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Three-dimensionally macroporous (3DOM) MnSmOx composite oxides were prepared via a hard-template method and utilized as catalytic materials for propane combustion. The modification effect of samarium dopant on both their physicochemical and catalytic properties were systematically investigated by means of characterization techniques and experimental approaches. Characterization results revealed that the increasing addition of samarium into MnOx favored the formation of 3DOM structure, and the doping of samarium induced the crystalline phase transformation of Mn2O3 into Mn3O4, concurrently leading to the remarkable improvement of redox ability and surface oxygen mobility as well as higher abundance of surface labile oxygen species. All above-mentioned properties were demonstrated to be the major determinants for boosting the propane combustion performances of Sm-doped catalysts. Among all, the 3DOM Mn0.85Sm0.15Ox (denoted as M0.85S0.15) exhibited the optimum catalytic activity and good regeneration capacity under humid conditions. Additionally, the comparative in situ DRIFTs analysis over M0.85S0.15 and the bulk counterpart (denoted as B-M0.85S0.15) emphasized the superiority of 3DOM architecture on promoting the surface adsorption and oxidation of propane molecules.

The viability of applying high capacity sulfur cathodes is hindered by the rapid capacity fading, structure degradation, and severe safety problem. Unfortunately, these problems still existed when the lithium-sulfur batteries (LSBs) faced with commercial applications. Consequently, it is urgent to find perfect strategies to modify the properties of LSBs for achieving wide applications. Herein, we present a detailed host material study by immersing sulfur into cobaltous sulfide host materials. Via the material characterization and electrochemical study, some meaningful results were obtained for the sulfur-based cathode during the electrochemical cycles. The electrochemical properties indicated that the as-prepared cobaltous sulfide/S composite cathode exhibited high initial specific capacity and low self-discharge in the LSBs.

α-MoO3 is a promising electrode material for electrocapacitive energy storage. However, it has poor stability in aqueous electrolytes due to dissolution in water. Here, we demonstrate that an α-MoO3 electrode prepared using the electrochemical deposition method is stable over a wide potential window of 2.2 V in a neutral aqueous electrolyte. The improved stability of the α-MoO3 electrode in water is attributable to enhanced electron conductivity, which minimizes the polarization-induced structural collapse, and the dense microstructure of the α-MoO3 film electrode. The widened potential window is related to the electrocatalytic inactivity of the α-MoO3 toward water electrolysis and the high overpotentials of the neutral electrolyte toward H2 and O2 evolution reactions. A symmetric supercapacitor cell fabricated with the electrochemically deposited α-MoO3 electrode delivers a specific energy as high as ∼22 Wh/kg at a specific power of ∼301 W/kg. This work demonstrates that the electrochemical deposition method is a viable approach to fabricating α-MoO3 electrodes for aqueous electrochemical energy storage.

Silica scalant and organic foulant are rapidly deposited onto the surface of a thin-film composite (TFC) reverse osmosis (RO) membrane during the desalination process. The scaling and fouling prope...

Lithium-sulfur batteries are considered to be an ideal high-performance rechargeable lithium battery. However, some problems have seriously hindered the practical application of lithium-sulfur batteries. A simple one-step hydrothermal method has been applied to design nitrogen-doped graphene aerogel (N-GA) with three different nitrogen sources. Subsequently, sulfur was encapsulated in N-GA by chemical deposition method to synthesize sulfur encapsulated in N-GA (N-GA/S) composites. Among them, the N-GA1/S composite with sulfur content reaching 75.5 wt% has a discharge specific capacity of 723.9 mAh g−1 after 100 cycles at 0.7 C, and the capacity retention rate is up to 87.4% while the coulombic efficiency still remains 98%. The outstanding electrochemical performance is owing to the good coating of sulfur by nitrogen-doped graphene aerogel, the improvement of the conductivity of the graphene skeleton by nitrogen doping, and the strong adsorption capacity of the doped nitrogen atom to lithium polysulfide. The graphene skeleton also helps to reduce the volume effect while charging and discharging. Furthermore, the proportion of pyridinic-N in N-GA1/S composites is higher than that in the two other composites, and it has a better adsorption capacity for lithium polysulfide.

Owing to the high energy density and rich resource, Li–S batteries are now considered as a promising direction in energy storage. Nevertheless, the electrochemical properties of sulfur host materials have been limited by the large volume changes during cycles, the dissolution of polysulfides in an electrolyte, and the insulating properties of lithium polysulfides. Based on the above conclusions, a novel cathode material of graphene nanosheet@spherical ordered mesoporous carbon/sulfur nanocomposite (GNs@s-OMC/S) where s-OMC/S was wrapped by GNs has been synthesized in this article and delivers superior cycle stability. According to the tests, GNs@s-OMC/S provides a capacity of 1159 mAh g−1 at a 0.4 C discharge rate. In addition, even at a high rate of 4 C, the discharge capacity of GNs@s-OMC/S can also remain 767 mAh g−1, representing a fantastic rate performance and high specific capacity. It can be ensured that the narrow channels provided by s-OMC and the graphene entrapment with high conductivity enhance the electrochemical performance of the cathode.

M–Nb–O compounds are regarded as advanced anode materials of lithium-ion batteries owing to their large capacities, high safety and fast Li+ transport. However, challenges remain in the exploitation of new M–Nb–O compounds with low strains to enable superior cyclability. Here, we exploit V3Nb17O50 as a low-strain M–Nb–O anode compound, and V3Nb17O50 micron-sized particles (V3Nb17O50-MP) and submicron-sized rods (V3Nb17O50-SR) are demonstrated. V3Nb17O50 owns an open and robust shear ReO3 crystal structure, which is constructed by 3 ​× ​3 ​× ​∞ (V,Nb)O6 octahedron-blocks linked by VO4 tetrahedra. The resulting A–B–A layered structure with a large interlayer spacing enables the superior Li+ diffusivity and significant intercalation-pseudocapacitive behavior in V3Nb17O50. The maximum unit-cell volume expansion of V3Nb17O50 discharged to 0.8 ​V is only 3.46% (the smallest value among the known M–Nb–O anode compounds with shear ReO3 structures), leading to the excellent cyclability of V3Nb17O50-MP/V3Nb17O50-SR with 90.0/91.8% capacity retention over 2000 cycles at 10C. V3Nb17O50-MP/V3Nb17O50-SR further exhibits a safe operating potential of 1.736/1.724 ​V, large reversible capacity of 207/254 ​mA ​h g−1 at 0.1C, and high rate performance with 68/123 ​mA ​h g−1 at 10C. A LiMn2O4//V3Nb17O50-SR full cell also exhibits comprehensively good electrochemical properties, including excellent cyclability with 85.7% capacity retention over 500 cycles at 5C. Therefore, V3Nb17O50 can be a very promising anode compound for stable, safe, large-capacity and fast-charging Li+ storage.

