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A kind of layered Li2MSiO4 material, Fe saponite with Na+ pillaring (Na+-FSAP) was developed as a low-cost and environment-friendly lithium-ion storage material. The Na+-FSAP follows the insertion/deinsertion working mechanism accompanied by valence change of Fe from Fe1.86+ to Fe2.71+ (average value) after stabilization, and displays a specific capacity of 125 mAh g–1 at 50 mA g–1 with retention ratio of 80.8% after 75 cycles. The Na+-pillaring effect and abundant structural water in the gallery urge Li+ migrate rapidly, resulting in a large Li+ diffusion coefficient within a range of 10−6.5–10−7.5 cm2 s−1. Thus, the Na+-FSAP provides a model material to design electrode materials with rapid lithium-ion migration and has great potential to take place of polyanionic-type Li2MSiO4 (M = Mn, Fe, Co) cathode materials.

Two-dimensional (2D) membranes have demonstrated potential for molecular separation; however, their applicability for Li/Mg ion separation has been restricted by their negatively-charged and easily-swellable properties in water. Moreover, their practical application has been hindered by the challenge of producing significant quantities of single-layer nanosheets. To overcome these challenges, we have developed a scalable method for synthesizing micro-sized nitrate ZnAl layered double hydroxide (LDH) and subsequent exfoliating to yield monolayer nanosheets for the construction of 2D membranes. The sub-nanometer channels of the LDH membrane is positively charged, which prevents the passage of magnesium ions. These channels also impede the flow of magnesium ions that are more difficult to dehydrate. As a result, the LDH membranes exhibit robust lithium-magnesium separation ability, with a separation ratio of 6 (Li/Mg). This work provides a method for producing high-quality LDH nanosheets and validates the enormous potential of LDH membranes in the field of lithium-magnesium separation.

The water gas shift reaction (WGS) process on the NiM(111) bimetallic surfaces (M = Fe, Co, Cu, Zn) are studied by density functional theory method and experimental studies. The NiCo and NiCu exhibit the optimum catalytic activity and CO2 selectivity.

In the present work, the two-phase mixture (HTLc) of hydrotalcite and its oxide were used to improve the barrier properties, UV resistance and antimicrobial activity of Poly(ethylene terephthalate) (PET) for their application in liquid milk packaging. Firstly, CaZnAl-CO3-LDHs with a two-dimensional layered structure were synthesized by hydrothermal method. CaZnAl-CO3-LDHs precursors were characterized by XRD, TEM, ICP and dynamic light scattering. A series of PET/HTLc composite films were then prepared, characterized by XRD, FTIR and SEM, and a possible mechanism of the composite films with hydrotalcite was proposed. Barrier properties to water vapor and oxygen have been studied in PET nanocomposites, as well as their antibacterial efficacy by the colony technique and their mechanical properties after exposure to UV irradiation for 24 h. By the presence of 1.5 wt% HTLc in the PET composite film, the oxygen transmission rate (OTR) was reduced by 95.27%, the water vapor transmission rate was reduced by 72.58% and the inhibition against Staphylococcus aureus and Escherichia coli was 83.19% and 52.75%. Moreover, a simulation of the migration process in dairy products was used to prove the relative safety. This research first proposes a safe technique for fabricating hydrotalcite-based polymer composites with a high gas barrier, UV resistance and effective antibacterial activity.

Transition-metal compounds (oxides, sulfides, hydroxides, etc.) as lithium-ion battery (LIB) anodes usually show extraordinary capacity larger than the theoretical value due to the transformation of LiOH into Li

As one kind of promising energy storage device, chloride ion batteries (CIBs) have attracted extensive attention due to their sustainability, safety and high theoretical volumetric energy density. ...

