LDH Precursor Research Articles

Construction of LDH-derived CoNiP modified W/Z-CdS homojunction for improved photocatalytic hydrogen evolution: Achieving broad solar light response and multiple phases charge transfer

Heterojunction engineering represents a robust strategy for accelerating carrier transfer, thereby enhancing the activity of photocatalytic hydrogen evolution. In this work, a series of innovative CoNiP@W/Z-CdS heterojunctions were prepared for the purpose of investigating the photocatalytic hydrogen evolution activity under visible light-driven. To achieve high efficiency, lamellar CoNiP was first synthesized through the phosphatisation of CoNi LDH precursor. Subsequently, the W/Z-CdS homojunction was in-situ grown on the CoNiP via the hydrothermal method, resulting in the formation of the CoNiP@W/Z-CdS homojunction/heterojunction. The hydrogen evolution rate of 3% CoNiP@W/Z-CdS composite reaches 60.6 mmol/g/h, which is 3.6 times, 7.0 times and 11.9 times higher than that of W/Z-CdS, W-CdS and Z-CdS, respectively. The enhanced photocatalytic performance of 3% CoNiP@W/Z-CdS can be attributed to the introduction of an ultra-thin CoNiP bimetallic phosphide as cocatalyst, which increases the specific surface area to provide a large number of active sites for the catalytic reaction, and broadens the absorption range of sunlight. In particular, the synergistic effect between homojunction and Schottky junction in 3% CoNiP@W/Z-CdS further accelerates separation and migration rate of double interfacial carriers, improving photocatalytic H2 rate. This work offers a new perspective for the rational design of three-phase binary photocatalysts with high activity and stability.

Facile Synthesis of Sodium Dodecyl Sulfate Intercalated Mg‐Al LDH and its Excellent Adsorption Performances for Cu2+ from Aqueous Solution

AbstractIn this study, the magnesium aluminum layered double hydroxide intercalated with sodium dodecyl sulfate (Mg‐Al S‐LDH) was synthesized by using a roasting–restoration method based on the Mg‐Al LDH precursor, and their effectiveness in removing Cu2+ from aqueous solutions was investigated. Detailed microstructural characterization of these adsorption materials involved employing X‐ray diffraction (XRD), Fourier‐transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption/desorption isotherms (N2 ad/desorption), and thermogravimetric‐differential thermal gravimetric analysis (TG‐DTG). The experimental results revealed that Mg‐Al S‐LDH displayed a plate‐like layered structure with a larger surface area and enhanced adsorption ability. Specifically, the maximum adsorption capacity, reaching 96.15 mg ⋅ g−1, was achieved at a temperature of 298 K, accompanied by a rapid adsorption rate. The adsorption kinetics adhered to the pseudo‐second‐order model, suggesting that chemisorption controlled the adsorption behavior. Furthermore, the adsorption of Cu2+ followed the Freundlich model, signifying a multi‐site adsorption mechanism onto the surface and layers of Mg‐Al S‐LDH. Thermodynamic investigations indicated that higher temperatures facilitated Cu2+ dissolution and strengthened the affinity with Mg‐Al S‐LDH, with a positive ΔHΘ value suggesting that the Cu2+ adsorption process was endothermic and temperature‐enhancing. Ion selectivity experiments demonstrated that Cd2+ and Pb2+ ions had a significant impact on Cu2+ adsorption, while the effects of Zn2+ and Fe2+ ions were less pronounced. The primary adsorption mechanisms of Cu2+ onto Mg‐Al S‐LDH encompassed precipitation, complexation on the surface and layers, and isomorphous substitution. This study sheds light on the promising potential of Mg‐Al S‐LDH as an effective adsorbent for heavy metal removal and provides valuable insights into its adsorption mechanisms and performance in different environmental conditions.

