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In this study, a facile synthesis of Cobalt oxyhydroxide (CoOOH) via the co-precipitation method at room temperature under vigorous stirring and compared the supercapacitor performance with that of manganese, aluminum, and iron oxyhydroxides. The prepared materials were confirmed by X-ray Diffraction (XRD), and Fourier Transform-Infrared Spectroscopy (FT-IR). The structural and surface area were investigated by Scanning Electron Microscopy (SEM), and Bruner-Emmert-Teller (BET) analyses. These materials were examined for their capacitance performance by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) in 1 M KOH aqueous electrolyte solution. Among these oxyhydroxides, CoOOH showed excellent capacitance than other oxyhydroxides. The CoOOH electrode exhibits a specific capacitance of 1096 F g− 1 at 25 mV s− 1 and 670 F g− 1 at 1 A g− 1 current density found from CV and GCD, respectively. Furthermore, the CoOOH electrode was investigated for cyclic stability and exhibited 91% capacitance retention after 5000 cycles. [ABSTRACT FROM AUTHOR]

Using green synthetic methods, a manganese-cobalt oxyhydroxide (MnCo-OOH) nanocomposite for electrocatalysis was prepared. Electrocatalysts were examined using powder X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FT-IR), and field-emission scanning electron microscopy (FESEM). In an alkaline medium, cyclic voltammetry and chronoamperometric analysis were applied to assess the electrocatalytic features of the MnCo-OOH nanocomposite. A strong correlation existed between MnCo-OOH's morphology, crystallinity, and electrochemical activity. Upon examining the electrochemical characteristics, the as-deposited MnCo-OOH catalyst demonstrated a significantly lower overpotential, achieving 75 mA·cm−2 OER current density at 370 mV, four times larger than 19.7 mA·cm−2 for CoOOH catalysts, signifying that the MnCo-OOH catalyst exhibits a higher electrocatalytic OER features. In addition, the MnCo-OOH nanocomposite demonstrated a high current density of 30 and 65 mA·cm−2 at 1.55 and 1.60 VRHE for 12 h in 1.0 M KOH aqueous electrolyte. As a result of this study, it was determined that the fabricated MnCo-OOH nanocomposite would be an appropriate electrocatalyst in water electrolysis. [ABSTRACT FROM AUTHOR]

Introduction: The possibility of resveratrol electrochemical determination, assisted by cobalt (III) oxyhydroxide and its composites with conducting polymers has been evaluated from the theoretical point of view. Methodology: The correspondent mathematical model has been developed and analyzed by means of the linear stability theory and bifurcation analysis. Results: The analysis of the model confirms that the cobalto oxyhydroxide may serve as an efficient electrode modifier for resveratrol electroanalytical determination. Conclusion: Depending on the analysis conditions, the electroanalytical process may be either diffusion- or kinetically controlled. On the other hand, the oscillatory behavior is also possible being even more probable than in the simplest cases, due to the impact of the chemical and electrochemical stages on DEL. [ABSTRACT FROM AUTHOR]

Traditional oxygen evolution reaction (OER) electrocatalysts such as IrO 2 and RuO 2 suffer from high costs and susceptibility to poisoning. Therefore, low-priced, efficient, and stable alternatives urgently need to be developed. In this work, Cu-doped Co metal-organic framework (MOF) was constructed by a one-step solvothermal method, exhibiting excellent OER activity in 1 M KOH with a low overpotential of 235 mV at 10 mA cm−2 and long-term electrochemical durability for 24 h. The mechanism study showed that the amorphous CoOOH formed by in-situ conversion of MOF structure in the electrochemical water oxidation environment was the real active species. The introduction of Cu significantly changed the morphology and surface electronic structure of Co-MOF-74, facilitated the adsorption of water molecules and accelerated the in-situ conversion of Co 3 Cu-MOF-74 to CoOOH, resulting in improved OER performance. Our work provides new insights into the design of efficient OER electrocatalysts and the mechanistic understanding of MOF-derived electrocatalysts. [Display omitted] • Cu-doping changed the morphology and surface electronic structure of Co-MOF-74. • Cu-doping facilitated the in-situ conversion of Co 3 Cu-MOF-74 to CoOOH. • The amorphous CoOOH acted as the true active center for OER. • It exhibites an overpotential of 235 mV at 10 mA cm−2 and remains stable for 24 h. [ABSTRACT FROM AUTHOR]

Introduction: For the first time, the possibility of anodic electroanalytical detection of ledol -- the main toxin in the nectars and honeys of some toxic flowers -- by the electrode, modified by the conductive polymer composite with cobalt oxyhydroxide is evaluated. Methodology: The electrooxidation of ledol will be realized via cyclopropane ring, followed by the oxidation of the secondary alcoholic group to ketone. Results and discussion: Analysis of the corresponding model using linear stability theory and bifurcation analysis confirms that cobalt oxyhydroxide in composite with conductive polymer can serve as an effective anode modifier for determining ledol in honeys, nectars and other sources natural. As ledol is poorly ionized, the oscillatory behavior will only be caused by the effects of the electrochemical stage in the double electric layer (DEL). Conclusions: Cobalt oxyhydroxide can be used for detection of ledol for safety verification of honeys. [ABSTRACT FROM AUTHOR]

