shells and an interconnected structure.

•Porous nano-sized Sn@C/graphene electrode material was designed and prepared.•The preparation method presented here can avoid the agglomeration of nanoparticles.•The prepared Sn@C/graphene electrode material exhibits outstanding cyclability.Tin is a promising high-capacity anode material for lithium-ion batteries, but it usually suffers from the problem of poor cycling stability due to the large volume change during the charge–discharge process. In this article, porous nano-sized Sn@C/graphene electrode material with three-dimensional carbon network was designed and prepared. Reducing the size of the Sn particles to nanoscale can mitigate the absolute strain induced by the large volume change during lithiation–delithiation process, and retard particle pulverization. The porous structure can provide a void space, which helps to accommodate the volume changes of the Sn nanoparticles during the lithium uptake-release process. The carbon shell can avoid the aggregation of the Sn nanoparticles on the same piece of graphene and detachment of the pulverized Sn particles during the charge–discharge process. The 3D carbon network consisted of graphene sheets and carbon shells can not only play a structural buffering role in minimizing the mechanical stress caused by the volume change of Sn, but also keep the overall electrode highly conductive during the lithium uptake-release process. As a result, the as-prepared Sn@C/graphene nanocomposite as an anode material for lithium-ion batteries exhibited outstanding cyclability. The reversible specific capacity is almost constant from the tenth cycle to the fiftieth cycle, which is about 600 mA h g−1. The strategy presented in this work may be extended to improve the cycle performances of other high-capacity electrode materials with large volume variations during charge–discharge processes.

A novel cathode material for lithium-ion batteries, carbon-coated Li3V2(PO4)3 particles which anchored onto graphene sheets (Li3V2(PO4)3@C/graphene) have been prepared by a modified Pechini method. It is first proposed that the graphene oxide can act as a chelating agent in the reaction process. The nanocomposite is characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and element analysis. The composite shows excellent C-rate performance, delivered capacities of 104, 91 and 85 mAh g−1 at 5, 30 and 50 C in the voltage range of 3.0–4.3 V, respectively. Moreover, the cycling performance is also improved in higher voltage range of 3.0–4.8 V. The capacity retention is 83% with the capacity of 131 mAh g−1 at 10 C after 100 cycles. The outstanding features are desirable and enable the material to be an excellent cathode for lithium-ion batteries.Graphical abstractA novel structured Li3V2(PO4)3@C/graphene composite was prepared via a modified Pechini method. The composite shows significantly improved C-rate and cycling performances. The graphene and the coated-carbon can form an electronic conducting network. The coated-carbon on the surface of LVP particles also can partly block the direct contacts between electrolyte and LVP particles, leading to an improved cycling performance in the wider voltage window.Highlights► Li3V2(PO4)3@C/graphene composite was prepared via a modified Pechini method. ► The cathode material shows significantly improved C-rate and cycling performances. ► It is first proposed that the graphene oxide can act as a chelating agent. ► Graphene could greatly improve the electronic conductivity. ► The coated-carbon can partly block the direct contact between electrolyte and LVP.

•The (Fe2.5Ti0.5)1.04O4–graphene nanocomposite was firstly prepared.•It was prepared by a novel gas/liquid interfacial synthesis approach.•Its electrochemical performances for the lithium storage were firstly studied.•It shows high reversible capacity, outstanding cyclability and excellent rate performance.A (Fe2.5Ti0.5)1.04O4–graphene nanocomposite was prepared by using a gas/liquid interfacial synthesis approach. The as-prepared nanocomposite was characterized by X-ray powder diffraction and transmission electron microscopy. The transmission electron microscopy characterization results indicate that (Fe2.5Ti0.5)1.04O4 nanoparticles were successfully deposited onto the surfaces of graphene sheets during the gas/liquid interfacial reaction process. The electrochemical performances were evaluated by using coin-type cells versus metallic lithium. The (Fe2.5Ti0.5)1.04O4–graphene nanocomposite exhibited a high reversible specific capacity of 1048 mAh g−1 after 60 cycles at a specific current of 300 mA g−1 and good rate capability, even at a high specific current of 2000 mA g−1, the reversible specific capacity was still as high as 480 mAh g−1. Most importantly of all, the (Fe2.5Ti0.5)1.04O4–graphene nanocomposite also showed excellent cyclic stability (1113 mAh g−1 after 100 cycles at the specific current of 300 mA g−1). These results indicate that the (Fe2.5Ti0.5)1.04O4–graphene nanocomposite is a promising anode material for lithium-ion batteries.

A K2NiF4-type oxide (Nd0.9La0.1)2(Ni0.74Cu0.21Al0.05)O4+δ (NLNCA) has been successfully synthesized by a sol–gel method. The oxygen permeation and stability of the NLNCA membrane under CO2 atmosphere were systematically studied. A steady oxygen permeation flux of 0.39 mL/(min·cm2) was obtained through the NLNCA membrane with a membrane thickness of 0.6 mm at 975 °C when CO2 was used as the sweep gas. More importantly, the oxygen permeation flux has no significant decrease during 250 h operation, which indicates that the NLNCA membrane is stable under CO2. X-ray diffraction analysis of the spent membrane shows that the membrane retains K2NiF4-type structure and no carbonate was formed even exposed to CO2 after 250 h operation. The results indicate that the NLNCA membrane has a great potential application in supplying oxygen for oxyfuel combustion with CO2 capture. Moreover, the cost of the NLNCA is low, and it is beneficial for industrial application.

TiO2/nitrogen-doped graphene nanocomposite was synthesized by a facile gas/liquid interface reaction. The structure and morphology of the sample were analyzed by X-ray diffraction analysis, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. The results indicate that nitrogen atoms were successfully doped into graphene sheets. The TiO2 nanoparticles (8–13 nm in size) were homogenously anchored on the nitrogen-doped graphene sheets through gas/liquid interface reaction. The as-prepared TiO2/nitrogen-doped graphene nanocomposite shows a better electrochemical performance than the TiO2/graphene nanocomposite and the bare TiO2 nanoparticles. TiO2/nitrogen-doped graphene nanocomposite exhibits excellent cycling stability and shows high capacity of 136 mAh g−1 (at a current density of 1000 mA g−1) after 80 cycles. More importantly, a high reversible capacity of 109 mAh g−1 can still be obtained even at a super high current density of 5000 mA g−1. The superior electrochemical performance is attributed to the good electronic conductivity introduced by the nitrogen-doped graphene sheets and the positive synergistic effect between nitrogen-doped graphene sheets and TiO2 nanoparticles.Highlights► TiO2/N-doped graphene composite was synthesized by a gas/liquid interfacial method. ► The nanocomposite was used to fabricate lithium-ion batteries. ► Its electrochemical performance was evaluated for the first time. ► The anode material exhibits a good cycling performance and rate capability.

