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The ordered ultrathin films (UTFs) based on CoFe-LDH (layered double hydroxide) nanoplatelets and manganese porphyrin (Mn-TPPS) have been fabricated on ITO substrates via a magnetic-field-assisted (MFA) layer-by-layer (LBL) method and were demonstrated as an electrochemical sensor for glucose. The XRD pattern for the film indicates a long-range stacking order in the normal direction of the substrate. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images of the MFA LDH/Mn-TPPS UTFs reveal a continuous and uniform surface morphology. Cyclic voltammetry, impedance spectroscopy, and chronoamperometry were used to evaluate the electrochemical performance of the film, and the results show that the MFA-0.5 (0.5 T magnetic field) CoFe-LDH/Mn-TPPS-modified electrode displays the strongest redox current peaks and fastest electron transfer process compared with those of MFA-0 (without magnetic-field) and MFA-0.15 (0.15 T magnetic field). Furthermore, the MFA-0.5 CoFe-LDH/Mn-TPPS exhibits remarkable electrocatalytic activity toward the oxidation of glucose with a linear response range (0.1-15 mM; R(2) = 0.999), low detection limit (0.79 μM) and high sensitivity (66.3 μA mM(-1) cm(-2)). In addition, the glucose sensor prepared by the MFA LBL method also shows good selectivity and reproducibility as well as resistance to poisoning in a chloride ion solution. Therefore, the novel strategy in this work creates new opportunities for the fabrication of nonenzyme sensors with prospective applications in practical detection., (© 2011 American Chemical Society)

Highly efficient and low‐cost electrodes have a key role in the development of advanced energy devices such as fuel cells and metal–air batteries. However, electrode performance is typically limited by low utilization of active sites, which causes a considerable drop in energy density. To overcome this issue, a single‐atom‐containing integrated electrode is developed through a confinement synthesis strategy by using organic molecule‐intercalated layered double hydroxides (LDHs) as precursors. The as‐prepared integrated electrode has a well‐defined nanosheet array structure with a homogeneous anchored single atomic Co catalyst and many exposed hierarchical pores. Moreover, the coordination environment of single atoms (CoN or CoS) is precisely controlled by regulating the type of interlayer molecules in the LDHs. Consequently, the optimized electrode exhibits high bifunctional activity toward both the oxygen reduction and oxygen evolution reactions. This electrode is directly assembled into an all‐solid‐state zinc–air battery that showed outstanding flexibility and long‐term charge/discharge stability. Because of the versatility of LDH materials, it is expected that the proposed strategy can be extended to the construction of other integrated electrodes for high‐performance energy storage and conversion devices. [ABSTRACT FROM AUTHOR]

Layered double hydroxides (LDHs) with two-dimensional lamellar structures show excellent electrocatalytic properties. However, the catalytic activity of LDHs needs to be further improved as the large lateral size and thickness of the bulk material limit the number of exposed active sites. However, the development of efficient strategies to exfoliate bulk LDHs into stable monolayer LDH nanosheets with more exposed active sites is very challenging. On the other hand, the intrinsic activity of monolayer LDH nanosheets can be tuned by surface engineering. Herein, we have exfoliated bulk CoFe LDHs into ultrathin LDH nanosheets through Ar plasma etching, which also resulted in the formation of multiple vacancies (including O, Co, and Fe vacancies) in the ultrathin 2D nanosheets. Owing to their ultrathin 2D structure, the LDH nanosheets expose a greater number of active sites, and the multiple vacancies significantly improve the intrinsic activity in the oxygen evolution reaction (OER). [ABSTRACT FROM AUTHOR]

