Cobalt Aluminum Layered Double Hydroxide Research Articles

Cobalt aluminum layered double hydroxide as a superior electrochemical probe for the sensitive detection of anti-inflammatory agent mesalazine

An anti-inflammatory medication termed Mesalazine (MLZ) is generally recommended to prevent inflammatory bowel diseases (IBD). However, its prolonged usage has been associated with the risk of kidney failure. Therefore, there is a pressing need for the development of effective electrocatalysts to enable rapid detection of MLZ in the environment. Layered double hydroxides (LDHs) have emerged as promising candidates in the realm of sensor technology due to their adjustable interlayer spacing and large surface area. In this study, we utilized the hydrothermal method to synthesize cobalt aluminum-layered double hydroxide (CoAl-LDH) and evaluated its suitability as an active electrocatalyst for MLZ detection. The prepared CoAl-LDH was characterized for its physicochemical attributes employing XRD, FT-IR, XPS, FESEM, and TEM analysis. Subsequent examination of its electrochemical properties via voltammetric techniques revealed that the CoAl-LDH-modified glassy carbon electrode (GCE) exhibited enhanced electrocatalytic activity. Notably, the CoAl-LDH/GCE demonstrated a lower detection limit of 0.029 µM and a linear detection range spanning from 0.049 to 665.1 µM. Furthermore, the modified electrode demonstrated favorable attributes such as good repeatability, reproducibility, and stability. Real-time application of the modified electrode in the spiked water and urine samples yielded satisfactory recovery results, indicating its potential for practical use in environmental monitoring.

Facile synthesis of hollow spherical g-C3N4@LDH/NCQDs ternary nanostructure for multifunctional antibacterial and photodegradation activities

Heterojunction nanostructure construction and morphology engineering are considered to be effective approaches to improve photocatalytic performance. Herein, ternary hierarchical hollow structures consisting of cobalt-aluminum-layered double hydroxide (CoAl-LDH) nanoplates grown on hollow carbon nitride spheres (HCNS) and decorated with N-doped carbon quantum dots (NCQDs) were prepared using a templating method and a subsequent solvothermal process. The obtained HCNS@LDH/NCQD composites presented an improved performance in photocatalytic degradation of tetracycline and inactivation of E.coli compared with pure HCNS and LDH under visible light illumination. The enhanced photocatalytic activity of the designed photocatalyst could be attributed to the following reasons: (1) A special hollow structure provides more active sites and has multiple capabilities of light reflection by helping with a high specific surface area that improves the harvesting efficiency of solar light and (2) the strong synergistic effect among the constituents, which promotes separation and transfer of charge carriers and broadens the photo-response range.

Preparation and electrochemical properties of cobalt aluminum layered double hydroxide/carbon-based integrated composite electrode materials for supercapacitors

Supercapacitors have been widely developed in electrochemical energy storage field. Cobalt aluminum layered double hydroxide (CoAl-LDH) has attracted much attention because of its potential characteristics in energy storage. However, this materials also have the disadvantages of poor electrical conductivity and short cycle life. In order to solve this problem, a special structure of CoAl-LDH/carbon-based composite integrated electrode materials are constructed by one-step hydrothermal method, and the electrochemical properties of the materials are improved by changing the solvent composition. It is found that the electrochemical properties of CoAl-LDH/graphitic carbon nitrides (g-C3N4), CoAl-LDH/carbon nanotube (CNT) and CoAl-LDH/activated carbon (AC) composites are superior to those of pure CoAl-LDH, and CoAl-LDH/AC, as a new type of lamellar structure electrode material, has the best capacitance performance. Compared with CoAl-LDH/AC prepared with pure water as the solvent, adding 5 mL ethanol to the solvent can increase the specific capacitance of CoAl-LDH/AC composites from 1700 F g−1 (850 C g−1) to 1891 F g−1 (946 C g−1) at 1 A g−1 current density. At 7 A g−1 high current density, after 5000 cycles, the capacitance retention rate is increased from 40.6% to 66.3%. These electrochemical properties suggest that CoAl-LDH/AC composites can be one of the high performance electrodes for supercapacitors.Hydrothermal method; CoAl-LDH/carbon-based composite integrated electrode materials; Solvent composition; Specific capacitance; Electrochemical performance.