•A novel cathode with the K2NiF4-type oxide Pr1.8La0.2Ni0.74Cu0.21Ga0.05O4+δ was prepared.•The maximum power density of the cell was 876 mW cm−2 with air as oxidant at 750 °C.•The Pr1.8La0.2Ni0.74Cu0.21Ga0.05O4+δ is a potential cathode with excellent CO2 resistance.Pr1.8La0.2Ni0.74Cu0.21Ga0.05O4+δ (PLNCG), a mixed ionic electron conductor (MIEC) with a K2NiF4-type structure, has been studied as a potential cathode material based on YSZ (ZrO2 with 8 mol% Y2O3) electrolyte for intermediate temperature solid oxide fuel cells (IT-SOFCs). The X-ray diffraction (XRD) analysis reveals that the good chemical compatibility between the PLNCG and YSZ. The maximum electric conductivity of the PLNCG appeared at about 460 °C and the value was 32 S cm−1 in air and 34 S cm−1 in O2, respectively. A hollow fiber SOFC was fabricated with the PLNCG as the cathode, NiO–YSZ (1:1; w/w) as the anode and YSZ as the electrolyte. The maximum power density of the cell is 876 mW cm−2 and the corresponding polarization resistance of the cell is 0.41 Ω cm2 at 750 °C. Furthermore, the PLNCG cathode shows an excellent CO2 resistance in the operation temperature range. The maximum power density of the cell is similar to that when the cathode is exposed to air. Furthermore, the cell performance is stable when the CO2 concentrations in the air vary from 0 to 10 vol.% at both 700 and 750 °C. These results indicate that the PLNCG can be a good candidate for CO2 resistance cathode materials of IT-SOFCs based on YSZ electrolyte.

A novel cobalt-free and noble metal-free dual-phase oxygen-transporting membrane with a composition of 40 wt % Pr0.6Sr0.4FeO3−δ–60 wt % Ce0.9Pr0.1O2−δ (40PSFO–60CPO) has been successfully developed via an in situ one-pot one-step glycine-nitrate combustion process. In situ XRD demonstrated that the 40PSFO–60CPO dual-phase membrane shows a good phase stability not only in air but also in 50 vol % CO2/50 vol % N2 atmosphere. When using pure He or pure CO2 as sweep gases, at 950 °C steady oxygen permeation fluxes of 0.26 cm3 min–1 cm–2 and 0.18 cm3 min–1 cm–2 are obtained through the 40PSFO–60CPO dual-phase membrane. The partial oxidation of methane (POM) to syngas was also successfully investigated in the 40PSFO–60CPO dual-phase membrane reactor. Methane conversion was found to be higher than 99.0% with 97.0% CO selectivity and 4.4 cm3 min–1 cm–2 oxygen permeation flux in steady state at 950 °C. Our dual-phase membrane - without any noble metals such as Ag, Pd or easily reducible metals oxides of Co or Ni - exhibits high oxygen permeation fluxes as well as good phase stability at high temperatures. Furthermore, the dual-phase membrane shows a good chemical stability under the harsh conditions of the POM reaction and in a CO2 atmosphere at high temperatures.Keywords: CO2-stable membrane; dual-phase membrane; glycine-nitrate combustion process (GNP); oxygen permeation; partial oxidation of methane (POM);

A novel U-shaped anode-supported hollow fiber solid oxide fuel cell (Ni–YSZ/YSZ/YSZ–La0.8Sr0.2MnO3−δ) was fabricated via wet spinning followed by sintering. The anode support has an asymmetric configuration with finger-like structure inside and sponge-like structure outside. The peak power densities are 104, 256, 584, 884 mW cm−2 at 600, 650, 700, 750 °C, respectively. The U-shaped anode-supported hollow fiber solid oxide fuel cell (SOFC) shows considerable thermal cycling performance with 65 cycles, which indicates an exciting way to solve the problem of breakage of the straight hollow fiber SOFC during increasing and decreasing temperatures. Furthermore, the cell was operated at 0.7 V and 600 °C for additional 100 h without significant degradation after the 65 cycles.Highlights► A novel U-shaped anode-supported hollow fiber solid oxide fuel cell was prepared. ► The maximum power density was 884 mW cm−2 at 750 °C. ►The U-shaped cell showed excellent thermal cycling performance with 65 cycles. ► The cell performed additional 100 h of stability at 600 °C after the cycles.

Porous Li3V2(PO4)3/C (LVP/C) cathode materials have been synthesized via a sol–gel-combustion method. The porous LVP/C shows stable and extremely high rate capacity, owing to the special porous structure and the nano-sized particle. In the potential range of 3.0–4.3 V, discharge capacities of 122, 114, 108 and 88 mAh g−1 can be delivered at high rates of 10, 20, 40 and 60 C after 100 cycles, respectively. In the potential range of 3.0–4.8 V, the corresponding discharge capacities are 145, 129, 122, 114 and 103 mAh g−1 after 500 cycles at 10, 20, 40, 60 and 100 C, which is the highest level for LVP so far.Graphical abstractPorous Li3V2(PO4)3/C (LVP/C) cathode materials have been synthesized via a sol–gel-combustion method. When filled with liquid electrolyte, the pores are responsible to reduce the distance of ion diffusion and increase the contact area between electrode and electrolyte, resulting in improved electrochemical performance.Highlights► Porous Li3V2(PO4)3/C composite was prepared via a sol–gel-combustion method. ► The porous Li3V2(PO4)3/C shows stable and extremely high rate capacity. ► The good performance is attributed to the porous structure and nano-sized particle.

TiO2-graphene nanocomposite was first synthesized by a facile gas/liquid interface reaction. The structure and morphology were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Brunauer–Emmett–Teller measurements. The results indicate that TiO2 nanoparticles (ca. 10 nm in mean grain size) were successfully deposited onto the graphene sheets during the gas/liquid interfacial reaction process. The electrochemical performance was evaluated by using coin-type cells versus metallic lithium in an enlarged potential window of 0.01–3.0 V. A high specific charge capacity of 499 mAh g−1 was obtained at a current density of 100 mA g−1. More strikingly, the TiO2-graphene nanocomposite exhibits excellent rate capability, even at a high current density of 3000 mA g−1, the specific charge capacity was still as high as 150 mAh g−1. The high specific charge capacities can be attributed to the facts that graphene possesses high electronic conductivity, and the lithium storage performance of graphene is delivered during discharge/charge processes of TiO2-graphene nanocomposite between 0.01 and 3.0 V.Highlights► TiO2-graphene composite was first synthesized by a gas/liquid interfacial method. ► The electrochemical performances were first evaluated between 0.01 and 3.0 V. ► The composite exhibits a high specific capacity and excellent rate performance.

