NiAl-layered Double Hydroxide Research Articles

Soft-chemical synthesis and catalytic activity of Ni-Al and Co-Al layered double hydroxides (LDHs) intercalated with anions with different charge density

Co-Al and Ni-Al layered double hydroxides (LDHs) intercalated with three types of anionic molecules, dodecylsulfate (C12H25SO4−, DS), di-2-ethylsulfosuccinate ([COOC2H3EtBu]2C2H3SO3−, D2ES), and polytungstate (H2W12O4210−, HWO) were prepared by means of ion-exchange and co-precipitation processes. With the use of DS and D2ES as intercalation agents, high crystallinity was maintained after intercalation into the LDHs. In the case of HWO, the intercalated LDHs could be obtained by ion-exchange as well as co-precipitation with a decline in the crystallinity; however, unreacted LDH was detected in the ion-exchange samples, and some unwanted phases such as hydroxide and pyrochlore were generated by the co-precipitation process. The maximum specific surface area and pore volume of the Ni-Al sample with intercalated HWO, prepared by the ion-exchange process were 74 m2/g and 0.174 mL/g, respectively. The occupancies of DS, D2ES, and HWO within the interlayer space were approximately 0.3–0.4, 0.5–0.6, and 0.1–0.2, respectively, in the Co-Al and Ni-Al LDHs. Analysis of the catalytic activity demonstrated that the DS-intercalated Ni-Al LDH sample exhibited relatively good catalytic activity for conversion of cyclohexanol to cyclohexanone.

Removal of Azo Dyes: Intercalation into Sonochemically Synthesized NiAl Layered Double Hydroxide

A sonochemical method was employed in the synthesis of nickel aluminum layered double hydroxides (NiAl-LDH) and the materials were used as adsorbents for the removal of the reactive azo dye, Remazol Brilliant Violet (RBV-5r). The experimental data obtained for microstructure were compared and both the arrangement and orientation of the intercalated dye species were examined using molecular dynamics (MD) simulations. The obtained materials were characterized by X-ray diffraction (XRD), nitrogen sorption (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and Fourier transformation infrared spectroscopy (FTIR). The adsorption characteristics were studied in a batch process by optimizing different parameters such as calcination temperature, contact time, initial dye concentration, solution pH, and solution temperature. NiAl-LDH material synthesized by sonochemical (SC) methods and calcined at 250 °C (NiAl-C250SC) showed the best dye removal effi...

Ordered mesoporous mixed metal oxides: remarkable effect of pore size on catalytic activity.

We report the synthesis of ordered mesoporous NiAl mixed metal oxides (MMOs) from NiAl-layered double hydroxides (LDHs) through a soft template method using pluronic-F127 as the structure-directing agent. Ordered mesopores were obtained by the thermal decomposition of as-synthesized LDHs at different temperatures. The effects of the pluronic-F127 amount and the calcination temperature on the pore size distribution of the MMO were investigated. NiAl MMOs exhibited excellent catalytic activity in the Knoevenagel condensation of benzaldehyde with acidic methylene group-containing malononitrile. Finally, the dependence of the catalytic activity on the surface properties of NiAl MMOs was investigated. The pore diameter and the pore volume of NiAl MMOs were well correlated with the performance of the catalysts. MMO obtained from the calcination of NiAl-F127(3%)LDH at 750 °C for 5 h gave the highest conversion (>99%) in the Knoevenagel condensation in 30 min. The optimum pore diameter for the model reaction described here was 7.7 nm, which gave rise to more than 99% conversion with 100% selectivity. Ethanol gave the best conversion at 60 °C. The regenerated catalyst showed 93.0 and 89.0% of the initial catalytic activity after the first and the second regeneration cycles, respectively.

Assembly of Ni-Al layered double hydroxide and graphene electrodes for supercapacitors

Delaminated Ni-Al layered double hydroxide (LDH) was incorporated between graphene nanosheets to form a layered structure as a new generation of supercapacitor electrode material. First, Ni-Al layered double hydroxide (LDH) was grown hydrothermally, then delaminated by ultrasonication, and combined with a graphene oxide suspension prepared by a modified Hummers method. Subsequently, the graphene oxide in this mixture was reduced to graphene. It is the first time to prepare such layered hybrid structure from these two pre-prepared layered materials: graphene oxide and delaminated Ni-Al LDH in aqueous medium—instead of the in-situ growth of Ni-Al LDH on graphene oxide nanosheets. Using both materials in their layered form provided more contact between electrochemically active areas which resulted in two favourable conditions to realize their electrochemical energy storage capacity: graphene has enhanced the conductivity of Ni–Al LDH and eliminated the need of conducting additives; the Ni-Al LDH has prevented the restacking of graphene sheets. The layer structured hybrid material demonstrated a superior electrochemical performance due to the synergistic effect from the pseudocapacitance of Ni-Al LDH and the electrical double layer capacitance of graphene. The graphene/Ni-Al LDH–based electrodes provided a specific capacitance of 915F/g at a current density of 2A/g based on the total mass of active materials in the absence of conductive additives. After 1500 cycles at a current density of 10A/g, 95% of the initial capacitance was retained. The high electrochemical performance and facile aqueous-based synthesis route demonstrated that the G/Ni-Al LDH composite can be a promising electrode material for supercapacitor applications.