Room-temperature gas sensors based on three-dimensional Co3O4/Al2O3@Ti3C2Tx MXene nanocomposite for highly sensitive NOx detection

A self-sacrificial template and a hydrothermal method were utilized to successfully synthesize Ti3C2Tx MXene-supported Co3O4/Al2O3 assembled with nanosheets derived from layered double hydroxides. Within three-dimensional Co3O4/Al2O3@Ti3C2Tx MXene composite, Co3O4, as the active center component, was evenly distributed on Ti3C2Tx MXene nanosheets and Al2O3 as the addition. The 3D structure could expose more active center sites on the surface of Co3O4/Al2O3@Ti3C2Tx MXene and provide more gas diffusion channels, which were beneficial to the gas sensing performance. Comparing to CoAl-LDH@Ti3C2Tx MXene (CAM, and CoAl-LDH represents the cobalt-aluminum layered double hydroxide), Co3O4/Al2O3@Ti3C2Tx MXene (CAM-AC) exhibited an enhancing response (S = R0/Rg = 40.3) and a shorter response time of 1.3 s to 100 ppm NOx. Besides, CAM-AC also showed an ultra-low detection limit of 10 ppb and excellent repeatability, selectivity and long-term stability. The outstanding gas sensing performance could be attributed to the 3D structure, porous structure and the heterostructure between Co3O4/Al2O3 and Ti3C2Tx MXene. Therefore, the Co3O4/Al2O3@Ti3C2Tx MXene is an excellent NOx gas sensor candidate.

New insight into peroxymonosulfate activation by CoAl-LDH derived CoOOH: Oxygen vacancies rather than Co species redox pairs induced process

Cobalt oxyhydroxide (CoOOH) has received much attention as a environmental friendly mineral for activating peroxymonosulfate (PMS) for organics elimination in environment remediation. Yet, it suffered from unsatisfactory catalytic activity. This work presents a facile self-sacrifice method to synthesize highly effective hexagonal CoOOH microplate (B-CoOOH) from cobalt aluminum layered double hydroxide (CoAl-LDH). 40 μM of sulfamethoxazole (SMX) was 100% eliminated in 6 min in the presence of 0.1 g/L B-CoOOH and 0.3 mM PMS. B-CoOOH/PMS system achieved a high degradation (0.60 min−1), which was 12 times higher than CoOOH/PMS system (0.05 min−1). Besides, B-CoOOH also displayed satisfactory recyclability during the repeating tests, excellent physicochemical stability with low cobalt ions leaching (0.05 mg/L), and high mineralization efficiency (97.5% of TOC removal). Quenching tests signified the dominant role of 1O2 in SMX degradation. Mechanisms exploration revealed that the abundant oxygen vacancies (OV) on B-CoOOH acted as the electron donator in PMS activation process, which differed from previous report, in which Co species redox pairs was responsible for activating PMS and producing reactive oxygen species. In the initial stage of PMS activation, the dissolved oxygen in solution contributed to the generation of 1O2, while in the later stage PMS was regarded as the main precursor for the 1O2 formation. This study provides a convenient approach for the synthesis of cobalt oxyhydroxide with excellent catalytic activity, and sheds a new insight into the indispensable role of OV in heterogeneous catalysis.

