CO3 Layered Double Hydroxide Research Articles

In-situ engineering catalytically active surfaces for tribocatalysis with layered double hydroxide nanoparticles

Ensuring long-lasting lubrication is vital for sustainable machinery operation, made possible by self-regenerating carbon-based tribofilms via tribocatalysis. Conventional methods use expensive catalytic coatings, posing challenges for replacement and maintenance in practice. Here, we are proposing catalytic layered double hydroxide (LDH) nanoparticles as cost-effective and easily replenished lubricant additives to engineer catalytically active surfaces in situ where binary and ternary LDHs with Ni2+, Co2+, and/or Cu2+ divalent cations alongside Al3+ trivalent cations are investigated for lubrication performance. Under 100 °C sliding condition equivalent to the lubricating temperature in an internal combustion engine, NiCoAl–CO3 LDH exhibits the lowest wear losses alongside the durable low-friction regime. This excellent performance is attributed to Co-containing spinel and oxide phases in the catalytic tribo-oxide layer which help stabilize and maintain the microstructures of the tribo-oxide layer. In contrast, deterioration in lubrication performance at this temperature was observed for copper-containing LDHs, especially NiCuAl–CO3 LDHs, which is due to the reduction of metallic oxides that drive phase separation in the catalytic oxide tribo-layers. The more stable tribo-oxide layers can result in thick, durable carbon-based tribofilm during sliding along with higher resistance to plastic deformation bulk interlayer. This study offers valuable insight into the synergy of catalytic oxide materials, opening avenues for a rational design of innovative catalytic nano-materials for tribocatalysis processes.

Improving the composite-structured supercapacitor assembled with Ni–Co-layered double hydroxide and polymer cement electrolyte through structural optimization

The optimized nickel–cobalt double hydroxide electrode by electrodeposition has a high specific area capacitance of 10.53 F cm−2. Capacitors assembled using the optimized electrodes have a specific capacitance of up to 1.442 F cm−2.

Synthesis and characterization of new biocatalyst based on LDH functionalized with l-asparagine amino acid for the synthesis of tri-substituted derivatives of 2, 4, 5-(H1)-imidazoles

In this study, a new and recyclable biocatalyst (MgAl CO3-LDH@Asn) was synthesized by immobilizing l-asparagine amino acid (Asn) on the surface of 3-(chloropropyl)-trimethoxysilane modified MgAl CO3-layered double hydroxide (LDH). The physicochemical properties of the samples were identified by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and thermogravimetric analysis (TGA) techniques. The MgAl CO3-LDH@Asn was employed in the multi-component assembly process for the synthesis of tri-substituted derivatives of 2,4,5-(H1)-imidazoles from benzyl, various benzaldehyde derivatives, and ammonium acetate. For optimizing the reaction, the main factors, including the amount of MgAl CO3-LDH@Asn, type of solvent, reaction time, and temperature were evaluated. The optimum conditions of the model reaction were achieved using 20 mg of MgAl CO3-LDH@Asn biocatalyst in ethanol solvent after 20 min at reflux temperature. According to the findings above, the results indicated that high-yield products are achieved within a short time frame. Moreover, the high catalytic activity of the MgAl CO3-LDH@Asn was maintained for four cycles without significantly diminishing its performance.

Relative extents, mechanisms, and kinetics of fluoride removal from synthetic groundwater by prevalent sorbents

