•Mesoporous MgFe2O4/ZnFe2O4/MgO is derived from MgZnFe-LDH.•The carbon-free composite exhibits a super-long cycling stability.•Alloying/conversion mechanism and mesoporous feature support the enhancement.Layered double hydroxides (LDHs), also known as hydrotalcite-like anionic clays, are very convenient precursors with a tunable flexibility toward multifunctional nanomaterials, especially in energy storage. Typical methods to improve lithium storage are to introduce additional or self-generating carbonaceous supports to LDH-derived transition metal oxides as anode nanomaterials which can host lithium mainly though a conversion mechanism. Here, we describe a preparation of mesoporous spinel ferrite composite (MgFe2O4/ZnFe2O4) for lithium storage, which is assisted by a combined conversion and alloying mechanism. The composite is derived by a thermal decomposition of a scalablely produced single-resource precursor of ternary Mg2+Zn2+Fe3+-layered double hydroxide (Mg2+Zn2+Fe3+-LDH), and subsequent selective etching. Electrochemical test shows that the electrode delivers an exceptional electrochemical performance, i.e., a reversible capacity of 1190 mA h g−1 after 100 cycles at 100 mA g−1, and, in particular, a reversible capacity of 981 mA h g−1 at 500 mA g−1 after 330 cycles, as well as a reversible capacity of 541 mA h g−1 at 2000 mA g−1 after 1000 cycles. The high electrochemical performance could be attributed to the following features: the combined alloying and conversion mechanisms of ZnFe2O4, synergistic MgFe2O4, and slight-content MgO as a non-active matrix, as well as an appropriate specific area and mesoporous size distribution. Our results show that the cation-tunable LDH precursor-derived synthesis route might be an alternative to prepare multiple-component composites of spinel ferrites and transition metal oxides.

Transition metal phosphide (TMP) nanostructures have stimulated increasing interest for use in water splitting owing to their abundant natural sources and high activity for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Typically, the preparation of hierarchical TMPs involves the utilization of expensive or dangerous phosphorus sources, and, in particular, the understanding of topotactic transformations of the precursors to crystalline phases—which could be utilized to enhance electrocatalytic performance—remains very limited. We, herein, report a controllable preparation of CoP/CoP2 nanoparticles well dispersed in flower-like Al2O3 scaffolds (f-CoP/CoP2/Al2O3) as a bifunctional electrocatalyst for the HER and OER via the phosphorization of a flower-like CoAl layered double hydroxide precursor. Characterization by in situ X-ray diffraction (XRD) monitored the topotactic transformation underlying the controllable formation of CoP/CoP2via tuning the phosphorization time. Electrocatalytic tests showed that an f-CoP/CoP2/Al2O3 electrode exhibited a lower onset potential and higher electrocatalytic activity for the HER and OER in the same alkaline electrolyte than electrodes of flower-like and powdered CoP/Al2O3. The enhanced electrochemical performance was experimentally supported by measuring the electrochemically active surface area. The f-CoP/CoP2/Al2O3 composite further generated a current density of 10 mA cm−2 at 1.65 V when used as a bifunctional catalyst for overall water splitting. Our results demonstrate that the preparation route based on the LDH precursor may provide an alternative for investigating diverse TMPs as bifunctional electrocatalysts for water splitting.

Co nanoparticle-encapsulated N-doped carbon nanotubes (Co@N-CNTs) are prepared as a Pt-free electrocatalyst for oxygen reduction reaction (ORR) via direct pyrolysis of a CoAl-layered double hydroxide (CoAl-LDH)/melamine mixture. The approach could bundle the following distinct features: (i) commercially available melamine as both carbon and nitrogen bi-functional sources; (ii) scalably prepared CoAl-LDH precursor chosen to play a triple role in catalyzing the formation of N-CNTs and serving the electroactive Co nanoparticles, as well as in facilitating the growth of long N-CNTs owing to the confinement effect of the non-active Al2O3 matrix formed; (iii) an alternative to prepare one-dimensional length-and-performance-tunable N-CNTs, which are obtained typically by using catalytic chemical vapor deposition (CCVD) of two gaseous carbon and nitrogen resources on the surface of an LDH layer. The long Co@N-CNTs exhibits the highly enhanced electrocatalytic activity and stability for ORR (onset potential at 929 mV, half-wave potential at 849 mV vs. RHE, and limited current density at 6.0 mA cm−2). The CoAl-LDH precursor-based approach may open up a simple and feasible alternative to design and produce low-cost electrocatalysts for fuel cells.