Dense perovskite hollow-fiber membranes based on BaCo0.7Fe0.2Ta0.1O3−δ (BCFT) are prepared by a phase inversion spinning process. The thermal cycling performance and the dependences of oxygen permeation on the air flow rate on the shell side, the helium flow rate on the core side, the oxygen partial pressures, and the operating temperatures are experimentally investigated. The oxygen transport through the U-shaped hollow-fiber membrane is controlled by both surface reaction and bulk diffusion at the temperature ranges of 750–950 °C, whereas the oxygen permeation is predominantly controlled by the surface reaction at 700 °C. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses of the spent hollow-fiber membrane after oxygen permeation for 250 h show the good stability of the U-shaped BCFT hollow-fiber membrane.

Varied graphene sheets were prepared from the graphite oxide (GO) with different degrees of oxidation and furthermore their structural characteristics and electrochemical properties as anode materials for Li-ion batteries were investigated. From the expandable graphite with a low oxidation level, the obtained graphene sheets had a thick and intact sheet structure with good crystallinity. Its specific surface area was quite low and no porous structure was detected. The graphene sheets prepared from the GO precursor with a high degree of oxidation were quite thin and disordered, along with high specific surface area and plenty of pores. These ultrathin graphene sheets demonstrated high reversible capacity mainly in the way of lithium absorption, where the specific surface area was the key structural parameter. The thick graphene sheets prepared from the expandable graphite had good crystallinity with few defects and pores, and had a similar lithium storage mechanism to graphite, whereby lithium storage is carried out by intercalation reactions.

A dual phase membrane of 60 wt % Ce0.9Gd0.1O2-δ-40 wt % Ba0.5Sr0.5Co0.8Fe0.2O3-δ (60CGO-40BSCF), which exhibits high oxygen permeation, has been prepared. X-ray diffraction (XRD) results reveal that the two oxides are compatible. An oxygen permeation flux of 2.1 mL/(min·cm2) is obtained with a 0.5 mm thick membrane under the gradient of air/He at 975 °C, which keeps steady during 180 h of operation. The oxygen permeation process is mainly controlled by the bulk diffusion of oxygen ions in 60CGO-40BSCF membrane when the membrane thickness is higher than 0.8 mm and controlled by both the surface reaction and the bulk diffusion at reduced thickness of ∼0.5 mm as the temperature increased from 800 to 975 °C.

Mixed conducting perovskite oxide SrCo0.9Ta0.1O3−δ (SCT) is synthesized by solid-state reaction method. The activation in the initial stage of oxygen permeation through the SCT membrane is investigated. The results show that the activation in the initial stage of oxygen permeation has activate-memory, the first activation can only help to reduce active time of the next cycles, but it is helpless to increase the final oxygen permeation flux. XRD characterization shows that the imperfect perovskite phase structure is gradually improved and the crystal lattice has made some self-adjustment under the permeation conditions, therefore, the oxygen permeation flux of SCT disk membrane increases gradually and till it reaches a steady state.

An integrative cell with a porous Al2O3 membrane as both a support and a separator has been fabricated. LiFePO4 and graphite were coated onto the both sides of the rigid porous Al2O3 separator, while an electrolyte was infiltrated inside. The LiFePO4/graphite integrative cells were evaluated in coin-type cells and exhibited good cycle capacity. The self-standing integrative cell was a simple and promising technology to assemble the battery stacks and meanwhile had an obvious advantage of forming a firm structure, which could avoid inner short circuit during being moved or crashed.

In this study, LiFePO4/C is synthesized via a novel two-step method. The first step is the synthesis of nano-sized intermediate FePO4 by a modified sol–gel method. A fast and full combustion procedure is involved to remove carbon and control the size of the intermediate particles. The second step is to prepare LiFePO4/C by combining solid-state reaction with controllable carbon coating. This two-step method is facile to prepare nano-sized LiFePO4 and easy to optimize the carbon content for surface coating. X-ray diffraction shows that the LiFePO4/C composite possesses good crystallinity. Spherical morphology with a diameter of 30–150 nm is observed by scanning electron microscope and transmission electron microscope. Electrochemical measurements indicate that the LiFePO4/C composite exhibits discharge capacities of 162, 144, 126, and 106 mAh g−1 at 0.1, 1, 2, and 5C, respectively. No capacity fading is observed in 50 cycles.

An Al2O3 inorganic separator is prepared by a double sintering process. The Al2O3 separator has a high porosity and good mechanical strength. After the liquid electrolyte is infiltrated, the separator exhibits quite high ionic conductivities, and even the conductivity reaches 0.78 mS cm−1 at −20 °C. Furthermore, the inorganic separator has an advantage over the polymer separator in the electrolyte retention. The LiFePO4/graphite cell using the Al2O3 inorganic separator shows higher discharge capacity and rate capability, and better low-temperature performance than that using the commercial polymer separator, which indicates that the Al2O3 separator is very promising to be applied in the lithium-ion batteries.Highlights• Pure Al2O3 inorganic separator for lithium-ion batteries is prepared by a double sintering process. • The inorganic separator soaking the electrolyte solution exhibits quite high ionic conductivities, and specially the conductivity reaches 0.78 mS cm−1 at −20 °C. • The inorganic separator has the higher electrolyte retention at 50 °C than the commercial polymer separator. • The LiFePO4/graphite cell using the inorganic separator shows higher discharge capacity and rate capability, and better low-temperature performance than that using the commercial polymer separator.

The mixed ion and electron conducting oxides of SrCo1−yTayO3−δ (0 ≤ y ≤ 0.3) powders were prepared by solid state reaction. By doping 10 mol% of tantalum on the B-site of SrCoO3, the cubic perovskite structure of the SrCoO3 is stable and a high oxygen permeation flux is achieved. The phase structure of the perovskite-type oxide of SrCo0.9Ta0.1O3−δ was characterized by X-ray diffraction (XRD) and oxygen temperature-programmed desorption (O2-TPD) revealing that SrCo0.9Ta0.1O3−δ exhibits a good phase structure stability and reversibility in air. The oxygen permeation is predominated by oxygen ion bulk diffusion at the temperature ≥ 900 °C. During the long-term operation, the SrCo0.9Ta0.1O3−δ membrane is operated at 900 °C for more than 520 h with a steady oxygen permeation flux of around 1.36 × 10−6 mol/s cm2 with a membrane thickness of 0.65 mm under He/air gradient.Research highlights▶ A proper amount of Ta can stabilize the cubic perovskite structure of SrCoO3−δ. ▶ A highest oxygen permeation flux of 25 × 10−7 mol/s cm2 through SrCo0.9Ta0.1O3−δ membrane was obtained at 950 °C with a sweep He flow rate of 160 mL/min. ▶ SrCo0.9Ta0.1O3−δ (SCT) membrane is steadily operated for more than 520 h for oxygen separation with a stable permeation flux of 1.36 × 10−6 mol/s cm2.