Using green synthetic methods, a manganese-cobalt oxyhydroxide (MnCo-OOH) nanocomposite for electrocatalysis was prepared. Electrocatalysts were examined using powder X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FT-IR), and field-emission scanning electron microscopy (FESEM). In an alkaline medium, cyclic voltammetry and chronoamperometric analysis were applied to assess the electrocatalytic features of the MnCo-OOH nanocomposite. A strong correlation existed between MnCo-OOH’s morphology, crystallinity, and electrochemical activity. Upon examining the electrochemical characteristics, the as-deposited MnCo-OOH catalyst demonstrated a significantly lower overpotential, achieving 75 mA·cm−2 OER current density at 370 mV, four times larger than 19.7 mA·cm−2 for CoOOH catalysts, signifying that the MnCo-OOH catalyst exhibits a higher electrocatalytic OER features. In addition, the MnCo-OOH nanocomposite demonstrated a high current density of 30 and 65 mA·cm−2 at 1.55 and 1.60 VRHE for 12 h in 1.0 M KOH aqueous electrolyte. As a result of this study, it was determined that the fabricated MnCo-OOH nanocomposite would be an appropriate electrocatalyst in water electrolysis.

The role of β‐CoOOH crystallographic orientations in catalytic activity for the oxygen evolution reaction (OER) remains elusive. We combine correlative electron backscatter diffraction/scanning electrochemical cell microscopy with X‐ray photoelectron spectroscopy, transmission electron microscopy, and atom probe tomography to establish the structure–activity relationships of various faceted β‐CoOOH formed on a Co microelectrode under OER conditions. We reveal that ≈6 nm β‐CoOOH(011‾ ${\bar{1}}$ 0), grown on [1‾21‾ ${\bar{1}2\bar{1}}$ 0]‐oriented Co, exhibits higher OER activity than ≈3 nm β‐CoOOH(101‾ ${\bar{1}}$ 3) or ≈6 nm β‐CoOOH(0006) formed on [022‾1] ${\bar{2}1]}$ ‐ and [0001]‐oriented Co, respectively. This arises from higher amounts of incorporated hydroxyl ions and more easily reducible CoIII−O sites present in β‐CoOOH(011‾ ${\bar{1}}$ 0) than those in the latter two oxyhydroxide facets. Our correlative multimodal approach shows great promise in linking local activity with atomic‐scale details of structure, thickness and composition of active species, which opens opportunities to design pre‐catalysts with preferred defects that promote the formation of the most active OER species. [ABSTRACT FROM AUTHOR]

The oxygen evolution reaction (OER) is crucial in systems for sustainable production of hydrogen and other fuels. Catalytic OER materials often undergo potential‐induced redox transitions localized at metal sites. For volume‐active catalyst‐materials, these are necessarily coupled to charge‐compensating relocation of ions entering or leaving the material, which is insufficiently understood. The binding mode and mechanistic role of redox‐inert ions for a cobalt‐based oxyhydroxide material (CoCat) when operated at neutral pH in potassium‐phosphate (KPi) electrolyte are investigated by i) determination of K:Co and P:Co stoichiometries for various KPi‐concentrations and electrode potentials, ii) operando X‐ray spectroscopy at the potassium and cobalt K‐edges, and iii) novel time‐resolved X‐ray experiments facilitating comparison of K‐release and Co‐oxidation kinetics. Potassium likely binds non‐specifically within water layers interfacing Co‐oxyhydoxide fragments involving potassium–phosphate ion pairs. The potassium‐release kinetics are potential‐independent with a fast‐phase time‐constant of about 5 s and thus clearly slower than the potential‐induced Co oxidation of about 300 ms. It is concluded that the charge‐compensating ion flow is realized neither by potassium nor by phosphate ions, but by protons. The results reported here are likely relevant also for a broader class of volume‐active OER catalyst materials and for the amorphized near‐surface regions of microcrystalline materials. [ABSTRACT FROM AUTHOR]

Introduction: methaqualone is a calming drug, generally used to replace barbiturates, since it does not have side effects, which they cause, causing, however, their own - and quite significant ones. Its performance strongly depends on the applied dose, which is why the measurement of its concentration is current. Methodology: for the first time, the behavior of the system with the electroanalytical determination of methaqualone in basic medium on the electrode, modified by the composite of poly(5-amino-1,4-naphthoquinone) with cobalt oxyhydroxide, has been theoretically described. The corresponding mathematical model was developed and analyzed using linear stability theory and bifurcation analysis. Results: as the ionic function of the reaction product is opposed to the ionic function of the reactant, the oscillatory behavior will increase its probability of realization, given the sudden changes in the structure and ionic strength of the electrical double layer (ECD). Nevertheless, the poly(5-amino-1,4-naphthoquinone)/CoO(OH) composite is an efficient modifier for methaqualone detection, which can be shown with the model. Conclusion: the poly(5-amino-1,4-naphthoquinone)/CoO(OH) composite can be an effective modifier for the electrochemical detection of methaqualone in basic medium. [ABSTRACT FROM AUTHOR]