Low-content ultrathin coating of non-active alumina (Al2O3) has been extensively utilized as one of the most effective strategies to improve electrochemical performances of electrodes for lithium-ion batteries (LIBs), however, typically by employing expensive atomic layer deposition equipment. We herein demonstrate a simple preparation of high-content and well-dispersed Al2O3 (24.33 wt.%)-containing multi-component composite (CoO/Co3O4/N–C/Al2O3) by calcination of melamine/CoAl-layered double hydroxide (CoAl-LDH) mixture. The resulting composite bundles the advantages expected to improve electrochemical performances: (i) bi-active CoO/Co3O4, (ii) highly conductive N-doped carbon, and (iii) N-doped carbon and high-content non-active Al2O3 as buffering reagents, as well as (iv) good distribution of bi- and non-active components resulted from the lattice orientation and confinement effect of the LDH layers. Electrochemical evaluation shows that the composite electrode delivers a highly enhanced reversible capacity of 1078 mA h g−1 after 50 cycles at 100 mA g−1, compared with the bi-active CoO/Co3O4 mixtures with and without non-active Al2O3. Transmission electron microscopy/scanning electron microscopy observations and electrochemical impedance spectra experimentally provide the information on the good distributions of multiple components and the improved conductivity underlying the enhancements, respectively. Our LDH precursor-based preparation route may be extended to design and prepare various multi-component transition metal oxides for efficient lithium storage.

Dispersion of multiple chemically active components strongly affects the electrochemical performances of electrode nanomaterials for lithium-ion batteries. We herein describe highly improved lithium storage of a graphene-supported binary active solid solution (Mn0.25Co0.75O) derived from CoMn-layered double hydroxide/graphene oxide precursor (CoMn-LDH/GO). Ex situ X-ray diffraction characterization clarifies the topotactic transformation from the CoMn-LDH/GO precursor to the resulting Mn0.25Co0.75O solid solution with increasing temperatures. The electrochemical test shows that the Mn0.25Co0.75O solid-solution electrode is able to exhibit highly improved electrochemical performances, which are superior to those of the electrodes of individual CoO/G, MnO/G, and the mixture (mMnO + CoO/G). The reversible capacity of the Mn0.25Co0.75O electrode reaches 980 mA h g−1 after 100 cycles at 100 mA g−1, and especially up to 1087 mA h g−1 after 1300 cycles at a high current density of 2 A g−1. TEM observations and Nyquist plots provide information on the morphological preservation of the solid-solution nanoplatelets consisting of small nanoparticles observed after the super-long cycling, and the low charge transfer resistance to underlie the improvements, respectively. Our LDH precursor-based protocol may be extended to prepare other multiple-component well-dispersed metal oxides or even sulfides, and thus provide a new strategy for construction of high-performance electrodes for energy storage.

Layered double hydroxides (LDHs), also known as hydrotalcite-like anionic clay compounds, have attracted increasing interest in electrochemical energy storage, in the main form of LDH precursor-derived transition metal oxides (TMOs). One typical approach to improve cycling stability of the LDH-derived TMOs is to introduce one- and two-dimensional conductive carbonaceous supports, such as carbon nanotubes and graphene. We herein demonstrate an effective approach to improve the electrochemical performances of well-dispersed biactive NiCo2S4/Ni0.96S as anode nanomaterials for lithium-ion batteries (LIBs), by introducing a three-dimensional graphene aerogel (3DGA) support. The resultant 3DGA supported NiCo2S4/Ni0.96S (3DGA/NCS) composite, obtained by sulfuration of NiCo-layered double hydroxide (NiCo-LDH) precursor in situ grown on the 3DGA support (3DGA/NiCo-LDH). Electrochemical tests show that the 3DGA/NCS composite indeed delivers the greatly enhanced electrochemical performances compared with the NiCo2S4/Ni0.96S counterpart on two-dimensional graphene aerogel, i.e., a high reversible capacity of 965 mA h g–1 after 200 cycles at 100 mA g–1 and especially a superlong cycling stability of 620 mA h g–1 after 800 cycles at 1 A g–1. The enhancements could be ascribed to the compositional and structural advantages of boosting electrochemical performances: (i) well-dispersed NiCo2S4/Ni0.96S nanoparticles with interfacial nanodomains resulting from both the dual surface confinements of the 3DGA support and the crystallographic confinement of NiCo-well-arranged LDH crystalline layer, (ii) an appropriate specific surface area and a wide pore size distribution of mesopores and macropores, and (iii) highly conductive 3DGA support that is measured experimentally by using electrochemical impedance spectra to underlie the enhancement. Our results demonstrate that the tunable LDH precursor-derived synthesis route may be extended to prepare various transition metal sulfides and even transition metal phosphides for energy storage with the aid of tunable cationic type and molar ratio.Keywords: graphene aerogel; layered double hydroxide precursor; lithium-ion batteries; transition metal sulfide; triple confinement effects;

