Cobalt Hydroxide Research Articles

Enhanced energy storage performance of surfactant assisted grown cobalt hydroxide

The use of surfactant during synthesis process is critical in determining morphology as well as properties of nanomaterials. In this line, this work reports surfactant assisted synthesis of Co(OH)2 nanomaterials and their characterizations for energy storage applications. Cobalt hydroxide nanoparticles are synthesized using chemical co-precipitation method at 80 °C using hexamethylenetetramine (HMTA) as surfactant. The sample prepared using surfactant and without surfactant are labelled as CHHMTA and CH, respectively. Scanning electron microscopy, X-ray diffraction, and FTIR techniques were used to evaluate the structural, morphological, and elemental features of the produced products. To understand the energy storage capabilities of the collected products, cyclic voltammetry (CV) and galvanometric charge/discharge (GCD) are used. In comparison to bare Co(OH)2 nanoparticles, HMTA coated particles exhibits improved charge storage characteristics. The specific capacitance for CH and CHHMTA was determined as 127 and 344 Fg−1 at 1 Ag−1 current density, respectively.

Structural engineering and electronic state tuning optimization of molybdenum-doped cobalt hydroxide nanosheet self-assembled hierarchical microtubules for efficient electrocatalytic oxygen evolution

Cobalt-based hydroxide are ideal candidates for the oxygen evolution reaction. Herein, we use molybdenum oxide nanorods as sacrificial templates to construct a self-supporting molybdenum-doped cobalt hydroxide nanosheet hierarchical microtubule structure based on a structural engineering strategy to improve the active area of the catalyst. X-ray-based spectroscopic tests revealed that Mo (VI) with tetrahedral coordination intercalated into the interlayer of cobalt hydroxide, promoting interlayer separation. At the same time, Mo is connected with Co through oxygen bonds, which promotes the transfer of Co charges to Mo and reduces the electron cloud density of Co ions. In 1 M KOH, optimized molybdenum-doped cobalt hydroxide nanosheet microtubules only needs an overpotential of 288 mV to drive a current density of 10 mA cm−2, which is significantly better than that of pure Co(OH)2 nanosheets and RuO2. Structural engineering and electronic state regulation can effectively improve the oxygen evolution activity of cobalt-based hydroxide, which provides a design idea for the development of efficient oxygen evolution catalysts.

Synthesis of amorphous Nickel-Cobalt hydroxides with high areal capacitance by one-step electrodeposition using polymeric additive

Nowadays, in order to gain high-performance supercapacitors with well-designed nanostructures, the preparation processes always possess sophisticated and time-consuming multiple steps. Here, we developed a facile and time-saving electrodeposition strategy to prepare amorphous nickel–cobalt hydroxides (NiCo-OHs) electrode with high areal specific capacitance by introducing polymers into the electrolyte. Polymer, with long chain, high solution viscosity and coordination effect, could induce a nondirectional growth of NiCo-OHs and form disordered structure with plentiful mesopores. After investigating the effects of polymers’ type and concentration on the growth process, amorphous NiCo-OHs with high mass loading were well anchored on the surface of carbon cloth. The amorphous phase and ample mesopores offer quantities of electrochemical active sites and high specific capacitance. The as-prepared amorphous NiCo-OHs electrode exhibits a highest areal capacitance of 9.0 F cm−2 at 2 mA cm−2, good rate capability with an areal capacitance of 4.5 F cm−2 at 50 mA cm−2 and long cyclic life (63% retention, 10,000 cycles). Moreover, the assembled asymmetric supercapacitor exhibits a maximum power density of 58.1 mW cm−2 at a 260 μWh cm−2 energy density. This work offers a new sight to build transition metal hydroxides-based high performance supercapacitor electrodes with a fast and facile preparation technology.