The oxygen evolution reaction (OER) is pivotal in sustainable fuel production. Neutral‐pH OER reduces operational risks and enables direct coupling to electrochemical CO2 reduction, but typically is hampered by low current densities. Here, the rate limitations in neutral‐pH OER are clarified. Using cobalt‐based catalyst films and phosphate ions as essential electrolyte bases, current–potential curves are recorded and simulated. Operando X‐ray spectroscopy shows the potential‐dependent structural changes independent of the electrolyte phosphate concentration. Operando Raman spectroscopy uncovers electrolyte acidification at a micrometer distance from the catalyst surface, limiting the Tafel slope regime to low current densities. The electrolyte proton transport is facilitated by diffusion of either phosphate ions (base pathway) or H3O+ ions (water pathway). The water pathway is not associated with an absolute current limit but is energetically inefficient due to the Tafel‐slope increase by 60 mV dec−1, shown by an uncomplicated mathematical model. The base pathway is a specific requirement in neutral‐pH OER and can support high current densities, but only with accelerated buffer‐base diffusion. Catalyst internal phosphate diffusion or other internal transport mechanisms do not limit the current densities. A proof‐of‐principle experiment shows that current densities exceeding 1 A cm−2 can also be achieved in neutral‐pH OER. [ABSTRACT FROM AUTHOR]

• The quasi‐amorphous R-(Ni)CoP 3 is constructed by ion exchange reconstruction. • The R-(Ni)CoP 3 has a strong synergy of cation (Ni) and anion (PO 4 3-). • The strong synergy visibly reduces the energy barrier. • The strong synergy optimizes the electronic state of active sites. • The resultant R-(Ni)CoP 3 exhibits superb OER activity and stability. Deep insight into the synergy between anion and cation aids in the maximization of catalytic activity and the rational exploitation of efficient oxygen-evolving catalysts. However, how to use ion exchange reconstruction to devise highly active and cost-efficient oxygen evolution reaction (OER) catalysts with anion and cation synergies for water electrolysis is rarely reported. Herein, the cobalt triphosphide (CoP 3) nanowires are elaborately devised as a component-flexible precatalyst for directing an anodic reconfiguration with Ni cation exchange to construct a highly active and quasi‐amorphous cobalt oxyhydroxide (CoOOH) catalyst integrated with cation (Ni) substitution and oxyanion (PO 4 3-) decoration (denoted by R-(Ni)CoP 3). Interestingly, the structural evolution and the Ni cation exchange processes are captured through various in/ex situ techniques. The resultant R-(Ni)CoP 3 nanowires display a splendid activity with low overpotentials of 406 and 420 mV to respectively deliver industrial grade current densities of 1000 and 1500 mA cm−2, and an outstanding stability over 300 h at a large current density of 500 mA cm−2, superior to most progressive cobalt-based OER materials and the benchmark IrO 2. The combination of theoretical calculations with experimental studies demonstrate that the synergy of cation (Ni) substitution and oxyanion (PO 4 3-) decoration can significantly modulate the electronic states of CoOOH and optimize the adsorption free energy of OER intermediates, thus immensely expediting the kinetics process and enhancing the charge transfer ability and the intrinsic OER activity. This research suggests ion-regulatory reconfiguration as a flexible and changeable strategy to construct various efficient and advanced catalysts for water electrolysis and beyond. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electrooxidation process to recover Co from chloride solution was proposed. • Increase of pH, Co concentration and temperature had a positive effect on oxidation. • Mixed Co 3 O 4 /Co(OH) 2 /CoOOH precipitate could be obtained by potentiostatic deposition. The green transition, despite recent advances in cobalt-free battery technologies, is still highly dependent on the availability of critical cobalt-based materials. Consequently, there has been increasing interest towards the development of new methods that maximize critical metals recovery from industrial hydrometallurgical solutions. In the current study, direct anodic oxidation of cobalt species from cobalt chloride solutions was studied as one alternative future strategy for cobalt recovery. Electrochemical methods were used (cyclic voltammetry, potentiostatic anodic deposition) and the effect of pH, temperature, and the concentration of cobalt and chloride ions on cobalt precipitation were investigated. The increase of pH and temperature was shown to stabilize the electrochemical oxidation of cobalt, while a decrease in cobalt concentration had a negative effect on precipitation. Scanning Electron Microscope, Atomic Force Microscopy and X-ray Photoelectron Spectroscopy were exploited to evaluate the morphology, structure, and composition of obtained anodic product. Calculated for potentiostatic anodic deposition (at highest studied potential of 1300 mV vs. Ag/AgCl) nucleation mechanism shows that the rate of nucleation for oxygen-cobalt species is faster than the subsequent growth rate of nuclei (instantaneous mechanism). XPS results confirmed that mixed Co 3 O 4 /Co(OH) 2 /CoOOH precipitate could be obtained by optimized anodic potentiostatic deposition in the range from 900 to 1150 mV and pH from 3 to 6 at 60 °C. [ABSTRACT FROM AUTHOR]

Merely all transition-metal-based materials reconstruct into similar oxyhydroxides during the electrocatalytic oxygen evolution reaction (OER), severely limiting the options for a tailored OER catalyst design. In such reconstructions, initial constituent p-block elements take a sacrificial role and leach into the electrolyte as oxyanions, thereby losing the ability to tune the catalyst's properties systematically. From a thermodynamic point of view, indium is expected to behave differently and should remain in the solid phase under alkaline OER conditions. However, the structural behavior of transition metal indium phases during the OER remains unexplored. Herein, are synthesized intermetallic cobalt indium (CoIn 3 ) nanoparticles and revealed by in situ X-ray absorption spectroscopy and scanning transmission microscopy that they undergo phase segregation to cobalt oxyhydroxide and indium hydroxide. The obtained cobalt oxyhydroxide outperforms a metallic-cobalt-derived one due to more accessible active sites. The observed phase segregation shows that indium behaves distinctively differently from most p-block elements and remains at the electrode surface, where it can form lasting interfaces with the active metal oxo phases., (© 2024 The Authors. Small published by Wiley‐VCH GmbH.)