A fluoride-ion battery (FIB) is a novel type of energy storage system that has a higher volumetric energy density and low cost. However, the high working temperature (150 °C) and unsatisfactory cycling performance of cathode materials are not favorable for their practical application. Herein, fluoride ion-intercalated CoFe layered double hydroxide (LDH) (CoFe-F LDH) was prepared by a facile co-precipitation approach combined with ion-exchange. The CoFe-F LDH shows a reversible capacity of ∼50 mAh g

Two-dimensional Fe-beidellite/carbon (Fe-BEI@C) superlattice-like heterostructure was prepared by intercalation of glucose in the gallery of layered Fe-BEI followed by calcination. The interlaminar and superficial carbon coating enables Fe-BEI to have good rate performance, fast lithium-ion diffusion, and high pseudocapacitance contribution, leading to excellent lithium storage performance as anode material for lithium-ion batteries (LIBs). The Fe-BEI@C/Li half cell delivers a maximum specific capacity of 850 mAh·g

Two-dimensional (2D) nanosheets with thickness of one to several atoms serve as ideal building units for separation membranes. Herein, we report the construction of ultrathin membranes with layered double hydroxides (LDHs) nanosheets, polyacrylic acid (PAA) and polyethyleneimine (PEI) alternately deposited on porous substrates. The chemical tuning of PEI leads to an accurate regulation of interlayer spacing in angstrom scale, resulting in selective nanochannels for CO2 permeation. The laminar membranes with CO2 transport-facilitated channels exhibit excellent gas separation performance and exceed the limit of the state-of-the-art membranes with CO2 permeance of 1068 GPU, CO2/N2 and CO2/CH4 selectivity of 126 and 330 respectively. A synergistic effect of solution-diffusion and molecular sieving was proposed for this prominent CO2 separation performance. The strategy demonstrated in this work would open up new avenues for effective CO2 separation and capture in recycling of carbon resources.

NiFe saponite (NF-SAP) with Na+ pillaring was investigated for the first time, as a new anode material for high-performance lithium-ion batteries (LIBs). In this material, non-metallic element Si and metallic elements Fe and Ni all act as active components (providing capacity) and undergo valence state changes during electrochemical progress. Si changes between Si2+ and Si4+, while Fe and Ni transform between a nearly metallic state and Fex+ and Niy+ (0 < x < 3, 0 < y < 2). In the fully lithiated state, Ni–Ni bonds appear but only Fe–O bonds can be observed in NF-SAP. The NF-SAP/Li half cell delivers a gradually increasing specific capacity in the initial hundreds of cycles (maximum capacity of 815 mA h g−1 at the 350th cycle) and maintains a capacity of 646 mA h g−1 after 1000 cycles at 500 mA g−1. The pre-pillaring effect of Na+ is responsible for the good Li+ storage performance, which leads to the decrease of Li+ transport hindrance and high contribution of pseudocapacitance. Furthermore, a full cell of LiMn2O4/NF-SAP was assembled, which shows an initial specific capacity of 104 mA h g−1 at 100 mA g−1 and maintains a capacity of 68% after 50 cycles, demonstrating the bright application prospects of NF-SAP as a promising anode material. This work shows a new kind of anode for LIBs and provides an in-depth understanding of its energy-storage mechanism. Considering the easy preparation, low cost and environment-friendly characteristics of NF-SAP, this kind of material is applicable to large-scale energy storage.

Two-dimensional layered materials with large interlayer distance to guarantee facilitated electrolyte diffusion are regarded as good candidates for high-performance supercapacitors. In this work, NiAl-layered double hydroxide (LDH) nanoplate arrays with NO3–, pentanesulfonate (PS) and dodecanesulfonate (DS) ions in their interlayer were synthesized, and the effect of different pillaring anions on the electrochemical properties of LDH electrodes was investigated. Combined studies of experiments and theoretical calculations show that the pillaring-effect of long-chain molecules drastically reduces the ion transport resistance between the electrode and electrolyte. An enhanced specific capacitance (1125 F g–1 at 1 A g–1) and a ultrahigh-rate capability (72.8% retention at 200 A g–1) were achieved for the NiAl(DS)-LDH electrode. Such an electrode was further assembled into an all-solid-state supercapacitor, which exhibits a significantly improved energy and power densities as well as long-term stability. This...