Arsenic contaminated water and soil is seriously threatening the ecosystems safety and human health. Specially, the As(III) has higher toxicity, mobility and lower affinity to typical adsorbents, thus posing substantial obstacles for remediation. Herein, we report a zinc-iron layered double hydroxide (ZnFe-LDH) that exhibits high removal capacity of 134.5 mg/g toward As(III) with the aid of photo-oxidation at the initial concentration of 200 mg/L with pH of 8.4, and can efficiently reduce the total concentration of As from 20 mg/L to 8.2 μg/L within 240 min, lower than the 10 μg/L upper limit for As in drinking water. Detailed investigations suggested that the active oxidative species of photogenerated holes, superoxide and hydroxyl radicals take part in the transformation of As(III) to As(V), which enhances the adsorption capacity. For As(III)-pollutant soil remediation, the bioavailability of As in soil dramatically decreased by 87.7% and 78.1% under visible and nature light in 3 days after introduction of ZnFe-LDH as in-situ immobilization amendment. Moreover, the plant cultivation experiment demonstrated that the bioaccumulation of As in Brassica chinensis effectively reduced to safety range after remediation of the As(III)-contaminated soil with ZnFe-LDH. We envision that the strategy of photocatalytic oxidation will open a new door to address the problem of As(III)-contaminated water and soil. • Photogenerated active oxidative species play great effect on the removal of As(III). • The capture capacity of ZnFe-LDH to As(III) reach to 134.5 mg/g. • The bioavailability of As in soil obviously decreased with ZnFe-LDH as stabilizer. • ZnFe-LDH can effectively reduce the As accumulation in vegetables. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials have attracted increasing interest in electrochemical energy storage and conversion. As typical 2D materials, layered double hydroxides (LDHs) display large potential in this area due to the facile tunability of their composition, structure and morphology. Various preparation strategies, including in situ growth, electrodeposition and layer-by-layer (LBL) assembly, have been developed to directly modify electrodes by using LDH materials. Moreover, several composite materials based on LDHs and conductive matrices have also been rationally designed and employed in supercapacitors, batteries and electrocatalysis with largely enhanced performances. This feature article summarizes the latest developments in the design, preparation and evaluation of LDH materials toward electrochemical energy storage and conversion. [ABSTRACT FROM AUTHOR]

Hierarchical MgFe-layered double hydroxide (LDH) microspheres with tunable interior structure are synthesized by a facile and cost-effective surfactant-templated method. Scanning and transmission electron microscopy images reveal that the obtained microspheres display a three-dimensional architecture with hollow, yolk−shell and solid interior structure, respectively, with continuous changes in specific surface area and pore-size distribution. Moreover, the hollow MgFe-LDH microspheres exhibit excellent electrocatalytic oxidation of ethanol in alkaline fuel cell, including high activity, long-term durability and cycling stability, owing to the significantly improved faradaic redox reaction and mass transport. Therefore, this work provides a promising approach for the design and synthesis of structure tunable materials with largely enhanced ethanol electrooxidation behavior, which can be potentially used in noble metal-free alkaline fuel cells. [ABSTRACT FROM AUTHOR]

Abstract: Zn–Ti layered double hydroxides (LDHs) with different Zn/Ti ratio have been synthesized by co-precipitation of zinc and titanium salts from homogeneous solution, which were demonstrated as efficient visible-light photocatalysts. Powder X-ray diffraction (PXRD), scanning electron microscope (SEM), high-resolution transmission electron microscopy (HRTEM) and Brunauer–Emmett–Teller (BET) revealed that the resulting Zn–Ti LDHs possess high crystallinity, hierarchical structure as well as large specific surface area (91.96–107.9m2 g−1). UV–vis diffuse reflection spectroscopy (DRS) confirmed that Zn–Ti LDHs show a broad absorption in visible light region (400–700nm). With a low band gap of ∼3.06eV, the as-prepared Zn–Ti LDHs displayed significant photocatalytic activity for the degradation of methylene blue (MB) under visible-light irradiation (∼100% of degradation percentage in 100min), which is much higher than that of commercial product (Degussa P25). Therefore, this work provides a detailed understanding of semiconductor properties of Zn–Ti LDHs which was unrevealed previously, and demonstrates its potential application in the field of photocatalysis. [Copyright &y& Elsevier]