We describe a reliable preparation of MgAl-layered double hydroxide (MgAl-LDH) micropatterned arrays on gold substrate by combining SO3–-terminated self-assembly monolayer and photolithography. The synthesis route is readily extended to prepare LDH arrays on the SO3–-terminated polymer-bonded glass substrate amenable for cell imaging. The anion-exchangeable MgAl-LDH micropattern can act both as bioadhesive region for selective cell adhesion and as nanocarrier for drug molecules to regulate cell behaviors. Quantitative analysis of cell adhesion shows that selective HepG2 cell adhesion and spreading are promoted by the micropatterned MgAl-LDH, and also suppressed by methotrexate drug released from the LDH interlayer galleries.Keywords: cell adhesion; in situ growth; layered double hydroxide; methotrexate; micropatterned arrays; photolithography

Endowing multi-component anode nanomaterials for lithium-ion batteries (LIBs) with integrated features for synergistically enhancing electrochemical performance is challenging via a simple preparation method. We herein describe an easy approach for preparing a multi-component Co2SnO4/Co3O4/Al2O3/C composite as the anode nanomaterial for LIBs, derived from a laurate anion-intercalated CoAlSn-layered double hydroxide (CoAlSn-LDH) single-source precursor. The resultant Co2SnO4/Co3O4/Al2O3/C electrode delivers a highly enhanced reversible capacity of 1170 mA h g−1 at 100 mA g−1 after 100 cycles, compared with the bi-active composites designed without Al2O3 or carbon (Co2SnO4/Co3O4/C, Co2SnO4/Co3O4/Al2O3, and Co2SnO4/Co3O4) which are easily derived through the same protocol by choosing LDH precursors without Al cation or surfactant intercalation. The distinctly different cycling stability and rate capability of Co2SnO4/Co3O4/Al2O3/C among the different composite electrodes suggest that the high enhancement could result from the following synergistic features: the combined conversion and alloying reactions of bi-active Co2SnO4/Co3O4 during cycling, the buffering role of non-active Al2O3 and carbon, and the improved conductivity of the self-generated carbon matrix. The LDH precursor-based approach may be extended to the design and preparation of various multi-component transition metal oxide composite nanomaterials for synergistic lithium storage.

An eco-efficient synthesis route is developed to prepare carbon-encapsulated Ni3P nanoparticles embedded in carbon nanosheets as a cycling-stable anode material for lithium ion batteries. The green method is achieved by calcining the precursor of intercalated sodium dodecyl phosphate/Ni(OH)2, and is readily extended to prepare the transition metal sulphide by altering the intercalated surfactant.