Morphology and Particle Size of a Synthesized NMC 811 Cathode Precursor with Mixed Hydroxide Precipitate and Nickel Sulfate as Nickel Sources and Comparison of Their Electrochemical Performances in an NMC 811 Lithium-Ion Battery

Cathode precursors of lithium-NMC 811 were synthesized by the coprecipitation method using two different nickel sources, namely mixed nickel–cobalt hydroxide precipitate (MHP) and nickel sulfate. The characteristics of the synthesized precursors were compared with the characteristics of the commercial NMC 811 cathode precursor obtained from the international market. The XRD analyses identified that the diffraction peaks of the three precursor materials were in close agreement to that of Li0.05Ni0.75Co0.1Mn0.1O2, with the figure(s) of merit (FoM) of 0.81, 0.88, and 0.9, respectively, for the synthesized precursor that used MHP as the source of nickel (SM-LNMCO-811), nickel sulfate as the source of nickel (SX-LNMCO-811), and the commercial precursor (K-NMC-811). The elemental analysis of the synthesized precursors revealed the Ni:Mn:Co mol ratios of 0.8:0.08:0.12 and 0.76:0.11:0.13 for SM-LNMCO-811 and SX-LNMCO-811, respectively. The SEM analysis revealed that SX-LNMCO-811 and K-NMC-811 showed a similar particle morphology with a spherical shape; the SM-LNMCO-811 exhibited an irregular particle morphology. The particle size analysis showed that SM-LNMCO-811 had the largest average particle size (285.2 μm) while K-NMC-811 and SX-LNMCO-811 samples had almost the same average values (i.e., 18.28 and 17.16 µm, respectively). The results of the charge–discharge measurement of the fabricated battery cylindrical cells with SM-LNMCO-811, SX-LNMCO-811, and K-NMC-811 as cathode materials showed the best discharge value of the SX-LNMCO-811 sample at 178.93 mAh/g with an initial efficiency of 94.32%, which is in line with the electrochemical impedance measurement results that showed the largest ion conductivity and lithium ion diffusion coefficient value of the SX-LNMCO-811 sample that utilized the synthesized nickel sulfate as the source of the nickel.

Synthesis of core-shell structured cobalt-based zeolitic imidazolate framework to expose active metal sites for catalytic conversion of acidic microalgal lipids to biodiesel

To improve metal atom utilization of Co-based zeolitic imidazolate framework (ZIF) in conversion of microalgal lipids to biodiesel, core-shell structured ZIF-67 with two-dimensional ultrathin layered cobalt hydroxide was synthesized to allow more Co atoms to be distributed on the crystal surface. The competition between deprotonated 2-methylimidazole and hydroxyl anions for coordination to Co2+ led to the formation of more crystal defects and thus a higher number of coordinatively unsaturated Co-Nx (x < 4) and pyridinic-N sites, which enhanced acid-base properties of catalyst. By density functional theory calculations, the adsorption energies of acetic acid on CoN1, CoN2, CoN3, and Co(OH)2 sites were − 1.370, −0.785, −0.585, and − 0.631 eV, respectively, while that on CoN4 site was −0.186 eV. Stronger interaction between acetic acid and active sites enhanced electron transfer to increase the electropositivity of carbonyl carbons, which promoted nucleophilic attack of methanol on carbonyl carbons in esterification reaction. The pyridinic-N sites and cobalt hydroxyl groups promoted the deprotonation of methanol to form methoxy anions to attack triglycerides in transesterification step. Thus, the optimum catalyst achieved efficiency of 96.1% in catalytic conversion of microalgal lipids to biodiesel, which was higher than that of conventional ZIF-67 (75.4%).

NiCoAl Ternary Metal Hydroxides Prepared by Fluorine Ion Assisted Electrodeposition Process for Long Lifespan Supercapacitor Electrodes

NiCo-based layered double hydroxides (NiCo-LDHs) have plenty of superior properties as electrode materials of supercapacitors, while the poor cycle performance heavily limits their application. An effective strategy to tackle this issue is to dope inactive Al that could stabilize the metallic layers to form ternary hydroxides. However, the desired ternary electrodes with appropriate content of Al3+ can hardly be prepared by conventional electrodeposition due to the great difference in solubility product constants (K sp) of corresponding hydroxides, where the non-electroactive Al(OH)3 (K sp = 1.3 × 10‒33) are preferentially deposited than the hydroxides of nickel and cobalt (K sp = 2.0 × 10‒15, 1.6 × 10‒15). Here, we propose a novel electrodeposition method assisted by F‒ to control Al3+ content in NiCoAl-LDHs. By adjusting the concentration of F‒ in the electrolyte, Al3+ content, as well as the morphology and electrochemical performance of the electrodes, could be manipulated. With the optimum ratio of F− to Al3+, the as-obtained electrode shows high specific capacitance along with a long lifespan (54.1%, 10000 cycles). An asymmetric supercapacitor is assembled using active carbon as the negative electrodes, which displays the maximal energy density of 35.5 Wh kg−1 at the power density of 477.3 W kg−1, with a long lifespan (75%, 10000 cycles).

