Cobalt Oxide Materials Research Articles

Phase-Selective Synthesis of Cobalt Oxide Materials Via Electrochemical Chloride-Mediated Oxidation

The rapid growth of the global economy has led to an elevating human demand for energy and chemicals, which is heavily reliant on the utilization and conversion of fossil fuels. Electrochemical conversion is arising as a viable strategy for synthesizing a various high-value chemicals thanks to the mild operation conditions, adjustable selectivity, and potential for scalability in industrial settings. Chlor-alkali process can be utilized for removing microorganisms, disinfecting water, and so on. Furthermore, in an electrochemical system, the oxidation half reaction of the chloride oxidation can be coupled with a value-added reduction in half reaction, such as H2 evolution, N2 reduction, CO2 reduction, and organic reduction.In this study, β-CoOOH and γ-CoOOH, distinct cobalt oxyhydroxides, were synthesized via a chloride-mediated electrochemical oxidation process. This method employed heterogeneous reactions, where the oxidation of metal hydroxides was facilitated by electrochemically generated oxidants—active chlorine species—directly formed on the electrode surface through the oxidation of chloride ions. Characterization through X-ray diffraction (XRD) confirmed the synthesis of these two distinct metal oxide phases, elucidating their phase purity and crystal structures. Furthermore, the adjustable surface morphology and composition of intercalated ions were observed under varying electrosynthetic conditions. This synthetic strategy can be extended to the fabrication of other metal oxides, including manganese oxides. The resulting cobalt oxyhydroxide and manganese dioxide materials display versatile properties suitable for a wide range of applications in energy, environmental, and biotechnological fields.

Study on Cycle Performance and Rate Performance of Lithium Cobalt Oxide

Lithium cobalt oxide (LiCoO2 ) cathode material, with its high energy density and operating voltage, is currently a mainstream material for lithium-ion battery cathodes.   However,  the  crystal  structure  collapse  and  lattice  oxygen  evolution under high-voltage conditions lead to rapid capacity decay, severely limiting its practical applications.   This paper  analyzes the main factors affecting the cycle performance and rate performance of lithium cobalt oxide, considering the physic- ochemical properties of the particles, including elemental content and particle size, and provides a mathematical model linking these properties to electrochemical per- formance.  The study offers insights for the practical production of high-voltage lithium cobalt oxide materials. At the beginning, we embarked on investigating the correlation between the physicochemical attributes (encompassing elemental composition and particle size) of lithium cobalt oxide and its cycle performance. An Ordinary Least Squares (OLS) linear regression model was formulated, yielding a robust fit with an R-Squared value of 0.94. This model was subsequently optimized through the application of an XGBoost algorithm, achieving an R-Squared value nearing unity, signifying a remarkable enhancement in model accuracy. Visual analysis of the results pinpointed the primary determinants of cycle performance, arranged in descending order of significance: 'Cycle Index,' Mg content, particle size distribution (D10), Zn, and Al. Then, our attention shifted to examining the link between the aforementioned physicochemical characteristics and the rate performance of lithium cobalt oxide. The Jarque-Bera and Shapiro-Wilk tests confirmed the normality of the data, fulfilling the prerequisites for hypothesis testing. An OLS linear regression model was developed, demonstrating a strong goodness-of-fit with an R-Squared value exceeding 0.8. This model was further honed with an XGBoost model, which achieved an R-Squared score approaching 1, indicating a substantial refinement in model precision. The visualization of model outcomes illuminated the key factors influencing rate performance, ranked in descending order of importance: particle size distribution (D50), Al, Mn, Zn, Mg, Ni, and Fe. Lastly, we devised an optimal strategy that encompasses the incorporation of strategic doping elements, the utilization of high-temperature sol-gel methods to bolster cycle performance, and coating modifications aimed at enhancing rate performance. This holistic approach fosters the structural stability of lithium cobalt oxide crystals, fortifying their high-potential cycle capabilities, and concurrently elevating their rate performance.

A Proton-Conductive Co(II)-Polyoxometalate Acts as a Precatalyst for Efficient Electrocatalytic Water Oxidation.

A cobalt(II)-containing polyoxometalate, [H3O]5[{Co(H2O)4}3{Na(H2O)4}W12O42]·3H2O (Co-POM), has been isolated in a one-step facile aqueous synthesis and characterized unambiguously using single-crystal X-ray crystallography along with routine spectral analysis. The paratungstate cluster anion [W12O42]12- coordinates with {CoII(H2O)4}2+ and {Na(H2O)4}+ complex cations resulting in the formation of the water-insoluble Co-POM compound having three-dimensional (3-D) extended structure. Motivated by the protonated water molecules existing as the counter cations in Co-POM, herein, we demonstrate the detailed proton conductivity studies of the Co-POM, reaching a value of 1.04 × 10-2 S cm-1 at 80 °C and 98% relative humidity (RH). The temperature- and humidity-dependent proton conductivity in Co-POM is governed by Grotthus mechanism with Ea = 0.25 eV. In addition, we examined the electrochemical behavior of Co-POM, in an alkaline borate buffer where it is found to be electrochemically unstable and acts as a precatalyst (and not a true catalyst) for oxygen evolution reaction (OER). We also discuss the "post-mortem" analysis of the postelectrolysis sample to identify the active species which turns out to be a cobalt oxide material (Co3O4) incorporating small amounts of tungsten. Thus, in the present electrocatalysis work, the Co-POM molecule transforms into an efficient water oxidation catalyst (WOC).