SrCaAl mixed metal oxides derived from LDH precursor as a novel and efficient solid base catalyst for Knoevenagel condensation reaction: Multivariate optimization study

The Knoevenagel condensation reaction is one of the most important reactions in the industry for the synthesis of organic materials, medicinal, and biological compounds. In this work, we have proposed an original and efficient solid-base catalytic system for the Knoevenagel condensation reaction. For the first time, a mixed oxide catalyst derived from hydrotalcite-like Sr0.5Ca2.5Al precursor was synthesized by co-precipitation method and subsequently calcined for 5 h at 850 °C. The catalysts were characterized by various techniques. The Sr0.5Ca2.5Al mixed oxide was also compared with the usual Ca3Al sample in terms of structural characteristics and catalytic activity in the Knoevenagel reaction between active methylene compounds and benzaldehyde. The findings revealed that the Sr0.5Ca2.5Al mixed oxide sample is considerably active in this reaction compared to the Ca3Al sample due to its stronger basicity. The kinetics of the Knoevenagel condensation reaction over the Sr0.5Ca2.5Al catalyst was investigated and indicated that it follows from the second-order model. The stability and reusability of the catalyst sample were studied and it was found that the Sr0.5Ca2.5Al catalyst has high stability and a good lifetime. The effects of reaction time, amount of catalyst, and reaction temperature on benzaldehyde conversion (%) and product selectivity (%) were assessed in this study using the Box-Behnken design. The appropriateness of the quadratic regression model was evaluated through the ANOVA method. Under optimal conditions, the conversion percentage of benzaldehyde and product selectivity reached 97% and 84%, respectively.

Preparation of layered double oxides encapsulated in carbon nanotubes to boost selective synthesis of higher alcohols from syngas: Modifying hydrogenation activity and restricting particle sizes by confinement effect

In this work, CuZnAl layered double oxides (LDOs) were encapsulated in carbon nanotubes (CNTs) with different diameters by an ultrasonic-assisted sol-gel method. The CuZnAl LDOs filled in CNTs showed higher catalytic activity and good selectivity for higher alcohols. The catalysts were investigated by varied characterization technologies in order to explore confinement effect of CNTs. It is found that distortion of octahedral unit structure in LDH precursor is enhanced by confinement effect of CNTs. The electron-deficient inner surfaces of CNTs are responsible for the efficient dissociation of CO adsorbed inside CNTs. In addition, hydrogenation ability of the LDOs filled in CNTs is improved due to an obvious decrease in reduction temperature and auto-reduction effect of CNTs, and the restriction effect of CNTs on growth of LDO nanoparticles lead to a rise in their specific surface area. As mentioned above, the changes in structure and properties of LDOs loaded inside CNTs facilitate conversion of syngas into higher alcohols. Moreover, CNTs with small inner size show stronger confinement effect.

Effect of different anion intercalations on the corrosion resistance of layered double hydroxides on the surface of LA43M

AbstractLayered double hydroxides (LDH) are widely used in the field of Mg alloy surface protection due to their interlayer anion exchangeable and physical barrier. To explore the effect of corrosion inhibitor modification on the growth and corrosion resistance of LDH coating, MgAl‐NO3−‐LDH precursor film was obtained on the surface of LA43M alloy by in situ growth method, and then MgAl‐V2O74−‐LDH, MgAl−Cl−‐LDH and MgAl‐ASP‐LDH were prepared by the ion exchange method. The morphology, composition, and corrosion resistance of the LDH film with different anion intercalation were studied systematically by scanning electron microscope, energy disperse spectroscopy, X‐ray diffractometer, Fourier‐transform infrared spectroscopy, and electrochemical tests. The results show that the modified LDH nanosheets are larger in size and uniformly tightly bonded to the substrate, and the thickness of the film is increased. Electrochemical tests and hydrogen precipitation experiments demonstrated that all four LDH films provided protection to the substrate, and the corrosion resistance of the V2O74−, Cl− and ASP‐containing films modified by corrosion inhibitors was improved compared with that of the precursor films, among which the MgAl‐V2O74−‐LDH had the best corrosion resistance.