Fluoride (F) contamination in groundwater affects millions of people across the world. Although several sorbents have been identified for low-cost F removal, the choice of the optimal sorbent is dictated by the specific chemistry of contaminated groundwater. In this contribution, eight prevalent sorbents—activated alumina (AA), calcite, hydroxyapatite-coated calcite (HCC), natural chitosan, chalk, Mg–Al–CO3 layered double hydroxide (LDH), calcined Mg–Al–CO3 LDH (cLDH), and hydrous ferric oxide (HFO)—were categorized on their relative F removal mechanisms, extents, and kinetics from a typical synthetic groundwater, representative of contaminated aquifers of North India. Initially, batch experiments containing sorbents at 4 g·L−1 were conducted at a high F concentration (2.9 mM). The dominant F removal processes were identified by aqueous- and solid-phase characterization of reaction by-products. While chalk and calcite removed F by secondary precipitation of fluorite, HCC removed F by fluorapatite precipitation, and other sorbents removed F by sorption. Depending on the immobilization mechanism identified, the F uptake kinetics on each sorbent was modeled with either pseudo-second order or generalized rate equations. Among sorptive F uptake, cLDH exhibited the highest (10−2.15 mg·g−1·h−1) and HFO showed the lowest (10−4.15 mg·g−1·h−1) rates. Fluoride removal by precipitation was the fastest with chalk at 10−1.3 (h−1) (0.16). Subsequent experiments with AA and HCC at lower initial F concentration (0.42 mM) suggested increased uptake by ∼30x and ∼7x, respectively, relative to uptake in 2.9 mM initial F systems. For AA, apart from the widely-accepted mechanism of adsorption, an unidentified F-containing surface precipitate was formed. HCC was identified as the most promising sorbent with no sludge generation.

Scalable Synthesis of Amine-Grafted Ultrafine Layered Double Hydroxide Nanosheets with Improved Carbon Dioxide Capture Capacity from Air

The development of efficient adsorbents is one of the key technologies for direct air capture (DAC). Herein, a facile and scalable method to synthesize amine-functionalized layered double hydroxides (LDHs) as efficient DAC adsorbents is presented. Specifically, ultrafine and exfoliated Mg2Al–CO3 LDH nanosheets were generated within 2 min via rapid nucleation and aging followed by organic solvent treatment, and they remained exfoliated on the powders after vacuum drying. The well-dispersed LDH nanosheets were grafted with a high density of monolayered aminosilane (5.51 mmol N g–1), leading to a good CO2 adsorption capacity (0.68 mmol g–1) among amine-grafted adsorbents. Additionally, it exhibited good stability with no degradation over 200 adsorption–desorption cycles under ∼20% humid air at 25 °C.

The Crystal Structure of Mg–Al–CO3 Layered Double Hydroxide

The crystal structure of quintinite, Mg4Al2(OH)12(CO3)·3H2O, from the Jacupiranga alkaline complex (Cajati, São Paulo, Brazil), was refined for two samples (91002 and C7029) using single-crystal X-ray diffraction data. The mineral crystallizes in the P-3c1 space group, a = 5.246/5.298, c = 15.110/15.199 Å for samples 91002/C7029. The crystal structure consists of octahedral sheets with Mg and Al ordering according to a 3 × 3 superstructure. The Mg and Al atoms are coordinated by six hydroxylated oxygen atoms; the average <Mg–O> and <Al–O> bond distances are in the ranges 2.022–2.053 Å and 1.974–1.978 Å, respectively. The interlayer structures are identical (in contradiction to the previous assumptions), and consist of disordered (CO3)2− groups and (H2O)0 molecules. The samples from Jacupiranga can be identified as quintinite-2T, which is the second finding of this polytype after the Kovdor alkaline complex (Kola peninsula, Russia). The powder X-ray diffraction pattern of quintinite-2T contains weak superstructure reflection at 4.57 Å (010), indicative of Mg and Al ordering. An important crystal-chemical criterion of quintinite is the interlayer distance (d00n-value) of ~7.56 Å, which is steady among natural specimens from various findings worldwide.

A composite structural supercapacitor based on Ni–Co-layered double hydroxide–coated carbon cloth electrodes

Composite structural supercapacitors (CSSs) are valuable for their use in structural optimization because they can provide energy storage capacity while bearing mechanical loads, thereby enabling weight and volume reduction. Herein, flexible energy storage devices are embedded into carbon fiber reinforced polymer (CFRP) to form a CSS. In the flexible device, a positive electrode (carbon cloth coated with Ni–Co-layered hydroxide, NiCo-LDH@CC), a negative electrode (activated carbon–coated carbon cloth, AC@CC), and a separator (glass fabric) are bonded together by PVA-KOH gel electrolyte. The CSS (5:5 NiCo-LDH-CSS) provides competitive electrochemical properties (specific capacitance of 610 mF g−1, energy density of 191 mWh kg−1, and power density of 1,508 mW kg−1) and good mechanical properties (flexural strength of 495 MPa and flexural modulus of 125 GPa). The study conducts a systematic analysis of capacity decay during the electrochemical cycling process of 5:5 NiCo-LDH-CSS. In-situ mechano-electrochemical tests are also performed to verify the stable electrochemical behavior under external dynamic and static loads, which is a rarely studied aspect in other reports. This investigation provides assurance for the safety and reliability of future CSS applications. The study findings suggest that the 5:5 NiCo-LDH-CSS possesses good multifunctionality, and can provide a new idea for further development in CSSs.

