•Corrosion protection of reinforcement due to carbonation, chloride penetration and carbonation by MgAl-NO2 LDHs was examined.•The inhibition mechanism of MgAl-NO2 LDHs was revealed.•The change of pH ...value and Cl− uptake in carbonated solutions due to MgAl-NO2 LDHs addition were evaluated.
This paper aims to examine the corrosion protection of reinforcing steel in concrete due to carbonation alone and the coupled action of chloride penetration and carbonation by MgAl-NO2 layered double hydroxides (LDHs), which was synthesized by calcination rehydration method. The results reveal that MgAl-NO2 LDHs have a better inhibition effect on the steel corrosion by carbonation alone than the coupled action of chloride penetration and carbonation. The inhibition mechanism for carbonation alone is mainly attributed to the alkalinity increase and NO2− release. The Cl- uptake additionally contributes to the corrosion inhibition for the coupled action of chloride penetration and carbonation.
Display omitted
•A broad overview of biochar/LDH-based materials in water purification is presented.•The potential of biochar/LDH for the uptake of pollutants is critically evaluated.•Adsorption ...mechanisms and regeneration capability of biochar/LDH are appraised.•The catalytic degradation of various pollutants by biochar/LDH is reviewed.•Challenges and prospects of biochar/LDH in water treatment are highlighted.
Biochar/layered double hydroxide (LDH) composites have gained considerable attention in recent times as low-cost sustainable materials for applications in water treatment. This paper critically evaluates the latest development in applications of biochar/LDH composites in water treatment with an emphasis on adsorption and catalytic degradation of various pollutants. The adsorption of various noxious contaminants, i.e., heavy metals, dyes, anions, and pharmaceuticals onto biochar/LDH composites are described in detail by elaborating the adsorption mechanism and regeneration ability. The synergistic effect of LDH with biochar exhibited significant improvement in specific surface area, surface functional groups, structure heterogeneity, stability, and adsorption characteristics of the resulting biochar/LDH composites. The major hurdles and challenges associated with the synthesis and applications of biochar/LDH composites in water remediation are emphasized. Finally, a roadmap is suggested for future research to assure the effective applications of biochar/LDH composites in water purification.
Polyoxometalates (POMs) exhibit attractive properties and great potential to meet with contemporary society demands regarding environment, materials, energy, health and information technologies, etc. ...The development of POM-based advanced functional materials is of significance to effectively utilize POMs in meeting various challenges. In recent years, the intercalation of POM anions into layered double hydroxides (LDHs) has been a versatile and important approach for the development of POM-based multifunctional materials. The current review summarizes the latest progress on the preparation of POM intercalated LDHs (denoted as POM/LDHs) and their material application.
Polyvinyl chloride (PVC), known for its chemical stability and flame-retardant qualities, has many uses in various fields, such as pipes, electric wires, and cable insulation. Research has ...established its potential recovery as a fluidic fuel through pyrolysis, but the use of PVC pyrolysis oil, which is tainted by chlorine, is constrained by its low heat value and harmful environmental effects. This study engineered a layered double hydroxide (LDH) to tackle these challenges. The LDH facilitated dechlorination during PVC pyrolysis and bolstered thermal stability via cross-linking. During pyrolysis with LDH, PVC was transformed into carbon-rich precursors to sorbents. Chemical activation of these residues using KOH created sorbents with a specific surface area of 1495.4 m2 g⁻1, rendering them hydrophilic. These resulting sorbents displayed impressive adsorption capabilities, removing up to 486.79 mg g⁻1 of methylene blue and exhibiting the simultaneous removal of cations and anions.
Display omitted
•Ultrafast dye removal microporous carbons are fabricated waste PVC and with one-step pyrolysis utilizing LDH-based catalyst.•Microporous carbons activated with KOH have special selectivity for cations that can remove 90% methylene blue within 1 min.•Microporous carbons show promising dye removal stability and recovery performance.•Microporous carbons have realized the green closed-loop preparation, recovery, and regeneration.