Stretchable gas barrier films achieved by hydrogen-bond self-assembly of nano-brick multilayers

Chloride ion batteries (CIBs) are an example of a promising new emerging rechargeable battery technology, that exhibits large theoretical volumetric energy density performance and good safety. However, unsatisfactory capacity and poor cycling lifetime of the cathode currently hinder the development of CIBs. Herein, we report the use of an Ni2+Fe3+-based layered double hydroxide (LDH) intercalated by chloride ions as a promising cathode material for CIBs. [Ni2Fe(OH)6]Cl·1.37H2O (NiFe–Cl LDH) exhibits a high maximum capacity of 350.6 mA h g−1and a long lifetime of over 800 cycles (at 101.1 mA h g−1) at a current density of 100 mA g−1, which is superior to most currently reported CIB cathodes.In situX-ray absorption near-edge structure (XANES) andex situX-ray photoelectron spectroscopy (XPS) reveal the valency changes of the Fe2+/Fe3+and Ni2+/Ni3+redox pairs within the metal hydroxide layers of the LDH during electrochemcial cycling.In situXRD reveals that 2D anion diffusion within the LDH results in only ∼3% structural change. Oxygen K-edge soft X-ray absorption spectroscopy (SXAS) reveals the oxygen atoms within the MO6octahedra reversibly participate in the electrochemical reaction. In view of the extensive chemical variation, low-cost, and ease-of-preparation of LDH-based materials we regard LDHs as a promising materials platform for application as cathode materials in chloride ion batteries.

Stretchable gas barrier films achieved by hydrogen-bond self-assembly of nano-brick multilayers

A CoFe layered double hydroxide (LDH) with nitrates in its interlayer has been developed for the first time as an intercalation-type anode material for sodium ion batteries (SIBs). Unlike the well-recognized conversion reaction for metal hydroxides in lithium ion batteries, an exceptional intercalation/de-intercalation mechanism for Na+-storage was revealed. The CoFe–NO3−-LDH anode delivers an initial discharge capacity of 498 mA h g−1 and a reversible capacity of 209 mA h g−1 after 200 cycles at 1 A g−1. The superb Na+-storage performance is attributed to the expanded interlayer distance of the CoFe-LDH pillared by the interlayer nitrates, benefiting the intercalation/de-intercalation of Na+ ions. Besides, the topochemical transformation property of LDH materials guarantees high structural stability during the valence state change of Co2+/Co2−x and Fe2+/Fe3+ in their host layers. In addition, theoretical calculation reveals a low Na+ diffusion barrier of 0.147 eV in the interlayer space of CoFe–NO3−-LDH, which manifests LDH as a good Na+ ion conductor. Therefore, this work not only develops a novel intercalation-type anode for SIBs, but also provides new insights into the energy-storage mechanism of layered metal hydroxides.

Gas barrier films with water-vapor-permeability have exhibited broad application prospects in gas separation and dehumidification. Herein, multilayer films comprised of layered double hydroxides (LDH) nanosheets and carboxymethyl cellulose sodium (CMC) were fabricated via layer-by-layer assembly. The resulting (LDH/CMC) n films show excellent gas barrier properties, which are ascribed to the significantly increased pathway for gas permeation originating from the large aspect ratio and high orientation of two-dimensional LDH nanosheets. Unlike traditional gas barrier films with nonselective blocking effect for various gases (including water vapor), the (LDH/CMC) n films exhibit an unusual moisture permselective property. The moisture-permeable property was related to the hygroscopicity of CMC and hydrophilicity of LDH, which can enrich the water molecules from the surroundings and aggrandize the osmotic pressure for water vapor, resulting in an uncommon improvement of water vapor transmission. It is interesting to find that the (LDH/CMC) n films exhibit enhanced gas (O2, CO2, CH4, and N2) barrier properties upon treatment in a humid environment, due to the formation of hydrogen bonds between the infiltrated water molecules and hydrophilic groups in CMC, thus padding the interstitial space of the CMC molecular chains and increasing the gas transmission path. The reduction of free volume and extension of the gas transmission path further enhance the gas barrier properties of (LDH/CMC) n films. Moreover, the (LDH/CMC) n films represent the water vapor permselective property in mixed gas (including O2, CO2, CH4, N2, and water vapor), while maintaining the barrier for other gases, which can be potentially applied in air dehydration and dehumidification of natural gas.