Intercalated-Laurate-Enhanced Photocatalytic Activities of Ni/Cr-Layered Double Hydroxides

Laurate (LA−)-intercalated nickel–chromium-layered double hydroxides (LDHs) were synthesized using the co-precipitation method and investigated as a potential photocatalyst for methylene orange (MO) degradation. For comparison, a series of LDHs with various molar ratios of Ni2+(or Mg2+)/Cr3+(or Fe3+)/LA−(or CO32−) were prepared. X−ray diffraction (XRD) and element analysis showed that Ni/Cr(2/1)−1.0 LA LDH had the most ordered crystal structure, and showed the same photocatalytic decolorization performance as Mg/Cr(2/1)−1.0LA LDH towards MO, which was significantly superior to Ni/Cr−CO3 LDH, Ni/Fe(2/1)−1.0LA LDH, and Ni/Cr−CO3 LDH with LA−, and Cr3+ with LA−. The photocatalytic removal rate of MO with the initial concentration of 100 mg/L by Ni/Cr(2/1)−1.0LA LDH (0.5 g/L) could be up to 80% with UV light irradiation for 3 h, which was almost twice higher than that of the sorption test. The photocatalytic reaction was in accordance with the pseudo-first-order kinetics, which implied that the catalytic process took place on the surface of the catalyst. All the results indicate the photodegradation of MO by Ni/Cr−LA LDHs was enhanced by the sorption of MO onto the intercalated LA− in the interlayer. The free radical capture experiments suggest that the main role of the photocatalytic mechanism of Ni/Cr−LA LDHs could be the •O2− with high oxidation activity produced by the electron-hole pairs of LDH, as excited by UV light. Additionally, the •O2− further reacted with the adjacent MO molecule pre-sorbed on the intercalated LA.

An MgAl layered double hydroxide as a new transition metal-free anode for lithium-ion batteries.

A carbonate intercalated magnesium aluminum layered double hydroxide is used as an anode material for lithium-ion batteries, displaying a maximum discharge specific capacity of 814 mA h g-1 at 200 mA g-1 in this work through utilizing the valence variation of Mg and the conversion between LiOH and LiH/Li2O.

Introduction of high valent Mo6+ in Prussian blue analog derived Co-layered double hydroxide nanosheets for improved water splitting

Herein, we report a facile method for synthesizing MoCo-layered double hydroxide (LDH) nanosheets employing Prussian blue analog (PBA) as the precursor. The introduction of Mo in Co-LDH modulates the electronic structure, increases the number of active sites and electrochemical surface area to improve the hydrogen evolution, oxygen evolution, and overall water splitting activity. As a result, PBA-derived Mo0.25Co0.75-LDH nanosheets demonstrated 10 mA cm−2 current density at only 220 mV and 115 mV overpotentials for OER and HER, respectively. The overall water splitting was attained at 1.52 V cell voltage for 10 mA cm−2 current density.

Microwave-assisted synthesis of hybrid supercapacitors consisting of Ni, Co-layered double hydroxide shell assembled around wood-derived activated carbon fiber core

Activated carbon fibers (ACFs) are prepared from the discarded fir wood using two-step melt-spinning and CO2 activation post-treatment. Then, composites composed of these ACFs and Ni, Co-layered double hydroxides (NiCo-LDH@ACF) are synthesized by a microwave-assistant hydrothermal strategy. NiCo-LDHs agglomerated around ACFs, forming core-shell structures with sheet- or microsphere-like morphologies, which provide large surface area, hierarchical porosity, and numerous active sites for efficient charge and mass transfer. The NiCo-LDH@ACFs are used as an active material to construct the supercapacitors, the highest of capacitance and the corresponding rate performance of which are equal to 1453.3 F/g at 1 A/g and 78% at 10 A/g by microwave-assistant hydrothermal at 120 °C, respectively. We also use this material to assemble an asymmetric supercapacitor using activated carbon derived from fir bark as a negative electrode. The resulting device demonstrates excellent capacitance (equal to 146.9 F/g at 1.6 V), very high energy density (equal to 52.2 Wh/kg at 800 W/kg), and cycle life (judging by the 79.8% capacitance retention after 10000 cycles).

