Cobalt-based Compounds Research Articles

Strategic design of cobalt-based bimetallic compounds using NH4BF4 as a structure-directing agent for enhancing energy storage ability of battery supercapacitor hybrids

Modifying morphology and composition of metal-organic frameworks (MOFs) can enhance their electrical conductivities and redox states. Structure-directing agents (SDAs) play a key role in shaping surface properties of materials. Ammonium fluoride-based complexes are useful in designing MOF derivatives with excellent energy storage capabilities. Metal species involved also affect redox reactions, which are crucial for energy storage in battery-type electrodes. In this study, cobalt-based bimetallic compounds derived from ZIF-67 are synthesized using 2-methylimidazole and the SDA of NH4BF4. The secondary metal species contain Cu, Al, Zn and Mn, and resulting compositions include hydroxides and hydroxide nitrates. With the optimal 2-methylimidazole to NH4BF4 ratio, the best-performed cobalt-based compound is related to Ni (MB21-CoNi) which demonstrates the highest specific capacitance (CF) of 763.2 F/g at 20 mV/s, attributed to high theoretical capacities and sheets-assembled flower-like structures. A battery-supercapacitor hybrid (BSH) composed of carbon and MB21-CoNi electrodes achieves a maximum energy density of 17.2 Wh/kg at 650 W/kg. A CF retention of 94.9% and a Coulombic efficiency of 88.9% after 10,000 cycles are attained for this BSH. This work provides a blueprint for designing novel active materials with helps of 2-methylimidazole and NH4BF4, and for discussing significant parameters to achieve excellent energy storage ability.

Successful In Situ Growth of Conductive MOFs on 2D Cobalt-Based Compounds and Their Electrochemical Performance.

Conductive metal-organic frameworks (cMOFs), as a kind of porous material, are considered to be highly promising materials in the field of electrochemistry due to their excellent conductivity. However, due to the low specific capacitance of pure cMOFs, their application in supercapacitors is limited. By virtue of the high theoretical capacity and excellent chemical stability of Co-based compounds, in this work, cMOFs' M-HHTP (M = Ni, Co, NiCo, HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) are grown in situ on Co(OH)2, CoP, and Co3O4 nanosheets, resulting in a series of electroactive compounds as electrode materials used in supercapacitors. Among all of the compounds, Ni-HHTP@Co(OH)2 shows the most excellent energy storage performance and outstanding cyclic stability in the application of aqueous asymmetric supercapacitors.

DFT+U, TB-mBJ, and hybrid approaches: investigating electronic topology and magnetic properties in Sn-doped Co2TiGa

Cobalt-based Heusler compounds represent a new class of Heusler alloys which absorbed a lot of attention due to their performance in spintronics and magnetic devices. in this paper we have studied and analyzed the electronic structure and half-metallic ferromagnetic properties of Co2TiGa and Sn substituted at Ga site via the density functional theory (DFT) based first principle calculations with GGA-PBE, PBE+U, TB-MBJ exchange correlation potential and HSE06 approach. The band structure topology indicates that the parent ternary Heusler compound is ferromagnetic half-metallic with a half-metallic gap (band gap in the minority channel). The gap is increased according to the correction made on the exchange correlation potential. The half-metallic ferromagnetic behavior is confirmed by the total magnetizations which are very close to integrals Bohr magneton (1 μ B and 3μ B for Co2TiGa and Mn2TiGa0.5Sn0.5, respectively). The origin of half-metallic ferromagnetic is the p − d exchange and double-exchange interaction between the Co d-t2g states and neighboring Ti atom. The substitution effect on half-metallicity for Co2TiGa0.5 Sn0.5 was investigated in the tetragonal structure. The spontaneous magnetization obeyed the Slater-Pauling rule, indicating the Co2TiGa0.5 Sn0.5 is half-metal with 100% spin polarization.

Construction of Ag─Co(OH)2 Tandem Heterogeneous Electrocatalyst Induced Aldehyde Oxidation and the Co-Activation of Reactants for Biomass Effective and Multi-Selective Upgrading.

The electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF) provides a feasible way for utilization of biomass resources. However, how to regulate the selective synthesis of multiple value-added products is still a great challenge. The cobalt-based compound is a promising catalyst due to its direct and indirect oxidation properties, but its weak adsorption capacity restricts its further development. Herein, by constructing Ag─Co(OH)2 heterogeneous catalyst, the efficient and selective synthesis of 5-hydroxymethyl-2-furanoic acid (HMFCA) and 2,5-furan dicarboxylic acid (FDCA) at different potential ranges are realized. Based on various physical characterizations, electrochemical measurements, and density functional theory calculations, it is proved that the addition of Ag can effectively promote the oxidation of aldehyde group to a carboxyl group, and then generate HMFCA at low potential. Moreover, the introduction of Ag can activate cobalt-based compounds, thus strengthening the adsorption of organic molecules and OH- species, and promoting the formation of FDCA. This work achieves the selective synthesis of two value-added chemicals by one tandem catalyst and deeply analyzes the adsorption enhancement mechanism of the catalyst, which provides a powerful guidance for the development of efficient heterogeneous catalysts.

Hybrid Photoelectrocatalytic TiO2-Co3O4/Co(OH)2 Materials Prepared from Bio-Based Surfactants for Water Splitting.

The development of new photoanode materials for hydrogen production and water treatment is in full progress. In this context, hybrid TiO2-Co3O4/Co(OH)2 photoanodes prepared using the sol-gel method using biosurfactants are currently being developed by our group. The combination of TiO2 with a cobalt-based compound significantly enhances the visible absorption and electrochemical performance of thin films, which is mainly due to an increase in the specific surface area and a decrease in the charge transfer resistance on the surface of the thin films. The formation of these composites allows for a 30-fold increase in the current density when compared to cobalt-free materials, with the best TiO2-CoN0.5 sample achieving a current of 1.570 mA.cm-2 and a theoretical H2 production rate of 0.3 µmol.min-1.cm-2 under xenon illumination.

Engineering of binder-free cobalt carbonate hydroxide hydrate nanostructure for high-performance hybrid supercapacitors

Cobalt-based binder-free electrode materials, such as Co(CO3)0.5(OH)⋅0.11H2O nanowires (Co@Urea) and Co(OH)F microcrystals (Co@NH4F), were synthesized on a nickel foam substrate by a traditional hydrothermal method using urea and ammonium fluoride (NH4F) as the complexing reagents. The nanowire structure of the Co@Urea electrode promoted efficient charge transfer and high electrochemical active centers. The Co@Urea electrode exhibited a large specific capacity (693.0 C g−1 at 1 A g−1), better rate performance (50.8 % after 20 A g−1), and exceptional cyclic durability (84.0 % capacity retention after 10,000 cycles) compared to Co@NH4F electrode in a three-electrode configuration. A hybrid supercapacitor device was fabricated with Co@Urea as the cathode and activated charcoal as the anode, exhibiting high specific energy and specific power of 53.8 Wh kg−1 and 799.9 W kg−1, respectively. Furthermore, this hybrid device shows excellent long-term stability with 88.2 % capacity retention after 10,000 cycles at a current density of 40 A g−1. This study proposes developing binder-free cobalt-based compounds for electrochemical energy storage applications.

Interfacial and Electronic Modulation of W Bridging Heterostructure Between WS2 and Cobalt-Based Compounds for Efficient Overall Water Splitting.

The development of high performance electrocatalysts for effective hydrogen production is urgently needed. Herein, three hybrid catalysts formed by WS2 and Co-based metal-organic frameworks (MOFs) derivatives are constructed, in which the small amount of W in the MOFs derivatives acts as a bridge to provide the charge transfer channel and enhance the stability. In addition, the effects of the surface charge distribution on the catalytic performance are fully investigated. Due to the optimal interfacial electron coupling and rearrangement as well as its unique porous morphology, WS2 @W-CoPx exhibits superior bifunctional performance in alkaline media with low overpotentials in hydrogen evolution reaction (HER) (62mV at 10mA cm-2 ) and oxygen evolution reaction (OER) (278mV at 100mA cm-2 ). For overall water splitting (OWS), WS2 @W-CoPx only requires a cell voltage of 1.78V at 50mA cm-2 and maintains good stability within 72 h. Density functional theory calculations verify that the combination of W-CoPx with WS2 can effectively enhance the activity of OER and HER with weakened OH (or O) adsorption and enhanced H atom adsorption. This work provides a feasible idea for the design and practical application of WS2 or phosphide-based catalysts in OWS.