Fe3O4–SnO2–graphene ternary nanocomposite was firstly synthesized by using a gas–liquid interfacial synthesis approach. The as-prepared nanocomposite was characterized by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. The scanning electron microscopy and transmission electron microscopy characterization results indicate that Fe3O4–SnO2 nanoparticles were successfully deposited onto the surfaces of graphene sheets during the gas–liquid interfacial reaction process. The electrochemical performances were evaluated by using coin-type cells vs. metallic lithium. The Fe3O4–SnO2–graphene nanocomposite exhibits a high reversible specific capacity of 1198 mAh g−1 in the 115th cycle at a specific current of 100 mA g−1 and good rate capability, even at a high specific current of 2000 mA g−1, the reversible capacity is still as high as 521 mAh g−1. The good electrochemical performance of the Fe3O4–SnO2–graphene nanocomposite can be attributed to the synergistic effect existing not only between the graphene and metal oxides but also between the Fe3O4 and SnO2.Highlights► The Fe3O4–SnO2–graphene ternary nanocomposite was firstly designed. ► It was prepared by a novel gas–liquid interfacial synthesis approach. ► Its electrochemical performances for the lithium storage were studied. ► It shows high reversible capacity, outstanding cyclability and good rate performance.

A gas–liquid interfacial synthesis approach has been developed to prepare SnO2/graphene nanocomposite. The as-prepared nanocomposite was characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and Brunauer–Emmett–Teller measurements. Field emission scanning electron microscopy and transmission electron microscopy observation revealed the homogeneous distribution of SnO2 nanoparticles (2–6 nm in size) on graphene matrix. The electrochemical performances were evaluated by using coin-type cells versus metallic lithium. The SnO2/graphene nanocomposite prepared by the gas–liquid interface reaction exhibits a high reversible specific capacity of 1304 mAh g−1 at a current density of 100 mA g−1 and excellent rate capability, even at a high current density of 1000 mA g−1, the reversible capacity was still as high as 748 mAh g−1. The electrochemical test results show that the SnO2/graphene nanocomposite prepared by the gas–liquid interfacial synthesis approach is a promising anode material for lithium-ion batteries.Highlights► Gas-liquid interfacial reaction was used to prepare SnO2/graphene nanocomposite. ► SnO2/graphene nanocomposite as an anode for lithium-ion batteries. ► It exhibited high reversible specific capacity and excellent cycle capability. ► Graphene sheets can improve the cycling performance and reverible capacity of SnO2.

CO2-stable oxygen-permeable Fe2O3 (FO) - Ce0.9Gd0.1O2-δ (CGO) dual phase composite membranes of the composition χ wt % FO - (100 – χ) wt % CGO with χ = 25, 40, 50 were successfully prepared via a one-pot single-step method. X-ray diffraction (XRD) demonstrated that all FO - CGO composite membranes after sintering at 1300 °C for 5 h represent a microscale mixture of only the two pure phases FO and CGO. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS), and oxygen permeation revealed that the microstructure of the composition of the χ FO - (100 – χ) CGO dual phase membranes has a great influence on the oxygen permeability including its time-dependence. It was found that the composition of 40FO - 60CGO displays the highest oxygen permeability. An oxygen permeation flux of 0.18 mL/min·cm2 was obtained through the uncoated 40FO - 60CGO membrane with a thickness of 0.5 mm under an air/He oxygen gradient at 1000 °C. In situ XRD demonstrates that the 40FO - 60CGO material possesses a good phase stability not only in an atmosphere of 50 vol % CO2/50 vol % Ar but also in other atmospheres with a low oxygen partial pressure like reduced pressure (vacuum) and 5 vol % H2/95 vol % He. After coating the 40FO - 60CGO dual phase membrane with a porous La0.6Sr0.4CoO3-δ (LSC) layer of a few μm thicknesses on the air side, the oxygen permeation flux reaches the steady state immediately. This steady oxygen permeation flux of the LSC coated membrane was found to be 0.20 mL/min·cm2 unchanged for more than 150 h even when pure CO2 was used as the sweep gas, which indicates that the coated 40FO - 60CGO dual phase membrane is CO2 stable.

The first oxygen permeation data for a dense hollow-fiber membrane based on a K2NiF4-type oxide are reported. The U-shaped (Pr0.9La0.1)2(Ni0.74Cu0.21Ga0.05)O4+δ (PLNCG) hollow-fiber membranes were prepared by a phase-inversion spinning process. The dependences of the oxygen permeation on the feed air flow rate, sweep helium flow rate, oxygen partial pressure on the shell side, and operating temperature were experimentally investigated. The effects of the bulk diffusion and the surface exchange on the oxygen permeation flux through the U-shaped PLNCG hollow-fiber membranes are also discussed. During around 320 h of operation, a steady oxygen permeation flux of 1.0 mL/(min·cm2) was obtained at 975 °C under conditions of an air feed flow rate of 180 mL/min and a helium sweep flow rate of 55 mL/min. XRD and SEM analyses of the spent hollow-fiber membrane showed the good stability of the U-shaped PLNCG hollow-fiber membranes.

Partial oxidation of methane (POM) co-fed with CO2 to syngas in a novel catalytic BaCo0.6Fe0.2Ta0.2O3−δ oxygen permeable membrane reactor was successfully reported. Adding CO2 to the partial oxidation of methane reaction not only alters the ratio of CO/H2, but also increases the oxygen permeation flux and CH4 conversion. Around 96% CH4 conversion with more than 93% CO2 conversion and 100% CO selectivity is achieved, which shows an excellent reaction performance. A steady oxygen permeation flux of 15 mL/(cm2 min) is obtained during the 100-h operation, which shows good stability as well.