Introduction:olanzapine is one of the most used antipsychotic drugs in the world. Although it is efficient, it may be toxic in excess. Therefore, in this work the possibility of olanzapine electrochemical determination over an electrode, modified by the cobalt (III) oxyhydroxide in pair with its dioxide in a composite with squaraine dye. Methods: the trivariant correspondent mathematical model includes two scenarios of the drug oxidation, possible for the case, including the indirect electropolymerization of the condensed benzodiazepine molecule, like also its oxidation by sulfur atom. This model has been developed and analyzed by means of stability theory and bifurcation analysis. Results and discussion: the analysis of the model has shown that the mechanism hybridity of the electroanalytical process, alongside with the formation and decomposition of ionic compounds during its realization, augments the possibility for the oscillatory behavior realization, relatively to the simplest and commonest case. Nevertheless, the oscillatory instability is realized in parameter values far beyond the detection limit. On the other hand, the stable steady-state is easy to obtain and maintain, indicating an efficient electroanalytical process, controlled by the analyte diffusion. Conclusions: the electroanalytical process is efficient. The cobalt compound is acting as an active substance, and the dye is the mediator. [ABSTRACT FROM AUTHOR]

Cobalt oxyhydroxide (CoOOH) has been turned out to be a high-efficiency catalyst for peroxymonosulfate (PMS) activation. In this study, CoOOH was loaded on bismuth oxide (Bi2O3) using a facile chemical precipitation process to improve its catalytic activity and stability. The result showed that the catalytic performance on the 2,4-dichlorophenol (2,4-DCP) degradation was significantly enhanced with only 11 wt% Bi2O3 loading. The degradation rate in the CoOOH@Bi2O3/PMS system (0.2011 min−1) was nearly 6.0 times higher than that in the CoOOH/PMS system (0.0337 min−1). Furthermore, CoOOH@Bi2O3 displayed better stability with less Co ions leaching (16.4% lower than CoOOH) in the PMS system. These phenomena were attributed to the Bi2O3 loading which significantly increased the conductivity and specific surface area of the CoOOH@Bi2O3 composite. Faster electron transfer facilitated the redox reaction of Co (III) / Co (II) and thus was more favorable for reactive oxygen species (ROS) generation. Meanwhile, larger specific surface area furnished more active sites for PMS activation. More importantly, there were both non-radical (1O2) and radicals (SO4−•, O2−•, and OH•) in the CoOOH@Bi2O3/PMS system and 1O2 was the dominant one. In general, this study provided a simple and practical strategy to enhance the catalytic activity and stability of cobalt oxyhydroxide in the PMS system. [ABSTRACT FROM AUTHOR]

Aim: In this work, the theoretical evaluation of the electroanalytical detection of antisyphilitic drug salvarsan is given for the first time. Cobalt oxyhydroxide in a composite with the squaraine dye is used as electrode modifier. Methodology: By means of the stability analysis the efficiency of the salvarsan determination is confirmed. The linearity of the dependence between the electrochemical parameter and drug concentration is easily obtained and maintained. Conclusion: The oscillatory and monotonic instabilities are realized in this system, being caused by the electrochemical stages' influences to the double electric layer (DEL). [ABSTRACT FROM AUTHOR]

Plate‐like cobalt oxyhydroxide (β‐CoOOH, heterogenite) single crystals, with a width of ~5 mm and a thickness of ~100 μm, were successfully synthesized using a simple method of heating a mixture of Co3O4 and NaOH in air at 650°C, and then soaking the resultant crystals in water at room temperature. The crystals were topotactically formed from sodium cobalt oxyhydrate (Na0.2(H3O)0.54CoO2·0.48H2O) by ion exchange between Na+ and H3O+, and by intercalation of water molecules in the as‐grown NaCoO2 crystals. The sodium cobalt oxyhydroxide crystals had spherical nanopores with diameters of ~5 nm. [ABSTRACT FROM AUTHOR]

Octahedral coordinated trivalent cobalt cations (CoOh3+) in metal oxyhydroxides are highly active catalytic sites for the oxygen evolution reaction (OER), a critical bottleneck for efficient water splitting; however, previous synthetic methods have limited control over these sites. Herein, a scalable electrodeposition method coupled with in situ oxidation to produce amorphous Co–Fe–W trimetallic oxyhydroxides enriched with CoOh3+ is developed. X‐ray absorption, in operando spectroscopic analysis, and computational studies reveal that 72% of the Co atoms are present in CoOh3+ sites. Fe and W synergistically affect the electronic structure of Co and provide a favorable coordination environment. The Co–Fe–W oxyhydroxide exhibits superior OER catalytic performance with an impressive turnover frequency of 1.96 s−1 at an overpotential of 300 mV, a low Tafel slope of 32 mV dec−1, and small activation energy of 53 kJ mol−1 in alkaline electrolyte. The catalyst directly deposited on Ni foams can serve as a robust OER electrode in two‐electrode water electrolyzers; they deliver a current density of 100 mA cm−2 at a small overpotential of 234 mV in alkaline electrolyte with excellent durability under 100 mA cm−2 over 120 h. These catalysts are excellent for practical water splitting applications. [ABSTRACT FROM AUTHOR]