Aerobic Oxidation of Alcohols on Au Nanocatalyst: Insight to the Roles of the Ni–Al Layered Double Hydroxides Support

AbstractAu nanoparticles (NPs) supported on Ni–Al layered double hydroxides (LDHs) were shown to be efficient heterogeneous catalysts for the highly selective oxidation of alcohols to the corresponding aldehydes or ketones under base‐free or even solvent‐free conditions with O2 as the sole oxidant. The Au NPs can be uniformly distributed on Ni–Al LDHs support, which is beneficial to the catalytic activity. In addition, the weak Brønsted basic property of the support enables the aerobic oxidation of alcohols under base‐free conditions. More importantly, unlike Al2O3, which is inert, Ni–Al–LDHs are redox‐actively involved in prompting the electron transfer to O2 via the Au nanocatalyst because of the presence of NiII. Both of the basic and the redox properties of Ni–Al–LDHs can be tuned by adjusting the ratio of Ni:Al to achieve the best synergistic effects between Au NPs and the supports. The activity of the obtained Au catalysts was found to be structurally associated with the arrangements of NiO6 and AlO6 octahedra in the surface hydroxide layers which were different from the bulk Ni:Al ratio.

NiAl-layered Double Hydroxide/Reduced Graphene Oxide Composite: Microwave-assisted Synthesis and Supercapacitive Properties

Pure NiAl-layered double hydroxides (LDHs) and graphene oxide (GO)/NiAl-LDHs composites are both fabricated by refluxing solution with the assistance of microwave irradiation within 2hours. The structural characterization and morphological observation of the composites suggest that small NiAl-LDHs crystals are in situ grown on the surface of GO nanosheets, preventing the compact stacking of GO as an intercalated spacer. The electrochemical performances of pure LDHs and GO/NiAl-LDHs composites with different content of GO are investigated and compared. The GO/NiAl-LDHs composite containing 23 wt% GO exhibits a higher specific capacitance of 1630 F g−1 at 1 A g−1 in 6M KOH solution and more stable rate capability than others. When GO is substituted by microwave reduced graphene oxide (rGO) or the GO in the GO/NiAl-LDHs composite is thermally reduced at a rational temperature, rGO/NiAl-LDHs composites are obtained with enhanced electrochemical behavior in rate capability and cycle life. Critical comparisons indicate that rGO/NiAl-LDHs composite prepared by thermal reducing GO/NiAl-LDHs has better cycling performance and rate capability than the counterpart directly prepared with rGO.

Photocatalytic Conversion of CO2 in H2o over Solid Based Materials

Conversion of the greenhouse gas CO2 into carbon and useful carbon sources such as CO, HCOOH, HCHO, CH3OH, and CH4 is a potential method of solving energy and environmental problems. Photocatalytic conversion of manmade CO2 is attractive from the viewpoint of sustainable energy production and greenhouse gas reduction. Layered double hydroxides (LDH) are synthetic or natural crystalline clays that consist of brucite (Mg(OH)2)-like positively charged two-dimensional sheets in which some divalent cations such as Mg2+ are substituted by trivalent cations; further, water and exchangeable charge-compensating anions are present in the interlayer. In this study, we carried out the photocatalytic conversion of CO2 in H2O using various LDHs. Considerable amount of CO was obtained over various LDHs in the photocatalytic conversion of CO2 and photocatalytic H2 evolution from H2O competitively took place in all cases. Ni-Al LDH exhibited high selectivity to CO because the amount of H2 evolved was relatively low. Ni-Al LDH (Ni/Al = 4) which was aged for 20 h under hydrothermal condition at 383 K after coprecipitation showed the highest activity for the evolution of CO. GC/MS analysis for the photocatalytic conversion of 13C-labeled CO2 clarified that 13CO (m/z = 29) was evolved in priority to 12CO (m/z = 28). Accordingly, CO2 introduced in the gas phase was adsorbed on the surface of LDHs, and then reduced into CO in the photocatalytic conversion of CO2 in water.