Capacitor properties of 3D hierarchical structured electrodes prepared by one-step electrodeposition of cobalt nanowires on stainless steel fiber sheets

Redox or pseudo-capacitors using a cobalt (II) hydroxide (Co(OH)2) material have been regarded as promising options for renewable energy storage. In this study, we deposited cobalt nanowires with a Co(OH)2 surface layer on a newly developed stainless steel fiber sheet by a one-step electrodeposition method, without any templates, to form a 3D hierarchical structured electrode. This electrode achieved a specific capacitance of 880 F g−1 at a current density of 1.8 A g−1, which is much higher than the values attained with cobalt-nanowire-deposited stainless steel (200 F g−1) and indium-tin-oxide-coated glass (455 F g−1) plates. Moreover, the cobalt nanowire electrode coupled with a nickel-plated stainless steel fiber sheet exhibited increasing capacitance performance with repeated charge–discharge cycles, eventually developing approximately twice the capacity of the above electrode. These results demonstrate the potential of stainless steel fiber sheets for developing high-performance redox capacitors using a very facile method.

Strain-Induced Self-Rolling of Electrochemically Deposited Co(OH)2 Films into Organic–Inorganic Microscrolls

Strain-induced self-folding is a ubiquitous phenomenon in biology, but is rarely seen in brittle geological or synthetic inorganic materials. We here apply this concept for the preparation of three-dimensional free-standing microscrolls of cobalt hydroxide. Electrodeposition in the presence of structure-directing water-soluble polyelectrolytes interfering with solid precipitation is used to generate thin polymer/inorganic hybrid films, which undergo self-rolling upon drying. Mechanistically, we propose that heterogeneities with respect to the nanostructural motifs along the surface normal direction lead to substantial internal strain. A non-uniform response to the release of water then results in a bending motion of the two-dimensional Co(OH)2 layer accompanied by dewetting from the substrate. Pseudomorphic conversion into Co3O4 affords the possibility to generate hierarchically structured solids with inherent catalytic activity. Hence, we present an electrochemically controllable precipitation system, in which the biological concepts of organic matrix-directed mineralization and strain-induced self-rolling are combined and translated into a functional material.

Constructing a defect-rich hydroxide nanoenzyme sensor based on dielectric barrier discharge microplasma etching for sensitive detection of thiamine hydrochloride and hydrogen peroxide

In this work, a novel approach was designed to fabricate a defect-rich hydroxide nanoenzyme sensor based on transition metal cobalt derived from metal-organic framework (MOF). Facile preparation was realized by room-temperature reaction and chemical etching via dielectric barrier discharge (DBD) microplasma, which possesses great chemical reactivity to obtain defect-rich and ultrathin structures. The prepared cobalt hydroxide (Co(OH)2) emerges with superior catalytic activity for thiamine hydrochloride (TCL) and hydrogen peroxide (H2O2) assay. The linear ranges were 0.0006 mM to 2.75 mM for TCL detection and 0.001 mM to 5.5 mM for H2O2 detection with low limit of detections (LODs) of 14 nM and 93 nM, respectively. Meanwhile, the as-prepared sensor provides excellent long-term durability (>25 days), as well as high sensitivity (12730 μA mM−1cm−2 and 5199.3 μA mM−1 cm−2) for TCL and H2O2 assay. TCL in serum samples has been detected with satisfactory results by the proposed material, while the H2O2 in Hela cells was also successfully measured. The developed sensor provides several advantages including simplicity, high sensitivity, and efficient preparation.