Low-temperature catalytic performance of toluene oxidation over Cu-Mn oxide catalysts derived from LDH precursor

A series of CuMn mixed oxides catalysts (CMO-T) were prepared by calcination of CuMn layered double hydroxides (CuMn-LDH) for catalytic oxidation of toluene. The obtained CMO-400 catalyst exhibited a high catalytic activity with T50 and T90 of 210 and 231 °C (WHSV = 30000 mL·g−1·h−1). Meanwhile, the CMO-400 exhibited high stability and durability even at 20 vol% water vapor. The effects of calcination temperature on the texture and structural properties were investigated systematically, which proved the formation of copper-manganese solid solution with abundant multiple-phase interfaces. In addition, the strong interaction between Cu and Mn could lead to more surface adsorbed oxygen due to oxidation reduction cycle of Mn3++Cu2+=Mn4++Cu+. Accordingly, for CMO-500 catalyst, the formation of spinel Cu1.5Mn1.5O4 phase prevented good dispersion of the manganese-oxide phases and weakened the reducibility and oxygen mobility. In-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) revealed that the intermediates accumulated continuously were difficult to be oxidized rapidly without the replenishment gaseous oxygen. Moreover, the complete transformation of the intermediate benzoate may be the key rate-controlling step in the reaction. The Facile method of preparing mixed-metal solid solution from LDH precursor system could be widely developed for the design of transition metals in catalytic oxidation of toluene.

Core-shell silica@CuxZnAl LDH catalysts for efficient CO2 hydrogenation to methanol.

The efficient production of methanol by reduction of CO2 using green hydrogen is a promising strategy from both a green chemistry and a carbon net zero perspective. Herein, we report the synthesis of well-dispersed core-shell catalyst precursors using silica@CuxZnAl-LDHs that can convert CO2 to methanol. The catalyst precursors can be formed using either a commercially available silica (ES757) or a mesoporous silica (e.g. MCM-48). These hybrid materials show significantly enhanced catalytic performance compared to the equivalent unsupported CuxZnAl LDH precursor. Space-time yields of up to 0.7 gMeOH gcat-1 h-1 under mild operating conditions were observed.

Highly efficient semi-hydrogenation of acetylene over Ni supported mesoporous MgAl2O4 spinel derived from aluminate-intercalated layered double hydroxide

Even though Ni catalysts have shown promising performance in the semi-hydrogenation of ethylene, the selectivity and stability remain to be improved so that they may be used to replace expensive noble metal catalysts. Herein, an aluminate-intercalated NiMgAl-layered double hydroxide (LDH) was prepared through a facile co-precipitation approach, and then a topotactic transformation strategy was employed to convert the tailored LDH precursor to the spinel catalyst. More than 99% of the Ni/MgAl2O4 catalyst's conversion was achieved toward the semi-hydrogenation of acetylene at 140 °C, with a selectivity of more than 80%. Additionally, due to high specific surface area (309 m2/g) with tuned acidity, this catalyst showed outstanding resistance to the deposition of carbonaceous compounds and satisfactory long-term stability during a 28 hr test. It is hoped that this study will inspire the design of supported non-noble metal materials with high activity and efficiency towards organic or organo-thermal reactions, as well as provide a basic understanding of the role and impacts of intercalated aluminates in LDH.