A novel anode material for lithium-ion batteries, tin nanoparticles coated with carbon embedded in graphene (Sn@C/graphene), was fabricated by hydrothermal synthesis and subsequent annealing. The structure and morphology of the nanocomposite were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The size of the Sn@C nanoparticles is about 50–200 nm. The reversible specific capacity of the nanocomposite is ∼662 mAh g−1 at a specific current of 100 mA g−1 after 100 cycles, even ∼417 mAh g−1 at the high current of 1000 mA g−1. These results indicate that Sn@C/graphene possesses superior cycle performance and high rate capability. The enhanced electrochemical performances can be ascribed to the characteristic structure of the nanocomposite with both of the graphene and carbon shells, which buffer the volume change of the metallic tin and prevent the detachment and agglomeration of pulverized tin.Graphical abstractTin nanoparticles coated with carbon embedded in graphene have been successfully fabricated by hydrothermal synthesis and subsequent annealing. This nanocomposite as an anode material for lithium-ion batteries exhibits superior cycle performance.Highlights► A novel Sn@C/graphene nanocomposite as an anode material for lithium-ion batteries. ► Carbon coating and graphene improve the cycle performance of the Sn anode material. ► Possess large capacity, superior cycle performance, and high rate capability.

Ultra-thin LiFePO4 platelets are prepared by a hydrothermal process using tetraethylene glycol as co-solvent. The prepared LiFePO4 platelets have a very thin thickness of about 50–80 nm, which is beneficial for Li ions to fast transfer in the bulk of the electrode. It is found that the as-synthesized LiFePO4 cathode material exhibits a quite high reversible capacity of 137 mAh g−1 at 0.2 C. After carbon coating, the obtained LiFePO4/C composite cathode has the enhanced electronic conductivity, and thus the rate capability has been improved significantly. At 8 and 12 C, the composite has the discharge capacity of 104 and 95 mAh g−1, respectively, which suggests that the ultra-thin LiFePO4 platelets are a promising candidate for the large-scale Li-ion batteries.

Effect of the content of vinyl ethylene carbonate (VEC) on the compatibility between the graphite anode and the electrolytes containing 10–30% dimethyl methyl phosphonate (DMMP) was investigated by cyclic voltammetry measurement. Impact of the contents of VEC and DMMP on the formation of the solid electrolyte interface layer was discussed, and a competitive mechanism between the destructive effect of DMMP decomposition and the positive effect of VEC was proposed. In the LiCoO2/graphite cells, the electrolytes modified by DMMP and VEC exhibited satisfying cell performances, especially for the electrolyte with 10% DMMP and 2% VEC.

Fe3O4–graphene nanocomposite was prepared by a gas/liquid interface reaction. The structure and morphology of the Fe3O4–graphene nanocomposite were characterized by X-ray diffraction, scanning electron microscopy and high-resolution transmission electron microscopy. The electrochemical performances were evaluated in coin-type cells. Electrochemical tests show that the Fe3O4–22.7 wt.% graphene nanocomposite exhibits much higher capacity retention with a large reversible specific capacity of 1048 mAh g−1 (99% of the initial reversible specific capacity) at the 90th cycle in comparison with that of the bare Fe3O4 nanoparticles (only 226 mAh g−1 at the 34th cycle). The enhanced cycling performance can be attributed to the facts that the graphene sheets distributed between the Fe3O4 nanoparticles can prevent the aggregation of the Fe3O4 nanoparticles, and the Fe3O4–graphene nanocomposite can provide buffering spaces against the volume changes of Fe3O4 nanoparticles during electrochemical cycling.

Niobium doped lithium titanate with the composition of Li4Ti4.95Nb0.05O12 has been prepared by a sol–gel method. X-ray diffraction (XRD) and scanning electron microscope (SEM) are employed to characterize the structure and morphology of Li4Ti4.95Nb0.05O12. The Li4Ti4.95Nb0.05O12 electrode presents a higher specific capacity and better cycling performance than the Li4Ti5O12 electrode prepared by the similar process. The Li4Ti4.95Nb0.05O12 exhibits an excellent rate capability with a reversible capacity of 135 mAh g−1 at 10 C, 127 mAh g−1 at 20 C and even 80 mAh g−1 at 40 C. Electrical resistance measurement and electrochemical impedance spectra (EIS) reveal that the Li4Ti4.95Nb0.05O12 exhibits a higher electronic conductivity and faster lithium-ion diffusivity than the Li4Ti5O12, which indicates that niobium doped lithium titanate (Li4Ti4.95Nb0.05O12) is promising as a high rate anode for the lithium-ion batteries.

High quality graphene sheets were prepared from graphite powder through oxidation followed by rapid thermal expansion in nitrogen atmosphere. The preparation process was systematically investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and Brunauer–Emmett–Teller (BET) measurements. The morphology and structure of graphene sheets were characterized by scanning electron microscope (SEM) and high-resolution transmission electron microscopy (HRTEM). The electrochemical performances were evaluated in coin-type cells versus metallic lithium. It is found that the graphene sheets possess a curled morphology consisting of a thin wrinkled paper-like structure, fewer layers (∼4 layers) and large specific surface area (492.5 m2 g−1). The first reversible specific capacity of the prepared graphene sheets was as high as 1264 mA h g−1 at a current density of 100 mA g−1. Even at a high current density of 500 mA g−1, the reversible specific capacity remained at 718 mA h g−1. After 40 cycles, the reversible capacity was still kept at 848 mA h g−1 at the current density of 100 mA g−1. These results indicate that the prepared high quality graphene sheets possess excellent electrochemical performances for lithium storage.

A mixed proton–electron conducting perovskite made of BaCe0.95Nd0.05O3−δ (BCN) was prepared by EDTA/citric acid complexing method. The precursor was characterized by differential scanning calorimetry (DSC), thermogravimetry (TG), and X-ray diffraction (XRD). In order to learn the perovskite formation process during the calcination, the intermediate, i.e. the sample calcined at 750 °C for 5 h, was investigated by scanning (STEM), energy-filtered (EFTEM), and high-resolution transmission electron microscopy (HRTEM) as well as electron energy-loss spectroscopy (EELS). The results revealed that the perovskite structure was formed via a solid-state reaction between barium–cerium mixed carbonate and cerium–neodymium mixed oxide particles. Dense mixed proton–electron conducting BCN membranes were made by pressing BCN powder followed by sintering. The microstructure of the sintered membranes was investigated by scanning electron microscopy (SEM). Hydrogen permeation through the BCN membrane was studied using a high-temperature permeator. The hydrogen permeation fluxes under wet conditions are higher than those under dry conditions, which is due to increased proton concentrations in the H+ hopping via OH groups. The hydrogen permeation increased with increasing hydrogen and steam concentrations in the feed. For a steam concentration of 15 vol.%, the hydrogen permeation flux reaches 0.026 ml/min cm2.