Interfacial carrier transportation is a key step in photocatalytic water splitting reaction. Herein, we fabricated a series of Cu2O@ZnCr-layered double hydroxide (LDH) photocatalysts with tunable interfacial properties, by precise regulation over a covalent-bonding-bridge structure at the heterointerface. The Cu2O@ZnCr-LDH photocatalyst with an optimized interface exhibits a stoichiometric production of H2 and O2 with a generation rate of 3.42 and 1.63 μmol h−1, respectively, without any sacrificial agents or co-catalysts. This activity is among the highest reported for photocatalysts under the same conditions. By using extended X-ray absorption fine structure (EXAFS) and coincidence Doppler broadening positron annihilation spectroscopy (CDB-PAS), for the first time, we substantiated that a bridge-type bonding at the heterointerface strongly facilitates the interfacial transportation of photo-induced carriers via a Z-scheme route. This provides direct experimental evidence for carrier interfacial transportation, beyond previously reported theoretical predictions and simulations. It is expected that this modulation and optimization over the heterostructure interface can be extended to other dual-semiconductor photocatalysts with high performance.

Gas and moisture barrier materials are of crucial importance in various application fields, including food/drug packaging and encapsulation of electronic devices. Herein, a dual-barrier film to gas and water vapor was fabricated by a facile and cost-effective spin-coating of amphiphilic surfactant (Tween 80) modified LDH nanoplatelets (denoted as LDH-80) and polydimethylsiloxane (PDMS). The resultant (LDH-80/PDMS)15 film exhibits low O2 and H2O transmission rates with ∼0.701 and ∼0.049 cm3 m−2 d−1 atm−1, respectively, smaller than those for most of the reported barrier materials. The remarkable barrier properties are ascribed to the prolonged diffusion length for gas permeation and improved inorganic–organic interfacial compatibility between LDH-80 and PDMS. Taking advantage of this unique dual-barrier property, an aluminum foil substrate coated with (LDH-80/PDMS)n film displays an excellent anti-corrosion effect due to the inhibition of oxygen-consuming corrosion, which enables the (LDH-80/PDMS)n films to be promising candidates in metal surface protection.

Rubber nanocomposites with high gas barrier property have extensive application prospects in sealing and packing industry, while developing a novel and cost-effective rubber-based material with low gas permeability and good mechanical property still remains a challenge. Herein, we designed and fabricated an excellent gas barrier film by using polyvinyl pyrrolidone modified ultrathin layered double hydroxide nanoplatelets (U-mLDH) and nitrile butadiene rubber (NBR) as building blocks. The resultant (U-mLDH/NBR)30 film displays significantly decreased (reduced by 92.2% compared with NBR film) oxygen transmission rate with 0.626 cm3 m–2 day–1 atm–1, and much lower relative permeability in comparison with reported rubber composites. The improved gas barrier performance is ascribed to the prolonged passage of oxygen molecules and the decreased free space arising from large aspect ratio of U-mLDH and good interfacial compatibility. In addition, the (U-mLDH/NBR)30 film also possesses high thermal stability and satisfactory mechanical property, which would guarantee its practical applications.