Influence of organically modified Ni[sbnd]Al layered double hydroxide (LDH) loading on the rheological properties of poly (methyl methacrylate) (PMMA)/LDH blend solution

This work deals with the synthesis of organically modified NiAl layered double hydroxide (LDH) and the effect of NiAl LDH loading on the rheological behavior of PMMA/NiAl LDH blends prepared by solvent blending method. Firstly, NiAl LDH was synthesized by co-precipitation method at constant pH using their nitrate salts and subsequently modified using sodium dodecyl sulfate (SDS). Then, PMMA blends with various LDHs content (3 and 5wt.% with respect to PMMA) were prepared by solvent blending method using methylene chloride as a solvent. The structural properties of the modified NiAl LDH were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and FTIR analysis. The XRD analysis reveals that the d-spacing value of the modified LDH increases to 1.35nm from 0.80nm for the unmodified LDH, which confirms the insertion of SDS molecules into the NiAl LDH interlayers. The presence of sulfate groups in the modified LDH is confirmed by FTIR analysis. The rheological characteristics of PMMA/NiAl LDH blends were performed on rotational rheometer using HAAKE Rheostress RS1 with cup and cylinder geometry at room temperature. It is observed that the rheology of PMMA blends is affected by increasing LDH loading as well as shear rate. All the PMMA/LDH blends exhibit enhanced shear viscosity as compared to neat PMMA. In addition, the obtained rheological data are fitted with various models, like Power law, Herschel–Bulkley, Casson, Sisko, Cross, and Carreau models to explain the rheological behavior. The results clearly indicate that the Herschel–Bulkley model fits the rheological data better than other models.

Effect of Non-Thermal Plasma Modified NiAl Layered Double Hydroxides on the Removal of Fluoride from Aqueous Solution

In this paper, NiAl layered double hydroxides (NiAl-LDHs) has been modified by non-thermal plasma (NTP) to enhance the fluoride removal capacity of materials. The samples were characterized by X-ray diffraction, Fourier transform infrared spectrometer (FTIR), Thermogravimetric differential thermal analyzer (TG-DTA) and N2 adsorption-desorption. Effects of pH, co-existing anions, temperature and kinetics on F﹣ adsorption were investigated. The results showed that pH affects the adsorbent surface charge. The effective pH range for F﹣ removal was between 4.5 and 10. Lower pH potentially causes dissolution of NiAl-LDHs. The negligible interference of coexisting ions such as makes the NiAl-LDHs a promising sorbent for fluoride polluted water treatment.

Synthesis of graphene/Ni–Al layered double hydroxide nanowires and their application as an electrode material for supercapacitors

Graphene oxide (GO) as a template for the morphology controllable synthesis of inorganic particles has recently attracted enormous attention. In this study, we report the synthesis of graphene/Ni–Al layered double hydroxide (LDH) nanowires by using GO and adjusting the loading of urea in hydrothermal reactions. Transmission electron microscopy observation demonstrates that the graphene/Ni–Al LDH nanowires are composed of nano-sized Ni–Al LDH sheets. This finding demonstrates a new assembly form of LDH materials. Symmetric supercapacitors have been prepared by using the graphene/Ni–Al LDH nanowires as an electrode material. Compared to other Ni–Al LDH materials, the graphene/Ni–Al LDH nanowires exhibit much better performance as an electrode material for supercapacitors, due to the preferential conductive behaviour of the nanowire structures and the conductive networks formed by the nanowires in the corresponding electrodes.

Three-dimensional NiAl-mixed metal oxide film: preparation and capacitive deionization performances

A NiAl layered double hydroxide (NiAl-LDH) film was grown on the surface of a three-dimensional (3D) nickel foam by an in situ hydrothermal method using a nickel foam substrate as a nickel source, and boehmite (AlOOH) sol as an aluminium source.