Carbon-Encapsulated Cobalt Phosphide Nanowires as Trifunctional Catalysts for Water Splitting Devices

Cobalt-based catalysts have been widely proved to be promising electrocatalysts for oxygen reduction (ORR), hydrogen evolution (HER), and oxygen evolution (OER). In this paper, to maximize the trifunctional reactivity of the catalyst, a series of one-dimensional carbon-coated cobalt-based compound nanowires with changed anions were reported, and their trifunctional activities were systematically investigated. Among the cobalt-based compounds with different anions, carbon-encapsulated cobalt phosphide nanowires (CoP/C NWs) show impressive trifunctional catalytic activity toward ORR, OER, and HER. Using CoP/C NWs as a trifunctional electrocatalyst, an integrated device of the two-electrode water splitting device powered by the zinc–air battery system was realized. The assembled zinc–air battery exhibits high power density (115 mW cm–2) and long-term cycle stability (over 350 h, 1050 cycles). This work provides an insight into the effects of anion substitution on electrocatalytic activity and provides a highly effective feasibility for the design of energy-related devices with high-activity and durable catalysts.

In Situ Construction of Heterostructured Co3O4/CoP Nanoflake Arrays on Carbon Cloth as Binder-Free Anode for High-Performance Lithium-Ion Batteries

Cobalt oxide (Co3O4) is regarded as the anode material for lithium-ion batteries (LIBs) with great research value owing to its environmental friendliness and exceptional theoretical capacity. However, the low intrinsic conductivity, poor electrochemical kinetics, and unsatisfactory cycling performance severely limit its practical applications in LIBs. The construction of a self-standing electrode with heterostructure by introducing a highly conductive cobalt-based compound is an effective strategy to solve the above issues. Herein, Co3O4/CoP nanoflake arrays (NFAs) with heterostructure are constructed skillfully directly grown on carbon cloth (CC) by in situ phosphorization as an anode for LIBs. Density functional theory simulation results demonstrate that the construction of heterostructure greatly increases the electronic conductivity and Li ion adsorption energy. The Co3O4/CoP NFAs/CC exhibited an extraordinary capacity (1490.7 mA h g-l at 0.1 A g-l) and excellent performance at high current density (769.1 mA h g-l at 2.0 A g-l), as well as remarkable cyclic stability (451.3 mA h g-l after 300 cycles with a 58.7% capacity retention rate). The reasonable construction of heterostructure can promote the interfacial ion transport, significantly enhance the adsorption energy of lithium ions, improve the conductivity of Co3O4 electrode material, promote the partial charge transfer throughout the charge and discharge cycles, and enhance the overall electrochemical performance of the material.

PIM-1 mixed matrix membranes incorporated with magnetic responsive cobalt-based ionic liquid for O2/N2 separation

Membrane technology for O2/N2 separation is a mature industrial unit. Membranes with excellent permeation-separation performance are still one of the critical requirements. The cobalt-based compounds have been well known for their good affinity for O2, which can facilitate O2 transfer and improve the O2/N2 selectivity in membranes. The cobalt-based compounds, moreover, have a magnetic responsive effect, which can lead to a further improvement in O2/N2 separation under a magnetic field. A class of PIM-1 mixed matrix membranes (MMMs), containing cobalt-based ionic liquid (CILs)@polyarylate (aromatic polyester) (PAR) (core-shell) composite nanospheres (CILs@PAR (c-s) CNPs), were prepared. Chemical compositions of CILs@PAR (core-shell) CNPs were determined by Fourier transform infrared spectroscopy (FTIR). Morphologies and structures of CILs@PAR (core-shell) CNPs were observed by transmission electron microscopy (TEM). Gas adsorption properties of CILs@PAR (core-shell) CNPs were tested. Thermal properties of the (CILs@PAR (c-s) CNPs)/PIM MMMs were investigated by simultaneous thermal analysis (TGA-DSC). Gas permeation-separation performances of the (CILs@PAR (c-s) CNPs)/PIM MMMs were also reported. Compared with the original PIM-1 membrane, the (CILs@PAR (c-s) CNPs)/PIM MMMs display higher O2/N2 selectivity because of cobalt-based ionic liquid as O2 carrier, coupled with a reduction in O2 permeability. With increasing the content of the CILs@PAR (c-s) CNPs, the O2/N2 selectivity increases, and the O2 permeability decreases. It is also found that, as a magnetic field on the MMMs, the O2/N2 selectivity further increases; and it increases more, as a higher content of CILs@PAR (c-s) CNPs. Therefore, the (CILs@PAR (c-s) CNPs)/PIM MMMs exhibit excellent O2/N2 selectivity of ∼5 coupled with good O2 permeability of ∼140 Barrer under a 180 mT magnetic field and show great potential for air separation.