CoOOH/Co(OH)2/CNT nanocomposite was rapidly prepared through one-step microwave method and characterised by XRD, SEM and XPS. Electrochemical performance was analysed via cyclic voltammetry, chronopotentiometry, cyclic charge-discharge and electrochemical impedance in a 6 M KOH electrolyte. The optimum capacitance of CoOOH/Co(OH)2/CNT can achieve 768 F g−1 at 2 A g−1 and could be further increased by 144% (1104 F g−1) after 700 cycles. An excellent cycling stability of 77.5% capacitance retention of the highest value (111% capacitance retention of the original value) was achieved after 3000 cycles. An asymmetric supercapacitor device on the basis of the CoOOH/Co(OH)2/CNT//AC showed the maximum energy density of 25 Wh kg−1 at a power density of 0.42 kW kg−1 and maintained 85% of the highest specific capacitance value after 20,000 cycles, thereby indicating its immense potential in energy storage devices. [ABSTRACT FROM AUTHOR]

Cobalt oxyhydroxide (CoOOH) has recently emerged as a promising electrode material for energy storage. Herein amorphous CoOOH and Mn-doped CoOOH films were prepared by anodic deposition, and the effect of Mn doping on the pseudocapacitive behaviors of CoOOH material was investigated. When tested in 1 M NaOH, the area specific capacitance (CA, F cm−2) of CoOOH material can be increased by doping 7.59 at. % Mn due to much increased surface area. When tested in 1 M NaCl, the CA of 7.59 at. % Mn-doped CoOOH film increased with the increasing CV cycle number during ~ 100–1000 CV cycle, and became more and more larger than that of CoOOH film during 434–1000 CV cycle, which was mainly attributed to the increasing surface area during CV test. These indicated that surface area was a vital factor to improve the pseudocapacitive behaviors of CoOOH material. Consequently, depositing a fine nanostructured CoOOH film onto a conductive, porous and high surface area substrate is considered as an effective method to further improve its pseudocapacitive behaviors. [ABSTRACT FROM AUTHOR]

A facile ratiometric fluorescence method for ascorbic acid (AA) detection was established by combining the fluorescence of MoS 2 quantum dots (QDs) with second-order scattering (SOS) of CoOOH. In MoS 2 QDs/CoOOH nanohybrid system, the fluorescence of MoS 2 QDs was quenched by CoOOH whereas the intensity of SOS was relatively close to the fluorescence due to the intrinsic high scattering ability of large size CoOOH nanoflakes. With the addition of AA, CoOOH nanoflakes were reduced to Co2+ accompanied the size decline and the disappearance of characteristic absorption in UV–vis spectrum, resulting in the fluorescence recovery and SOS fading. Thus, the ratiometric detection of AA was obtained through the opposite changes of fluorescence and SOS. Under optimized conditions, the detection limit of AA was 0.21 μmol L−1 with a linear range from 0.80 to 32.0 μmol L−1. Furthermore, the MoS 2 QDs/CoOOH nanohybrid system was applied to the detection of AA in human serum samples and vitamin C tablets with satisfactory results. Image 1 • The MoS 2 QDs/CoOOH nanoflakes based ratiometric fluorescence-scattered light system for AA detection was established. • Fluorescence increased and scattering declined after CoOOH were etched by AA. • The method was applied to the detection of AA in human serum and vitamin C tablets. [ABSTRACT FROM AUTHOR]

Nanostructuration is one of the most promising strategies to develop performant electrode materials for energy storage devices, such as hybrid supercapacitors. In this work, we studied the influence of precipitation medium and the use of a series of 1-alkyl-3-methylimidazolium bromide ionic liquids for the nanostructuration of β(III) cobalt oxyhydroxides. Then, the effect of the nanostructuration and the impact of the different ionic liquids used during synthesis were investigated in terms of energy storage performances. First, we demonstrated that forward precipitation, in a cobalt-rich medium, leads to smaller particles with higher specific surface areas (SSA) and an enhanced mesoporosity. Introduction of ionic liquids (ILs) in the precipitation medium further strongly increased the specific surface area and the mesoporosity to achieve well-nanostructured materials with a very high SSA of 265 m2/g and porosity of 0.43 cm3/g. Additionally, we showed that ILs used as surfactant and template also functionalize the nanomaterial surface, leading to a beneficial synergy between the highly ionic conductive IL and the cobalt oxyhydroxide, which lowers the resistance charge transfer and improves the specific capacity. The nature of the ionic liquid had an important influence on the final electrochemical properties and the best performances were reached with the ionic liquid containing the longest alkyl chain.