Electrochemical Properties of the Composites Based on Multiwall Carbon Nanotubes Modified with Nanoparticles of Mixed Cobalt and Nickel Hydroxides

A simple and reproducible method of chemical deposition was used to modify carbon nanotubes cobalt and nickel hydroxides. Thus the composites containing 5 and 10 wt.% Co0.5Ni0.5(OH)2(the ratio of hydroxides1:1)were obtained based on the matrix of multiwall carbon nanotubes: non-functionalized (MWCNT) and functionalized (MWCNT-f). The physicochemical properties of the obtained nanocomposites were investigated with a focus on the characteristics that are relevant for use as the electrode materials of supercapacitors. Electrical capacity characteristics (specific electrical capacitance, internal resistance, etc.) of nanocomposites were determined using cyclic voltammetry and impedancemetry. The effect of matrix functionalization and filler content on the electrochemical characteristics of the composites was considered. It is established that the surface of carbon nanotubes allows the accumulation of the charge in the electrical double layer, in particular at high polarization rates. At low rates, the contribution from the pseudo-capacity component increases on the filler nanoparticles, on the surface of channels in nanotubes, and pore surface in hydroxide aggregates. An increase in the specific electrical capacitance of the composites by a factor of 1.5 to the capacitance of MWCNTs was achieved. The schemes of electrode processes in the nanocomposite are proposed, and the nature of redox peaks on voltammetric curves providing the occurrence of the pseudo-capacity component is revealed. Relying on the analysis of impedancemetry results, the equivalent series resistance and the charge transfer resistance are evaluated. An equivalent circuit of the cell with the working composite electrode is proposed, and its major parameters are calculated.

All-Printed High-Performance Flexible Supercapacitors Using Hierarchical Porous Nickel–Cobalt Hydroxide Inks

All-Printed High-Performance Flexible Supercapacitors Using Hierarchical Porous Nickel–Cobalt Hydroxide Inks

In-situ formation of co particles encapsulated by graphene layers

The process of encapsulating cobalt nanoparticles using a graphene layer is mainly direct pyrolysis. The encapsulation structure of hybrids prepared in this way improves the catalyst stability, which greatly reduces the leaching of non-metals and prevents metal nanoparticles from growing beyond a certain size. In this study, cobalt particles surrounded by graphene layers were formed by increasing the temperature in a transmission electron microscope, and they were analyzed using scanning transmission electron microscopy (STEM). Synthesized cobalt hydroxide nanosheets were used to obtain cobalt particles using an in-situ heating holder inside a TEM column. The cobalt nanoparticles are surrounded by layers of graphene, and the number of layers increases as the temperature increases. The interlayer spacing of the graphene layers was also investigated using atomic imaging. The success achieved in the encapsulation of metallic nanoparticles in graphene layers paves the way for the design of highly active and reusable heterogeneous catalysts for more challenging molecules.

Defect engineered 2D mesoporous Mo-Co-O nanosheets with crystalline-amorphous composite structure for efficient oxygen evolution

Two-dimensional (2D) mesoporous metal-oxide (hydroxide) nanomaterials with defects are promising towards the realization of efficient electrocatalysis. Herein, we report a facile and effective one-pot solvothermal route to synthesize mesoporous Mox-Co-O hybrid nanosheets (NSs) which is composed of crystalline Mo4O11 and amorphous cobalt hydroxide. Due to the corrosion of 1-octylamine at high temperatures, abundant mesoporous holes are created in situ over the Mox-Co-O hybrid NSs during the solvothermal process, which is beneficial to increasing the electrochemical surface area. The dimension of the Mox-Co-O NSs, size of mesoporous and the concentration of defects can be easily modulated by controlling the molar ratio of Mo/Co. Electrochemical measurements reveal that the 2D mesoporous Mox-Co-O NSs show an excellent activity for the oxygen evolution reaction with the highest catalytic activity of η10 = 276 mV at 10 mA cm−2 in 1 mol L−1 KOH. Enhanced adsorption of intermediates and abundant oxygen vacancies achieved by appropriate Mo doping are the two main factors that contribute to the excellent catalytic activity of Mo0.2-Co-O NSs. This work, with the construction of 2D metal-oxide (hydroxide) crystalline-amorphous nanomaterials possessing abundant holes, oxygen vacancies and enhanced adsorption of intermediates, provides important insight on the design of more efficient catalysts.