A sandwich-type three-dimensional layered double hydroxide nanosheet array/graphene composite: fabrication and high supercapacitor performance

In this study, we have developed, for the first time, a facile in situ growth process to prepare a hierarchical three-dimensional (3D) composite composed of graphene layers with layered double hydroxide (LDH) nanosheet arrays grown on both sides. The fabrication process involves coating AlOOH colloids onto the graphene surfaces and the subsequent in situ growth of layered NiAl–LDH nanosheet arrays on the surfaces of graphene sheets via a hydrothermal process. It is found that the NiAl–LDH nanosheet arrays grow perpendicularly and uniformly on both sides of the graphene sheets, constructing a hierarchical 3D nanocomposite with an interesting sandwich structure. This uniquely structured composite has a large specific surface area (184.7 m2 g−1) and typical mesoporous characteristics, which are favorable for achieving high pseudocapacitance performance. Our results reveal that the composite has a specific capacitance of 1329 F g−1 at a current density of 3.57 A g−1, and the specific capacitance still remains as high as 851 F g−1 even when the current density is increased to 17.86 A g−1. The specific capacitance remains at 91% (823 F g−1) after 500 cycles at 15.30 A g−1 compared with 74% for pure Ni/Al–LDH. The in situ growth method may pave a way to design and fabricate diverse LDH/graphene composites with interesting structures for potential application in supercapacitors and other fields.

Electrodeposition of nickel hexacyanoferrate/layered double hydroxide hybrid film on the gold electrode and its application in the electroanalysis of ascorbic acid

Nickel hexacyanoferrate (NiHCF) and Ni-Al layered double hydroxide (LDH) hybrid film was fabricated on the gold electrode by a two-step electrodeposition method. Varying the strategies of electrodeposition of NiHCF, the hybrid films showed different morphology, composition and electrochemical behavior. As a demonstration, the hybrid film fabricated by using the absorbed Ni2+ on Ni-Al LDH modified gold electrode for the next electrodeposition of NiHCF was used for the electroanalysis of ascorbic acid (AA). The analytical performance of the proposed electrode was investigated by cyclic voltammetry and chronamperometry. The linearity range of AA was from 0.1 to 3.5mM with a detection limit (S/N=3) of 21μM. The developed method was found to be linear, sensitive, selective, precise and accurate. The applicability of the method was confirmed by the satisfactory results in real sample analysis.

Co-precipitation synthesis of reduced graphene oxide/NiAl-layered double hydroxide hybrid and its application in flame retarding poly(methyl methacrylate)

A reduced graphene oxide/NiAl-layered double hydroxide (RGO-LDH) was synthesized through a simple co-precipitation route. NiAl-layered double hydroxide (NiAl-LDH) nanoparticles were homogeneously dispersed on the reduced graphene oxide (RGO) nanosheets, which were simultaneously reduced during the process. RGO-LDH exhibited three steps of weight loss, leaving high residue. RGO-LDH was then solution blended into poly(methyl methacrylate) (PMMA) to investigate its effect on reducing flammability of the composite. With the incorporation of RGO-LDH, the thermal stability of PMMA composite was improved. Moreover, RGO-LDH endowed PMMA with the largest reduction in the heat release rate, smoke production and CO production rate relative to RGO or NiAl-LDH alone. RGO-LDH could decrease the production of volatiles including hydrocarbons, carbonyl compounds and epoxy compounds from the PMMA composite. The improved flame retardancy was ascribed to the combined effect of the physical barrier of RGO and the catalytic carbonization of NiAl-LDH.

Two steps in situ structure fabrication of Ni–Al layered double hydroxide on Ni foam and its electrochemical performance for supercapacitors

In this paper, two steps in situ growth method has been used to solve the accumulation of layered double hydroxide (LDH) in oriented growth. Moreover, the petal-like Ni–Al LDH displays excellent pseudocapacitance performance: a specific capacitance of 795 F g−1, a long cycle life with 80% performance remains after 1000 cycles and good charge/discharge stability, owing to the improvement of pseudocapacitive reaction by the large sheet structure of Ni–Al LDH on Ni foam. And the comparison results of different electrode preparation process and different growth process reflect the great advantages of our synthesis method.

Heterostructure of Au Nanoparticles—NiAl Layered Double Hydroxide: Electrosynthesis, Characterization, and Electrocatalytic Properties

A heterostructure based on gold nanoparticles (AuNPs) and NiAl layered double hydroxide (LDH) was prepared by one-step electrosynthesis, directly onto the electrode surface. The resulting material (AuNPs–NiAl LDH) was characterized by SEM, TEM, UV–vis, XRD, EXAFS, and XANES spectroscopy and by electrochemical techniques. The deposition process of the heterostructure on the Pt electrode was investigated by the electrochemical quartz crystal microbalance (EQCM). The electrocatalytic behavior of AuNPs–NiAl LDH toward the oxidation of methanol in basic media was compared with those of individual AuNPs and NiAl LDH, and an enhancement of the catalytic efficiency over a wide methanol concentration range was pointed out.

