Layered Double Hydroxide Precursor Research Articles

Synthesis of Gold Nanoparticles over CoAl Mixed Oxide for Ethanol Oxidation Reaction.

Catalytic total oxidation is an effective technique for the treatment of industrial VOCs principally resulting from industrial processes using solvents and usually containing mono-aromatics (BTEX) and oxygenated compounds (acetone, ethanol, butanone). The aim of this work is to deposit gold nanoparticles on CoAl mixed oxide issued from layered double hydroxide (LDH) precursor by using the deposition precipitation (DP) method, which is applied with two modifications, labeled method (A) and method (B), in order to enhance the interaction of the HAuCl4 precursor with the support. Method (A) involves the hydrolysis of the HAuCl4 precursor after addition of the support, while in method (B), the gold precursor is hydrolyzed before adding the support. The two methods were applied using as support the CoAl mixed oxide and the LDH precursor. Samples were characterized by several physical chemical techniques and evaluated for ethanol total oxidation. Method (B) allowed the ethanol oxidation activity to be enhanced for the resulting Au/CoAlOx catalysts thanks to the high surface concentration of Co2+ and improved reducibility at low temperature. The presence of gold permits to minimize the formation of by-products, notably, methanol, allowed for a total oxidation of ethanol at lower temperature than the corresponding support.

ZnAl LDH-based Derivative Materials as Photocatalysts: Synthesis, Characterization, and Catalytic Performance in Tetracycline Degradation

Layered Double Hydroxide (LDH)-derived materials exhibited different characteristics from LDH precursors. The conversion of ZnAl LDH into its derivative material has been carried out to find the best catalyst for TC degradation. ZnAl (LDH)-based catalysts in this study have been effectively synthesized using coprecipitation, calcination, and restacking procedures. ZnAl Layered Double Oxide (LDO) is derived from the calcination of ZnAl LDH at 500°C. ZnAl LDH was also modified by adding Garcinia mangostana pericarp extract (GME). XRD, FT-IR, UV-DRS, and SEM-EDX were used to investigate the synthesized catalyst. ZnAl LDH exhibited the typical LDH FT-IR spectra, whereas ZnAl LDO showed metal oxide-like spectra, and the ZnAl-GME composite displayed the combination spectra of precursor material. The ZnAl LDH XRD diffraction pattern exhibited the attributes of a layered material, whereas the other three catalysts did not. Calcination destroyed the layered structure of ZnAl LDH, whereas the addition of GME to LDH and LDO generated a single-layered composite. The modified ZnAl-GME composite showed a decrease in both particle size and bandgap energy. At an ideal pH of 5, the synthesized catalyst was used in a batch system photodegradation of 5 mg/L Tetracycline (TC), employing solar light irradiation. ZnAl LDO holds the most significant catalytic activity and structural stability through the fifth regeneration cycle, degraded TC up to 100% in 90 minutes.

Ultra-stable Co3O4/NiCo2O4 double-shelled hollow nanocages as headspace solid-phase microextraction coating for enhanced capture of polychlorinated biphenyls

Polychlorinated biphenyls (PCBs) are persistent toxic pollutants that tend to accumulate in food and cause damage to human health. This work reports the ultra-sensitive detection of PCBs in beverage samples (green tea, honey, and bottled drinking water) by headspace solid-phase microextraction (HS-SPME) coupled with a gas chromatography-flame ionization detector (GC-FID). The Ultra-stable Co3O4/NiCo2O4 double-shelled hollow nanocages (DSHNC) as SPME fiber coating were synthesized with pyrolysis of zeolitic imidazolate framework-67/layered double hydroxide precursor. The fiber coating material Co3O4/NiCo2O4 DSHNC demonstrated excellent thermal stability (＞1000 °C) and long usage lifespan (≥160 times). The extract ability to polar PCBs was significantly enhanced by oxygen-containing groups, π-π stacking, and electrostatic interaction. Experiments results illustrated that the adsorption is controlled by chemical adsorption with a monolayer molecular adsorption. The HS-SPME-GC-FID method possessed good linearity (R2 ≥ 0.9961) in the linear range of 0.10–50000 pg·mL−1 and low detection limits (0.03–1.5 pg·mL−1). The enrichment factors were determined between 6884 and 9765. The method was successfully applied to enrich PCBs in real samples and obtained a good recovery rate in the range of 78.26–112.1 %.