Advanced thermoelectric performance of a textured ceramic composite: Encapsulation of NaxCoO2 into a triple‐phase matrix

AbstractSodium cobaltite (NaxCoO2) is one of the most renowned and thermoelectrically promising p‐type cobalt oxide materials, showing exceptional performance in this domain. Nonetheless, its thermal instability in air renders it unsuitable for high‐temperature applications such as energy harvesting from industrial waste heat. To utilize the beneficial properties of NaxCoO2, microscale NaxCoO2 template particles of significantly larger size were effectively embedded within a thermally stable Ca3Co4−yO9+δ–NaxCoO2–Bi2Ca2Co2O9 triple‐phase matrix. This approach additionally aimed to enhance the texture and boost the thermoelectric performance of the ceramic composite. Highly textured p‐type ceramic composites were fabricated via uniaxial cold‐pressing and pressureless sintering in air. The unique hexagonal NaxCoO2 template particles, produced through molten‐flux synthesis, allowed precise control over their shape and dimensions, while the matrix was synthesized via a sol–gel synthesis. The integrated NaxCoO2 particles of the textured composite exhibited increased thermal stability, showing no sign of decomposition at 1173 K in air, whereas the sole template particles decomposed at 1073 K during sintering. A 20 wt% template particle content in the textured composites resulted in a remarkably high and nearly temperature‐independent power factor of 8.8 µW cm−1 K2, corresponding to an improvement of 13% compared to that of the pure matrix material.

Investigation of monovalent Li and divalent Ni doping in Co3O4 for enhanced hydroelectric cell performance

The hydroelectric cell (HEC) produces green power at room temperature using non-photocatalytic water splitting. To achieve this goal, pure Ni (Nickel) and lithium (Li) substituted in cobalt oxide (Co3O4), a mesoporous oxygen-deficient material, is introduced. The substance splits water into H3O+/OH− ions by an electrolytic chain reaction, resulting in a 1.06 V potential difference between the electrodes. LCO-based HEC produced 39 mW of peak output (Pout) at 1.06 V. EPR spectroscopy and EIS curve have confirmed the presence of oxygen defects and ionic diffusion in Li-doped cobalt oxide materials. Similar to solar cells, an LCO-based HEC offers a low-cost, water-based method of producing green energy with the extra benefit of being able to function in the dark. The process also produces hydrogen gas (green hydrogen technology), which creates prospects for the manufacture of hydrogen, diversifying hydrogen supply chain options and developing new routes for industrial decarbonization, globally.

Utilization of spray pyrolyzed porous nickel cobaltite electrode as an advanced material for NiCo2O4@Graphite asymmetric supercapacitor device

Nickel-based probe ingredients are vastly promoted in energy storage devices due to their simply variable structure, greater electrochemical movement and nominal noisomeness. In the existing manuscript, we did a comparative study of spray pyrolyzed nickel oxide and nickel cobaltite thin film electrodes and their asymmetric supercapacitor devices for supercapacitor applications. In a three-electrodes arrangement, pristine nickel oxide shows a maximum specific capacitance of 397.10 Fg−1 at 0.002 V scan rate with 86.40 % retention after 5000 cycles. The same electrode shows the values of energy density and power density 45.16 Whkg−1 and 05 Wkg−1 respectively. Nickel cobaltite (NiCo2O4) electrode exhibits the highest value of specific capacitance is 676.82 Fg−1 with 89.23 % retention after 5000 cycles and the values of energy and power densities are 1123.41 Whkg−1 and 5.76 Wkg−1 respectively. The fabricated NiCo2O4@graphite asymmetric device shows a specific capacitance (according to CV analysis) of 495.10 Fg−1. According to the GCD analysis, the NiCo2O4@Graphite device exhibits a specific capacitance of 675.72 Fg−1 and the energy and power densities are 3249.6 Whkg−1 and 10 Wkg−1 respectively. The outcomes show that nickel–cobalt oxide materials play an important role in the field of energy storage.