Potassium‐ion storage is being explored by researchers for its advantages in forming graphite‐based intercalation compounds, with cost‐effective production compared to lithium‐ion systems. However, its poor performance in graphite‐based platforms, owing to the volume expansion required for intercalation, has demanded alternative materials for reversible potassiation. Herein, we demonstrate a simple one‐step pyrolysis approach to develop an amorphous hard carbon material from commercial cellulose for high‐performance potassium‐ion batteries (KIB). The larger interlayer spacing (~0.4 nm) alongside the electronegative oxygen functional groups promotes potassium‐ion storage. High capacity, good rate and long cycling performance with lower‐volume expansion could be credited to the amorphous carbon that possesses turbostratic nanodomains. Further, oxygen functional groups on the carbon material are identified in our experimental studies, and density functional theory simulations indicate that these are likely to enhance the potassium ion capacity of the materials.

A series of chitosan (CS)-coated metal–organic-framework (MOF) nanoparticles, which combined excellent chemical stability, thermal stability, and recyclability, were synthesized by an in situ growt...

Three-dimensionally macroporous (3DM) MnZrOx catalysts were fabricated to reveal the structure and Zr-doping effects on both physicochemical properties and propane combustion behaviors. The increasing addition of zirconium is favorable for the formation of 3DM structure and amorphous Mn-Zr solid solution, leading to tunable physicochemical properties. The significant activity improvement after zirconium addition was originally attributable to the superior redox ability, higher oxygen mobility and more abundant oxygen vacancy. The excellent catalytic activity, cycling stability and water resistant ability over 3DM Mn0.6Zr0.4Ox make it a promising material for hydrocarbons elimination. The comparative TPSR, in situ DRIFTs and kinetics study over 3DM and bulk catalysts emphasize the advantageous function of 3DM architecture on promoting propane adsorption, oxidation and lattice oxygen mobility.

Hollow perovskite oxide La0·5Sr0·5MnO3 nanospheres are synthesized by using carbon spheres as template in the presence of citric acid. Among the samples investigated in this work, the one obtained at a sintering temperature of 700 °C exhibits the highest catalytic activity in the oxygen reduction reaction (ORR) in an alkaline electrolyte. The electrochemical measurement data shows that the sample has a positive onset potential (0.860 V) and a high limiting current density (6.48 mA cm−2). Furthermore, the catalyst shows a high selectivity towards methanol and a better stability than a commercial Pt/C catalyst. The hollow La0·5Sr0·5MnO3 nanoshperes described in this manuscript hold a great promise for applications in metal-air batteries and alkaline fuel cells.

Highlights Cobalt sulphide nanoparticles are encapsulated in nitrogen-rich carbon cages via a simple and scalable method.Insight into sodium storage mechanism is systematically studied via in situ TEM and XRD techniques.The sodium-ion capacitor device achieved high energy densities of 101.4 and 45.8 Wh kg−1 at power densities of 200 and 10,000 W kg−1, respectively, holding promise for practical applications. Electronic supplementary material The online version of this article (10.1007/s40820-020-0391-9) contains supplementary material, which is available to authorized users., Conversion-type anode materials with a high charge storage capability generally suffer from large volume expansion, poor electron conductivity, and sluggish metal ion transport kinetics. The electrode material described in this paper, namely cobalt sulphide nanoparticles encapsulated in carbon cages (Co9S8@NC), can circumvent these problems. This electrode material exhibited a reversible sodium-ion storage capacity of 705 mAh g−1 at 100 mA g−1 with an extraordinary rate capability and good cycling stability. Mechanistic study using the in situ transmission electron microscope technique revealed that the volumetric expansion of the Co9S8 nanoparticles is buffered by the carbon cages, enabling a stable electrode–electrolyte interface. In addition, the carbon shell with high-content doped nitrogen significantly enhances the electron conductivity of the Co9S8@NC electrode material and provides doping-induced active sites to accommodate sodium ions. By integrating the Co9S8@NC as negative electrode with a cellulose-derived porous hard carbon/graphene oxide composite as positive electrode and 1 M NaPF6 in diglyme as the electrolyte, the sodium-ion capacitor full cell can achieve energy densities of 101.4 and 45.8 Wh kg−1 at power densities of 200 and 10,000 W kg−1, respectively. Electronic supplementary material The online version of this article (10.1007/s40820-020-0391-9) contains supplementary material, which is available to authorized users.

Sodium-sulfur batteries (NaSBs) have emerged as a promising energy storage technology for large-scale stationary applications such as smart electrical grids due to their exceptionally high energy density and cost-effectiveness. However, one of the challenging problems impeding their practical applications is the sulfur shuttle effect by which the active redox intermediates are gradually dissolved in electrolytes. In this work, we have employed first-principles density functional theory (DFT) calculations to unravel the suppression of the shuttle effect in NaSBs with a two-dimensional (2D) As2S3 monolayer as the anchoring material. We show that semiconducting As2S3 is a suitable anchoring layer to inhibit the dissolution of the polysulfide intermediates in common electrolytes because of its stronger chemical binding with sodium polysulfides than with the electrolytes. The immense adsorption is attributed to the electron donation from the unfilled S-3p states of the polysulfides to As2S3. These mechanisms increase the carrier population and consequently improve the electrical conductivity of As2S3. Hence, the use of As2S3 can both reduce the shuttle effect and enhance the cathode electron conductivity to enable improved cycling stability and coulombic efficiency of the battery.