Improved nickel nanocatalysts for selective cleavage of lignin model compounds and lignin

The selective hydrogenolysis of lignin offers a promising avenue for converting lignin into valuable chemicals and fuels. However, the development of highly active catalysts for this process remains challenging. In this study, a series of Nix/Al2O3 catalysts were synthesized by calcining and reducing layered double hydroxides (LDHs) precursors. These catalysts were evaluated for their effectiveness in catalyzing the conversion of lignin-derived model compounds (2-phenoxy-1-phenylethanol and diphenyl ether). Remarkably, the optimized Ni3/Al2O3 catalyst demonstrated exceptional performance in cleaving C–O bonds, achieving complete conversion with high selectivity for monomers product under reaction conditions of 200 °C, 1 MPa H2, and 1 h. The catalyst's outstanding performance can be attributed to its relatively large specific surface area, Ni loading exceeding 50 wt%, well-dispersed Ni metal particles, abundant surface oxygen vacancies, and a significant number of acid sites. Additionally, the hydrogenolysis of lignin using the Ni3/Al2O3 catalyst resulted in a substantial production of monophenols (15.0 wt%). This study introduces a novel approach for tailoring highly active Ni nanocatalysts and highlights the capability of Nix/Al2O3 catalysts to efficiently cleave C–O bonds in lignin under mild reaction conditions.

Intimately mixed copper, cobalt, and iron fluorides resulting from the insertion of fluorine into a LDH template.

The advancement of lithium-ion batteries (LIBs) with high performance is crucial across various sectors, notably in space exploration. This advancement hinges on the development of innovative cathode materials. Our research is dedicated to pioneering a new category of cathodes using fluorinated multimetallic materials, with a specific focus on diverging from the traditional Ni, Co, and Mn-based NMC chemistries by substituting nickel and manganese with copper and iron which are more sustainable elements. Our goal is also to enhance the robustness of cathodes upon cycling by substituting oxygen with fluorine as the metal-ligand. To achieve this, an intimate composite blend of CuF2 and FeF3, through the multi-metallic template fluorination (MMTF) methodology using a layered double hydroxide (LDH) as a precursor has been designed. Each of these components was carefully selected for its distinct attributes, including high redox potential, elevated energy density, substantial theoretical capacity, and improved cyclability. The composition denoted as (Cu1.5Co0.5)2+(Fe0.75Al0.25)3+ has been selected for fluorination because it maximizes Fe3+ and Cu2+ amount in the screened LDHs. Subsequently, this particular LDH was fluorinated through solid-gas fluorination at different temperatures (200, 350, and 500 °C) using gaseous molecular fluorine (F2). A comprehensive characterization of these materials using various techniques, including X-ray diffraction (XRD), 57Fe Mössbauer spectrometry, scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX), and inductively coupled plasma analyses (ICP-AES) was conducted, and the evolution of LDH upon fluorination has revealed an intermediate porous texture particularly sensitive to hydration. Two original crystallographic phases are else obtained by fluorination: one formed by the hydration of the amorphous intermediate compound: Cu3Fe1.5Al0.5F12(H2O)12 an anti-perovskite structure and another stabilized through the combination of solid gas fluorination and LDH precursor yielding an original CoFeF5-type phase. Raman operando during cyclic voltammetry measurement applied on a sample fluorinated at 500 °C and used as a cathode in front of lithium metal was finally conducted to validate redox activity and mechanism.