This study introduces a novel combination of sulfur-doped reduced graphene oxide (S-rGO), zinc ferrite (ZnFe2O4) and nickel cobalt layered double hydroxide (NiCoLDH) as an efficient and low-cost ...electrocatalyst for oxygen reduction reaction (ORR) for the first time. The hydrothermal method is used to synthesize all samples including graphene oxide (GO), S-rGO, NiCoLDH, ZnFe2O4 and S-rGO/ZnFe2O4/NiCoLDH hybrids. X-ray diffraction (XRD) analysis, field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), energy dispersive x-ray analysis (EDX), electrochemical surface area (ECSA), and fourier transform infrared spectroscopy (FTIR) analysis are used to determine the structure of synthesized electrocatalysts, physical properties, and morphology. The electrochemical measurements are carried out using cyclic voltammetry (CV), linear scanning voltammetry (LSV), chronoamperometry (ChA), and electrochemical impedance spectroscopy (EIS). The results for all samples are compared with the Pt/C commercial catalyst. According to the electrochemical results, the S-rGO/ZnFe2O4/NiCoLDH electrocatalyst has the best electrochemical performance. Moreover, the nanocomposite exhibited better electrocatalysis, a high diffusion limiting current density of −5.4 mA cm−2 and an onset potential of 0.03 V. Based on the results of this study, the LDH enhances electrical conductivity, electrocatalytic activity, active surface area, and stability of the catalyst for ORR after combining with carbon bases and ferrite.
Display omitted
•An electrochemical method was utilized for NiCo-LDH on S-rGO/ZnFe2O4.•S doped reduced graphene oxide was used in a composite for improving its ORR activity.•NiCo-LDH was used as electrocatalyst for ORR.•S-rGO/ZnFe2O4/NiCo-LDH hybrid showed better ORR activity.
Display omitted
•Metal, vacancy, anion and material structure as activate origins of LDO/LDH.•The crucial mechanism of memory effect is metal eight-ligand microstructure.•Memory effect controlled by ...temperature, anion, pH and metal consisting.•Adsorption is the basic properties for environment application and material modification.•Memory effect materials need to be enhanced in terms of reusability and selectivity.
Layered double hydroxides (LDHs), are ideal inorganic materials for versatile fields, such as catalysis, energy, and medicine. Memory effect means the ability of reconstruction into their initial structure after decomposition treatment for some special materials. Based on the unique property, the layered structure can be regenerated from the calcined LDHs (layered double oxide, LDO) in an aqueous solution or moist air. This effect provides a new paradigm for modification of LDHs, increasing the abundance of active sites in LDHs as well as preserves original active sites for multifunctional environmental applications. Therefore, this review summarizes the memory effect of LDHs from basic mechanisms to real applications. Firstly, various kinds of active sites on LDHs/LDOs and the importance of sites structure are concluded. Secondly, the modification methods of LDHs are briefly introduced and the characteristics of memory effect are summarized. Then, the mechanism of chemical reaction, topology, and thermodynamics of memory effect are discussed as well as the microscopic mechanism of memory effect through theoretical chemical calculation. The influencing factors and applications in environmental remediation are also presented. Finally, the challenges and prospects of memory effect-based LDHs are proposed. We hope the review could open a new path for the environmental application of memory effect-based LDHs.
Display omitted
Photocatalytic CO2 reduction holds promise as a future technology for the manufacture of fuels and commodity chemicals. However, factors controlling product selectivity remain poorly ...understood. Herein, we compared the performance of a homologous series of Zn-based layered double hydroxide (ZnM-LDH) photocatalysts for CO2 reduction. By varying the trivalent or tetravalent metal cations in the ZnM-LDH photocatalysts (M = Ti4+, Fe3+, Co3+, Ga3+, Al3+), the product selectivity of the reaction could be precisely controlled. ZnTi-LDH afforded CH4 as the main reduction product; ZnFe-LDH and ZnCo-LDH yielded H2 exclusively from water splitting; whilst ZnGa-LDH and ZnAl-LDH generated CO. In-situ diffuse reflectance infrared measurements, valence band XPS and density function theory calculations were applied to rationalize the CO2 reduction selectivities of the different ZnM-LDH photocatalysts. The analyses revealed that the d-band center (εd) position of the M3+ or M4+ cations controlled the adsorption strength of CO2 and thus the selectivity to carbon-containing products or H2. Cations with d-band centers relatively close to the Fermi level (Ti4+, Ga3+ and Al3+) adsorbed CO2 strongly yielding CH4 or CO, whereas metal cations with d-band centers further from the Fermi level (Fe3+ and Co3+) adsorbed CO2 poorly, thereby yielding H2 only (from water splitting). Our findings clarify the role of trivalent and tetravalent metal cations in LDH photocatalysts for the selective CO2 reduction, paving new ways for the development of improved LDH photocatalyst with high selectivities to specific products.
PDF