The oxygen reduction reaction (ORR) is one of the most important electrochemical reactions in energy conversion and storage technologies, such as fuel cells and metal–air batteries. However, the sluggish kinetics of the ORR is a key factor limiting the performance of these energy storage and conversion devices. Perovskite oxides are a promising family of electrocatalysts for the ORR because of their unique physical and chemical properties, such as variable crystal structure and non-stoichiometric chemistry. Studies have shown that the catalytic properties of perovskite oxides in the ORR are largely related to oxygen vacancies, which alter their electronic and crystal structures and surface chemistry. This review summarizes recent research advances on understanding the role of oxygen vacancies of the ABO3 perovskite oxides in catalyzing the ORR. With a brief introduction of perovskite oxides, approaches to creating oxygen vacancies in the ABO3 perovskite oxides and the role of oxygen vacancies in improving their catalytic performance for the ORR are discussed. Research perspectives in this important area are highlighted.

The removal of radioiodine from the exhaust gas streams produced in spent fuel reprocessing plants is of paramount importance for the nuclear fuel cycle's security. Here, millimeter-sized poly(vinylidene fluoride) (PVDF) composites containing zirconium-based metal–organic frameworks, MOF-808, were synthesized by a facile phase inversion method to adsorb the volatile iodine. MOF-808@PVDF composites have inherited the crystallinity and pore accessibility of MOF-808, as well as its outstanding iodine capture performance. The MOF-808@PVDF composite beads containing 70 wt% MOFs, exhibited ultrahigh iodine adsorption capacity, 1.42 g g−1 at 80 °C, much higher than other millimeter-sized adsorbents reported in the literature. Raman mapping suggests that the negative iodine ions were formed at the early stage of iodine adsorption, while the close-packed iodine molecules were subsequently trapped in the frames. Using dynamic adsorption, the influences of iodine concentration, operating temperature and humidity were analyzed to evaluate its application potential in industrial conditions. The iodine adsorption capacity could reach 1.36 g g−1 at 80 °C, 100 °C and 120 °C in flow gas. And the elevated temperature (120 °C) is beneficial to accelerating the mass transfer of iodine vapor, as well as slightly inhibiting the competitive adsorption of water molecules under humidity. Besides, only one-third of the loaded iodine was released in nitrogen purging after saturated adsorption. The remaining majority was trapped firmly by the beads due to their strong interactions with the frameworks. This work highlights the millimeter-sized MOF-808@polymer composite beads with ultrahigh iodine adsorption capacity, providing experimental references for their application in radioiodine removal from hot and moist streams.

There is a growing demand for high-rate rechargeable batteries for powering electric vehicles and portable electronics. Here, we demonstrate a strategy for improving electrode performance by controlling the formation of solid electrolyte interphase (SEI). A composite electrode consisting of hard carbon (HC) and carbon nanotubes (CNTs) was used to study the formation of the SEI at different charging rates in an electrolyte consisting of 1 M NaClO4 in a mixed solvent with ethylene carbonate (EC) and propylene carbonate (PC), as well as fluoroethylene carbonate (FEC) additive. The half-cell method was used to form the SEI at different charging rates (e.g., 1, 10, and 100 A/g). Symmetric capacitor cells were employed to study ion transport properties through the SEI. It was found that the SEI is a primary factor responsible for limiting the capacity of the composite anode material in conventional ester-based electrolytes. The electrode with the SEI formed at 100 A/g exhibited the lowest impedance and delivered nearly twice the capacity of the electrode with the SEI formed at 1 A/g. This significant difference is due to a thin SEI formed at the fast charging rate, as has been observed with ether-based electrolytes. An identical decay rate (0.11 mA h/g per cycle) was observed on the electrodes with SEIs formed at different charging rates in an ester electrolyte. No chemical difference among the three SEI layers was found. However, morphological differences of the SEI layers were observed. This difference is believed to account for the different electrochemical behaviors of the electrodes. This work shows that high charging rates can result in the formation of an optimal SEI layer, contradicting the widely accepted practice of using low charging rates during the SEI formation in alkali-ion batteries.

This work investigates the performance of amine functionalised 2D/3D sorbents for CO2 capture. The 2D/3D structures were based on a combination of flake-like reduced graphene-silica oxide (G-Si) aerogel and rod-like mesoporous silica SBA-15. The G-Si aerogel formed mainly silica microporous structures which enveloped graphene sheets. The SBA-15 displayed the classical rod-like mesoporous features with high pore volume. The addition of G-Si aerogel to SBA-15 for the amine functionalised samples significantly reduced the combined total surface area and pore volume. Interestingly, the CO2 sorption capacity increased and peaked for samples containing G-Si aerogel/SBA-15 at 1:20 mass ratio (4.7 wt%), though declining thereafter. This counterintuitive effect of increasing CO2 sorption capacity but decreasing surface area and pore volume was attributed to the special morphological features of the 2D/3D sorbent assembly. At these optimal conditions, the flake-like G-Si aerogel was well intercalated with the rod-like SBA-15. As a result, the inter-particle space formed between the flake-like and rod-like assembly accommodated TEPA which facilitate the mass transfer and reaction between the amine groups and CO2. These special 2D/3D morphological features delivered high CO2 sorption capacity of 6.02 mmol g−1. The 2D/3D sorbents were also very stable under sorption and desorption cycles whilst heat of sorption were up to 22% lower than the analogue 3D SBA-15/TEPA sorbent.