Cobalt-based electroactive compounds: synthesis and their electrochemical and pseudocapacitance performance

Cobalt-based electroactive compounds: synthesis and their electrochemical and pseudocapacitance performance

A general rule for predicting the magnetic moment of Cobalt-based Heusler compounds using compressed sensing and density functional theory

We propose a general rule for estimating the magnetic moments of Co2(cobalt)-based Heusler alloys, especially when doped with late transition metals. We come up with a descriptor that can characterize both pure Co2YZ compounds and the doped ones with the chemical formula Co2Y1−xMxZ (M is the dopant) using online data for magnetic moments of Heusler alloys with Co2YZ structure and compressive sensing approach. The newly proposed descriptor not only depends on the number of valence electrons of the compound also it depends on the number of unoccupied d-electrons in the doping site. A comparison of the performance of the proposed descriptor and the Slater–Pauling rule is made. Unlike the Slater–Pauling rule, which is only effective for half-metallic Heusler compounds, our machine-learning approach is more generic since it applies to any Co2YZ Heusler compounds, regardless of whether they are half-metals or not. We use this new rule to estimate the magnetic moments of a few yet-to-be-discovered Heusler compounds and compare the results to density functional theory (DFT) based calculations. Finally, we use DFT and machine learning investigations to prove their stability.

A cobalt-based coordination compound with high capacity as the anode of lithium-ion battery and its stepwise reaction mechanism

Metal-coordination compounds are regarded as the most promising electrodes for lithium-ion batteries compared to inorganic anode materials because they are environmentally benign, rich in coordination, abundant in active sites, and low cost. In contrast, their possible molecular structures and reaction mechanisms are still mysteries. Here, using a microwave-assisted solvothermal process, we created the Co-1,3,5-trioxy-2,4,6-Triamino-benzo (Co-TB) coordination compound, which exhibits a flower-like shape of tiny flakes with a typical crystal feature. When applied as the anode of lithium-ion battery (LIB), Co-TB has shown a high reversible capacity of 1092 mAh g−1 at 1 A g−1 after 800 cycles and remarkable rate performances (497 mAh g−1 at 5 A g−1). This is significantly better than pure TB with similar functional groups but without coordination cations. Based on several electrochemical characterization techniques, ex-situ X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and in-situ X-ray diffraction techniques, a possible molecular structure, and stepwise reaction mechanism are postulated. All of them have demonstrated that the stepwise redox reactions between Co-TB and Li relied on these reactions of Li+ ions and Co2+/various multiple organic functional groups in Co-TB, including CO, CN, and CC of benzene rings. The synthesized method and characterization approaches can be extended to study other organic metal-coordination compounds.

Recent progress in application of cobalt-based compounds as anode materials for high-performance potassium-ion batteries

Recent progress in application of cobalt-based compounds as anode materials for high-performance potassium-ion batteries

Statistics on magnetic properties of Co compounds: A database-driven method for discovering Co-based ferromagnets

Accelerating material discovery remains one of the greatest challenges in material research. Here, the authors introduce a method for discovering materials with specific magnetic properties. They demonstrate their approach by identifying several materials with room-temperature ferromagnetism, or with easy-axis magnetic anisotropy. The identified compounds are then confirmed using band structure calculations, experimental synthesis, and characterization measurements. The method relies on statistics from a literature survey of the magnetic properties of thousands of cobalt-based compounds with different crystal structures. This manuscript presents the method, statistics, database, identification and confirmation of a few compounds.

Cobalt (III) complex exerts anti-cancer effects on T cell lymphoma through induction of cell cycle arrest and promotion of apoptosis.

Cobalt-based compounds are emerging as a non-platinum-based anti-cancer effective therapeutic agent. However, there is a limited study regarding the therapeutic efficacy of Cobalt-based drugs against Non-Hodgkin's Lymphoma (NHLs) such as T cell lymphoma. Therefore, in the present study we investigated the anti-tumor role of cobalt(III) complex [Co(ptsm)NH3(o-phen)]·CH3OH on Dalton's Lymphoma (DL) cells. Cytotoxicity of the cobalt complex was estimated by MTT assay. Analysis of mitochondrial membrane potential, cell cycle and Reactive oxygen species (ROS) generation, and Annexin V/PI staining was done by Flow cytometry, while AO/EtBr staining by fluorescence microscopy in cobalt complex treated DL cell. Expression of cell cycle and apoptosis regulatory protein was analyzed by Western blotting. In addition, in vivo study of the cobalt complex was evaluated in well-established DL bearing mice by monitoring physiological parameters and mean survival time. Our study showed that cobalt complex triggered apoptosis and induced cell cycle arrest in DL cells. Furthermore, this also decreased mitochondrial membrane potential and increased intracellular ROS generation in cancer cells. In addition, changed expression of cell cycle and apoptosis regulatory protein was found with enhanced activity of caspase-3 and 9 in the treated cells. Additionally, administration of cobalt complex showed a significant increase in the survivability of tumor-bearing host, which was accomplished by decreasing physiological parameters. Taken together, these data revealed anti-tumor potential of cobalt complex against DL cells through cell cycle arrest and mitochondrial-dependent apoptosis. Henceforth, cobalt-based drugs could be a new generation therapeutic drug to treat hematological malignancies.