Bifunctional oxygen electrode cobalt–nickel sulfides catalysts originated from intercalated LDH precursors

Bimetallic cobalt–nickel sulfide nanoparticles anchored on S-, N-codoped holey carbon nanosheets (CoNi-S-T@NCFs) with a hydrangea-like morphology, were synthesized via a confinement synthesis route, in which an intercalated LDH precursor was subjected to the interlayer-confined carbonization and host-layer sulfurization. The phase transformation and structure evolution (e.g., atom site occupancy, crystallite size, and cell volume) of the CoNi-S-T@NCFs electrocatalysts, as a function of sulfurization temperatures, were confirmed by X-ray diffraction and Rietveld analyses. The sulfur vacancies effectively enhance the electrocatalytic activity, while the synergistic effect of (Co,Ni)7S8 alloy and S, N-codoped carbon matrix facilitates the electron transfer and accelerates reaction kinetics, making CoNi-S-900@NCFs an efficient and stable bifunctional electrocatalyst for oxygen reduction reaction (ORR). The rich high-valence Co (III) and Ni (III) of CoNi-S-900@NCFs facilitates the in-situ transformation of the metal (oxy)hydroxides intermediates with high catalytic activity for oxygen evolution reaction (OER). Thus, with a bifunctional parameter, ΔE, of 0.75 V (Ej=10, OER - E1/2, ORR), this electrocatalyst slightly outperforms the state-of-the-art commercial Pt/C + RuO2/C catalyst (ΔE = 0.76 V) in alkaline medium. This work demonstrates the influence that the sulfurization temperature has on the relationship between the structure and electrocatalytic performance of bimetallic sulfides prepared by the synthesis strategy using the intercalated LDH precursor. This strategy can be extended to prepare other chalcogenides with binary or ternary transition metals.

Porous NiCoS nanosheets decorated activated carbon cloth for flexible asymmetric supercapacitors

Flexible electrodes with advantageous architectures have emerged as an urgent necessity. Herein, we demonstrate a novel approach to designing and fabricating porous nickel cobalt sulfide sheets anchored on thermally activated carbon cloth (NiCoS/ACC) for use as a flexible anode in supercapacitors. The thermally activated carbon cloth with functional groups provides a framework for the growth of the nickel cobalt aluminum layered double hydroxide (NiCoAl LDH) precursor, which provides an excellent rate of utilization for the active material. Through hydrothermal sulfuration, NiCoAl LDH precursor can be transformed into porous NiCoS nanosheets, yielding NiCoS/ACC, which shows excellent electrochemical performance in a three-electrode system. Excellent electrical conductivity and the enriched redox-active site provided by ACC together with the high porosity, abundant active sites, and large electrode-electrolyte contact area provided by thin NiCoS nanosheets are believed to account for the enhanced electrochemical properties. Moreover, the flexible supercapacitor can exhibit high energy density and excellent cycling stability when equipped with a NiCoS/ACC positive electrode and an activated carbon cloth negative electrode.

Mechanochemically prepared Zn–Al LDH precursor for rare earth elements recovery

The ionic rare earth elements (REEs) was mainly recovered by in-situ leaching process. The concentration of rare earth ions in the leaching solution after long-term leaching process would be too low for traditional precipitation process for REEs recovery. The adsorption process was ideal for the low concentration REEs recovery. In this study, Zn–Al LDH precursor were successfully synthesized by mechanochemical method for the adsorption of REEs (including La−, Eu3+ and Er3+). X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron energy spectrometer (XPS), and Zeta potential test was applied for adsorption mechanism illustration. The maximum adsorption capacity of the Zn–Al LDH precursor for La3+, Eu3+ and Er3+ reached 492 mg/g, 346 mg/g, and 1154 mg/g which was significantly higher than other types of adsorbents. The adsorbed REEs on the Zn–Al LDH was hard to be desorbed. The Zn–Al LDH precursor after REEs adsorption could be directly used as high content REEs resources for further process.Therefore, the Zn–Al LDH precursor could be a promising adsorbent for REEs recovery in practical application.

The Performance and Mechanism of a Mg-Al Double-Layer Oxide in Chloride ion Removal from an Aqueous Solution.