A high-quality porous CoNi2S4 nanoplates array was in situ synthesized on carbon fibers (CFs) by a hydrothermal method via a CoNi-layered double hydroxide (LDH) precursor transformation process. The CoNi2S4@CFs electrode exhibits largely enhanced supercapacitor performance with a specific capacitance of 1724 F/g at 1 A/g, in comparison with that of the CoNi-LDH (1302 F/g) precursor. Furthermore, the CoNi2S4@CF electrode shows an extremely high rate capability with capacity retention of 79% under a charge density of 60 A/g, whereas the retention rate of CoNi-LDH@CFs is only ∼34%. The abundant pore structure, improved electrical conductivity, and lower internal resistances of CoNi2S4@CFs (1.0 Ω) compared to those of CoNi-LDH@CFs (9.5 Ω) are responsible for the enhancement of energy storage performance. By using the CoNi2S4 nanoplate array as the positive electrode, an all-solid-state asymmetric fiber-shaped supercapacitor was further obtained, which exhibits outstanding flexible, foldable, and wearable capability. In view of the component tunability for LDH materials, the hydroxide precursor transformation method with merits of mild conditions and easy operation can be extended to the synthesis of a variety of metal sulfides for broad applications in electronic devices.

The rapid development of novel renewable energy storage systems promotes the evolution of sodium ion batteries. Among various anode materials, the conversion-type material with high sodium storage capacity suffers from large irreversible volume change during charge–discharge, which eventually results in inferior cycling performance. Herein, heterostructure hollow ZIF-67-C/layered double oxides (LDO) nanoparticles as an anode material are constructed to realize high sodium storage performance. The hollow ZIF-67-C/LDO anode with high electrical conductivity and specific surface area endows electrodes with fast electron/ion transport and reduced voltage hysteresis. As a consequence, the ZIF-67-C/LDO with calcination under 350 °C possesses a high sodium storage capacity of 341 mAh g−1 at 0.1 A g−1 and superior rate performance with a capacity of around 200 mAh g−1 at 2 A g−1. The hollow core/shell structure can not only improve the specific surface area but also alleviate the stress during the electrochemical reactions, leading to enhanced capacity and improved structural stability of the electrode material.

Layered double hydroxides (LDHs), as one type of typical 2D inorganic layered materials, have been extensively used in drug loading and release, functional additive, adsorption, catalysis, energy storage, photochemistry and other fields, owing to their tunable interlayer space, good anisotropy and thermal stability. However, the application of LDHs powder normally suffers from mass losing and serious aggregation. Recent years, LDHs-based flexible composite films have shown promising application prospect in the field of electrochemical storage, optoelectronic devices, and gas barrier materials, due to their portability, ductility and good mechanical properties. This review introduced the preparation methods and application fields of LDHs-based flexible films and pointed out the future research directions.

Overall water splitting through solar radiation is highly attractive for alternative energy utilization. Herein, we designed and fabricated a Cu2O@ZnCr-layered double hydroxide (LDH) core-shell photocatalyst to achieve a high-performance, visible-light overall water splitting. The Cu2O@ZnCr-LDH nanostructure exhibits a high activity (with H2 and O2 production rate of 0.90 and 0.44 μmol h−1, respectively) under visible-light without any sacrificial agent and co-catalyst, which is among the highest level of reported photocatalysts under the same conditions. Both experimental and computational investigations demonstrate that the Cu2O@ZnCr-LDH heterostructure fully exploits the synergistic effect of Cu2O and ZnCr-LDH, in terms of band structure matching. Most significantly, the S2O32− group in the gallery of ZnCr-LDH acts as an effective mediator between these two individual components, which not only inhibits the photocorrosion of Cu2O but also accelerates the immigration of photo-induced electron-hole pairs. Therefore, this work provides a deep insight for the design and preparation of visible-light-responsive photocatalysts, which show promising applications in photochemical reactions and energy conversion.