In this work, we have firstly achieved the construction of bismuth oxyiodide (Bi5O7I)/reduced graphene oxide (rGO)/ZnO Z-scheme photoelectrochemical (PEC) system without backward reactions through loading large-area ZnO quantum dots (QDs)/rGO films on Bi5O7I nanosheets. Single-crystal porous Bi5O7I nanosheets with numerous oxygen vacancies (OVs) were firstly fabricated through the calcination of BiOI in reductive glycols. The single-crystal facilitates charge transport, nanoporous structure promotes light absorption and OVs improves charge separation efficiency. As a result, single-crystal porous Bi5O7I nanosheets with OVs exhibited higher PEC performance than other morphologies reported before. Moreover, The PEC activity of Bi5O7I can be further enhanced through loading large-area ZnO QDs/rGO films to construct a pure Z-scheme charge transfer system, which not only achieves efficient separation of electron-hole pairs but also retains its excellent redox ability. To the best of our knowledge, the photocurrent density of Bi5O7I/rGO/ZnO heterostructures is the highest among Bi5O7I-based samples. For comparison, an opposite Z-scheme model has also been built up by replacing Bi5O7I with WO3, in which the photocurrent density decreased conversely. Therefore, it can be known that a pure Z-scheme system without backward reactions can be successfully prepared through loading ZnO QDs/rGO films on photoelectrodes.

High-performance nitrogen-doped porous carbon adsorbents were prepared from waste cellulose fibers using the spray-drying method and used to remove methyl orange (MO) from water. The carbon adsorbents possessed a honeycomb-like turbostratic microstructure with hierarchical pores. Such waste-cellulose-derived carbon adsorbents were found to exhibit a fast adsorption rate towards MO. A sample thermally treated at 800 °C with the highest specific surface area (about 1259.4 m2/g) and total pore volume (about 2.7 cm3/g) exhibited the best MO adsorption capacity (337.8 mg/g), which is significantly higher than that of ZnCl2-activated carbon. The effect of MO initial concentration, pH and temperature on the carbon adsorption was investigated systematically. It was found that the adsorption system is heterogeneous while the isotherm data on the carbon sample can be well described by both Langmuir and Freundlich isotherm models. The high-performance and cost-effective carbon adsorbent described in this paper holds a great promise for dye removal from aqueous solutions.

Polyamide (PA) thin film composite membranes consisting of a PA film (skin layer) formed via interfacial polymerization (IP) on a porous support are state of the art reverse osmosis (RO) membranes. The skin layer is thought to provide most resistance for transport and be responsible for separation. An ideal skin layer should be very thin with sufficient selectivity. However, it is challenging to obtain such a kind of skin layer. Herein, a novel concept of confining skin layer growth to reduce the resistance of skin layer significantly without sacrificing the selectivity of skin layer was proposed. The skin layer growth can be confined by a barrier, which can hinder the diffusion of aqueous phase monomers toward the organic phase during IP. Zeolitic imidazolate framework-8 (ZIF-8) particles were used as barriers in this work. By controlling the confinement, the skin layer thickness was reduced, meanwhile the sufficient selectivity of skin layer was maintained. Then, the flux was improved dramatically from 49.8 ± 1.1 L m−2 h−1 to 76.2 ± 3.4 L m−2 h−1 (by 53.0%), meanwhile a high rejection (99.06 ± 0.20%) was retained. Besides, the confinement led to a surface with lower roughness. The comparison of utilizing the barriers (ZIF-8 particles) and shortening the reaction time was also done. The results showed that (1) utilizing the barriers and shortening the reaction time share similarities and (2) utilizing the barriers is superior to shortening reaction time. The performance of membrane fabricated via the concept of confining the skin layer growth exceeds that of many previously reported membranes. This work might inspire the development of high performance membranes fabricated by IP with great potential for applications in molecular separations.

There has been rapidly growing interest in developing fast-charging batteries for electric vehicles. The solid electrolyte interphase (SEI) layer formed at the graphite/electrolyte interface plays an important role in determining the lithiation rate of lithium-ion batteries (LIBs). In this work, we investigated lithium-ion transport behavior in thin-film graphite electrodes with different graphite particle sizes and morphologies for understanding the role of the SEI layer in fast charging LIBs. We varied the properties of the SEI by changing the current rate during the SEI formation. We observed that forming the SEI layer at a much higher current density than is traditionally used leads to a substantial reduction in electrode impedance and a corresponding increase in ion diffusivity. This enables thin-film graphite electrodes to be charged at current rates as high as 12 C (i.e., about 5 min charging time), demonstrating that graphite is not necessarily prevented from fast charging. By comparing the SEI layers formed at different current densities, we observed that lithium-ion diffusivity across the SEI layer formed on a 23 μm commercial graphite at a current density currently used in the industry (e.g., 0.1 C) is approximately 8.9 × 10-10 cm2/s.

High-performance extraction of polar phenols from aqueous samples is challenging because of their hydrophilicity, extremely low concentration, and complicated matrices. Covalent organic frameworks (COFs) are new types of porous organic materials. In this work, spherical TPB-DMTP-COF was fabricated via a simple room-temperature solution-phase approach. The material exhibited high acid/base stability, remarkable thermostability, high crystallinity, and large surface area of 1560 m2 g−1 and thus could be an excellent coating for solid-phase microextraction (SPME) of phenols. This coating provided superior adsorption affinity toward phenols over commercial coatings. TPB-DMTP-coated fiber showed high enhancement factors (EFs, 1741–4265), and EFs increased with the number of chlorine or methyl substituents and high hydrophobicity of phenols. Hence, the strong adsorption affinity could be derived from hydrophobic and steric hindrance effects together with π−π affinity, H-bonding, van der Waals forces, and size-matching effect. The proposed approach based on TPB-DMTP-COF-coated fiber and gas chromatography-tandem mass spectrometry achieved low limits of detection (0.0048–0.015 ng L−1), wide linearity (0.05–1000 ng L−1), good precision (

In this work, the effects of support surface pore structures (including surface pore size, surface pore density and surface porosity) on the performance of thin film composite (TFC) gas separation membrane over a wide pressure range (from 0.3 to 2.0 MPa) were studied. To fulfill it, the polysulfone (PSf) supports with different surface pore structures were prepared. Two kinds of wide-accepted polymeric membrane materials, i.e., polyvinylamine (PVAm) and Pebax 1657 copolymer, were used as skin layer materials. We pointed out for the first time that the support surface average pore size and pore density could affect the chain mobility of polymer of skin layer at the support surface pore entrance, then, can affect the TFC membrane performance. Besides, we also discussed the effects of support on the TFC membrane performance when the feed pressure changes for the first time. This work can provide guidance for choosing a suitable support for TFC gas separation membrane.