Electrochemical hydrogen evolution reaction over Co/P doped carbon derived from triethyl phosphite-deposited 2D nanosheets of Co/Al layered double hydroxides

Hydrogen is widely considered an emissions-free alternative energy carrier for sustainable energy devices, such as fuel cells and nickel-metal hydride batteries. Recently, electrochemical hydrogen evolution reaction (HER) from water splitting has been attracted as an eco-friendly process for producing hydrogen. Herein, we report a Co/P-doped carbon material (Co/P/C) derived from cobalt-aluminum layered double hydroxide nanosheets (LDHs) for HER. The Co/P/C was synthesized using triethyl phosphite as phosphate and carbon sources by a one-step chemical vapor deposition (CVD) process. The regular arrangement of Co and Al atoms in the precursor LDHs allowed Co/P species to be highly dispersed under optimized CVD conditions. The carbon nanotube formed by the CVD process improved the catalytic activity of Co/P/C. The optimized Co/P/C exhibits a low overpotential of 240 mV at −10 mA cm −2 for HER, comparable to the commercial Pt/C catalyst. This work provides a new direction for developing transition-metal and hetero-atom co-doped carbon materials with high catalytic activity for HER. • Co/P-doped carbon materials are prepared by using layered double hydroxide. • The metal aggregation was prevented by the unique of the layered double hydroxide. • The deposition process using triethyl phosphite can introduce desire Co/P species. • The synthesized Co/P/C shows excellent activity for HER in an acidic media.

Waffle-Like Carbons Combined with Enriched Mesopores and Highly Heteroatom-Doped Derived from Sandwiched MOF/LDH/MOF for High-Rate Supercapacitor.

Supercapacitors (SCs) are promising for powering mobile devices, electric vehicles and smart power grids due to their fast charge/discharge rate, high power capability and robust cycle stability. Nitrogen-doped porous carbons are great alternatives because they provide pseudocapacitance without losing their power rate. Nanoporous carbon derived from metal organic frameworks (MOFs) is an ideal precursor for preparing heteroatom-doped carbons due to their abundant nitrogen contents and incredible specific surface areas. However, severe aggregations and the leakage of nitrogen can occur during harsh carbonization. In this study, we used CoAl-LDH (cobalt aluminum layered double hydroxide) as an in-situ growth substrate, allowing Co-based MOF to uniformly grow onto the CoAl-LDH to form a sandwiched MOF/LDH/MOF structure. After acid etching, we obtained waffle-like nanoporous carbons (WNPC). WNPC exhibited high nitrogen and oxygen retention (7.5 wt% and 9.1 wt%) and a broad mesopores distribution with specific surface areas of 594 m2g−1, which promoted a sieving effect. This renders a specific capacitance of 300.7 F·g−1 at 1 A·g−1 and the high retention (72%) of capacitance at 20 A·g−1, ensuring its use at high-rate supercapacitor electrodes. Finally, the WNPC symmetric supercapacitor reaches a superior specific energy of 27 W·h·kg−1 at a power of 500 W·kg−1, and a good cycle stability (85% capacitance retention after 10,000 cycles).

Synthesis and thermal behavior of Co/AlCe layered double hydroxide

Cerium-containing cobalt-aluminum layered double hydroxide was successfully synthesized via coprecipitation followed by hydrothermal treatment. Molar ratios of metal cations were predetermined as following: Co2+/(Al3+ + Ce3+) = 3 and Ce3+/(Al3+ + Ce3+) = 0.05. According to X-ray diffraction data, the obtained sample was well crystallized single-phase product with a hydrotalcite-like structure. The presence of cerium was confirmed by elemental analysis. The synthesized material consisted of hexagonal plate-like particles with an average size of 277 nm. The study of thermal behavior showed that the compound decomposed with the formation of oxides mixture, which is typical for layered double hydroxides. Its rehydration ability was expressed very weakly and the “memory effect” was observed only after heat treatment at a temperature not higher than 200 °C.