The persulfate/Fe2+ system has been proposed for the chemical oxidation for soil remediation, however, the homogeneous iron catalyst was hard to reuse which limited the further application. Cobalt oxyhydroxide (CoOOH) existed as a mineral in nature, which was environmentally friendly. Thus, in this study, CoOOH was selected as an efficient heterogeneous catalyst for peroxymonosulfate (PMS) activation to remediate oil contaminated soil by chemical oxidized reaction. 88.3% of oil at the initial concentration of 78–99 mg/kg can be removed within 24 h under the conditions of 1.0 g/L CoOOH and 0.1 M PMS at room temperature. The residual oil content was approximately 11.5 mg/kg which was lower than the standard of petroleum hydrocarbons for residential land (30 mg/kg), published by the Canadian Council of Ministers of the Environment (CCME). Specifically, the PMS/CoOOH system had a relatively high apparent reaction rate constant (0.3078 h−1), which was approximately twice that of the PS/Fe2+ system (0.1601 h−1). Furthermore, multiple radicals and reactive oxygen species (ROS), such as SO 4 −, O 2 − and 1O 2 , were involved in the oil removal oxidation reaction. Moreover, 73% total organic carbon (TOC) had been removed after the reaction. The findings of this study suggested that the oil-contaminated soil and CoOOH could both be recycled after remediation using the PMS/CoOOH system. In summary, the results indicated that CoOOH is a promising heterogeneous catalyst, and the PMS/CoOOH system could be considered as a feasible alternative to the PS/Fe2+ system for the remediation of oil-contaminated soil. Unlabelled Image • CoOOH was an efficient peroxymonosulfate activator. • SO 4 −, O 2 − and 1O 2 were involved in the PMS/CoOOH system. • CoOOH displayed good stability during the catalytic oxidation. • The PMS/CoOOH system was a potential alternative for soil remediation. [ABSTRACT FROM AUTHOR]

Highlights • CoOOH/phosphorus-doped hematite photoanodes were successfully synthesized. • The hybrid photoanodes displayed enhanced photoelectrochemical activity. • Phosphorus-dopind enhanced the conductivity, charge separation, and carrier migration. • CoOOH modification enhanced the OER kinetics and promoted surface charge separation. Abstract In order to improve the carrier mobility and restrain the charge recombination of hematite (α-Fe 2 O 3) for water oxidation performance, a P-doped and CoOOH modified α-Fe 2 O 3 electrode was synthesized using a hydrothermal method and photo-assisted electrodeposition process. The as-obtained CoOOH/P:Fe 2 O 3 photoelectrode presented a significant enhancement in the PEC current density, conversion efficiency and stability for water oxidation with simulated light irradiation. The photocurrent density of CoOOH/P:Fe 2 O 3 photoanode is up to 1.11 mA cm−2 at 1.23 V vs. RHE, which is 1.65, 2.02 and 2.78 times higher than those of P:Fe 2 O 3 , CoOOH/Fe 2 O 3 and pristine α-Fe 2 O 3 , respectively. The significantly improved PEC performance is attributed to the enhanced conductivity in α-Fe 2 O 3 electrode and improved interfacial charge transfer at the surface of α-Fe 2 O 3 , from the synergistic effects of P-doping and CoOOH modification. Our results proposed a new paradigm to construct hybrid photoanode materials with high activity, conversion efficiency and stability for PEC water oxidation. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A ratiometric fluorescent strategy for alkaline phosphatase (ALP) activity assay was proposed. • g-C3N4 and CoOOH nanoflakes were used to develop the sensing platform. • The assay system based on the g-C3N4/CoOOH hybrid responded to ALP sensitively. • Competitive redox reaction was responsible for the ratiometric fluorescence response. • The ratiometric method was applied to quantitative analysis of ALP activity in serum samples. Abstract The development of ratiometric fluorescent strategy is very significant and challenging in bioanalysis. Herein, graphitic carbon nitride (g-C 3 N 4) nanosheets and cobalt oxyhydroxide (CoOOH) nanoflakes are exploited for ratiometric fluorescence assay of alkaline phosphatase (ALP) activity. In the g-C 3 N 4 /CoOOH nanohybrid, g-C 3 N 4 nanosheets serve as a signal unit and the CoOOH nanoflakes function as a recognition element, and initially, the fluorescence of g-C 3 N 4 is quenched by the CoOOH nanoflakes. In the absence of target, the CoOOH nanoflakes of the nanohybrid system are able to oxidize o-phenylenediamine (OPD), and the resultant oxidation product (OxOPD) quenches the blue emission of g-C 3 N 4 and meanwhile emits orange fluorescence which acts as another signal element. However, an efficient redox reaction between ascorbic acid (AA) and CoOOH can cause decomposition of the CoOOH nanoflakes, and additionally, ALP can catalytically hydrolyze L-ascorbic acid-2-phosphate (AAP) to generate AA. Thus, in the presence of target, the CoOOH nanoflakes are destroyed by AA preferentially and the OPD is rarely oxidized to OxOPD, accompanied with strong blue emission of g-C 3 N 4 and weak orange fluorescence from OxOPD. Target-dependent dual-signal change made the ratiometric assay possible, and also AA-induced signal variation was investigated and attributed to the stronger reducing capacity of AA than OPD. The ratiometric sensing platform for ALP activity assay provides a new perspective for the applications of two-dimensional nanomaterials to develop novel and sensitive biosensors. [ABSTRACT FROM AUTHOR]