•Carbon-supported Ni@NiO/Al2O3 nanocomposite was prepared from LDH/C precursor.•Enhanced specific capacity and cycling stability are obtained.•EIS and TEM results provide convincing information underlying the enhancements.Transition metal oxides (MO) have been widely investigated as promising anode materials for lithium-ion batteries, but suffer from the problems of irreversible capacity loss and poor cycling stability resulting from intrinsic poor conductivity, large volume expansion/contraction during the discharge/charge processes. Despite two main types of effective efforts, i.e., preparing pre-designed nano/microstructures and hybridization with either active or conductive nanomaterials, these approaches have hitherto had difficulties in seeking deliberate nano/microstructural designs and guaranteeing homogeneous interface/chemical distributions of active MO material within the non-active matrix at the nanoscale. Herein, we report a preparation of carbon-supported Ni core @ NiO shell/Al2O3 (C-Ni@NiO/Al2O3) integrated nanocomposite derived from NiAl-layered double hydroxide (NiAl-LDH) single-resource precursor. The combined features of the C-Ni@NiO/Al2O3 nanocomposite involve the uniform dispersion of nanosized Ni@NiO, the conductive carbon support and Ni core, as well as the buffer role of the newly generated non-active Al2O3. Electrochemical evaluation shows that the C-Ni@NiO/Al2O3 nanocomposite maintains much enhanced electrochemical performances and good cycling stability in comparison with the pristine NiO. Results of TEM visualizations and electrochemical impedance spectra provide experimentally convincing rationales of the information of Al2O3 buffer and improved the conductivity underlying the enhanced performances. The route could extend to design and prepare various nanostructured metal oxides with uniform-dispersion components based on the versatility in varying the metal cations of LDH precursors.

CoO/CoFe2O4 nanocomposites, derived from scalably prepared CoFe-layered double hydroxide (CoFe-LDH) single-resource precursors, exhibit tunable cycle performances and rate capabilities, which are supported by the homogenous dispersion of bi-component active CoO and CoFe2O4 phases.

Layered double hydroxides (LDHs), also known as hydrotalcite-like anionic clays, have been proposed as a potential biocompatible carrier for gene and drug molecules. Gene molecules (such as DNA and siRNA molecules) were either typically intercalated into the layer galleries of powdered LDH nanoparticles, or encapsulated within spherical LDH nanoshells. Herein, we describe a preparation of the (DNA/LDH)n ultrathin films via layer-by-layer (LbL) assembly between DNA and exfoliated LDHs nanosheets prepared by a scalable method. Atomic force microscopic observations show that the DNA/LDH monolayer consists of the linearly aligned DNA and the supported LDH nanosheets. Results of UV–vis spectra and XRD patterns reveal the homogenous LbL assembly of the resulting (DNA/LDH)n multiple thin films. Our results may initiate preparation of the integrated bio-LDH films with possible application in film sensors.Graphical abstractHighlights► The (DNA/LDH)n ultrathin films were prepared via layer-by-layer (LbL) assembly. ► DNA/LDH monolayer film shows the assembly of the linearly aligned DNA. ► (DNA/LDH)n multilayer film exhibits the homogenous LbL assembly.

Layered double hydroxides (LDHs), also known as hydrotalcite-like anionic clays, have been investigated widely as promising electrochemical active materials. Due to the inherently weak conductivity, the electrochemical properties of LDHs were improved typically by utilization of either functional molecules intercalated between LDH interlayer galleries, or proteins confined between exfoliated LDH nanosheets. Here, we report a facile protocol to prepare NiAl-LDH/graphene (NiAl-LDH/G) nanocomposites using a conventional coprecipitation process under low-temperature conditions and subsequent reduction of the supporting graphene oxide. Electrochemical tests showed that the NiAl-LDH/G modified electrode exhibited highly enhanced electrochemical performance of dopamine electrooxidation in comparison with the pristine NiAl-LDH modified electrode. Results of high-resolution transmission electron microscopy and Raman spectra provide convincing information on the nanostructure and composition underlying the enhancement. Our results of the NiAl-LDH/G modified electrodes with the enhanced electrochemical performance may allow designing a variety of promising hybrid sensors via a simple and feasible approach.

CoO/CoFe2O4 nanocomposites, derived from scalably prepared CoFe-layered double hydroxide (CoFe-LDH) single-resource precursors, exhibit tunable cycle performances and rate capabilities, which are supported by the homogenous dispersion of bi-component active CoO and CoFe2O4 phases.

An eco-efficient synthesis route is developed to prepare carbon-encapsulated Ni3P nanoparticles embedded in carbon nanosheets as a cycling-stable anode material for lithium ion batteries. The green method is achieved by calcining the precursor of intercalated sodium dodecyl phosphate/Ni(OH)2, and is readily extended to prepare the transition metal sulphide by altering the intercalated surfactant.