Two-dimensional graphene materials as supercapacitors electrode have attracted tremendous attention owing to their high surface area and exceptionally electrical conductivity, while it is still a great challenge to achieve desired mesoporous graphene electrodes as the easy aggregation of graphene nanosheets. Here we report the design and fabrication of mesoporous free-standing reduced graphene oxide (rGO)-based films by introducing layered double hydroxides (LDHs) nanoplatelets into the interlayer of rGO nanosheets. The nanostructures regular evolutions of rGO/CoAl-LDH free-standing film due to the embedding of LDHs were rationally investigated with detail experiments. Moreover, the flexible all-solid-state asymmetric supercapacitor device fabricated by using rGO/CoAl-LDH as positive electrode demonstrates a superior performance compared to most reported rGO-based free-standing film electrodes. The results presented here provide valuable insights into exploring mesoporous graphene-based free-standing architectures for highly-efficient and stable energy storage devices.

Anion insertion electrochemistry is a new frontier that leads to exciting applicable technologies including anion-based rechargeable batteries. Herein, we demonstrate a family of room temperature anion-type “rocking-chair” batteries by employing halide ions (F−, Cl− or Br−) intercalated CoNi layered double hydroxide (LDH) and metal lithium as electrochemical couples, ionic liquid as electrolyte. Reversible shuttles of anions can be realized in all these three systems and the anion batteries show high capacity (maximum capacity of 338 mAh g−1) and acceptable cycling stability (above 100 mAh g−1 after 50 cycles). A topological transformation energy storage mechanism of reversible anions intercalation/de-intercalation accompanied by oxidation/reduction of intralayer metals is revealed, by using bromide ions battery as a model. The proof-of-concept for LDH materials as cathodes of anion-type rechargeable batteries fills the void in the anion inserted materials innovation landscape, and allows their potential application in next-generation energy storage systems, owing to their variability in chemical composition, high structural stability, and low cost.

A series of polyvinylidene fluoride (PVDF)/layered double hydroxide (LDH) composite membranes were prepared via phase inversion method, in which the presence of LDH promotes the formation of β-phase PVDF. This work reveals the key role of hydrogen-bonds on the nucleation mechanism and crystallization behavior of PVDF. The composite membranes exhibit improved porosity and hydrophilicity, leading to an enhanced antifouling property against proteins.

Poly(ethylene terephthalate) (PET) generally suffers from low crystallization rate and long molding duration, which as a result limit its application as engineering plastics. To overcome these drawbacks, series of PET/layered double hydroxide (LDH) nanocomposites were prepared by a solution blending process. The effect of metal composition (MgAl and CaAl) and organo-modification (stearic acid intercalated) for LDH fillers on the crystallization behavior of the nanocomposites was investigated. It was revealed that, compared with PET/CaAl-LDH, the PET/MgAl-LDH nanocomposite exhibits a higher crystallization temperature and faster crystallization rate, which is associated with the superior nucleation ability of MgAl-LDH. The nucleation mechanism of PET induced by LDHs was explored by means of Avrami equation and theory of Hoffman-Lauritzen, pointing out that the incorporation of LDHs reduce the free energy of nucleation and the fold surface free energy of PET. In order to improve the compatibility between LDH and PET, stearic acid (SA) intercalated MgAl-LDH was prepared and filled into PET matrix. The resultant PET/MgAl-LDH-SA shows a further enhanced crystallization temperature and accelerated crystallization rate, in comparison with PET/MgAl-LDH nanocomposites. In addition, the thermal stability, gas barrier and mechanical properties of PET/LDH composites were improved upon incorporation of LDH fillers.

A dual-functional organic–inorganic film with gas barrier and hydroxide ion conductivity properties was fabricated via the layer-by-layer assembly of layered double hydroxide (LDH) nanoplates and quaternary ammonium grafted polysulfone (QAPSF). By incorporating inorganic flakes with high ionic conductivity and gas barrier effects into an ion-conductive polymer matrix, this work overcomes the commonly-believed incompatibility between gas blocking and ionic conduction.