Abstract The engineering of electrocatalysts with high performance for methanol oxidation reaction (MOR) is of great urgency for the development of direct methanol fuel cells (DMFCs). Here, we designed and fabricated cobalt oxyhydroxide and carbon dots modified by platinum (Pt-CoOOH-CDs/C) hybrids with low content of Pt (13 wt%) as electrocatalyst, which exhibit high activity (856.3 mA·mg−1 Pt), stability (3 h) and better anti-poisoning ability for MOR. The Pt-CoOOH-CDs/C was synthesized by precipitate method followed with photochemical deposition. In the catalytic system, the Pt nanoparticles serve as the active center toward MOR, CoOOH-CDs use as the co-catalyst to oxidize CO-like poisonous species to CO 2 on neighbouring Pt sites, and the cost-efficient carbon black enhances the conductivity for the system. The cost-efficient Pt-CoOOH-CDs/C system with improved kinetics for anodic methanol oxidation has promising application in alkaline DMFCs. Graphical abstract Image 1 Cobalt oxyhydroxide and carbon dots modified by low content platinum (13 wt %) (Pt-CoOOH-CDs/C) as electrocatalyst for MOR. Highlights • Pt-CoOOH-CDs/C with low loading of Pt (13 wt%) as electrocatalyst was constructed for MOR. • Pt-CoOOH-CDs/C electrocatalyst shows high activity, stability and anti-poisoning property. • The Pt-CoOOH-CDs/C electrocatalysts have been characterized in detailed. [ABSTRACT FROM AUTHOR]

Highlights • This is the first report on the peroxidase-like activity of CoOOH nanoflakes for the detection of MTase activity. • The peroxidase-like activity of CoOOH nanoflakes can be improved by adsorbing ssDNA. • The colorimetric sensor with a low detection limit of 0.069 U/mL for M.SssI MTase activity detection. • The colorimetric sensor allows detection of M.SssI MTase in cell lysates of lung cancer cells (A549). Abstract A label-free colorimetric assay for MTase activity based on the nanozyme activity of cobalt oxyhydroxide (CoOOH) nanoflakes and the difference in affinity of the nanoflakes with single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) has been developed. In this strategy, ssDNA can enhance the nanozyme activity of CoOOH nanoflakes, which could be attributed to the electrostatic attraction and π-π stacking interaction between 3,3′,5,5′-tetramethylbenzidine (TMB) and ssDNA. The proposed method presents a wide linear range from 0.08 to 50 U/mL and a low detection limit (LOD) of 0.069 U/mL. Additionally, this colorimetric sensor also has been proved to detect MTase in the cell lysates of lung cancer cells (A549) with good recovery and reproducibility. Furthermore, the novel strategy can be applied for high-throughput evaluation and screening the inhibitors for M.SssI MTase by using representative anticancer drugs as model inhibitors, therefore, the colorimetric sensor can not only achieve the purpose of sensitively detecting the activity of MTase, but also has the potential in clinical diagnostics and drug discovery. [ABSTRACT FROM AUTHOR]

Highlights • Mesoporous CoO(OH) with high surface area was synthesized successfully via one-pot hydrothermal method. • The impedance of mesoporous CoO(OH) based humidity sensor changed nearly four orders of magnitude from 11%RH to 95%RH. • The humidity sensor is of fast response time 1.6 s. • The present sensor possessed good long term stability and cyclic stability. Abstract A humidity-responsive material of mesoporous CoO(OH) was synthesized successfully via one-pot hydrothermal method and the influence of CoO(OH) precursor concentration on humidity sensitive performance was studied. The structure and morphology of mesoprous CoO(OH) was characterized by X-ray Diffraction, Infrared spectra, Nitrogen adsorption and desorption, Scanning electron microscope, Transmission electron microscope and so on. The optimized mesoporous CoO(OH) based sensor showed the best linearity and high humidity sensitivity over a wide range of the humidity range (11–95% RH). Its impedance changed nearly four orders of magnitude and the response time was about 1.6 s. Humidity sensing mechanism was discussed in detail. [ABSTRACT FROM AUTHOR]

In the present work, CoOOH films are synthesized from the electrochemical oxidation of α-Co(OH)2 as precursor. The substrate influences on the material electrochemical properties are studied. The samples are structural and morphologically characterized using techniques of X-ray diffraction (XRD) and scanning electronic microscopy (SEM). The cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy techniques are used for the electrochemical characterization. The films deposited on steel substrate grew in the vertical hexagonal platelet form. Meanwhile, films on Ti plate presented morphology in agglomerated sphere form. After electrochemical oxidation, the film initial morphology is maintained. The films deposited on steel plate have a structure which favors charge storage showing a high specific capacity value (110.92 mA h g−1) and cyclic stability of 92% after 1000 cycles. Finally, the relaxation time constant value calculated was 5.6 s. This fact is making this material as a possible good candidate for application as electrode material or additive for other materials, in energy storage devices. [ABSTRACT FROM AUTHOR]