Highly efficient photocatalytic hydrogen production by ZnCdS composite catalyst modified with NiCoP nanosheets prepared by LDH precursor

The unique characteristics and diverse applications of 2D transition metal phosphides have aroused significant interest. In this paper, we successfully prepared 2D NiCoP modified ZnCdS composite. The NiCoP nanosheets were successfully obtained by phosphating layered double hydroxide (LDH) precursor. The results show that the ZnCdS-8%NiCoP has the highest photocatalytic performance among all the composite photocatalysts with the H2 evolution rate of 1370.1 µmol h−1, which is 17.9 folds higher than obtained with pure ZnCdS. Detailed analysis reveal that NiCoP nanosheets functions as an excellent electron acceptor, speeding up the directed migration of electrons. Furthermore, the rational mechanism of photocatalytic has been presented based on density function theory (DFT) calculations, which is well congruent with experimental results. Our research offers a simple, environmentally benign, and scalable technique for making highly effective photocatalysts, as well as a novel perspective on transition metal phosphides rational design.

CuCeOx/CuO Catalyst Derived from the Layered Double Hydroxide Precursor: Catalytic Performance in NO Reduction with CO in the Presence of Water and Oxygen.

Valencies of metal species and lattice defects, such as oxygen vacancies, play a pivotal role in metal oxide-catalyzed reactions. Herein, we report a promising synthetic strategy for preparing CuO-supported CuCeOx catalysts (CuCeOx/CuO) by calcination of a hydrotalcite precursor [Cu6Ce2(OH)16]CO3·nH2O. The structural and chemical properties of catalysts were characterized by XRD, ICP-AES, TEM, TPR, NH3-TPD, XPS, Raman spectroscopy, and N2 adsorption, which revealed that the thermal pretreatment in an oxidative atmosphere caused segregation and reconstitution processes of the precursor, resulting in a mesoporous catalyst consisting of well-dispersed CuO-supported CuCeOx clusters of 1.8-3.2 nm in size with a high population of oxygen vacancies. The as-prepared catalyst shows excellent catalytic performance in the reduction of NO by CO in the absence as well as in the presence of water and oxygen. This behavior is attributed to its high oxygen defect concentration facilitating the interplay of the redox equilibria between Cu2+ and reduced copper species (Cu+/Cu0) and (Ce4+/Ce3+). The high surface population of oxygen vacancies and in situ-generated metallic copper species have been evidenced by Raman spectroscopy and X-ray photoelectron spectroscopy. The layered double hydroxide-derived CuCeOx/CuO also showed good water tolerance and long-term stability. In situ infrared spectroscopy investigations indicated that adsorbed hyponitrite species are the main reaction intermediates of the NO conversion as also corroborated by theoretical simulations.

Layered double hydroxide‐derived copper‐based oxygen carriers for chemical looping applications: Oxygen release kinetics and impact of loading on long‐term performance

AbstractChemical looping with oxygen uncoupling, a variant of chemical looping combustion, requires chemically and physically stable oxygen carriers over long‐term redox cycling. Copper‐based oxygen carriers are characterised by high oxygen release rates but experience sintering at high temperatures. The use of layered double hydroxides (LDHs), prepared via co‐precipitation, as oxygen carrier precursors has been shown to effectively limit deactivation of copper‐based mixed metal oxides (MMOs) over extended redox cycling. The LDH‐derived MMOs have highly dispersed metal oxide within a stable support; the high dispersion of metals is due to the LDH precursor structure. In this work, a fluidised bed reactor (FBR) was used to study the intrinsic kinetics of oxygen release from CuO/MgAl2O4 oxygen carriers synthesised via the LDH‐MMO design strategy. The long‐term performance of MMOs with higher loadings of CuO, calcined from LDHs with higher Cu contents, was also investigated using an FBR. The intrinsic kinetics were determined using a kinetic model incorporating an effectiveness factor. By minimising the effects of intra‐ and inter‐particle mass transfer, the activation energy and the pre‐exponential factor of the lower loading MMOs were determined to be 51 ± 3 kJ mol−1 and 0.0567 s−1, respectively. All MMOs showed excellent stability over 100 redox cycles in a thermogravimetric analyser. However, the pH during co‐precipitation of the LDHs affected the stability of the MMOs in an FBR. The MMOs calcined from LDHs synthesised at pH 9.5 disintegrated during operation, whilst those produced from LDHs synthesised at pH 11 maintained high conversion and physical integrity over 100 redox cycles. © 2023 The Authors. Greenhouse Gases: Science and Technology published by Society of Chemical Industry and John Wiley & Sons Ltd.

