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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.

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. ...

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.

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. Th...

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.

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.

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 (

Layered double hydroxide (LDH) platelets with nanosized and microsized level were synthesized and used as fillers in an isotactic polypropylene (PP) matrix. The nucleation and crystallization behavior of PP/LDH composites (denoted as 1-PPLx and 2-PPLx for composites containing nanosized and microsized LDH, respectively; x represents the mass percentage of LDH) was investigated by differential scanning calorimetry and polarized optical microscopy techniques. It is found that the crystallization temperature of PP/LDH composites is largely enhanced and the half crystallization time is reduced remarkably relative to pure PP, especially for 2-PPLx composite. The 2-PPLx composite exhibits stronger heterogeneous nucleating ability and faster crystallization rate than 1-PPLx samples with the same LDH loading. In addition, the crystallized PP/LDH composites possess significantly enhanced thermal stability, gas barrier, and flame-retardant properties relative to neat PP, which would show a broad application prospect in engineering plastics and packing industry.

Wire-shaped supercapacitors (WSSCs) with high flexibility, tiny volume and high power density are promising candidates for flexible and wearable devices. However, the practical application of WSSCs is still restricted by their low energy density and poor cycling stability. Herein, we report the design and preparation of well-aligned Ni/NiO@CoNi layered double hydroxide (LDH) arrays via a three-step procedure for high performance WSSCs, which consists of NiO nanobelt core and CoNi-LDH nanoplate shell on Ni wire current collector. The obtained hierarchical Ni/NiO@CoNi-LDH electrode exhibits a high specific areal capacitance (1.63 F cm−2 at 2.5 A cm−2), a good rate performance (retention of 90.7% when the current density increases from 2.5 to 20 A cm−2) and an excellent cycling stability (capacitance retention of 97.6% after 1000 cycles). The Ni/NiO@CoNi-LDH electrode was further assembled with Ni/active carbon electrode to construct an all-solid-state WSSC, which can deliver superior energy and power output. When the power density increases from 150 to 900 mW cm−3, the energy density of the device varies from 6.98 to 6.02 mWh cm−3. This new type of supercapacitor deserves a broad application in next-generation wearable and portable electronic products.

A NiAl layered double hydroxide (LDH)@carbon nanoparticles (CNPs) hybrid electrode was fabricated via a facile and cost-effective approach and displays excellent pseudocapacitive behavior in asymmetric supercapacitors.

Transparent and flexible multilayer films are fabricated based on the alternating assembly of cellulose acetate (CA) and layered double hydroxide (LDH) nanoplatelets followed by thermal annealing treatment. The films exhibit tremendously enhanced oxygen barrier properties. The oxygen transmission rate (OTR) of the resulting (CA/LDH)n multilayer films can be tuned by changing the aspect ratio of high-crystalline LDH nanoplatelets from 20 to 560. The (CA/LDH)20 film displays excellent oxygen-barrier behavior with an OTR equal to or below the detection limit of commercial instrumentation (

Multifunctional mixed metal oxide (MMO) thin films on quartz substrates have been fabricated by layer-by-layer assembly of layered double hydroxide (LDH) nanoparticles and poly(sodium styrene 4-sulfonate) (PSS) followed by calcination, which exhibited properties of both antireflection (AR) and antifogging (AF). The AR and AF performances are related to the low refractive index and superhydrophilicity originating from the nanoporous structure. The influences of deposition cycle, LDH particle size and calcination temperature on AR and AF behavior were thoroughly studied. A maximum transmittance of 98.7% at 650 nm and a minimum time of 0.2 s for a droplet to spread flat (water contact angle ∼0°) were achieved with LDH particle size of 110 nm, 10 cycles of deposition and calcination temperature of 450 °C. Therefore, this work provides a facile approach for the fabrication of multifunctional coatings, which can be potentially used in photovoltaic devices, optical lens and underwater imaging systems.