Zincum-doped ceramic membrane materials based on BaCo0.4Fe0.4ZnxZr(0.2−x)O3−δ with 0 ≤ x ≤ 0.2 were synthesized by combining citric acid and ethylene-diamine-tetraacetic acid (EDTA) complexing method. X-ray diffraction (XRD) patterns show that the BaCo0.4Fe0.4Zn0.2O3−δ ceramic oxide exhibits a pure cubic perovskite structure. Oxygen temperature-programmed desorption (O2-TPD) profile indicates that BaCo0.4Fe0.4Zn0.2O3−δ possesses a good phase reversibility. An oxygen permeation flux of 0.65 ml/min cm2 was obtained at 950 °C and a single activation energy of 67 kJ/mol was observed for the oxygen permeation in the temperature range of 600–950 °C. No decline was found during more than 100 h oxygen permeation.

A novel cobalt-free perovskite based on Ba0.5Sr0.5Fe0.8Zn0.2O3−δ (BSFZ) were prepared by EDTA-citric acid method. The lattice constants of the BSFZ perovskite were characterized by in situ high-temperature X-ray diffraction (HTXRD). The thermal expansion coefficient of BSFZ is 10.5 × 10−6 K−1, which is lower than that of cobalt-based perovskite materials. The BSFZ membrane was also used to construct reactors for the partial oxidation of methane (POM) to syngas. Results show that the BSFZ membrane can be operated for the POM reaction for more than 100 h without any fractures. The CO selectivity of 97% is obtained. The steady oxygen permeation flux reaches around 2.5 mL/min cm2 during POM reaction.

LiFePO4-C was prepared by the solid-state reaction using LiH2PO4, Fe2O3, and glucose as raw materials, which is a green and low-cost method. Thermogravimetry, differential scanning calorimetry, X-ray diffraction, and element analyzer were used to study the phase and carbon content of the synthesized samples. The optimum conditions for synthesizing LiFePO4 are identified. The discharge capacity of 120 mAh g−1 was achieved at a current density of 100 mA g−1 between 2.5 and 4.2 V during the first 50 cycles.

A dense perovskite hollow fiber made of BaCoxFeyZrzO3−δ (BCFZ) was evaluated for the oxygen separation at low temperatures (400–500 °C). An oxygen permeation flux of 0.45 ml/min cm2 was obtained at 500 °C, which is the first oxygen permeation data reported at such low temperature so far. A degradation of the oxygen permeation at 500 °C was observed, but the oxygen fluxes through the hollow fiber membrane can be regenerated by thermal treatment at 925 °C for 1 h in air. Energy-dispersive X-ray spectroscopy (EDXS) shows that a strong element segregation occurs in the membrane during operation at low temperature.

Dense mixed proton and electron conducting membrane made of BaCe0.95Nd0.05O3−δ (BCNd5) was prepared by pressing followed by sintering. X-ray diffraction (XRD) was used to characterize the phase structure of both the powder and the sintered membranes. The microstructure of the sintered membranes was studied by scanning electron microscopy (SEM). Hydrogen permeation through the BCNd5 membrane was studied using a high temperature permeator. The hydrogen permeation fluxes under wet conditions are higher than those under dry conditions, which is due to H+ hopping via surface OH groups. At 925 °C, a hydrogen permeation flux of 0.02 mL/min cm2 was obtained under wet condition, which recommends BCNd5 as a potential material for hydrogen-selective membranes.

Cobalt-free oxides GdxBa1−xFeO3−δ (0.01 ≤ x ≤ 0.1) were achieved by a solid state reaction method. It is found that GdxBa1−xFeO3−δ (0.025 ≤ x ≤ 0.1) exhibits the cubic perovskite structure. Among GdxBa1−xFeO3−δ (0.025 ≤ x ≤ 0.1), the Gd0.025Ba0.975FeO3−δ (GBF2.5) membrane shows the outstanding phase structure stability and the highest oxygen permeation, which can reach 1.44 ml·cm− 2·min− 1 at 950 °C under air/He oxygen partial pressure gradient. The GBF2.5 membrane was successfully operated for more than 100 h at 800 °C and the oxygen permeation flux through the membrane is 0.62 ml·cm− 2·min− 1. After 100 h oxygen permeation experiment at 800 °C, X-ray diffraction (XRD) and energy dispersive X-ray spectrometer (EDXS) demonstrate that the GBF2.5 exhibits phase structure stability even at intermediate temperature.Cobalt-free oxides GdxBa1 − xFeO3 − δ (0.01 ≤ x ≤ 0.1) were achieved by a solid state reaction method. It is found that GdxBa1 − xFeO3 − δ (0.025 ≤ x ≤ 0.1) exhibits the cubic perovskite structure. Among them, the Gd0.025Ba0.975FeO3 − δ membrane shows the outstanding phase structure stability and the highest oxygen permeation, which can reach 1.44 ml·cm− 2·min− 1 at 950 °C under air/He oxygen partial pressure gradient. Membranes with high oxygen permeability and excellent stability have potential industrial application in oxygen enrichment air production.Download full-size image

Cobalt-free perovskite-type oxides BaFe1−yTayO3−δ (0 ≤ y ≤ 0.2) were synthesized via a simple solid state reaction. The cubic perovskite structure can be obtained when y is over 0.1. BaFe0.9Ta0.1O3−δ (BFT0.1) membrane shows the highest oxygen permeation flux, which can reach 1.6 ml·min− 1·cm− 2 at 950 °C under the gradient of air/He. The O2-TPD results reveal that BaFe0.9Ta0.1O3−δ material shows an excellent reversibility and phase structure stability in air. The oxygen permeation flux is limited by the bulk diffusion when the membrane thickness is over 0.8 mm, and it is limited by both the bulk diffusion and the surface exchange when the membrane thickness is below 0.5 mm. Stable oxygen permeation fluxes are obtained during 180 h operation.Novel cobalt-free perovskite oxide based on BaFe1 − yTayO3 − δ (0 ≤ y ≤ 0.2) were synthesized via a simple solid state reaction. The structure stability, the oxygen permeation, as well as the rate-limiting step for the oxygen permeation were systematically studied. BaFe0.9Ta0.1O3 − δ (BFT0.1) membrane shows the highest oxygen permeation flux, which can reach 1.6 ml · min− 1·cm− 2 at 950 °C under the gradient of air/He. Compared with other perovskite membranes, the BaFe0.9Ta0.1O3 − δ membrane exhibits good reversibility, oxygen permeability and stability, which possibly recommends it to be a promising candidate for practical industrial applications in the future.Download full-size image