Flexible and lightweight wire-shaped supercapacitors (WSSCs) have recently attracted increasing interest, due to their versatility in the device design and application potentials in portable or wearable electronics. However, practical applications of WSSCs are still limited by the relatively poor performances, owing to the challenges in the rational modification of one-dimensional (1D) substrates with sophisticated nanostructure. Herein, we demonstrate a WSSC by virtue of material exploration and fabrication strategy. A 1D nanoarray electrode consisting of CuO nonowires core and CoFe-layered double hydroxide (CoFe-LDH) nanoplatelets shell supported on a copper wire is prepared with fine control over the structure/morphology, which displays a largely improved specific capacitance, high rate capability and long cycling lifespans. Based on this sophisticated core–shell nanostructure, a flexible all-solid-state asymmetric WSSC was fabricated, which exhibits excellent supercapacitive performances with a high energy density (1.857 mWh cm−3) and long-term cycling stability (99.5% device capacitance retention over 2000 cycles).By virtue of the versatility of metal wire substrates, transition metal oxides and LDHs materials, the synthesis strategy presented here can be extended to the fabrication of other portable and flexible micro energy storage devices.

Electrochromic films have shown great application prospects in electronic display and information storage. In this work, we report the fabrication of electrochromic ultrathin films (UTFs) by layer-by-layer (LBL) assembly of layered double hydroxide (LDH) nanosheets with poly(3,4-ethylene-dioxythiophene)–poly(styrene sulphonate) (PEDOT:PSS). UV-vis absorption spectra illustrate the uniform and regular growth of the UTFs. The X-ray diffraction results indicate that the (PEDOT:PSS/LDH)n UTFs possess long-range ordered stacking in the normal direction of the substrate, with PEDOT:PSS accommodated between the LDH nanosheets. SEM and AFM images demonstrate a continuous smooth surface of the (PEDOT:PSS/LDH)n UTFs without aggregation. The (PEDOT:PSS/LDH)n UTFs exhibit an improved ion transfer kinetics, owing to the high dispersion of PEDOT:PSS and the presence of an ordered superlattice architecture. This leads to significantly enhanced electrochromic performance, including ultrafast switching speed (0.27/0.18 s for coloring/bleaching response), high optical contrast (ΔT = 32%, at 650 nm) and satisfactory coloration efficiency (159 cm2 C−1). Therefore, this work provides a feasible method to construct high-performance electrochromic films, which are promising candidates for application in optical/optoelectronic devices.

A hierarchical CoAl–OH layered double hydroxide (H-OH-LDH) electrode was prepared via a continuous calcination–rehydration treatment of a plate-like CoAl–CO3 layered double hydroxide (P-CO3-LDH) array on a nickel foil substrate. The H-OH-LDH electrode shows a well-defined hierarchical structure with a greatly increased accessible interlaminar surface area, leading to improved electrochemical energy storage ability. Most significantly, the interlayer space of H-OH-LDH acts as an electrolyte micro-reservoir to store OH− ions, which dramatically decreases the diffusion resistance of OH− to the inner surface of LDH lamella, and consequently results in an ultrahigh-rate-capability (capacitance reservation of 66% when the current density increases from 1 to 100 A g−1). The remarkable rate capability is superior to that of ever-reported transition metal oxide/hydroxide-based electrodes. In addition, an all-solid-state hybrid capacitor device was fabricated based on this H-OH-LDH electrode, exhibiting outstanding energy and power output (35.5 W h kg−1 at 27.3 kW kg−1) as well as excellent cycling stability. Therefore, this work demonstrates a new approach for the design and fabrication of LDH-based materials with self-generated electrolyte reservoirs, which have promising potential application in energy storage/conversion systems.