This paper reports the preparation of cobalt phthalocyanine/layered double hydroxide ultrathin films (UTFs) through an electrostatic layer-by-layer (LBL) technique as well as its application in electrocatalysis for dopamine oxidation. UV-vis absorption and electrochemical impedance spectra indicate the uniform deposition of the LBL films. XRD measurements demonstrate the long-range ordered structure of organic/inorganic UTFs, with an average repeating distance of 1.89 nm. SEM images show that the film surface displays a continuous and uniform morphology, with the root-mean-square (rms) roughness of ∼6.4 nm revealed by AFM. The UTF modified ITO electrode exhibits significant electrocatalytic performance for the oxidation of dopamine which is related to the Co(II)/Co(III) couple in the (LDH/CoPcTs)n UTF. The dopamine biosensor shows rather high sensitivity, low detection limit and excellent anti-interference properties in the presence of ascorbic acid. Furthermore, compared with pristine organic multilayer (PDDA/CoPcTs)n modified electrodes, the (LDH/CoPcTs)nelectrodes show superior repeatability and long-term stability, due to the immobilization and dispersion of electroactive CoPcTs molecules by LDH nanosheets. Therefore, this work demonstrates a successful paradigm for the fabrication of electroactive species in an inorganic 2D matrix, which can be potentially used for practical applications in bioanalysis and biodetection.

A drug−inorganic composite involving prednisone−cholate ion micelles intercalated Mg−Al layered double hydroxide (LDH) has been assembled by a coprecipitation method. Powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and UV−vis absorption spectroscopy indicate a successful intercalation of prednisone-containing micelles into galleries of the LDH matrix. The in vitro drug release studies show that no burst release phenomenon was observed at the beginning of release tests, and the pH value imposes very little influence on the release performance of prednisone in the studied pH range 4.8−7.6. It is, therefore, concluded that the MgAl-LDH can be used as an excellent inorganic drug carrier for prednisone in a wide range of pH values. Four kinetic models (first-order equation, Higuchi equation, Bhaskas equation, and Ritger−Peppas equation) were chosen to study the release kinetics of prednisone from the LDH carrier, and it was found that this process can be described by the Ritger−Peppas equat...

The depletion of traditional energy resources as well as global warming has evoked considerable attention in developing advanced energy-storage and delivery systems. Layered double hydroxides (LDHs) are a family of inorganic clay materials, whose structure is based on positively-charged brucite-like layers and interlayer charge compensating anions. Recently, transition metal-containing LDHs materials have attracted much interest in the field of electrochemical energy storage and conversion (e.g., electrocatalysts, supercapacitors and water splitting),1-2 owing to their high redox activity, low cost and environmentally friendly nature. We demonstrate the design and fabrication of LDH-based hierarchical materials, including LDHs materials with core-shell structure, LDHs/carbon nanotube architectures, LDHs/conducting polymer materials and LDHs/semiconductor composites; in addition, their performances as electrocatalysts toward ethanol oxidation, photoelectrochemical water splitting and as high-performance pseudocapacitors are studied in detail.3-7 The results show that LDHs-based hierarchical materials can serve as promising candidates in a variety of areas including electrocatalysts, solar energy conversion and supercapacitor devices.

A CoAl-layered double hydroxide (LDH)@poly(3,4-ethylenedioxythiophene) (PEDOT) core/shell nanoplatelet array (NPA) is grown on a flexible Ni foil substrate as a high-performance pseudocapacitor. The LDH@PEDOT core/shell NPA shows a maximum specific capacitance of 649 F/g (based on the total mass) by cyclic voltammetry (scan rate: 2 mV/s) and 672 F/g by galvanostatic discharge (current density: 1 A/g). Furthermore, the hybrid NPA electrode also exhibits excellent rate capability with a specific energy of 39.4 Wh/kg at a current density of 40 A/g, as well as good long-term cycling stability (92.5% of its original capacitance is retained after 5000 cycles). These performances are superior to those of conventional supercapacitors and LDH NPA without the PEDOT coating. The largely enhanced pseudocapacitor behavior of the LDH@PEDOT NPA electrode is related to the synergistic effect of its individual components: the LDH nanoplatelet core provides abundant energy-storage capacity, while the highly conductive PEDOT shell and porous architecture facilitate the electron/mass transport in the redox reaction.