•U-shaped NWM hollow fiber membrane has been prepared and used for H2 separation.•A H2 permeation flux of 1.29 mL/min·min2 can be obtained at 975 °C.•NWM hollow fiber membrane shows good CO2 stability.Tungstates (Ln6WO12) are considered as one of the most promising candidates for hydrogen separation membrane materials. Among varies Ln6WO12 materials, the molybdenum doped neodymium tungsten oxides have attracted increasing attention due to their sufficient mixed proton-electron conductivity and high tolerance towards acid gases, such as CO2 and H2S. The hydrogen permeation properties of the U-shaped Nd5.5W0.5Mo0.5O11.25-δ (NWM) hollow fiber membranes have been studied systematically in this work. A high hydrogen permeation flux of 1.29 mL/min·min2 was obtained at 975 °C using 80% H2–20% He as feed gas and humidified Ar as sweep gas. Furthermore, the U-shaped NWM hollow fiber membrane present a hydrogen permeation flux with only a slight decrease during 80 h's operation feeding with the CO2-containing gas.

A-site deficient (Pr0.9La0.1)1.9Ni0.74Cu0.21Ga0.05O4+δ ((PL)1.9NCG), with the K2NiF4 structure, is found to exhibit higher oxygen transport rates compared with its cation-stoichiometric parent phase. A stable oxygen permeation flux of 4.6 × 10−7 mol cm−2 s−1 at 900 °C at a membrane thickness of 0.6 mm is measured, using either helium or pure CO2 as sweep gas at a flow rate of 30 mL min−1. The oxygen flux is more than two times higher than that observed through A-site stoichiometric (PL)2.0NCG membranes operated under similar conditions. The high oxygen transport rates found for (PL)1.9NCG are attributed to highly mobile oxygen vacancies, compensating A-site deficiency. The high stability against carbonation gives (PL)1.9NCG potential for use, e.g., as a membrane in oxy-fuel combustion processes with CO2 capture.

We report a novel CO2-stable reduction-tolerant dual-phase oxygen transport membrane 40 wt% Nd0.6Sr0.4FeO3−δ–60 wt% Ce0.9Nd0.1O2−δ (40NSFO–60CNO), which was successfully developed by a facile one-pot EDTA–citric sol–gel method. The microstructure of the crystalline 40NSFO–60CNO phase was investigated by combined in situ X-ray diffraction (XRD), scanning electron microscopy (SEM), back scattered SEM (BSEM), and energy dispersive X-ray spectroscopy (EDXS) analyses. Oxygen permeation and long-time stability under CO2 and CH4 atmospheres were investigated. A stable oxygen flux of 0.21 cm3 min−1 cm−2 at 950 °C with undiluted CO2 as sweep gas is found which is increased to 0.48 cm3 min−1 cm−2 if the air side is coated with a porous La0.6Sr0.4CoO3−δ (LSC) layer. All the experimental results demonstrate that the 40NSFO–60CNO not only shows good reversibility of the oxygen permeation fluxes upon temperature cycling, but also good phase stability in a CO2 atmosphere and under the harsh conditions of partial oxidation of methane to synthesis gas up to 950 °C.

We demonstrate here a novel strategy to prepare a flexible and free-standing sulfur cathode with improved mechanical strength, the matrix of which is constructed from graphitized nitrogen-doped mesoporous carbon nanofibers (NPCFs). Benefiting from a unique micro/mesoporous structure and highly graphitic carbon, the NPCF film is capable of accommodating more sulfur, and maintains substantially higher mechanical strength and flexibility after sulfur loading as compared with traditional microporous carbon nanofiber films. As a free-standing and flexible cathode for Li–S batteries, the robust composite film exhibits excellent rate capability (540 mA h g−1 at 5C) and cycling stability (76.5% retention after 500 cycles at 5C).

Exploring high-performance negative electrode materials is one of the great challenges in the development of high-energy density asymmetric supercapacitors (ASCs). Herein, a new kind of high-performance nitrogen-doped nanoporous carbon (NPC) electrode with a large surface area and abundant micropores/mesopores was derived from conveniently available fruit waste (shaddock peel) via a facile pyrolysis process. Electrochemical measurements showed that the as-synthesized NPC electrodes possessed a remarkably large capacitance of 321.7 F g−1 with good rate capability and excellent long-term cycling stability. Such excellent electrochemical performance was achieved by shortening the diffusion distance, increasing the electrode–electrolyte contact area and improving the electron conductivity of the NPC electrode arising from its nanoporous architecture and nitrogen doping. As a prototype, an all-solid-state ASC device based on the NPC negative electrode and a MnO2 positive electrode achieved an ultrahigh energy density of 82.1 W h kg−1 at a power density of 899 W kg−1, which is considerably larger than most reported carbon based supercapacitor devices.

Supercapacitors and Li-ion batteries are two types of electrical energy storage devices. To satisfy the increasing demand for high-performance energy storage devices, traditional electrode materials, such as transition metal oxides, conducting polymers and carbon-based materials, have been widely explored. However, the results obtained to date remain unsatisfactory, and the development of inexpensive electrode materials (especially for commercial manufacturing) with superior electrochemical performance for use in supercapacitors and in Li-ion batteries is still needed. The as-prepared NiMoO4 nanosheets (NSs) with interconnecting nanoscale pore channels and an ultrathin structure provide a large electrochemical active area, which facilitates electrolyte immersion and ion transport and provides effective pathways for electron transport. Therefore, the as-prepared NiMoO4 NS electrode exhibits a high specific capacity and an excellent rate capability and cycling stability in supercapacitors and in Li-ion batteries. Moreover, a high energy density (43.5 W h kg−1 at 500 W kg−1) was obtained for the symmetric supercapacitor (SSC) composed of two sections of NiMoO4 NSs.

Nitrogen-doped Li4Ti5O12 (LTO) is first synthesized by thermal decomposition of LTO and melamine. As indicated by TG, XPS and TEM analysis, nitrogen is successfully doped in LTO and the generated TiN layer is deposited on the surface of the LTO particle. The LTO with certain nitrogen modification (LTON12) on the surface exhibits enhanced electronic conductivity and Li ion diffusivity. The LTON12 electrode exhibits much better rate capability and cycling performance than the pristine LTO. The LTON12 electrode delivers a capacity of 124.2 mA h g−1 after 500 cycles at 5 C with a high capacity retention of 89.1% while the capacity retention of the pristine LTO is only 43.7%. In addition, the LTON12 exhibits a capacity of 74.3 mA h g−1 at even 100 C with a fixed discharge rate of 1 C. The excellent electrochemical performance of N-doped LTO is attributed to the improved electronic and ion conductivities provided by the thin TiN coating layer on the particle surface.