Corrosion Behavior of Mg(OH)2/Mg–Al Layered Double Hydroxides/AlO(OH) Composite Film Prepared by Steam Coating on Mg Alloy AZCa612

This study investigated the corrosion behavior of the corrosion-resistant films steam coated on AZCa612 magnesium alloy. The film samples were corroded by immersing them in 5 wt% NaCl aqueous solution for a predetermined time. The corroded films were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy, glancing angle X-ray diffraction, Fourier transform infrared spectroscopy, potentiodynamic polarization measurements, hydrogen generation measurements, and electrochemical impedance spectroscopy. The amount of Mg–Al–CO3 layered double hydroxides (LDHs) in the film slightly decreased from the beginning of immersion to 120 h after immersion and gradually increased thereafter. Mg–Al–Cl LDHs were formed after 6 h of immersion and rapidly grew as the immersion progressed. In addition, even with the gradual decrease in the corrosion resistance of the film, there was no major damage observed on the substrates. These results indicate that the corrosion protection mechanism varied with the immersion time. The corrosion-resistant property under a short immersion time could be attributed to the high corrosion resistance of Mg(OH)2 and AlO(OH), whereas it is attributed to the coverage provided by the Mg–Al–Cl and Mg–Al–CO3 LDHs under a longer immersion duration.

Synthesis, Characterization and Application of Ternary Zn2[Feal]-Co3 Ldh for Cu(Ii) and Pb(Ii) Removal from Aqueous Solution

Synthesis, Characterization and Application of Ternary Zn2[Feal]-Co3 Ldh for Cu(Ii) and Pb(Ii) Removal from Aqueous Solution

Hybridized intercalation of CoMoS4 in interlayer-expanded cobalt-LMO nanosheets as high active bifunctional catalysts in Zn-air battery

The heterolayer intercalation between layered double hydroxide (LDH) and other nanosheets is a vital way to tailor the interfacial electronic coupling and the crystal defects, for optimizing functionality of 2D nanosheets. In this work, the CoMoS4 nanosheet-intercalated Co layered metal oxide (i-CoMoS4@Co-LMO) is synthesized by growth of CoMoS4 in Co layered double hydroxide (CoLDH), followed by calcination. The intercalated CoMoS4 enlarges the lattice spacing of Co-LMO and boosts oxygen vacancy of stacked nanosheets, and the produced i-CoMoS4@Co-LMO simultaneously shows exceptional bifunctional catalytic performances of oxygen evolution reaction and oxygen reduction reaction due to the enhanced mass transport pathways and the fostered catalytic sites. Accordingly, a large peak power density of 130 mW cm–2 and an excellent durability (over 270 cycles) are exhibited by Zn-air batteries based on i-CoMoS4@Co-LMO as electrocatalyst, with diffusion limited current -4.21 mA cm–2, half-wave potential of 0.77 V vs RHE and high capacity of 960 mA h g–1 at energy density of 1104 Wh kg–1. This work underscores a facile, low-cost and environmental-friendly strategy to synthesize bifunctional catalysts hold high potential as a practical zinc-air cathode.

Novel synthesis of α-Fe2O3@Mg/Al-CO3-LDH nanocomposite for rapid electrochemical detection of p-nitrophenol

A simple and efficient system has been described for selective detection of p-nitrophenol. Herein α-Fe2O3@MgAl-CO3-Layered double hydroxides nanocomposite was coated on carbon-paste electrode (CPE) to electrochemical determination of p-nitrophenol via voltammetric analysis. The α-Fe2O3@MgAl-CO3-LDH nanocomposite was synthesized by coprecipitation method and characterized by various physical–chemical techniques of analyses such as XRD, TG-dTG, IR-TF, BET and SEM/EDX. As a result, this novel methodology was effectively implemented to p-nitrophenol detection with the lowest detection limit (4, 98 μM).