Optimal Geometrical Configuration of Metal Cations in Single Spinel CoxRh3-XO4 Nanoparticles to Promote Oxygen Evolution Reaction

Hydrogen (H2), which is widely considered as an ideal energy carrier to alternate traditional fossil fuels, can be produced by water electrolysis. Water electrolysis is a simple and promising technology due to its eco-friendly advantages. However, an anodic oxygen evolution reaction (OER) in water splitting devices provokes significant energy loss owing to its sluggish reaction kinetics. Therefore, designing advanced OER electrocatalysts is a very popular topic, among which spinel oxides have been widely studied for OER.Hence, in this work, we construct single spinel of various Co x Rh3-x O4 with 0.95 ≤ x ≤ 2.05 nanoparticles (NPs) as an outstanding OER electrocatalysts in alkaline condition. First, rhodium hydroxide and cobalt hydroxide were precipitated through acid-base reaction between dilute 0.1M NaOH and metal precursors solutions, then purified metal hydroxides was synthesized into Co x Rh3-x O4 NPs via thermal annealing process. The morphology of Co x Rh3-x O4 NPs was measured by field-emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM). The physical properties of Co x Rh3-x O4 NPs were analyzed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The electrocatalytic activity and stability of Co x Rh3-x O4 NPs are studied toward OER in Ar-saturated 1 M NaOH aqueous solution with rotating disk electrode (RDE) voltammetry. Electrochemical impedance spectroscopy (EIS) was carried out to further investigate the electrochemical behaviors of the Co x Rh3-x O4 NPs. Conclusively, we have identified which atomic ratio and configuration of Co and Rh cations can produce optimal synergistic effect toward OER. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT& Future Planning (NRF-2020R1A2B5B01001984).

Enhancing Electrochemical Performance of Co(OH)2 Anode Materials by Introducing Graphene for Next-Generation Li-ion Batteries

To satisfy the growing demand for high-performance batteries, diverse novel anode materials with high specific capacities have been developed to replace commercial graphite. Among them, cobalt hydroxides have received considerable attention as promising anode materials for lithium-ion batteries as they exhibit a high reversible capacity owing to the additional reaction of LiOH, followed by conversion reaction. In this study, we introduced graphene in the fabrication of Co(OH)2-based anode materials to further improve electrochemical performance. The resultant Co(OH)2/graphene composite exhibited a larger reversible capacity of ~1090 mAh g−1, compared with ~705 mAh g−1 for bare Co(OH)2. Synchrotron-based analyses were conducted to explore the beneficial effects of graphene on the composite material. The experimental results demonstrate that introducing graphene into Co(OH)2 facilitates both the conversion and reaction of the LiOH phase and provides additional lithium storage sites. In addition to insights into how the electrochemical performance of composite materials can be improved, this study also provides an effective strategy for designing composite materials.

Self-assembled cobalt hydroxide micro flowers from nanopetals: Structural, fractal analysis and molecular docking study

A 2D structure of cobalt hydroxide was synthesized by the chemical bath deposition method on the glass substrate. The structure of thin-film was studied using X-ray diffraction (XRD) study. UV–vis. spectroscopy, Fourier transforms infrared spectroscopy (FTIR) and Raman spectroscopies were used for structural conformation. The morphological study of thin film has been characterized by field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). Cobalt hydroxide thin film is deposited observed in the form of micro-flowers which are self-created by nanosheets like petals structure. The surface growth of thin film was studied with the help of AFM. Fractal analysis was carried based on AFM data. Fractal dimension and surface topographical properties have been calculated from statistical metric. Theoretically and experimentally observed bandgap is well agreed with each other. The possible formation mechanism of flower‐like cobalt hydroxide is discussed based on experimental results. Further molecular docking analysis of cobalt hydroxide with deoxyribonucleic acid (DNA) was predicated. The study shows that interaction between cobalt hydroxide-DNA is observed via the hydroxyl group.