Low-temperature oxidative dehydrogenation of propane over NiV mixed oxides derived from LDH precursors

A series of NiV mixed metal oxide (MMO) catalysts were derived from the NiV layered double hydroxides (LDHs) synthesized by the constant pH coprecipitation method. The synthesis parameters, (i) Ni/V molar ratio and (ii) calcination temperature ( Tp), were controlled. The MMO catalysts were characterized by physicochemical characterization techniques and then tested for the oxidative dehydrogenation of propane (ODHP). The results showed that the calcination temperature affected the crystalline phase formation and grain size of NiO, as well as the activated temperature of propane, and the addition of V greatly regulated the activity and quantity of the surface oxygen species and improved the propylene selectivity. 4NiV-500 catalyst (Ni/V = 4, Tp = 500 °C) exhibited the best catalytic performance at low temperature (250 °C) with an initial propylene selectivity of about 70%. Therefore, it is an effective method to obtain NiV MMO catalysts with excellent low-temperature activity for ODHP, using LDHs as the precursors while controlling the appropriate amount of V and calcination temperature simultaneously.

Design of Multicationic Copper‐Bearing Layered Double Hydroxides for Catalytic Application in Biorefinery

AbstractEthanol has been used as a renewable hydrogen‐donor in the conversion of a lignin model molecule in subcritical conditions. Noble metal‐free porous mixed oxides, obtained by activation of Cu−Ni−Al and Cu−Ni−Fe layered double hydroxide (LDH) precursors, have been used as heterogeneous catalysts for Meerwein‐Ponndorf‐Verley (MPV) hydrogen transfer and further hydrogenation by ethanol dehydrogenation products. Both the Cu/(Cu+Ni) ratio and the nature of the trivalent cation (Al or Fe) affect the activity of the catalysts, as well as the selectivity towards the different steps of the hydrogenation reactions and the cleavage of lignin‐like phenylether bonds. Accounting for the peculiar behaviour of Cu2+ and M(III) cations in the synthesis of LDHs, the coprecipitation of the precursors has been monitored by titration experiments. Structural and textural properties of the catalysts are closely related to the composition of the LDH precursors.

NiFe Layered Double Hydroxide-Derived Catalysts with Remarkable Selectivity for the Oxidation of 5-Hydroxymethylfurfural to 2,5-Furanedicarboxylic Acid under Base-Free Conditions

In this work, we report the exciting discovery of inexpensive and durable catalysts for the selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furanedicarboxylic acid (FDCA) under base-free conditions. A nickel-iron layered double hydroxide (NiFe-LDH) precursor was first prepared then subjected to hydrothermal sulfidation with thioacetamide at 120 °C or thermal phosphidation with sodium hypophosphite at 400 °C to produce NiFeS and NiFeP-400 catalysts, respectively. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) showed these catalysts to contain FeNi2S4 and FeNi2P, respectively, as the dominant phases. The catalytic activity of each catalyst was optimized by studying the effect of the solvent, reaction temperature, oxidant, and reaction time on HMF conversions and product distributions. Under optimized conditions (acetonitrile solvent, 120 °C, tert-butanol peroxide as an oxidant, 12 h, respectively), the NiFeS catalyst afforded 100% HMF conversion with an 83.2% FDCA selectivity with the performance of the NiFeP-400 catalyst being almost identical (HMF conversion of 100%; FDCA selectivity of 82.7%). Both catalysts showed excellent stability over five cycles of catalyst tests with the catalysts able to be easily collected after use with a magnet. Based on the experimental findings, the similar reaction mechanisms used are to be proposed for HMF oxidation to FDCA over the two catalysts. Results show that metal sulfide-based and metal phosphide-based catalysts are promising alternatives to traditional noble metal-based catalyst for the valorization of bio-derived HMF.