Transparent and flexible gas-barrier materials have shown broad applications in electronics, food, and pharmaceutical preservation. Herein, we report ultrahigh-gas-barrier films with a brick-mortar-sand structure fabricated by layer-by-layer (LBL) assembly of XAl-layered double hydroxide (LDH, X=Mg, Ni, Zn, Co) nanoplatelets and polyacrylic acid (PAA) followed by CO2 infilling, denoted as (XAl-LDH/PAA)n-CO2. The near-perfectly parallel orientation of the LDH "brick" creates a long diffusion length to hinder the transmission of gas molecules in the PAA "mortar". Most significantly, both the experimental studies and theoretical simulations reveal that the chemically adsorbed CO2 acts like "sand" to fill the free volume at the organic-inorganic interface, which further depresses the diffusion of permeating gas. The strategy presented here provides a new insight into the perception of barrier mechanism, and the (XAl-LDH/PAA)n-CO2 film is among the best gas barrier films ever reported.

TiO2@CoAl-layered double hydroxide (LDH) core–shell nanospheres are fabricated via hydrothermal synthesis of TiO2 hollow nanospheres followed by in situ growth of CoAl-LDH shell, which exhibit an extraordinarily high photocatalytic activity toward oxygen evolution from water oxidation. The O2 generation rates of 2.34 and 2.24 mmol h−1 g−1 are achieved under full sunlight (>200 nm) and visible light (>420 nm), respectively, which are among the highest photocatalytic activities for oxygen production to date. The reason is attributed to the desirable incorporation of visible- light-active LDH shell with UV light-responsive TiO2 core for promoted solar energy utilization. Most importantly, the combined experimental results and computational simulations reveal that the strong donor–acceptor coupling and suitable band matching between TiO2 core and LDH shell facilitate the separation of photoinduced electron-hole pairs, accounting for the highly efficient photocatalytic performance. Therefore, this work provides a facile and cost-effective strategy for the design and fabrication of hierarchical semiconductor materials, which can be applied as photocatalyst toward water splitting and solar energy conversion.

Electrochromic materials are the most important and essential components in an electrochromic device. Herein, we fabricated high-performance electrochromic films based on exfoliated layered double hydroxide (LDH) nanosheets and Prussian blue (PB) nanoparticles via the layer-by-layer assembly technique. X-ray diffraction and UV-vis absorption spectroscopy indicate a periodic layered structure with uniform and regular growth of (LDH/PB)n ultrathin films (UTFs). The resulting (LDH/PB)n UTF electrodes exhibit electrochromic behavior arising from the reversible K(+) ion migration into/out of the PB lattice, which induces a change in the optical properties of the UTFs. Furthermore, an electrochromic device (ECD) based on the (LDH/PB)n-ITO/0.1 M KCl electrolyte/ITO sandwich structure displays superior response properties (0.91/1.21 s for coloration/bleaching), a comparable coloration efficiency (68 cm(2) C(-1)) and satisfactory optical contrast (45% at 700 nm), in comparison with other inorganic material-based ECDs reported previously. Therefore, this work presents a facile and cost-effective strategy to immobilize electrochemically active nanoparticles in a 2D inorganic matrix for potential application in displays, smart windows and optoelectronic devices.

A high performance gas barrier film was fabricated via alternate spin-coating of chitosan (CTS) and hierarchical layered double hydroxide (H-LDH). The H-LDH synthesized by a calcination–rehydration method shows a hierarchical structure with nanowalls aligned vertically on the LDH platelets, which were subsequently assembled in the CTS matrix, generating a hybrid film with excellent gas barrier properties. Compared with the (P-LDH/CTS)10 barrier film based on plate-like LDH (P-LDH), the (H-LDH/CTS)10 film exhibits significantly enhanced oxygen barrier properties with an oxygen transmission rate (OTR) below the detection limit of commercial instruments (