This work investigates the one-pot facile synthesis of novel 2D/3D assemblies containing graphene silica (templated) aerogel sorbents for CO2 capture, a greenhouse gas of major global concern. In t...

Hollow porous nanoparticles were proposed to transform the skin layer structure for enhancing the performance of reverse osmosis (RO) membrane in this work. Amino-modified hollow mesoporous silica nanospheres (AHMSS) with a size from 110 to 130 nm were successfully prepared via the hard template method. AHMSS were added in the organic phase and then incorporated into the RO membrane skin layer after the interfacial polymerization process. The hydrophilicity of RO membrane was improved by AHMSS. The performance evaluation results showed that AHMSS improved the RO membrane flux (improved by 41.5%) with rejection decreasing slightly. Amino-modified mesoporous silica nanospheres without hollow cores were also prepared and incorporated into the RO membrane skin layer to investigate the effects of the hollow cores of AHMSS on the membrane performance. The results showed that the hollow cores of AHMSS contributed to the improvement of membrane performance. This work demonstrates that AHMSS have huge potential in preparing RO membranes with both high flux and high rejection.

Carbon-coated NiO/reduced graphene oxide (NiO/rGO) composites with NiO nanoparticles (∼5 nm) homogeneously distributed and carbon skeletons on the surface were constructed in this work. Graphene ox...

This paper describes the syntheses and electrochemical properties of a new niobate compound, aluminum niobate (AlNb11O29), for Li+ storage. AlNb11O29-microsized particles and nanowires were synthesized based on the solid-state reaction and solvothermal methods, respectively. In situ X-ray diffraction results confirmed the intercalating mechanism of Li+ in AlNb11O29 and revealed its high structural stability against cycling. The AlNb11O29 nanowires with a novel bamboo-like morphology afforded a large interfacial area and short charge transport pathways, thus leading to the observed excellent electrochemical properties, including high reversible Li+-storage capacity (266 mA h g-1), safe operating potential (around 1.68 V), and high initial Coulombic efficiency (93.3%) at 0.1 C. At a very high rate (10 C), the AlNb11O29 nanowires still exhibited a capacity as high as 192 mA h g-1, indicating their good rate capability. In addition, at 10 C, 96.3% capacity was retained over 500 cycles, indicating superior cycling stability. A full cell fabricated with AlNb11O29 nanowires as the anode and LiNi0.5Mn1.5O4 microparticles as the cathode delivered a high energy density of 390 W h kg-1 at 0.1 C. This work suggests that the AlNb11O29 nanowires hold a great promise for the development of high-performance lithium-ion batteries for large-scale energy-storage applications.

The microwave sintering method is found to have advantages over the conventional thermal treatment method for preparing BaZr0.1Ce0.7Y0.2O3-δ powder. Comparing with the conventional thermal treatment, the microwave sintering method allows the solid material to be self-heated, enabling the formation of pure phase BaZr0.1Ce0.7Y0.2O3-δ powder at a relatively low temperature (900 °C) with a short dwell time of 1 h, while the same pure phase can only be formed at 1000 °C in an electric furnace. Importantly, the grain size for the microwave prepared BaZr0.1Ce0.7Y0.2O3-δ powder is much smaller than that of the conventionally thermal treated BaZr0.1Ce0.7Y0.2O3-δ powder. The small powder grain size is found to be beneficial for the densification and grain growth of the resultant electrolyte membrane during the electrolyte sintering procedure. A fuel cell fabricated using this electrolyte membrane with a conductivity of 7 × 10−3 S cm−1 delivers a power output of 791 mW cm−2 at 700 °C.

Here, a facile and low cost strategy combining co-solvent-optimized interfacial polymerization (CSO-IP) and protective coating-controlled chlorination (PCC-chlorination) for reverse osmosis membranes with high flux-rejection combinations is reported. CSO-IP, which provides a high performance membrane for the following chlorination, is the same as the conventional IP except adding a co-solvent in the organic phase. PCC-chlorination, which improves further the flux meanwhile retaining the high rejection, is the same as the conventional chlorination except adopting a protective coating. The coating preparation is fairly short and needs no complex chemistry. Due to the accelerated diffusion of aqueous phase monomer by the co-solvent, the membrane obtained by CSO-IP possessed a skin layer with thin and dense active layers. Besides, CSO-IP made membrane surface rougher. These endowed the membrane with a high performance (brackish water desalination testing conditions). Because of the heterogeneity of coating structure, some regions of membrane were attacked by chlorine and the others were protected during PCC-chlorination. Then, PCC-chlorination improved the flux further to 82.5 L m−2 h−1 meanwhile maintaining the high rejection (99.02%). This exceeds the performance of many previously reported membranes.

In this work, amorphous nickel–cobalt–manganese hydroxide (NiCoMn–OH) was hydrothermally synthesized using a mixed solvent strategy and used as positive electrode materials for supercapacitor-battery hybrid energy storage system. The experimental results show that the mixed solvent is indispensable to form the amorphous phase of NiCoMn–OH, which exhibits significantly improved electrochemical activity and rate capability in comparison with the crystalline counterpart because of more grain boundaries and ion diffusion channels in the former phase. A strong synergy between the transition metal ions in the amorphous NiCoMn–OH is found to significantly contribute to the electrochemical activity, rate capability and cycling stability. In addition to battery behavior, the amorphous NiCoMn–OH exhibits pseudocapacitive behavior, which contributes approximately 40% to the total energy storage capacity. The pseudocapacitive property significantly enhances the rate performance. The robust synthesis method described in this paper was also used to fabricate the NiCoMn–OH porous network on Ni foam, which shows a specific capacity close to its theoretical value, indicating a complete utilization of the electroactive material. Furthermore, a supercapacitor-battery hybrid cell fabricated with the amorphous NiCoMn–OH as the positive electrode and reduced graphene oxide (RGO) as the negative electrode exhibits both high-energy and high-power performances with a specific energy of 42.8 Wh kg–1 at a specific power of 749 W kg–1 or a specific energy of 19.9 Wh kg–1 at a specific power of 20.9 kW kg–1.