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Photocatalytic CO 2 reduction has drawn widespread attention across all sectors of society. Layered double hydroxides (LDHs) have emerged as promising photocatalysts, renowned for their adjustable bandgaps and reaction sites. As a typical anionic layered material, LDHs exhibit intricate interactions between interlayer anions and brucite-like metal layers, greatly influencing their inherent physicochemical properties. In this work, we synthesized ZnAl-LDH samples intercalated with four distinct anions: carbonate (CO 3 2–), chloridion (Cl–), nitrate (NO 3 –), and dodecyl sulfate (DS–), denoted as LDH-CO 3 , LDH-Cl, LDH-NO 3 , and LDH-DS, respectively. These LDHs samples have comparable crystallinity and morphology but differ in their interlayer spacing. XRD results reveal interlayer spacings of 0.77 nm for LDH-CO 3 , 0.78 nm for LDH-Cl, 0.88 nm for LDH-NO 3 , and 1.24 nm for LDH-DS, between adjacent brucite-like ZnAl hydroxide layers. Remarkably, LDH-NO 3 demonstrates the highest photocatalytic CO 2 reduction performance, with CO as the primary reduction product. Specifically, the average CO production rate of LDH-NO 3 are 3.80 μmol g–1 h–1, surpassing that of LDH-CO 3 , LDH-Cl, and LDH-DS by 1.9, 2.1, and 2.5 times, respectively. This superior performance can be attributed to the intermediate interlayer spacing of LDH-NO 3 , which facilitates strong light absorption and a robust local built-in electric field. Theses properties enhance charge generation and separation abilities, leading to efficient photocatalytic reactions. The obtained results highlight the critical role of controlling small molecules within the interlayer, alongside defects, in the design and fabrication of layered-structure photocatalysts. This study provides valuable insights into optimizing the performance of LDH-based photocatalysts for CO 2 reduction and potentially other photocatalytic applications. [Display omitted] • Four ZnAl-LDH samples with varying anion intercalation were prepared. • ZnAl-LDHs with CO 3 2–, Cl–, NO 3 –, and DS– anions intercalated exhibited increased interlayer spacing. • Among these ZnAl-LDH samples, LDH-NO 3 displayed the highest photocatalytic performance. • The intermediate interlayer spacing of LDH-NO 3 possesses strong local charge separation driving force. [ABSTRACT FROM AUTHOR]

Electrochemical organic oxidation into commodity products coupled with hydrogen evolution in aqueous media serves as a promising formulation for harvesting both value-added chemicals and clean energy. However, how to develop electrocatalysts for efficient oxidize organic compounds with depressed side-reaction (oxygen evolution reaction, OER) still remains a challenge. Herein, we report an integrated efficient electrocatalyst for the oxidation of 5-hydroxymethylfurfural (HMF) based on ultrathin layered double hydroxides (LDHs) nanosheet array (NSA) exposed with abundant oxygen vacancies. A high faradaic efficiency at a high potential (99.4% at 1.52 V vs. RHE) is achieved, which implies largely depressed OER process and stands at the highest level compared with previously reported electrocatalysts. Furthermore, A two-electrode electrolyzer was also assembled based on the LDHs NSA, giving rise to a much low voltage for HMF oxidation, a high H 2 yield of 44.16 L h−1 m−2 as well as excellent stability. Ultrathin LDHs nanosheets array was synthesized by electrochemical in-situ exfoliation of bulk LDH array on the conductive substrate, which exhibited largely enhanced electrocatalytic performance towards HMF oxidation. This work demonstrates a successful paradigm for the design and preparation of highly-active LDH nanosheets array with potential applications in commodity chemicals production couple with hydrogen evolution. [Display omitted] • An ultra-thin vacancy-rich CoAl-LDH was prepared via electrochemical exfoliation. • The E-CoAl-LDH-NSA exhibits excellent performance towards oxidation of HMF. • The introduction of vacancy optimizes the adsorption and oxidation process of HMF. • The E-CoAl-LDH-NSA displays a highly enhanced H 2 and FDCA production. [ABSTRACT FROM AUTHOR]

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. An all-solid-state wire-shaped supercapacitor (WSSC) was assembled using Ni/NiO@CoNi-LDH and Ni/active carbon as working and counter electrode, respectively, which shows high energy and power densities, good rate performance and excellent cycling stability. Image 1 • Ni/NiO@CoNi layered double hydroxide (LDH) arrays was prepared via a three-step procedure. • The Ni/NiO@CoNi-LDH based microsupercapacitor exhibits large energy density and excellent cycling stability. • The energy and power densities are among the highest level compared with those of the reported supercapacitors. [ABSTRACT FROM AUTHOR]