Ultrathin and highly-ordered 2D CoO nanosheet arrays (NSAs) composed of nanocrystals were fabricated via a facile galvanostatic electrodeposition technique. The as-prepared CoO NSAs exhibit excellent cyclability (retain 1000 mA h g−1 after 100 cycles at 1 A g−1) and rate capability (520 mA h g−1 at 10 A g−1) when they are directly used as an anode for LIBs.

Structure stability and fast charge–discharge capacity are highly desirable for electrode materials applied in lithium ion batteries (LIBs). In this report, binder-free Co–CoOx nanowire arrays (NWAs) were obtained by a simple H2 reduction of Co3O4 NWAs. The resulting Co–CoOx NWAs were grown directly on the current collector with enough open space between each nanowire, which provides fast charge transfer channels and large accessible surface area to the electrolyte. More importantly, the introduction of electrochemically inactive Co without volume change during cycling for LIBs could improve the structural stability of the Co–CoOx NWA electrode and the high electronic conductivity of metallic Co in the array structure greatly enhances the electron transfer ability of Co–CoOx nanowires. Benefitting from those designed structural features, the binder-free Co–CoOx NWAs achieved remarkable electrochemical performances with excellent cycle stability at high rates and high rate capacity. The Co–CoOx NWA electrode maintains highly stable capacities of 990 and 740 mA h g−1 after 1000 cycles at 10 and 20 A g−1, respectively. At an ultrahigh rate of 50 A g−1, a high reversible capacity of 413 mA h g−1 is achieved. The result demonstrates that such a novel Co–CoOx nanowire array structure is a new strategy to design high performance anode materials for LIBs.

A mixed protonic and electronic conductor material BaCe0.85Tb0.05Zr0.1O3−δ (BCTZ) is prepared and a Ni-BCTZ cermet membrane is synthesized for hydrogen separation. Stable hydrogen permeation fluxes can be obtained for over 100 h through the Ni-BCTZ membrane in both dry and humid conditions, which exhibits an excellent stability compared with Ni-BaCe0.95Tb0.05O3−δ membrane due to the Zr doping.

Nitrogen-doped bamboo-like carbon nanotubes (N-BCNTs) were synthesised using a facile one-step pyrolysis process. Due to their unique one-dimensional hollow structure and intrinsic high nitrogen content, N-BCNTs exhibit high capacity, superior rate capability, and excellent cycle stability and are, thus, promising anode materials for sodium-ion batteries.

Nanostructured Pt-metal alloys have shown impressive catalytic properties for the oxygen reduction reaction (ORR) in acidic medium, but their long-term stability has not been satisfactory. Herein, we look beyond the traditional Pt-metal alloys and have developed a new kind of Pt-nonmetal alloy electrocatalyst for the ORR. Specifically, the novel catalyst is composed of interconnected platinum monophosphide (PtP) alloy nanocrystals (∼3–4 nm) and featured supportless nanotube array morphologies. Due to the unique combination of composition and structure, the obtained PtP alloy nanotube arrays not only exhibited remarkable ORR activity, but also showed almost no degradation of the half-wave potential after accelerated durability tests. The result suggests that alloying Pt with a nonmetallic element (such as P) is indeed an effective approach to address the poor stability of Pt-based catalysts in acidic medium.

Porous Na3V2(PO4)3@C nanocomposites enwrapped in a 3D graphene network were prepared using a simple freeze-drying-assisted thermal treatment method. The carbon layer and 3D graphene network provide not only a 3D conductive network but also a double restriction on the aggregation of Na3V2(PO4)3 particles that have a high crystallinity under high temperature treatment. Due to the high electrochemical activity of the highly crystalline Na3V2(PO4)3 nanoparticles and 3D conductive network, the novel NVP@C/G material displays a superior rate capability (76 mA h g−1 at 60C) and ultra-long cyclability (82% capacity retention for 1500 cycles at 40C) when used in sodium-ion batteries.

Anode materials with capacitive charge storage (CCS) are highly desirable for the development of high-performance sodium-ion batteries (SIBs), because the capacitive process usually shows kinetically high ion diffusion and superior structural stability. Here, we report a new CCS anode material of graphene-based nitrogen-doped carbon sandwich nanosheets (G-NCs). The as-prepared G-NCs show a high capacitive contribution during the discharge/charge processes. As expected, the G-NCs exhibit excellent rate performance with a reversible capacity of 110 mA h g−1, even at a current as high as 10000 mA g−1, and outstanding cycle stability (a retention of 154 mA h g−1 after 10000 cycles at 5000 mA g−1). This represents the best cycle stability among all reported carbon anode materials for SIBs, thereby showing great potential as a commercial anode material for SIBs.

We report here a facile and efficient electrodeposition method to modify inexpensive porous stainless-steel nets for use as substrates in the in situ growth of metal–organic framework membranes, such as ZIF-8, ZIF-67 and HKUST-1. Using this method, different metal precursors can be electrodeposited depending on the central metals required in the target metal–organic frameworks. The inorganic modifiers prepared by this approach are sufficiently reactive for the one-step growth of continuous metal–organic framework membranes; their reactivity is comparable with that of organic functional groups. The procedure is also green and cost-effective, which is promising for use in large-scale production.

Designing oxygen cathodes with both high energy density and excellent cycling stability is a great challenge in the development of lithium–oxygen (Li–O2) batteries for energy storage systems. Herein, we design a novel structure of hierarchical NiCo2O4 nanosheets on porous carbon nanofiber films (denoted as NiCo2O4@CNFs) as an oxygen cathode for lithium–oxygen batteries. The NiCo2O4@CNFs cathode delivers a high specific discharge capacity of 4179 mA h g−1, a high energy density of 2110 W h kg−1 and superior cycling stability over 350 cycles. The excellent electrochemical performance of the NiCo2O4@CNFs cathode can be attributed to the rational design and engineering of catalysts and porous conductive electrodes. These results indicate that the NiCo2O4@CNFs electrode is a promising candidate for high energy density and long-life Li–O2 batteries. Additionally, the rational design of the hierarchical catalyst constructed low-dimensional nanostructure and the lightweight porous carbon nanofiber electrode can be also used for other metal–oxygen batteries, such as zinc–oxygen (Zn–O2) batteries, aluminum–oxygen (Al–O2) batteries, and sodium–oxygen (Na–O2) batteries.