Iron phosphides show promising but limited activity as hydrogen evolution reaction (HER) catalysts due to the low number of active sites and poor electroconductivity. Herein, iron phosphide nanosheets were synthesized and assembled to three-dimensional structures for the first time via a physical-vapor-infiltration assisted hard template strategy. The 3D structured FeP nanosheet assembly exhibits excellent electrocatalytic performance for hydrogen evolution reaction over a wide pH range, outperforming most of the FeP catalysts reported to date in activity and exhibiting superior stability to the commercial Pt/C catalyst. Spectroscopic analyses and electrochemical results support that the fast electron transfer, increased active sites and expedited mass transport, due to the 3D structure of the FeP nanosheets, boost the HER performance.

Developing mixed matrix membranes (MMMs) is challenging because the interface between different matrices often forms undesirable structures. Herein, we demonstrate a method of creating suitable CO2-selective channels based on interface regulation that greatly enhances membrane separation performance. The poly(vinylamine), which also acts as a polymer matrix, was immobilized onto covalent organic frameworks (COFs) to obtain polymer-COF hybrid materials (COFp). The COFp and polymer matrix are highly compatible because they have the same segment. The polymer matrix was induced to penetrate the oversized COFp, resulting in an amino-environmental pore wall and appropriately sized CO2-selective channels dispersed in MMMs. The MMMs exhibited satisfactory membrane performance for CO2/N2, CO2/CH4, and CO2/H2 separation. A CO2 transport model for preferential adsorption and transport is clearly presented for the first time. The membrane separation mechanism is also discussed. This work demonstrates potential applications for material, interface, and membrane investigations.

Membrane distillation (MD) has attracted great interest as a promising water purification technology suitable for the treatment of hypersaline wastewater, but its performance is constrained by mineral scaling at the membrane–water interface. Silica scaling is a common but unique type of scaling due to its amorphous nature, but its underlying mechanism has not been elucidated in the literature. In this study, we used a hydrophobic polyvinylidene fluoride (PVDF) membrane, a Janus PVDF membrane with hydrophilic coating, and a superhydrophobic PVDF membrane to investigate the mechanism of silica scaling in MD. The membranes were challenged with silica-containing feedwater with different saturation status. When silica was initially unsaturated, the water vapor flux of MD remained relatively stable, despite the formation of silica scale on the membrane surface. In contrast, a dramatic decline of water vapor flux occurred when the initial silica concentration was supersaturated. However, membrane surface wettability did not affect the starting time of the flux decline. The superhydrophobic membrane exhibited the slowest flux decline rate with time, while the Janus membrane displayed the best water productivity. In colloidal silica fouling that excluded heterogeneous nucleation, the superhydrophobic membrane was superior in both reducing the flux decline and extending water productivity. This difference, along with microscopic characterization of the scaling layer, provided explicit evidence that both homogeneous nucleation and heterogeneous nucleation contribute to the flux decline caused by silica scaling. A four-step mechanism of silica scaling in MD is proposed, in which the decline of water vapor flux is initiated by homogenous nucleation in the bulk solution but facilitated by surface-mediated heterogeneous nucleation.

In this work, we have firstly proposed a mild and facile method to deposit large-area RGO and ZnO QDs/RGO films on diverse substrates through a self-assembly strategy. RGO powders would aggregate to agglomerate in aqueous solution due to its hydrophobicity. Interestingly, it is found that RGO sheets would assemble to film when RGO ethanol solution is dropped into water, and the film layers could be rationally tuned by repeating the deposition procedure. Based on the convenient fabrication method, a co-current Z-scheme system could be constructed by subsequently depositing RGO and ZnO QDs/RGO films on FeVO4 photoelectrodes, in which RGO serves as an electron mediator. Different from the traditional disordered Z-scheme system, the photo-excited electrons in co-current Z-scheme would move toward the same direction due to the absolute separation between FeVO4 and ZnO. As a result, the PEC performances of FeVO4 could be significantly enhanced because the running direction of photo-excited electrons in co-current Z-scheme is consistent with that in external circuit. For comparison, a counter-current Z-scheme has also been built up by replacing FeVO4 with WO3, in which the ruing direction of photo-generated electrons is opposite to the external circuit, and the photo conversion efficiency decreased consequently. Therefore, it can be concluded that the design of pure Z-scheme is not only beneficial for improving the charge separation efficiency and retaining their redox capability, but also favorable for uncovering the charge transfer mechanism.

Low electrical conductivity and sluggish charge storage kinetics are the key issues of orthorhombic niobium pentoxide (T-Nb2O5) for sodium-ion batteries. Here, we report on an approach for improving the electrochemical properties of T-Nb2O5 using fluorine substitution and carbon modification strategies. The obtained orthorhombic niobium oxyfluoride/carbon nanobelt composite (T-Nb2O5−xFy⊂C-NBs) displayed significantly improved electrochemical properties with sodium ion storage capacity as high as 292 mA h g−1 at 0.05 A g−1, along with an excellent cycling stability over 10 000 cycles at 1 A g−1 (0.002% capacity decay per cycle) as measured using a half cell. An intercalation-pseudocapacitance mechanism (1.0–3.0 V vs. Na/Na+) for storing sodium ions was observed in T-Nb2O5−xFy⊂C-NBs, along with a conversion reaction mechanism (

W5Nb16O55 is a very promising negative electrode compound for lithium-ion storage owing to its good safety, durable cyclability and high rate performance. However, its commercialization is hindered by its limited capacity and high tungsten cost. Here, we designed a tungsten-free and niobium-rich zinc niobate (Zn2Nb34O87) with a large capacity (theoretically 389 mA h g−1) as a new insertion negative electrode compound. Micron-sized Zn2Nb34O87 blocks (Zn2Nb34O87-B) and one-dimensional Zn2Nb34O87 nanofibers (Zn2Nb34O87-N) were prepared via a solid-state reaction and electrospinning methods, respectively. Zn2Nb34O87-B and Zn2Nb34O87-N have 3 × 4 × ∞ shear ReO3 crystal structures of orthorhombic and monoclinic types, respectively. Both the Zn2Nb34O87 materials exhibited better electrochemical performance than W5Nb16O55 in terms of the capacity, lithium-ion diffusion coefficient, intercalation pseudocapacitive contribution, rate performance, and cyclability. In situ X-ray diffraction characterization demonstrated the excellent structural stability and electrochemical reversibility of Zn2Nb34O87, and revealed that lithium ions were stored in the (010) crystallographic planes. Furthermore, a LiNi0.5Mn1.5O4‖Zn2Nb34O87-N full cell exhibited outstanding electrochemical performance, including a large capacity, prominent rate performance, and especially ultra-long cyclability (96.5% capacity retention even after 1000 cycles at 5C). Therefore, Zn2Nb34O87 holds great promise as a practical negative electrode compound for large-capacity, cost-effective, rapid, durable and safe lithium-ion storage.