Boosting the capacitive property of nickel cobalt aluminum layered double hydroxide in neutral electrolyte

Layered double hydroxide (LDH) has shown great potential for energy storage due to their high theoretical specific capacitance, relatively low cost and eco-friendliness. LDH, however, always works in alkali aqueous electrolyte for supercapacitors, which brings serious environmental pollution. In this work, a reduced graphite oxide/Fe(CN)63−- nickel cobalt aluminum LDH (RGO/Fe(CN)63−-LDH) composite has been prepared via ion-exchange reaction using RGO/LDH as precursor. RGO/Fe(CN)63−-LDH electrode provides a specific capacitance of 221 F g−1 in a wide potential window of −1 ~ 0.8 V vs. SCE in Na2SO4 aqueous electrolyte, and which is much higher than that of LDH electrode (3.56 F g−1). Owing to the wide potential window of RGO/Fe(CN)63−-LDH electrode, a symmetrical solid supercapacitor device (RGO/Fe(CN)63−-LDH//RGO/Fe(CN)63−-LDH) with a high voltage of 2.0 V can deliver a high specific energy of 25.2 Wh kg−1 at a specific power of 250 W kg−1, and a capacitance retention of 75% after galvanostatic charging/discharging at 5 A g−1 for 5000 times. This work supplies enlightenment for boosting the capacitive performance of LDHs in neutral electrolyte.

Growth of cobalt-aluminum layered double hydroxide nanosheets on graphene oxide towards high performance supercapacitors: The important role of layer structure

Layered CoAl LDH (Cobalt-Aluminum layered double hydroxide) has been identified as a promising active electrode material for pseudocapacitors. However, some issues of CoAl LDH, such as poor conductivity and aggregation, limited its large-scale practical application. In addition, vague understanding of the role of the CoAl LDH's layer structure in pseudocapacitance process might mislead the research community on material modification. Herein, growth of CoAl LDH nanosheets with and without graphene oxide (GO) is prepared by hydrothermal method. To evaluate the role of layer structure in pseudocapacitance process, the CoOOH nanosheets with and without GO are also prepared by combining hydrothermal method with alkali etching treatment. As pseudocapacitance electrode material, the GO@CoAl LDH exhibits surpassing specific capacitance of 1725.71 F g−1 at a current density of 1 A g−1 and optimal 87.73% capacitance retention at 7 A g−1 which are much higher than the other as-obtained materials. The study provides not only a better perspective to explore the importance of LDH layered structure during the electrochemical process, but also a direction to subsequent design of the novel Co-based or LDH-based electrode materials.

In situ synthesis of hierarchical cobalt-aluminum layered double hydroxide on boehmite surface for efficient removal of arsenate from aqueous solutions: Effects of solution chemistry factors and sorption mechanism

A facile route is reported for the in situ formation of three-dimensionally structured hierarchical Co-Al layered double hydroxide (CoAl-LDH) crystals on a boehmite surface (CoAl-LDH@boehmite) via the dissolution of boehmite followed by the coprecipitation of Co and Al ions on the boehmite surface. The physicochemical properties of the as-prepared materials were characterized and tested for evaluating their sorption affinity toward arsenate (As(V)) in an aqueous solution. The characterization results confirmed that the plate-like CoAl-LDH nanocrystals were densely and uniformly formed on the boehmite surface with a three-dimensional hierarchical structure. Batch experiments were conducted systematically to evaluate the effects of the sorbent dosage, initial pH, competitive anions, and temperature on the sorption behavior of CoAl-LDH@boehmite. The sorption kinetics and isotherms studies indicated that the As(V) sorption processes could be well described by the pseudo-second-order and Sips isotherm models, respectively. The sorption mechanisms were confirmed by various solid phase analyses, including X-ray diffraction, Fourier transform infrared, transmission electron microscopy, X-ray photoelectron spectroscopy, and extended X-ray absorption fine structure. These findings suggest that the intercalation of As(V) into the interlayer region via anion exchange and bidentate-binuclear inner-sphere surface complexation due to ligand exchange were responsible for the removal of As(V) by CoAl-LDH@boehmite.

Core-Shell Structured Cobalt Sulfide/Cobalt Aluminum Hydroxide Nanosheet Arrays for Pseudocapacitor Application.