Magnetic nanomaterial derived from graphene oxide/layered double hydroxide hybrid for efficient removal of methyl orange from aqueous solution

Magnetic hybrid nanomaterials composed of reduced graphene oxide, zero-valent nickel, and NiAl-mixed metal oxides (rGO/Ni/MMO) have been synthesized by calcining graphene oxide (GO)/layered double hydroxide (LDH) hybrid in nitrogen atmosphere. Structural characterizations demonstrate that with the presence of GO substrate, NiAl–LDHs can be reduced into zero-valent Ni and NiAl–MMOs during calcination. Transmission electron microscopy (TEM) is used to investigate the morphology of the as-prepared hybrid nanomaterials, demonstrating that the introduction of GO substrate prevents the aggregation of LDHs. Magnetism characterization proves the ferromagnetic property of rGO/Ni/MMO hybrid. This magnetic hybrid nanomaterial exhibits excellent adsorption ability toward methyl orange (MO) in aqueous solutions. The kinetics of the adsorption process and the adsorption isotherm are investigated. The MO removal process is found to obey the Redlich–Peterson isotherm model, and its kinetics follows pseudo-second-order rate equation. In addition, the magnetic hybrid also exhibits good recycle ability for MO removal. This novel magnetic hybrid nanomaterial derived from GO/LDH hybrid demonstrates great potential in the applications of water treatment.

Carbon-supported Ni@NiO/Al2O3 integrated nanocomposite derived from layered double hydroxide precursor as cycling-stable anode materials for lithium-ion batteries

Transition metal oxides (MO) have been widely investigated as promising anode materials for lithium-ion batteries, but suffer from the problems of irreversible capacity loss and poor cycling stability resulting from intrinsic poor conductivity, large volume expansion/contraction during the discharge/charge processes. Despite two main types of effective efforts, i.e., preparing pre-designed nano/microstructures and hybridization with either active or conductive nanomaterials, these approaches have hitherto had difficulties in seeking deliberate nano/microstructural designs and guaranteeing homogeneous interface/chemical distributions of active MO material within the non-active matrix at the nanoscale. Herein, we report a preparation of carbon-supported Ni core @ NiO shell/Al2O3 (C-Ni@NiO/Al2O3) integrated nanocomposite derived from NiAl-layered double hydroxide (NiAl-LDH) single-resource precursor. The combined features of the C-Ni@NiO/Al2O3 nanocomposite involve the uniform dispersion of nanosized Ni@NiO, the conductive carbon support and Ni core, as well as the buffer role of the newly generated non-active Al2O3. Electrochemical evaluation shows that the C-Ni@NiO/Al2O3 nanocomposite maintains much enhanced electrochemical performances and good cycling stability in comparison with the pristine NiO. Results of TEM visualizations and electrochemical impedance spectra provide experimentally convincing rationales of the information of Al2O3 buffer and improved the conductivity underlying the enhanced performances. The route could extend to design and prepare various nanostructured metal oxides with uniform-dispersion components based on the versatility in varying the metal cations of LDH precursors.

Facile Fabrication of Highly‐Dispersed Nickel Nanoparticles with Largely Enhanced Electrocatalytic Activity

AbstractSupported nickel nanoparticles with high dispersion have been prepared by partial reduction of NiAl‐layered double hydroxide (NiAl‐LDH) precursors, which exhibit significant electrocatalytic behavior towards glucose. XRD and XPS results confirm that the nickel nanoparticles are successfully synthesized. TEM images reveal that the nickel nanoparticles are highly dispersed in the NiAl‐LDH matrix with a size of 6±0.3 nm. The resulting nanocomposite modified electrode displays significant electrocatalytic performance to glucose with a broad linear response range (8.0×10−5–2.0×10−3 M), low detection limit (3.6 µM), high sensitivity (339.2 µA/mM), selectivity and excellent reproducibility as well as repeatability.

Remarkable Stability of Graphene/Ni-Al Layered Double Hydroxide Hybrid Composites for Electrochemical Capacitor Electrodes

Graphene/Ni-Al layered double hydroxide (LDH) hybrid materials were synthesized by a hydrothermal reaction. Hexagonal Ni-Al LDH particles nucleated and grew on graphene sheets, thus preventing restacking of the graphene sheets and aggregation of the Ni-Al LDH nanoparticles upon drying. Electrode made from the graphene/Ni-Al LDH hybrid materials showed a substantial improvement in electrochemical capacitance relative to those made with pure Ni-Al LDH nanoparticles. In addition, the graphene/Ni-Al LDH hybrid composite materials showed remarkable stability after 4000 cycles with over 100% capacitance retention. These materials are thus very promising for use in electrochemical capacitor electrodes.