Covalent organic frameworks (COFs) via Schiff base-type linkages (1,3,5-triformylphloroglucinol–paraphenylenediamine, TpPa-1), as an ideal coating, possesses significant potential for solid-phase microextraction (SPME) due to their fascinating properties, such as outstanding thermal and chemical stabilities, inherent porosity, and high crystallinity. A novel SPME device was fabricated based on TpPa-1 as an enrichment coating for capturing trace polybrominated diphenyl ethers (PBDEs). This TpPa-1 coating exhibited a superior enrichment capacity in “catching” PBDEs over commercial SPME fibers. Such performance is attributed to multiple factors, including the coating’s hydrophobic nature, π-π stacked architectures, large specific surface area, high thermal stability, and size-matching effect. High enhancement factors of 2035–6859, low detection limits of 0.0058–0.022 ng L−1, satisfactory linear range of 0.01–100 ng L−1, good repeatability of 4.86%–9.33%, and excellent reproducibility of 5.62%–9.85% were achieved. Finally, as expected, as the most sensitive SMPE technique for detecting PBDEs, to the best of our knowledge, the developed SPME procedure in combination with gas chromatography–negative chemical ion–mass spectrometry analysis was proven to be ultrasensitive, dependable, and practical in analyzing PBDE species in real water. These exceptional results signify that the proposed method offers a fresh prospect to extend the potential applications of COFs to pick up pollutants at ultra-low levels from environmental samples.

An approach for producing defect-containing porous carbon from microcrystalline cellulose is proposed. A sample with intrinsic defects and a low level of nitrogen doping prepared at a carbonisation temperature of 600 °C followed by thermal treatment in a reducing environment exhibited excellent performance both as a supercapacitor electrode and oxygen reduction reaction (ORR) electrocatalyst. With 1 M H2SO4 aqueous electrolyte, it delivered a specific capacitance of 426 F g−1 at a current density of 0.25 A g−1 or 177 F g−1 at 100 A g−1 measured using a three-electrode system. About 90% of its original capacitance was retained after 60 000 cycles at 5 A g−1 measured in a symmetric supercapacitor cell. In addition, the electrode with a mass loading of 12 mg cm−2 exhibited areal capacitances of 2518 and 1128 mF cm−2 at current densities of 0.5 and 50 mA cm−2, respectively, along with a good cycling stability. Three-electrode system electrochemical analysis reveals that the porous structure and low amount of N/O doping of the sample were more fully and efficiently utilised for charge storage via electrical double-layer and pseudocapacitive mechanisms, respectively, as the presence of intrinsic defects further changed its electronic structure. A symmetric supercapacitor assembled with this carbon electrode in 1 M LiCl electrolyte exhibited an energy density of 20.7 W h kg−1 at a power density of 426 W kg−1. This sample also demonstrated good performance in the ORR due to the presence of intrinsic defects, which promoted electron transfer. It was observed that increasing the thermal treatment temperature is favourable for further improving the ORR activity.

Intercalation-type niobium-based oxides are considered as promising anode materials for lithium-ion batteries owing to their high theoretical/practical capacities, long-term cyclability, and high safety. However, studies in this research field are still very limited. Here, we explore MoNb12O33 as the first molybdenum niobium oxide anode material, and prepare microsized MoNb12O33 particles (M-MoNb12O33) and porous MoNb12O33 microspheres (P-MoNb12O33) based on solid-state reaction and solvothermal methods, respectively. MoNb12O33 shows a Wadsley–Roth crystal structure, consisting of 3 × 4 × ∞ NbO6 octahedra linked by corner-sharing MoO4 tetrahedra. This very open and stable structure results in fast Li+ diffusivity and superior structural stability, respectively. These structural merits together with the nanosizing effects in P-MoNb12O33 lead to outstanding electrochemical properties in its half cell, including a high practical capacity (321 mA h g−1 at 0.1C), significant intercalation pseudocapacitive contribution (85.5% at 1.1 mV s−1), prominent rate capability (200 mA h g−1 at 10C), and superior cyclability (capacity retention of 95.7% after 1000 cycles at 10C). Moreover, outstanding electrochemical properties of a LiMn2O4//P-MoNb12O33 full cell are also achieved, such as a high reversible capacity (274 mA h g−1 at 0.1C), good rate capability (106 mA h g−1 at 10C), and superior cyclability (capacity retention of 93.9% after 1000 cycles at 5C). All these findings indicate that P-MoNb12O33 can be a practical anode material for high-capacity, safe, rapid and durable Li+ storage.

Nb16W5O55 is considered as a promising anode material for lithium-ion batteries (LIBs) due to its high safety, good cyclability and high rate performance. However, it has not been practically used since it suffers from its limited capacity. Here, we demonstrate the design and synthesis of a tungsten-free and niobium-rich Al0.5Nb24.5O62 anode material having a very large theoretical capacity of 400 mA h g−1 and a stable shear ReO3 crystal structure. Both Al0.5Nb24.5O62 microsized particles (Al0.5Nb24.5O62-M) and porous microspheres (Al0.5Nb24.5O62-P) were successfully synthesized. In situ X-ray diffraction indicated the intercalated characteristic of Al0.5Nb24.5O62 and revealed the Li+ insertion into/extraction from its (010) crystallographic planes with high structural stability. Consequently, Al0.5Nb24.5O62-P exhibited a large practical capacity (321 mA h g−1 at 0.1C) and good cyclability (90.0% capacity retention after 500 cycles at 10C). In addition, Al0.5Nb24.5O62-P exhibited significant intercalation pseudocapacitive behavior (86.1% pseudocapacitive contribution at 1.1 mV s−1), high rate performance (192 mA h g−1 at 10C), high initial coulombic efficiency (94.9%) and safe working potential (∼1.68 V). Al0.5Nb24.5O62 also performed well in a LiNi0.5Mn1.5O4//Al0.5Nb24.5O62-P full cell. These research results indicate that Al0.5Nb24.5O62 is a practical anode material for high-energy, stable, fast-charging and safe LIBs.