The direct synthesis of nanostructured electrode materials on three-dimensional substrates is important for their practical application in electrochemical cells without requiring the use of organic additives or binders. In this study, we present a simple two-step process to synthesize a stable core-shell structured cobalt sulfide/cobalt aluminum hydroxide nanosheet (LDH-S) for pseudocapacitor electrode application. The cobalt aluminum layered double hydroxide (CoAl-LDH) nanoplates were synthesized in basic aqueous solution with a kinetically-controlled thickness. Owing to the facile diffusion of electrolytes through the nanoplates, thin CoAl-LDH nanoplates have higher specific capacitance values than thick nanoplates. The as-grown CoAl-LDH nanoplates were transformed into core-shell structured LDH-S nanosheets by a surface modification process in Na2 S aqueous solution. The chemically robust cobalt sulfide (CoS) shell increased the electrochemical stability compared to the sulfide-free CoAl-LDH electrodes. The LDH-S electrodes exhibited high electrochemical performance in terms of specific capacitance and rate capability with a galvanostatic discharge of 1503 F g-1 at a current density of 2 A g-1 and a specific capacitance of 91 % at 50 A g-1 .

Surface Area- and Structure-Dependent Effects of LDH for Highly Efficient Dye Removal

The surface area and structure of adsorbents are crucially important to its adsorption capacity. Herein, we focused on the correlation between the structures of 2D/3D materials and its adsorption properties by taking three kinds of cobalt–aluminum layered double hydroxide (CoAl-LDH) as adsorbents, including a 3D hierarchical flower-like hollow/solid sphere (FH/FS-CoAl) and 2D plate (P-CoAl). As expected, FH-CoAl showed the highest adsorption capacity (∼2189.23 mg/g) for methyl orange (MO), benefiting from the highly accessible surface areas and more active sites of unique hollow structural characteristics inherited from the hierarchical flower-like hollow structures. Interestingly, compared with FS/FH-CoAl, P-CoAl exhibited the highest adsorption capacity enhancement times after being normalized with surface area, but displayed an inferior maximum adsorption capacity. The reasons could be mainly ascribed to (1) P-CoAl with 2D plate structures possessed more fully exposed active sites than FH-CoAl and (2) ...

Fabrication of cobalt aluminum-layered double hydroxide nanosheets/carbon spheres composite as novel electrode material for supercapacitors

Abstract A new design route was presented to fabricate cobalt aluminum-layered double hydroxide(CoAl-LDH) thin layers which grow on carbon spheres(CSs) through a growth method. The CoAl-LDH thin layers consist of nanoflakes with a thickness of 20 nm. The galvanostatic charge–discharge test of the CoAl-LDH/CSs composite shows a great specific capacitance of 1198 F/g at 1 A/g (based on the mass of the CoAl-LDH/CSs composite) in 6 mol/L KOH solution, and the composite displays an impressive specific capacitance of 920 F/g even at a high current density of 10 A/g. Moreover, the composite remains a specific capacitance of 928 F/g after 1000 cycles at 2 A/g, and the specific capacitance retention is 84%, indicating that the composite has high specific capacitance, excellent rate capability and good cycling stability in comparison to pristine CoAl-LDH.

Preparation of CoAl layered double hydroxide nanoflake arrays and their high supercapacitance performance

Porous cobalt aluminum layered double hydroxide (CoAl-LDH) nanoflake arrays on nickel foam were synthesized by a facile hydrothermal synthesis method. The obtained CoAl-LDH film consisted of interconnected nanoflakes with the thicknesses of ~20nm and showed an extended net-like structure. The electrochemical performance of CoAl-LDH nanoflake arrays was tested by cyclic voltammetry and galvanostatic charge/discharge test. The porous CoAl-LDH nanoflake arrays showed good pseudocapacitive performances with high capacitance and good cycle stability. At room temperature, the porous CoAl-LDH nanoflake arrays exhibited a high specific capacitance of 930F/g at 2A/g and their specific capacitances were still up to 669F/g at 16A/g. A good cycling stability was also observed for the CoAl-LDH nanoflake arrays with a capacitance retention of 88.9% of the highest value after 2000cycles at 2A/g.