The increasing threat of chloride ions (Cl−) has led researchers to explore efficient removal technologies. Sewage treatment with a double-layer hydroxide/oxide (LDH/LDO) is receiving increasing attention. In this work, Mg-Al LDO adsorbents were produced by the calcination of the Mg-Al LDH precursor, which was constituted by improved coprecipitation. The influence of calcination temperature, calcination time, adsorbent dosage, Cl− initial concentration, contact time, and adsorption temperature on Cl− elimination was investigated systematically. The experimental results showed that a better porous structure endowed the Mg-Al LDO with outstanding adsorption properties for Cl−. The adsorption process was well matched to the pseudo-second-order kinetics model and the Freundlich model. Under optimal conditions, more than 97% of the Cl− could be eliminated. Moreover, the removal efficiency was greater than 90% even after 11 adsorption–desorption cycles. It was found that the electrostatic interaction between Cl− and the positively charged Mg-Al LDO laminate, coupled with the reconstruction of the layer structure, was what dominated the Cl− removal process.

F-decoration-induced partially amorphization of nickel iron layered double hydroxides for high efficiency urea oxidation reaction

The urea oxidation reaction (UOR) has been well-acknowledged as one of the promising alternatives for hydrogen production through electrochemical water splitting system because of the more favorable thermodynamic potential. But the shortage of cost-effective electrocatalysts with high catalytic activity and durability restricts its practical development. Herein, the partially amorphous fluorine-decorated nickel iron layered double hydroxides (NiFe-F) is constructed via a low-temperature fluoridation method. Our study found that HF acid etching of NiFe LDH precursor resulted in the partially amorphous feature and abundant oxygen vacancies, providing rich reaction sites. Simultaneously, the formation of ionic metal-F bond makes it easier to form high-valence metal oxygen hydroxide active sites. Specifically, the as-prepared NiFe-F-4 electrode demonstrates a superb mass activity of 1290 mA mg−1 at 1.6 V vs. RHE. Further experiments found that amorphous structure and F decorating decreased the activation energy of UOR from 30.71 kJ mol−1 (crystalline NiFe-F-4) to 20.17 kJ mol−1 (amorphous NiFe-F-4), leading to a rapid dynamic with a small Tafel slope of 31 mV dec-1. Moreover, NiFe-F-4 casts remarkable long-term durability for 40 h without performance decay. This work holds great promise to develop advanced electrocatalysts for pollution treatment of urea-rich wastewater and energy-saving H2 production.

Co Hydrogenation to Ethanol and Higher Alcohols Over Ultrathin Cucoal Nanosheets Derived from Ldh Precursor

Co Hydrogenation to Ethanol and Higher Alcohols Over Ultrathin Cucoal Nanosheets Derived from Ldh Precursor

Low-Temperature Catalytic Performance of Toluene Purification in Air Over Cu-Mn Oxide Catalysts Derived from Ldh Precursor

Low-Temperature Catalytic Performance of Toluene Purification in Air Over Cu-Mn Oxide Catalysts Derived from Ldh Precursor

Catalytic activity and stability of a Cr modified Co–Fe LDO catalyst in the simultaneous catalytic reduction of NOx and oxidation of o-DCB

In this paper, a Co–Fe LDO catalyst was prepared by combining K2Cr2O7 and Cr(NO3)3 to modify the LDH precursor.

Improved performance of Ni/Al2O3 catalyst deriving from the hydrotalcite precursor synthesized on Al2O3 support for dry reforming of methane

Exploiting Ni-based catalysts with excellent catalytic activity and anti-coking ability is significant for dry reforming of CH4 with CO2 (DRM) which is a promising route to CO2 utilization. In this work, the Ni/Al2O3 catalyst with hydrotalcite precursor (NiAl-LDH) was synthesized by a facile in-situ growth method. And the effect of the NiAl-LDH structure on the catalytic activity and anti-coking ability of Ni/Al2O3 catalyst was revealed. The H2-temperature programmed desorption (H2-TPD) revealed that better Ni dispersion and more Ni–Al2O3 interface could be obtained by the NiAl-LDH precursor, which were vital for the activation of CH4 and CO2. Moreover, the NiAl-LDH precursor with non-LDH phase or turbostratic structure was also created by insufficient or extra amount of urea, and the obtained catalysts exhibited a poor catalytic stability, further confirming the importance of the LDH structure. In comparison with the Ni-IMP catalyst prepared by the conventional impregnation method, the CH4 conversion increased by 16% and the carbon deposition decreased by 75% over Ni-6 catalyst with well-organized LDH precursor under the same reaction conditions. Hence, this work represents an important step toward developing Ni-based catalysts with excellent catalytic activity and anti-coking ability for DRM with the LDH precursor.