Designing Multifunctional Cobalt Oxide Layers for Efficient and Stable Electrochemical Oxygen Evolution

AbstractDisordered and porous metal oxides are promising earth‐abundant and cost‐effective alternatives to noble‐metal electrocatalysts. Herein, nonsaturated oxidation in plasma‐enhanced atomic layer deposition is leveraged to tune the structural, mechanical, and optical properties of biphasic cobalt hydroxide films, thereby tailoring their catalytic activities and chemical stabilities. Short oxygen plasma exposure times and low plasma powers incompletely oxidize the cobaltocene precursor to Co(OH)2 and result in carbon impurity incorporation. These Co(OH)2 films are highly porous and catalytically active, but their electrochemical stability is impacted by poor substrate adhesion. In contrast, long exposure times and high powers completely oxidize the precursor to Co3O4, reduce the carbon incorporation, and improve the crystallinity. While the Co3O4 films have high electrochemical stability, they are characterized by low oxygen evolution reaction activity. To overcome these competing properties, the established relation between deposition parameters and functional film properties is applied to design bilayer films exhibiting simultaneously improved electrochemical performance and chemical stability. The bilayer films combine a highly active Co(OH)2 surface with a stable Co3O4 interface layer. These coatings exhibit minimal light absorption, thus making them suitable as protective catalytic layers on semiconductor light absorbers for application in photoelectrochemical devices.

Low-temperature aerobic oxidation of thiophenic sulfides over atomic Mo hosted by cobalt hydroxide sub-nanometer sheets

<h2>Summary</h2> Aerobic oxidation desulfurization (AODS) represents a carbon-neutral way to desulfurize petroleum distillates, yet it currently suffers from low efficiency and high temperature for the activation of triplet oxygen. Here, we report a sub-nanometer-thick cobalt hydroxide nanosheet that hosts an atomic molybdenum (Mo/Co(OH)₂) catalyst for the efficient aerobic oxidation of thiophenic sulfides. The catalyst achieves a turnover frequency of two orders of magnitude over that of state-of-the-art multi-metallic oxide catalysts and activates the reaction at 60°C. Coupling detailed characterizations with theoretical calculations, we formulate a descriptor—the work function of hosting materials for this reaction, which well explains the host identity dependence of the corresponding catalytic performance. We achieve the complete AODS of real diesel at 80°C under ambient pressure with negligible decay in consecutive reuses, highlighting the appealing industrial potential of our catalyst. Our findings provide fundamental and technological insights into implementing high-efficiency catalysts for the carbon-neutral AODS process.

Deposition of Pd on Co(OH)2 nanoplates in stabilizer-free aqueous phase for catalytic reduction of 4-nitrophenol

Palladium-supported cobalt hydroxide (Co(OH)2-Pd) nanoplates were fabricated in an aqueous solution and employed as a catalyst for the reduction of 4-nitrophenol. For the preparation of Co(OH)2-Pd, Pd nanoparticles were anchored on the Co(OH)2 nanoplates after the reduction of Na2PdCl4 by ascorbic acid in the absence of a stabilizer at room temperature. The observations under transmission and scanning electron microscopy reveal that Pd nanoparticles with a size of 2–5 nm are uniformly dispersed on the surface of the Co(OH)2 nanoplates. In catalytic test, the conversion of 4-nitrophenol to 4-aminophenol is completed within 6 min in the presence of Co(OH)2-Pd(1000) nanoplates with 2.18 at.% Pd, and the corresponding kinetic constant is 0.0089 s-1 in the first test. The catalyst retains relatively high activity after several cycles. The results demonstrate that the Co(OH)2-Pd(1000) nanoplates exhibit high catalytic activity toward the reduction of 4-nitrophenol in the presence of NaBH4.

Scale like Co(OH)2/CoOOH modified platinum catalytic gas diffusion electrode and its application in ammonia detection

Platinum (Pt) is sputtered on porous PTFE membrane as the basic electrode. Cobalt hydroxide catalyst is deposited on the porous platinum/PTFE electrode by an electrochemical assisted deposition method with ammonia gas employed as precipitant. SEM image of the catalyst shows an integration of scale like flake of about 0.5 micrometer in diameter. The XRD analysis suggested that the catalyst is a mixture of β-Co(OH)2 and CoOOH. The mixture is regard as the effective constituent in the ammonia electrode reaction according to the electrochemical analysis. The cyclic voltammogram indicate that at higher than 0.4V (v.s. saturated HgO/Hg electrode reference) the catalytic activity of the working electrode increased significantly. With the modified electrode as working electrode and a pure platinum electrode as assistant electrode, a four electrodes sensor is established to measure ammonia in air successfully.