Fazhi Zhang

Layered double hydroxide films: synthesis, properties and applications

Layered double hydroxide (LDH) films have been widely investigated in the last few years because of their promising applications in areas such as catalysis, anti-corrosion coatings for metals, and as components in optical, electrical, and magnetic devices. In this Feature Article we review recent work, from our own laboratory and elsewhere, on the synthesis, properties and applications of functional LDH films, and also offer some perspectives for the design of future multifunctional LDH films.

One-step hydrothermal crystallization of a layered double hydroxide/alumina bilayer film on aluminum and its corrosion resistance properties.

A zinc-aluminum layered double hydroxide (ZnAl-LDH)/alumina bilayer film has been fabricated on an aluminum substrate by a one-step hydrothermal crystallization method. The LDH film was uniform and compact. XRD patterns and SEM images showed that the LDH film was highly oriented with the c-axis of the crystallites parallel to the substrate surface. The alumina layer existing between the LDH film and the substrate was formed prior to the LDH during the crystallization process. Polarization measurements showed that the bilayer film exhibited a low corrosion current density value of 10(-8) A/cm(2), which means that the LDH/alumina bilayer film can effectively protect aluminum from corrosion. Electrochemical impedance spectroscopy (EIS) showed that the impedance of the bilayer was 16 MOmega, meaning that the film served as a passive layer with a high charge transfer resistance. The adhesion between the film and the substrate was very strong which enhances its potential for practical application.

Morphologies, Preparations and Applications of Layered Double Hydroxide Micro-/Nanostructures

Layered double hydroxides (LDHs), also well-known as hydrotalcite-like layered clays, have been widely investigated in the fields of catalysts and catalyst support, anion exchanger, electrical and optical functional materials, flame retardants and nanoadditives. This feature article focuses on the progress in micro-/nanostructured LDHs in terms of morphology, and also on the preparations, applications, and perspectives of the LDHs with different morphologies.

Facile synthesis of NiAl-layered double hydroxide/graphene hybrid with enhanced electrochemical properties for detection of dopamine

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.

Enhanced photocatalytic performances of hierarchical ZnO/ZnAl2O4 microsphere derived from layered double hydroxide precursor spray-dried microsphere.

Layered double hydroxides (LDHs), also called hydrotalcites, have been widely investigated for degradation of dye molecules, in the forms of direct photocatalysts, supports or precursors to ZnO-containing photocatalysts. LDH precursor-derived ZnO/ZnAl2O4 photocatalytic nanostructures have hitherto been created, involving ZnO/ZnAl2O4 powder and templated hierarchical frameworks with laboratory-scale preparations. We herein report a scalable preparation of ZnO/ZnAl2O4 microsphere derived from ZnAl-LDH precursor spray-dried microsphere. Survey of textural properties shows that ZnO/ZnAl2O4 microspheres maintain the hierarchically spherical feature and the relatively large surface area. Photocatalytic evaluation under UV irradiation shows that the ZnO/ZnAl2O4 microspheres exhibit highly enhanced photodegradation performance to methylene blue (MB) in comparison with the commercial ZnO powder. A preferential photodegradation to methyl orange (MO) of the MO/MB mixture was also observed, which was illustrated experimentally in terms of the favorable interaction and distribution between basic MO molecules and the acidic-site ZnO/ZnAl2O4 photocatalyst. Our results may initiate large-scale production of microspheres with promising photocatalytic performances.

Pd Nanoparticles on Layered Double Hydroxide as Efficient Catalysts for Solvent-Free Oxidation of Benzyl Alcohol Using Molecular Oxygen: Effect of Support Basic Properties

Pd nanoparticles supported on basic layered double hydroxide (LDH) as highly efficient and reusable catalysts are prepared and characterized. The layered structure of LDH support could be reconstructed to different extent by controlling the activation conditions, which presented changing quantity of Brønsted-base sites. Besides, with the changing calcination temperature the LDH substrate imposed a restricted nano-size effect on the supported Pd particles under identical reduction condition, which demonstrated a convenient approach for controlling the size of supported Pd particles. The resulting Pd/LDH samples were tested as heterogeneous catalysts for solvent-free oxidation of benzyl alcohol using molecular oxygen. The sample with a larger amount of Brønsted-base sites is more active in the oxidation of benzyl alcohol, and after five catalytic runs it still gives benzaldehyde in excellent yields. The promotional effect of Brønsted-base sites of the LDH support on the catalytic activity for benzyl alcohol oxidation over Pd/LDH is studied.Graphical Abstract

Eco-efficient synthesis route of carbon-encapsulated transition metal phosphide with improved cycle stability for lithium-ion batteries

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.

Preparation of microspherical α-zirconium phosphate catalysts for conversion of fatty acid methyl esters to monoethanolamides

The performance of solid catalysts and catalyst supports is generally believed to be dependent on their morphology, surface area, and architecture. In order to fully exploit their attractive properties in actual practical applications, layered zirconium phosphate materials should be fabricated into macroscopic form. Here, we report the fabrication of microscopic spheres of alpha-zirconium phosphate (alpha-ZrP) by a spray-drying process. The layered alpha-ZrP nanoparticles were originally obtained using a synthesis route involving separate nucleation and aging steps (SNAS). The resulting products are composed of nanosize alpha-ZrP particles aggregated into solid microspheres with a diameter of 5-45 microm and a sphericity of 0.80. After calcination at 573 K, surface area of 43.8 m(2)/g could be obtained for alpha-ZrP microspheres, which is larger than that of the alpha-ZrP powder after similar thermal treatment (36.2 m(2)/g). Furthermore, the number of acidic sites of the alpha-ZrP microspheres is greater than for the alpha-ZrP powder due to its unique textual properties and higher surface area. The acylation reaction of fatty acid methyl esters (methyl stearate) with ethanolamine to form monoethanolamides was chosen as a probe reaction to evaluate the catalytic activity of the resulting microspherical alpha-ZrP materials, which showed high activity compared to the sample in the form of powders, with about 92.9% methyl stearate conversion at 393 K for 12 h. The enhanced performance in the reaction is determined by the large surface area and the increased number of acidic sites in the multiple-scales porosity of alpha-ZrP microspheres.

In Situ Crystallized Zirconium Phenylphosphonate Films with Crystals Vertically to the Substrate and Their Hydrophobic, Dielectric, and Anticorrosion Properties

The in situ crystallization technique has been utilized to fabricate zirconium phenylphosphonate (ZrPP) films with their hexagonal crystallite perpendicular to the copper substrate. The micro/nano roughness surface structure, as well as the intrinsic hydrophobic characteristic of the surface functional groups, affords ZrPP films excellent hydrophobicity with water contact angle (CA) ranging from 134 degrees to 151 degrees , without any low-surface-energy modification. Particularly, in the corrosive solutions such as acidic or basic solutions over a wide pH from 2 to 12, no obvious fluctuation in CA was observed for all the ZrPP film. The k values of the hydrophobic ZrPP films are in the low-k range (k < 3.0), meeting the development of ultra-large-scale integration (ULSI) circuits. The hydrophobicity feature is proposed to bear ZrPP film a more stable low-k value in an ambient atmosphere. Besides, the polarization current of ZrPP films is reduced by 2 orders of magnitude, compared to that of the untreated copper substrate. Even deposited in a vacuum oven for 30 days at room temperature, ZrPP films also show excellent corrosion resistance, indicating a stable anticorrosion property.

Synergistic lithium storage of a multi-component Co2SnO4/Co3O4/Al2O3/C composite from a single-source precursor

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.