Synthesis of SiO2@MnCo2O4 core–shell nanorattles using layered double hydroxide precursors and studies on their peroxidase-like activity

The current work demonstrates a simple soft chemical approach to synthesize SiO2@MnCo2O4 core–shell nanorattles using SiO2@MnCo-LDH (layered double hydroxide) precursors.

Layered double hydroxides as precursors for catalysts in Claisen-Schmidt condensation

MMgAlO and MAlO mixed oxides (where M = Cu, Co, Zn and Ni) were obtained by thermal decomposition of the corresponding layered double hydroxides (LDH) precursors and used as catalysts for Claisen-Schmidt condensation of 2’-hydroxyacetophenone and benzaldehyde under solvent-free conditions. The catalysts were characterized by X-ray diffraction (XRD), atomic absorption spectrometry and temperature-programmed desorption of CO2 (TPD-CO2). Gas chromatography – mass spectroscopy (GC/MS) methods were used for the identification and quantification of the product mixture. A 2’-hydroxychalcone and 2-phenyl-2,3-dihydro-4H-chromen-4-one (flavanone) were received as main products. 3-Benzyl-2-phenyl-4H-chromen-4-one (3-benzylflavone) was achieved as a new product.

Total hydrogenation of hydroxymethylfurfural via hydrothermally stable Ni catalysts and the mechanistic study

Total hydrogenation of hydroxymethylfurfural (HMF) (including hydrogenation of both furan ring and carbonyl group) produces 2,5-bis-(hydroxymethyl) tetrahydrofuran (BHTF), which can be used as rigid polymer monomer, green solvent, or precursor of high-value chemicals and has great market potential. Although Ni is regarded as the most selective metal for the total hydrogenation of HMF, Ni catalysts often suffer sintering and leaching under hydrothermal conditions. In this regard, development of hydrothermally stable Ni catalysts is highly desirable. Here, Ni on well mixed oxides (Ni/MgaAl10-aOx) derived from layered double hydroxide (LDH) precursors was successfully synthesized via co-precipitation. The Ni/MgaAl10-aOx showed superior hydrothermal stability during the aqueous phase total hydrogenation of HMF, without noticeable activity loss, leaching and sintering after multiple reuse. In contrast, significant activity loss, leaching and sintering was observed for impregnated Ni counterparts. Catalyst characterization revealed the formation of highly dispersed Ni and well mixed porous oxides after the thermal reduction of the NiMgAl-LDH precursors as well as the stronger metal-support interactions of the NiMgAl-LDH as compared to impregnated Ni catalysts with similar Ni particle size. The markedly improved hydrothermal stability was due to enhanced metal support interactions derived from the LDH precursors, which prevents the undesired agglomeration and leaching of Ni in the hydrothermal environment. Moreover, a high BTHF yield of 99.0% was obtained using the Ni/MgaAl10-aOx under optimal reaction conditions. Density functional theory calculations suggest that the total hydrogenation of HMF over the Ni catalysts proceeds through the alkoxy pathway via “flat-lying” adsorption.

Design and synthesis of NiCo-NiCoO2@C composites with improved lithium storage performance as the anode materials

The rapid capacity decay severely limits the commercial applications of metal oxide-based electrodes. Exploring innovative materials with enhanced lithium storage performance is urgent and challenging. Herein, we propose a strategy for the synthesis of NiCo-NiCoO2@C composites using layered double hydroxide (LDH) precursors. When used as the anode materials, the composites deliver enhanced capacity throughout the continuous charge–discharge process. In our design, the electrochemically active NiCoO2 nanoparticles pulverize the NiCo phases via a conversion reaction. The NiCo phases can increase capacity by reacting with the Li2O yielded from the conversion of NiCoO2 and participating in the reversible transformation of solid-electrolyte interface (SEI) films, thus ensuring fast charge transfer. Voids that appear with the consumption of NiCo phases can provide abundant channels for Li+ transportation. Carbon matrices can effectively alleviate the stress generated during repeated cycles of expansion and shrinkage. Benefiting from these features, NiCo-NiCoO2@C anode delivers a highly enhanced reversible capacity of 961.6 mAh g−1 after 300 cycles at 200 mA g−1. This LDH-based strategy may be extended to the design and synthesis of various enhanced anode materials for lithium-ion batteries (LIBs).