Sodium-ion capacitors with unique characteristics such as higher energy density than electrical double-layer capacitors, higher power density than rechargeable batteries, and abundant sodium resources represent current research trend in developing large-scale electrical energy storage technology. One of the key challenges presently facing the development of this technology is the imbalanced kinetics between the sluggish Faradaic sodium insertion in the anode and the fast capacitive ion adsorption on the cathode. Here we demonstrate the sol-gel synthesis of a novel, high-rate, stable composite anode material for sodium-ion capacitors (NICs). The composite consisted of Nb2O5 nanoparticles embedded in a carbon matrix (denoted by m-Nb2O5/C). Sodium-ion capacitors employing the m-Nb2O5/C anode and a commercial activated carbon as the cathode showed an admirable performance, delivering high energy densities in a wide range of power densities (73 Wh kg−1@250 W kg-1 and 16.8 Wh kg−1@20 kW kg−1). These favourable cell characteristics are attributed to the properties of the m-Nb2O5/C anode: the mesoporous structure that facilitates electron and ion transport, the presence of the niobium carbide interlayer between the Nb2O5 nanoparticles and the surrounding graphitic carbon that additionally improves the electron conductivity, and the predominant capacitive charge storage mechanism.

A microwave sintering technique is reported for fabricating co-sintered proton-conducting solid oxide fuel cells. With this method, high-quality ceramic electrolyte membranes can be prepared at 1100 degrees C, thus enabling the fabrication of entire cells in a single step. The microwave sintering method not only enhances electrolyte densification but also improves the cathode/electrolyte interface, which is critical for improving fuel cell performance. The power output of the co-sintered cell prepared under the microwave conditions (up to 449 mW cm(-2) at 700 degrees C) was significantly higher than that of the cell fabricated using the traditional co-sintering method (approximately 292 mW cm(-2) at the same temperature). Electrochemical analysis revealed that the enhanced electrolyte density and the improved cathode/electrolyte interface achieved by using the microwave sintering technique decrease both the ohmic resistance and the polarisation resistance of the cell, leading to good fuel cell performance.

Hierarchical porous carbon was synthesized using the spray drying method with cellulose as the carbon source. It was found that thermal treatment temperature had a significant influence on the microstructure of the carbon. A sample obtained at thermal treatment temperature of 1000 °C displayed a high specific surface area of 1096 m 2 /g, a large pore volume (1.59 cm 3 /g), and an appropriate pore system suitable for aqueous sodium chloride electrolyte. A flexible symmetric supercapacitor cell fabricated with this carbon as both electrode exhibited a high specific capacitance (194 F/g at current density 1 A/g), a good rate performance (137 F/g at 10 A/g) and long cycle life (only 4.8% capacitance loss after 5000 cycles). The cell delivered a specific energy of 15.2 Wh/Kg at a specific power of 751 W/Kg, and maintain its stable electrocapacitive performance and good flexibility at the bending condition.

Unique and novel Pd4Sn nanochain networks were successfully synthesized with an average diameter of 5 nm, rendering a modified Pd electronic structure with rich defects such as atomic corners, steps or ledges as catalytic active sites for great enhancement of charge transfer and electrode kinetics. The prepared Pd4Sn nanochain networks held an electrochemically active surface area as high as 119.40 m2 g−1, and exhibited higher catalytic activity and stability toward formic acid oxidation compared with Pd3Sn nanochain networks, Pd5Sn nanochain networks, Pd4Sn dendrites and Pd/C. The fundamental insight of the enhancement mechanism is discussed, and this work offers a novel, less expensive but highly active catalyst for direct formic acid fuel cells.

Nanofibers of alpha-Fe2O3 and gamma-Fe2O3 have been obtained after the controlled calcination of precursor nanofibers synthesized by electrospinning. alpha-Fe2O3 nanofibers showed an irregular toruloid structure due to the decomposition of poly (4-vinyl) pyridine in air while gamma-Fe2O3 nanoparticles decorated nanofibers were observed after the calcination under N-2 atmosphere. Electrochemical measurements showed that different electrochemical behaviors were observed on the glassy carbon electrodes modified by alpha-Fe2O3 and gamma-Fe2O3 nanofibers. The electrode modified by gamma-Fe2O3 nanofibers exhibited high electrocatalytic activities toward oxidation of dopamine, uric acid and ascorbic acid while alpha-Fe2O3 nanofibers cannot. Furthermore, the gamma-Fe2O3 modified electrode can realize the selective detection of biomolecules in ternary electrolyte solutions. The synthesis of nanofibers of alpha-Fe2O3 and gamma-Fe2O3 and their electrochemical sensing properties relationship have been discussed and analyzed based on the experimental results. (C) 2018 Elsevier B.V. All rights reserved.

Manganese dioxide nanowires with different diameters have been synthesized through a simple hydrothermal method. The morphology and microstructure of MnO2 nanowires were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The electrochemical studies showed that the capacitance of MnO2 nanowires with a smaller diameter is much higher than that with a larger diameter whether MgSO4 or Mg(NO3)2 electrolytes are used, both of which are higher than those based on Na2SO4 and Al2(SO4)3 electrolytes. Excellent stability, even more than 100% capacitance retention after 1000 cycles for the short MnO2 nanowire sample, was observed in electrolytes containing magnesium ions. The energy storage mechanisms of MnO2 nanowires in electrolytes containing multivalent and monovalent metal ions have been proposed based on the experimental results.