ZnO–Al2O3–CeO2–Ce2O3 mixed metal oxides as a promising photocatalyst for methyl orange photocatalytic degradation

In this research article, ZnO–Al2O3–CeO2–Ce2O3 mixed metal oxides phases were prepared by calcination of Zn–Al/Ce–CO3 layered double hydroxides (LDH) precursors, and evaluated for the photocatalytic degradation of methyl orange (MO) as a model textile dye from aqueous solution under UV irradiation. First, Zn–Al–CO3 and a series of Zn–Al/Ce–CO3 with different Ce content (5, 10, 15, 20%) were synthesized through co-precipitation method at Zn/(Al+Ce) molar ratio (r) of 3, then subjected to calcination at 500 °C for 6 h. Samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy coupled with energy dispersive X-ray analysis and pH point of zero charge. The experimental results of the photodegradation reveal that the photocatalyst developed from Zn–Al–Ce10%-CO3 LDH exhibits the highest photocatalytic activity, with a degradation efficiency of 99.8% after 300 min of irradiation. This performance was mainly ascribed to the presence of difference state of Ce, leading a highest separation efficiency of electrons and holes. The recycling tests suggests a much high photostability and reusability of the photocatalyst.

Synthesis of ZIF-9(III)/Co LDH layered composite from ZIF-9(I) based on controllable phase transition for enhanced electrocatalytic oxygen evolution reaction

The quest for desirable two-dimensional (2D) materials and facile strategies to construct 2D layered composites with fascinating structures and compositions for high-performance electrocatalysis is still a major challenge. In the present research, novel nanocomposites of 2D zeolitic imidazolate framework-9 (ZIF-9) combined with Co-layered double hydroxide (Co LDH) were successfully synthetized through a controllable phase transition from ZIF-9(I). The 3D to 2D structural transformation of ZIF-9 was induced by deionized water, and the formation of 2D Co LDH was simultaneously realized during the one-step fabrication of ZIF-9(III)/Co LDH nanocomposites. Due to the high surface area, the presence of abundant metal sites, and the interactions between 2D ZIF-9(III) and 2D Co LDH, the as-optimized ZIF-9(III)/Co LDH nanocomposite exhibits great electrochemical activities for oxygen evolution reaction (OER) (η = 297 mV at 10 mA cm−2) in 1.0 M KOH solution. The electrochemical performance of the ZIF-9(III)/Co LDH nanocomposite was superior to those of the pure Co LDH, ZIF-9(III), and commercial RuO2. The present work demonstrates that the proposed strategy can effectively boost catalytic activities and also design new routes to synthesize advanced MOF nanohybrids for various applications.

Hierarchical Micro-Nanoclusters of Bimetallic Layered Hydroxide Polyhedrons as Advanced Sulfur Reservoir for High-Performance Lithium-Sulfur Batteries.

Rational construction of sulfur electrodes is essential in pursuit of practically viable lithium–sulfur (Li–S) batteries. Herein, bimetallic NiCo‐layered double hydroxide (NiCo‐LDH) with a unique hierarchical micro‐nano architecture is developed as an advanced sulfur reservoir for Li–S batteries. Compared with the monometallic Co‐layered double hydroxide (Co‐LDH) counterpart, the bimetallic configuration realizes much enriched, miniaturized, and vertically aligned LDH nanosheets assembled in hollow polyhedral nanoarchitecture, which geometrically benefits the interface exposure for host–guest interactions. Beyond that, the introduction of secondary metal intensifies the chemical interactions between layered double hydroxide (LDH) and sulfur species, which implements strong sulfur immobilization and catalyzation for rapid and durable sulfur electrochemistry. Furthermore, the favorable NiCo‐LDH is architecturally upgraded into closely packed micro‐nano clusters with facilitated long‐range electron/ion conduction and robust structural integrity. Due to these attributes, the corresponding Li–S cells realize excellent cyclability over 800 cycles with a minimum capacity fading of 0.04% per cycle and good rate capability up to 2 C. Moreover, highly reversible areal capacity of 4.3 mAh cm−2 can be achieved under a raised sulfur loading of 5.5 mg cm−2. This work provides not only an effective architectural design but also a deepened understanding on bimetallic LDH sulfur reservoir for high‐performance Li–S batteries.