CO hydrogenation to ethanol and higher alcohols over ultrathin CuCoAl nanosheets derived from LDH precursor

Ultrathin CuCoAl nanosheets derived from layered double hydroxide (LDH) precursor (1–3 cationic-layers) were successfully synthesized by aqueous miscible organic solvent treatment (AMOST) strategy and performed for ethanol and higher alcohols production via CO hydrogenation. The ultrathin CuCoAl nanosheets (CuCo-LDH-aw) demonstrated a comparatively higher total alcohols (ROH) selectivity of 47.6 %, and the molar fraction of ethanol reached up to 37.5 % among the total alcohols. As revealed by XRD, TEM, SEM, BET and AFM characterizations, the uniform dispersion of CuCo NPs was observed over the ultrathin CuCoAl nanosheets. Moreover, the optimum ultrathin CuCoAl nanosheets exhibited a higher ratio of Cu+/(Cu0 + Cu+), which exerted a positive role on non-dissociative CO* insertion CHx intermediates. More significantly, XPS and in situ CO-DRIFT techniques uncovered the formation of CHx intermediates derived from bridge CO dissociation on the metallic Co species and the formate hydrodeoxygenation route, which involved CO* and surface hydroxyl groups (–OH) reaction. Consequently, it was concluded that the triply synergistic effect of Cu+, Co and surface hydroxyl groups (–OH) species contributed to the improvement in ethanol selectivity via CO hydrogenation.

Layered double hydroxide derived cobalt-iron sulfide heterostructures with enhanced reaction kinetics for use in sodium-ion batteries

Constructing a well-designed heterojunction on anodes of sodium ion batteries (SIBs) is an essential strategy for developing high-performance Na-storage devices. In this study, a CoS1.097/FeS lamellar heterostructure was built via a simple two-step hydrothermal treatment using layered double hydroxide precursors. The as-prepared sample exhibits a hydrotalcite-like intercalated structure and heterogeneous composition, which boosts the electrochemical reaction kinetics by shortening the transport distance, unifying move direction and accelerating mobility of Na+. Meanwhile, benefited from such advantages as additional active sites at surfaces, enhanced internal structure stability and relaxed stress from volume expansion etc., SIBs with as-prepared CoS1.097/FeS heterojunction anodes shows excellent sodium storage performances，including high rate capability (564.1 mAh g-1 at 10 A g-1), good the initial coulombic efficiency (80.65% at 0.5 A g-1) as well as great cyclability (543.9 mAh g-1 at 2 A g-1 after 450 cycles). Theoretical calculations based on the first principles are carried out to clarify the possible sodium storage mechanisms. The job may provide a feasible route and key technologies through structural designing and surface coating to prepare anode materials for high-performance sodium-ion batteries. It is expected that the current work can be extended to build other advanced electrode materials for various energy storage related applications.

Ga-Promoted CuCo-Based Catalysts for Efficient CO2 Hydrogenation to Ethanol: The Key Synergistic Role of Cu-CoGaOx Interfacial Sites.