Compositional and Morphological Investigations of Roman Glass from Cremation Deposits at Birdoswald Fort on Hadrian’s Wall, UK

Several different types of burial were identified during the excavation of the Roman military cemetery associated with the fort at Birdoswald, on Hadrian’s Wall (UK). Fragments of glass vessels and glass beads were recovered from many of the cremation deposits, as they were commonly used during cremation rituals, and many of these had been affected by heat. X-ray fluorescence spectroscopy and scanning electron microscopy were used to investigate the raw materials, colorants and opacifiers employed to produce the glass assemblage. Most of the large fragments are transparent with a blue-green colour, with a composition typical of recycled glass. The smaller fragments are from beads and are coloured and sometimes opaque. Colourants and opacifiers characteristic of Roman glass were added in this glass formulation, including cobalt-based compounds (blue glass), copper alloys (green glass), white calcium antimonate, and yellow lead antimonate. The multianalytical approach of this research has allowed for the distinguishing of the extreme depletion of sodium on the surface of the melted glass fragments due to the exposure to high temperatures during the cremation process, followed by surface weathering in a burial environment. Based on the chemical composition of the bulk of the samples, a model of high temperature viscosity of glass was applied in order to assess the cremation temperature in the pyre, providing relevant information about funerary rituals and cremation technology in Roman Britain.

A Cobalt-Based Coordination Compound with High Capacity as the Anode of Lithium-Ion Battery and its Stepwise Reaction Mechanism

A Cobalt-Based Coordination Compound with High Capacity as the Anode of Lithium-Ion Battery and its Stepwise Reaction Mechanism

Recent advances in cobalt-based catalysts for efficient electrochemical hydrogen evolution: a review.

Hydrogen (H2) is a new type of renewable energy that can meet people's growing energy needs and is environmentally friendly. In order to improve the industrial application prospects and electrochemical performance of hydrogen evolution catalysts, extensive research on transition metal materials has been carried out. Among the many catalytic materials, cobalt is an element with potential for the hydrogen evolution reaction (HER) due to its abundant reserves, low cost, and small energy barrier for H adsorption. This review classifies the latest research on cobalt-based catalysts according to the types of compound, including cobalt-based sulfides, phosphides, carbides, borides, oxides, etc., and summarizes the latest research progress of cobalt-based compound catalysts in acidic and alkaline media. Strategies to tune the properties of cobalt-based compound catalysts for high catalytic activity for HER are focused on, including structural engineering, defect engineering, and doping, etc. The advantages and limitations of each modified approach are reviewed. Not only that, but also the catalytic activity and advantages of the catalyst are evaluated by using density functional theory (DFT) calculation-related descriptors, activity evaluation parameters, etc. Finally, limitations and challenges of cobalt-based materials for HER are presented, as well as prospects for future research. This paper aims to understand the chemical and physical factors that affect cobalt-based catalysts, and to find directions for future research on cobalt-based catalysts.

Anions influence on the electrochemical performance of Co3X4 (X = O, Se) for supercapacitor: Experiments and theoretical calculations

In order to investigate the influence of the anions on the electrochemical performance of cobalt-based compounds, Co3O4 and Co3Se4 are studied and theoretically analyzed with the density functional theory (DFT). Avoiding of the traditional synthesis of the high-temperature annealing for the transition metal oxides, the cubic spinel phase Co3O4 on a nickel foam (NF) substrate with a simple two-step hydrothermal method and Co3Se4 with the core-branched structure by anions exchange method are prepared. The electrochemical measurements show that the capacitance and conductivity of Co3Se4 are significantly better than those of Co3O4, and Co3Se4 still maintain high capacity at high current density. Furthermore, the kinetics of electrode material Co3O4 and Co3Se4 are analyzed and compared. According to the calculation of the density of states, the results show the band gap of Co3O4 is 2.18 eV and the Fermi energy line of Co3Se4 enters into the conduction band, which means the conductivity of Co3Se4 is better than that of Co3O4. Additionally, three redox reactions during the charge and discharge process of Co3O4 are determined and the band gaps changes are also calculated.