In this paper we report the fabrication of layered double hydroxide (LDH) nanoparticles/poly(N-isopropylacrylamide) (pNIPAM) ultrathin films (UTFs) via the layer-by-layer assembly technique, and their switchable electrocatalytic performance in response to temperature stimuli was demonstrated. X-ray diffraction and UV-vis absorption spectroscopy indicate a periodic layered structure with uniform and regular growth of the (LDH/pNIPAM)(n) UTFs; an interaction based on hydrogen bonding between LDH nanoparticles and pNIPAM was confirmed by X-ray-photoelectron spectroscopy and Fourier transform infrared spectroscopy. Temperature-triggered cyclic voltammetry and electrochemical impedance spectroscopy switch for the UTFs was obtained between 20 and 40 °C, accompanied by reversible changes in surface topography and film thickness revealed by atomic force microscopy and ellipsometry, respectively. The electrochemical on-off property of the temperature-controlled (LDH/pNIPAM)(n) UTFs originates from the contraction-expansion configuration of pNIPAM with low-high electrochemical impedance. In addition, a switchable electrocatalytic behavior of the (LDH/pNIPAM)(n) UTFs toward the oxidation of glucose was observed, resulting from the temperature-controlled charge transfer rate. Therefore, this work provides a facile approach for the design and fabrication of a well-ordered command interface with a temperature-sensitive property, which can be potentially applied in electrochemical sensors and switching.

Three-dimensional (3D) WO(3) nanostructures were grown on carbon paper by a catalyst-free high temperature reactive vapor deposition process, which exhibit a good photoelectrochemical property and visible light driven photocatalytic performance.

We report the preparation of a reversible photoresponsive ultrathin film containing a photoactive azobenzene polymer poly{1-4[4-(3-carboxy-4-hydroxyphenylazo)benzenesulfonamido]-1,2-ethanediyl sodium salt} (PAZO) and exfoliated layered double hydroxide (LDH) nanosheets using a layer-by-layer (LBL) self-assembly technique. Alternate irradiation with UV and visible light (lambda450 nm) results in a reversible switching between the trans isomer and the cis-rich photostationary state of the azobenzene group with concomitant significant changes in film color. Fluorescence polarization measurements indicated that the orientation of the azobenzene chromophores in the LDH matrix undergoes a reversible realignment during the photoisomerization processes. Photoisomerization induced by alternate UV and visible light irradiation was accompanied by reversible morphological changes of the LBL film, observable by atomic force microscopy (AFM). Molecular dynamics (MD) studies demonstrated that the LDH monolayers allow sufficient free space for the PAZO to undergo isomerization of its azobenzene chromophores. The reversible photoalignment of PAZO was also followed by MD simulations, and the results are in reasonable agreement with the experimental findings, further validating the configurational and orientational changes proposed for PAZO during the reversible photoprocess. It has been demonstrated that the host (LDH nanosheet)-guest (PAZO) interactions are key factors in determining the reversible photoresponsive performances of the film, since the comparative pristine PAZO film shows no such properties. Therefore, the incorporation of a photoactive moiety within the inorganic nanosheets of LDH by the LBL technique provides an attractive and feasible methodology for creating novel light-sensitive materials and devices with potential read-write capabilities.

Hybrid films were fabricated via layer-by-layer assembly of layered double hydroxide (LDH) nanoplatelets and poly(sodium styrene-4-sulfonate) (PSS) followed by subsequent permeation of poly(vinyl alcohol) (PVA), which show excellent oxygen barrier performance with humidity-triggered self-healing capability.