Effect of Hydroxyl Groups on CuCoMg Nanosheets for Ethanol and Higher Alcohol Synthesis from Syngas

A series of CuCoMg nanosheets derived from the LDH precursor were prepared by co-precipitation (CP) strategy and evaluated for the production of ethanol and higher alcohols via CO hydrogenation. Th...

CdAl mixed metal oxides prepared by calcination of CdAl layered double hydroxides: Synthesis and properties for humidity sensing

In this work, CdAl mixed metal oxides (CdAl-MMOs), CdO/CdAl2O4 composites, were prepared by calcination of sodium dodecyl sulfonate (SDS) intercalated CdAl layered double hydroxide (CdAl-LDH) at different temperature, which was synthesized by traditional hydrothermal synthesis. The CdAl-MMOs were investigated at room temperature, which shows good humidity-sensing performance. Especially, the one calcined at 500 °C (CdAl-MMO-500) shows good linearity, small hysteresis, high humidity sensitivity as well as satisfactory response and recovery time. In addition, the composites CdO/CdAl2O4 have improved the humidity-sensing performances as compared to the one obtained by calcination of the blending inorganic salts. The experimental results further demonstrate that the approach of calcination LDH precursor can be generalized as an effective way of making mixed metal oxides (MMOs) with homogeneous dispersion between metal elements and thus specific properties.

Hierarchical zeolitic imidazolate framework-67 derived from in-situ synthesized CO-Al layered double hydroxide embedded within porous-anodized aluminum foil for thin film microextraction of caffeine followed by its high performance liquid chromatography-ultraviolet detection.

In this study, the in-situ conversion of the synthesized Co-Al layered double hydroxide (Co-Al LDH) nanosheets to three dimensional hierarchical zeolitic imidazolate framework-67 (3D HZIF-67) was presented as a cost-effective, highly efficient, flexible and robust sorbent to carry out the microextraction process. In the first stage, the anodized aluminum foil was prepared electrochemically. Then, the Co-Al LDH precursor was constructed on the surface of the previously-prepared anodized Al foil applying in-situ formation approach. The procedure is followed by the conversion of the prepared Co-Al LDH film to 3D HZIF-67 film via a facile solvothermal method without adding cobalt salt. The in-situ prepared 3D HZIF-67-anodized Al was used for the thin film microextraction (TFME) of caffeine. The effective factors in TFME procedure were investigated and optimized through applying Central Composite Design (CCD). In the obtained optimal condition, the calibration curves for TFME-HPLC-UV of caffeine were linear in the range of 1-200µg L-1 with the coefficient of determination (r2) higher than 0.9915. The limits of detection were 0.33 and 0.38µg L-1, in water and urine matrices, respectively. Moreover, the enrichment factors (EFs) and absolute recoveries (%AR) were also calculated as 173-198 and 57.1%-65.3%, respectively. The inter-day relative standard deviations (RSDs) were evaluated as the method precision for 20 and 200µg L-1 of spiked sample and were between 4.9-6.1%. The repeatability of the preparation step was investigated as batch-to-batch reproducibility and it was found to be 4.9%; as a result, the reproducibility of the presented film was approved. Finally, the proposed method was utilized to determine caffeine (as the model analyte) from different types of real samples including urine, coffee, beverage (Pepsi) and shampoo. The obtained recoveries (higher than 88%) confirmed the capability of the method for real sample analysis.