Currently, direct catalytic CO2 hydrogenation to produce ethanol is an effective and feasible way for the resource utilization of CO2. However, constructing non-precious metal catalysts with satisfactory activity and desirable ethanol selectivity remains a huge challenge. Herein, we reported gallium-promoted CuCo-based catalysts derived from single-source Cu-Co-Ga-Al layered double hydroxide precursors. It was manifested that the introduction of Ga species could strengthen strong interactions between Cu and Co oxide species, thereby modifying their electronic structures and thus facilitating the formation of abundant metal-oxide interfaces (i.e., Cu0/Cu+-CoGaOx interfaces). Notably, the as-constructed Cu-CoGa catalyst with a Ga:Co molar ratio of 0.4 exhibited a high ethanol selectivity of 23.8% at a 17.8% conversion, along with a high space-time yield of 1.35 mmolEtOH·gcat-1·h-1 for ethanol under mild reaction conditions (i.e., 220 °C, 3 MPa pressure), which outperformed most non-noble metal-based catalysts previously reported. According to the comprehensive structural characterizations and in situ diffuse reflectance infrared Fourier transform spectra of CO2/CO adsorption and CO2 hydrogenation, it was unambiguously revealed that CHx could be formed at oxygen vacancies of defective CoGaOx species, while CO could be stabilized by Cu+ species, and thus the catalytic synergistic role of Cu0/Cu+-CoGaOx interfacial sites promoted the generation of CHx and CO intermediates to participate in the CHx-CO coupling process and simultaneously inhibited alkylation reactions. The present work points out a promising new strategy for constructing CuCo-based catalysts with favorable interfacial sites for highly efficient CO2 hydrogenation to produce ethanol.

Construction of sulfide nanoparticles on hydrangea-like nickel‑cobalt hydroxide for enhanced pseudocapacitance

Transition metal hydroxides have been extensively studied due to their high theoretical capacity. However, poor electrical conductivity and limited active sites hinder further practical applications. Therefore, in this work, hydrangea-like NiCo-LDH(Layered double hydroxide) precursor was synthesized by hydrothermal method. Based on this precursor, sulfide nanoparticles were constructed on NiCo-LDH nanosheets through an ion-exchange strategy. Sulfide nanoparticles with high electrical conductivity are grown in NiCo-LDH nanosheets, and the construction of heterojunctions between NiCo-LDH and sulfide nanoparticles enables them to provide ion or electron transport paths to each other, significantly improving electrode materials conductivity. Also, the close contact between the nanoparticles and LDH provides additional active sites. Significant synergy between nanoparticles and LDH, which contributes to improved electrochemical performance. By adjusting the amount of thioacetamide added, the optimized NC/S-15(Means added 15 mg thioacetamide for NiCo-LDH)material(267.8 mAh g−1 at 1A g−1) showed better specific capacity than NiCo-LDH. Assembled hybrid supercapacitor (HSC) using NC/S-15 nanomaterials as cathode and activated carbon (AC) as anode with high specific capacitance of 126.76 F g−1 at 1 A g−1 and reasonable energy and power density (43.6 Wh kg−1 at 375 W kg−1) as well as excellent capacitance retention (83 % after 5000 cycles).

Showcasing advanced electrocatalytic behavior of layered double hydroxide wrapped on carbon nanotubes: Real-time monitoring of L-cysteine in biological matrices

L-cysteine is an imperative amino acid which exists in natural proteins and plays crucial roles in biological systems, thereby its sensitive and selective monitoring is extremely necessary. In this work, novel hybrid nanoarchitectures have been fabricated by wrapping positively charged NiAl layered double hydroxide (LDH) nanosheets on negatively charged carbon nanotubes (CNTs). The electrochemical behavior of CNTs@NiAl LDH hybrids having different concentrations of NiAl LDH precursor salts with fixed amount of CNTs have been explored in detection of L-cysteine using cyclic voltammetry and amperometry techniques. High conductivity of CNTs together with enhanced electrocatalytic properties of NiAl LDH and plentiful surface active sites are accountable to facilitate the direct detection of L-cysteine. Therefore, the fabricated electrode exhibits excellent sensing performance with 0.05 µM to 780 µM wide linear range, sensitivity of 351 μA mM−1 cm−2, low limit of detection upto 3 nM (S/N = 3), superb reproducibility and stability as well as brilliant selectivity against common interferents. Arising from remarkable efficiency, the CNTs@NiAl LDH based sensing system has been practically used in real-time detecting L-cysteine effluxes from different living cells upon stimulation as-well-as in-vitro monitoring of L-cysteine concentrations in human samples (urine and serum).