Abnormal concentration of hydrogen peroxide (H2O2) in blood plasma and cells may lead to several diseases. Thus, it is important to develop a selective and sensitive method to monitor H2O2. In the present work, a novel nonenzymatic H2O2-sensing platform based on cobalt oxyhydroxide (CoOOH)/reduced graphene oxide (RGO) nanocomposite was fabricated. CoOOH nanoflakes were firstly synthesized via soft chemistry routes and then assembled on the surface of RGO. A series of characterizations by X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy demonstrated that hexagonal CoOOH nanoflakes were well distributed on the surface of RGO. The nanocomposite exhibited excellent electrochemical performance for H2O2 detection. Two linear ranges of 6-200 μM and 200-1500 μM were obtained, and the detection limit was 0.01 μM (signal-to-noise ratio was 3). The good performance was attributed to more exposed catalytic active sites of CoOOH nanoflakes compared with zero-dimensional nanoparticles and outstanding conductivity of RGO as well as their synergistic effect. Moreover, the nanocomposite was used to detect H2O2 from human serum and HeLa cells with satisfactory results.ᅟ [ABSTRACT FROM AUTHOR]

The possibility of tramadol in vivo and in vitro electrochemical determination by means of the sensor, based on cobalt (III) oxyhydroxide and its composite with conducting polymers was evaluated from the mechanistic point of view. The mathematical model, correspondent to the suggested mechanism, was developed and analyzed by means of linear stability theory and bifurcation analysis. It was shown that CoO(OH) may be applied to the tramadol electrochemical determination in neutral and lightly alkaline pH values, correspondent to the more efficient oxidation of the compound. The possibility of oscillatory and monotonic instabilities has also been modified. [ABSTRACT FROM AUTHOR]

In this work, high-performance non-platinum group metal (non-PGM) electrocatalysts for oxygen reduction reaction (ORR) are synthesized from graphene oxide-supported cobalt oxyhydroxide nanoparticles via a one-pot gamma radiolysis method. Investigations are conducted into how cobalt precursor concentration and the amount of gamma radiation affect the electrocatalysts' ability to perform oxygen reduction reactions as well as their physicochemical characteristics. Results show that the electrocatalyst prepared with the 0.1 M cobalt precursor and gamma radiation dose of 25 kGy has an advantage over the other samples in displaying good oxygen reduction activity. The characterization results of the synthesized electrocatalyst obtained through field-emission scanning electron microscopy–energy dispersive spectroscopy and X-ray diffraction combined with Rietveld refinement confirm the presence of nanosized cobalt oxyhydroxide particles that are evenly distributed on the surface of graphene oxide. ORR results show that the electrocatalyst has an onset potential of 0.90 V (vs. the reversible hydrogen electrode or RHE), a half-wave potential of 0.75 V (vs. RHE), a low peroxide yield of 7.08%, and an electron transfer number of 3.86, indicating a four-electron transfer path-way in the ORR process. This work provides an alternative facile means to mass-produce competitive non-PGM ORR electrocatalysts for fuel cell applications. • Novel gamma radiolysis-synthesized GO-supported CoOOH. • Strategies to optimize ORR performance via gamma irradiation dosage and cobalt precursor concentration. • Facile and scalable technique to produce competitive non-platinum group metal (non-PGM) ORR electrocatalysts. [ABSTRACT FROM AUTHOR]

In this study, we report the in-situ hydrothermal synthesis of mesoporous nanosheets of cobalt oxyhydroxide (CoOOH) on nickel foam graphene (Ni-FG) substrate, obtained via atmospheric pressure chemical vapour deposition (AP-CVD). The produced composite were closely interlinked with Ni-FG, which enhances the synergistic effect between graphene and the metal hydroxide, CoOOH. It is motivating that the synthesized CoOOH on the Ni-FG substrate showed a homogenous coating of well-ordered intersected nanosheets with porous structure. The electrochemical properties of the material as electrode showed a maximum specific capacity of 199 mA h g −1 with a capacity retention of 98% after 1000 cycling in a three electrode measurements. [ABSTRACT FROM AUTHOR]

Divalent cation (Ni and Cu) doped and pure nano cobalt oxyhydroxide (CoOOH) are prepared by hydrothermal method using Morpho butterfly wing as template, whose gas sensing property is studied using various gases co-existing at early stages of fire as probe. The morphology, crystal structure and specific surface areas are studied to investigate the different doping effects on gas sensing property of biomorphic nano-CoOOH. The results indicated that the Ni- and Cu-doped biomorphic nano CoOOH sensors showed excellent sensitivity and good reproducibility towards carbon monoxide (CO) at low temperature. There was a good linear relationship between the frequency response and the testing concentration of CO gas. The results also showed that Ni- and Cu-doped biomorphic nano CoOOH sensor could be a good candidate for the real-time detection of early stages of fire. [ABSTRACT FROM AUTHOR]

Cobalt oxyhydroxide (CoOOH) nanorods were synthesized by fast hydrothermal process for supercapacitor electrodes. The structural and morphological studies revealed the formation of CoOOH with hexagonal rhomb-centered crystal structure and excellent rod like morphology of ∼5–10 nm diameter. The electrochemical characterization was performed for both half cell and symmetric full cell configuration using cyclic voltammetry, galvanostatic charge/discharge test and impedance spectroscopy in 3 M KOH aqueous electrolyte. The fabricated CoOOH electrodes showed maximum specific capacitance value of 198 F g −1 for a half cell and 94 F g −1 for a symmetric capacitor of 10 mg cm −2 active material per electrode and showed better energy and power densities. Moreover, the CoOOH electrode exhibits good capacitance retention (83%) after 5000 charge/discharge cycles. [ABSTRACT FROM AUTHOR]