Flexible and robust free-standing films are fabricated via layer-by-layer (LBL) assembly of layered double hydroxide (LDH) nanoplatelets, poly(vinyl alcohol) (PVA) and a styrylbiphenyl derivative (BTBS), and show enhanced magnetic and luminescent anisotropy simultaneously. UV-vis absorption and fluorescence spectra demonstrate a stepwise and regular growth of the films upon increasing the number of deposition cycles. XRD, AFM and SEM indicate that the films possess a periodic layered and uniform surface morphology. In contrast to the disordered LDH/PVA/BTBS film prepared by a solvent evaporation method, the (LDH/PVA/LDH/BTBS)n films with ordered structures exhibit enhanced magnetic and optical properties, including higher saturation magnetization, longer luminescence lifetime and stronger polarized photoemission. Moreover, owing to the highly arrayed 2D-organized structure formed through LBL assembly, the presence of the free-standing film means that the alignment of the spins of the LDH nanoplatelets in random directions is avoided and imparts a high level of dispersion and orientation to the BTBS, which displays enhanced magnetic and luminescent anisotropy. Therefore, this work provides a facile method for the fabrication of anisotropic 2D-organized materials based on the LDH/PVA/LDH/BTBS system, which can be potentially used in magneto-optical sensors, magnetic data storage and magneto-resistive devices.

This work reports the fabrication of porous mixed metal oxide (MMO)–TiO2 one-dimensional photonic crystals (1DPCs), which can be used as a colorimetric sensor for the detection and measurement of volatile organic compounds (VOCs) and relative humidity (RH). The 1DPCs were prepared via the alternate deposition of titania and layered double hydroxide (LDH) by the spin-coating technique followed by calcination (which induces the phase transformation of LDH to MMO material). A photonic stop band (PSB) of MMO–TiO2 1DPCs was obtained, which can be tuned throughout the whole visible light region by changing the thickness of either of the composing slabs, as a result of the sufficiently high refractive index contrast between TiO2 and MMO. The 1DPC film as a colorimetric sensor shows significant color variation towards VOCs or RH, due to the change of refractive index induced by the adsorption of volatile gas or water molecule in the mesopores of the MMO–TiO2 structure. In addition, the sensor displays high sensitivity, good stability and reproducibility. Therefore, this work provides a feasible method for the fabrication of 1DPCs based on porous MMO–TiO2 films, which have potential applications as portable, recyclable and visually readable colorimetric sensors.

LDH/TiO2 one-dimensional photonic crystals (1DPCs) covering the whole visible light range were fabricated by alternate deposition technique. The switchable color of LDH/TiO2 1DPCs can be achieved by repeating calcination–rehydration cycles, as a result of the associated changes in thickness and refractive index of the LDH slabs.

This paper reports the fabrication of layered double hydroxide nanosheets (LDH nanosheets)/Au nanoparticles (AuNPs) ultrathin films (UTFs) via the layer-by-layer (LBL) assembly technique, and their electrocatalytic performance for the oxidation of glucose was demonstrated. UV-vis absorption spectra show the uniform growth of the UTFs and the enhancement of interlayer plasmon coupling of AuNPs upon increasing deposition cycle. The XRD results indicate that the (LDH/AuNPs)n UTFs possess long-range order stacking in the normal direction of the substrate, with AuNPs accommodated between the LDH nanosheets as a monolayer arrangement. SEM, TEM and AFM images reveal a high dispersion of AuNPs on the surface of the LDH nanosheets without aggregation. The electrochemical behavior of the UTF modified fluorine-doped tin oxide (FTO) electrode was studied by cyclic voltammetry and electrochemical impedance spectroscopy. The (LDH/AuNPs)n UTF shows improved electron transfer kinetics, owing to the formation of electron tunneling junctions resulting from the interlayer plasmon coupling. This leads to new channels for facilitating electron transfer within the UTFs. In addition, the (LDH/AuNPs)8electrode displays significant electrocatalytic performance for glucose with a linear response range (50 μM–20 mM), low detection limit (10.8 μM), high sensitivity (343 μA mM−1 cm−2), good stability and reproducibility. Therefore, this work provides a feasible method to immobilize metal nanoparticles using the LDH nanosheet as a 2D matrix, which is promising for the development of enzyme-free sensors.

Inorganic nanoplatelet reinforced polymer films were fabricated via alternate layer-by-layer assembly of layered double hydroxide (LDH) nanoplatelets with poly(vinyl alcohol) (PVA), which showed largely enhanced strength and good ductility simultaneously.