Comparative study on As(III) and As(V) adsorption by -intercalated Fe/Mn-LDHs from aqueous solution

Abstract Arsenic pollution prevails in rivers and reservoirs in nonferrous metal mining areas, especially in lead–zinc mining areas, which affects the health of the people residing in such areas. Arsenic usually exists as As(III) and As(V) in water, and the adsorption of As(III) and As(V) changes with the type of adsorbent used. In this work, we report a novel adsorbent Fe/Mn–CO3-layered double hydroxide (Fe/Mn–CO3-LDH) composite that can efficiently remove both As(III) and As(V) from water. When the initial concentrations of As(III) and As(V) were 5, 10 and 50 mg/L, the adsorption capacities were 10.12–53.90 and 10.82–48.24 mg/g in the temperature range of 25–45 °C, respectively. The adsorption kinetics conformed well to the pseudo-second-order kinetic model, with all of the fitted correlation coefficients being above 0.998 for all the three initial concentrations (5, 10 and 50 mg/L) tested, suggesting a chemisorption-dominated process. The adsorption isotherms of As(III) and As(V) by Fe/Mn–CO3-LDHs conformed better to the Freundlich model than to the Langmuir one, indicating a heterogeneous reversible adsorption process. The theoretical maximum adsorption capacity increased with the increase in temperature. During adsorption, As(III) was partially converted to As(V), which was further interacted with intralayer anions. While the electrostatic attraction played an important role in the adsorption of As(V). HIGHLIGHTl Successful preparation of Fe/Mn–CO3-LDH material with a high-specific surface area and a large pore volume. Pseudo-second-order kinetic model and Freundlich model can all well described the adsorption of As(III) and As(V) on Fe/Mn–CO3-LDH Fe/Mn–CO3-LDH has good adsorption effect on As(III) and As(V) in a vast range of pH = 2-12. pH only have a slight effect on the As(III) adsorbed by Fe/Mn -CO3-LDH, but obvious for As(V) adsorption.

N and S co-doped graphene enfolded Ni-Co-layered double hydroxides: an excellent electrode material for high-performance energy storage devices.

The performance of hybrid supercapacitors (HSCs) can be increased via the selection of higher capacitive electrode materials. Thus, layered double hydroxides (LDHs) have received extensive consideration in HSCs owing to their good ion-exchange properties, structural flexibility, and large specific surface area. Ni–Co-based LDHs show better specific capacitance, good synergy, and high-rate capability in aqueous electrolytes. However, LDHs suffer from low conductivity, which curbs the charge transfer and mass diffusion throughout the electrochemical process. Thus, the high performance of LDH-based supercapacitors is impeded. Hence, composites of LDH and conducting materials are used. Owing to its extraordinary conducting property, huge surface area, and cost-effectiveness, reduced graphene oxide (rGO) is used as conducting material for LDH-based composite electrodes. Moreover, via the incorporation of heteroatoms (N, S, etc.) into rGO, its electrochemical properties are further enhanced. Here, a novel composite electrode is prepared by wrapping Ni–Co-LDH with N and S-co-doped rGO (LDH-rGO-NS) via a hydrothermal process. The XPS C 1s spectra established the existence of N and S doping in the rGO. The electrochemical performance is enhanced due to an excellent ion/charge transfer rate because of N and S co-doping. The LDH-rGO-NS electrode offers a good charge transfer resistance of 0.24 Ω. The obtained anodic and cathodic b-values are 0.73 and 0.72, respectively. An admirable specific capacitance of 1388 F g−1 is accomplished at a sweep rate of 100 mV s−1. Furthermore, the obtained retention capacity is ∼71% after 2000 cycles. Moreover, the achieved specific capacitance is 2193 F g−1 at the discharge current density of 5 A g−1. The excellent electrochemical properties reveal the LDH-rGO-NS composites as encouraging electrode materials for HSCs.