Operando Surface X-Ray Diffraction Studies of Co Oxide Catalyst Films for Electrochemical Water Splitting

The need for environmental friendly and sustainable energy conversion has triggered renewed interest into the electrochemical and photoelectrochemical splitting of water. A key challenge in this field is the development of economically viable electrocatalyst materials for the oxygen evolution reaction (OER). Transition-metal oxide catalysts, in particular the cobalt (hydr)oxide materials, have been found as promising candidates, since they are earth-abundant, efficient and scalable over a wide range of electrochemical conditions [1]. They present good catalytic properties and stability in alkaline solution under ambient conditions. Although a wide variety of different catalysts with rather diverse nanoscale morphologies have been synthesized and studied, the atomic scale surface structure usually is still unknown or poorly defined. This makes it difficult to compare their electrocatalytic activity and correlate it with ab initio theoretical studies, which hinders the development of clear structure-reactivity relationships and unambiguous determination of the OER reaction mechanism.We presentsystematic comparative studiesof structurally well-defined, 18-35nm thick Co3O4 films, prepared by electrodeposition or physical vapor deposition (PVD) on Au(111), Au(100) and Ir(100) single crystals. In all cases a well ordered epitaxial Co3O4(111) arrangement results, but the film morphology differs substantially, as shown by AFM and surface X-ray diffraction (SXRD). In order to elucidate the quantitative relationship between the catalyst surface structure and the OER reactivity, synchrotron-based operando SXRD and electrochemical measurements were performed simultaneously under reaction conditions, using a dedicated operando cell which allows massive gas evolution and current densities of up to 150 mA/cm2 [2,3].We find that the Co3O4(111) layers prepared by PVD on Ir(100) stay perfectly stable in the pre-OER and OER potential regime, whereas all electrodeposited films exhibit reversible changes in the oxide structure and oxidation state, in agreement with a previous study of Co3O4 catalysts [2]. Specifically, we observe the reverse formation of an ultrathin X-ray-amorphous CoOx(OH)y skin layer above 1 V vs. RHE and the gradual buildup of tensile lattice strain in the underneath, remaining Co3O4 layer with increasing potential. These structural changes occur for all electrodeposited samples, albeit to a different extent, depending on the film morphology [3]. Studying the relationship between the effective thickness of this skin layer and the OER reactivity, we found clear evidence that the entire skin layer is a three dimensional OER zone, which strongly exceeds one monolayer.Our results suggest that even subtle changes of the surface morphology have large influence on the OER activity of the Co3O4 catalyst, which may be expected also for other spinel-type transition metal oxides. On the one hand, this reveals that great care as to be taken in comparing the OER activity of differently prepared catalysts. On the other hand, these observations may provide a base for targeted preparation of highly reactive oxide catalysts.[1] C. C. L. McCrory et al., Journal of the American Chemical Society 2015, 137, 4347.[2] F. Reikowski, et al., ACS Catalysis, 2019, 9, 3811.[3] T. Wiegmann, et al., ACS Catalysis, 2022, 12, 256.

Preparation and theoretical analysis of NiCo2O4: xS series materials for high-performance supercapacitors

Nickel cobalt oxide and sulfide electrode materials with various nanostructures were synthesized via a facile hydrothermal method. The structural, morphological, electrochemical, and electronic properties of the electrode materials were studied to evaluate the effect of S addition into NiCo2O4. The results indicated that S atoms can influence the lattice structure and morphology, and appear to improve the electrochemical performance of the material. Excellent specific capacitance and cycling stability were found in the samples. The NiCo2S4 sample exhibited the highest specific capacitance of 1302 F/g at a current density of 1 A/g and a capacity retention of 92.4% after 5000 charge–discharge cycles. First-principles calculations were performed to provide more insight into the mechanism of improved electrochemical performance when S atoms were added to NiCo2O4 and demonstrate their potential as excellent electrode materials. In the NiCo2O4:xS series materials, the addition of S effectively manipulates the surface morphology and interfacial charge states of the materials to achieve superior electrochemical performance.

Candle soot-metal-organic framework-based hierarchical electrode as high-performance anode for Li-ion batteries

Recently, cobalt oxide-based materials have been considered high-performance anode materials. However, cobalt oxide materials display drawbacks such as capacity fade, poor cycle life, and substantial structural strain. In this work, we report a facile synthesis of carbon-cobalt oxide composite to improve the electrode's storage capabilities and cycle life. First, metal–organic framework-based cobalt oxide nano leaves are synthesized by simple coprecipitation followed by calcination. After that, candle soot-derived carbon nanoparticles are uniformly deposited on the cobalt oxide nano leaves by a simple flame synthesis method to form a composite electrode. The fractal-like interconnected carbon nanoparticles improve the electron conducting pathways. In contrast, metal–organic framework-derived porous cobalt oxide nano leaves enhance energy storage abilities through reversible conversion reactions. The superior performance of the composite electrode is established from the galvanostatic charge–discharge experiments. Also, the composite electrode has delivered outstanding specific capacities of 811 and 503 mAh g−1 at 50 and 1000 mA g−1 current densities, respectively. Furthermore, the composite electrode exhibited good cyclic stability at 1000 mA g−1 current density by delivering an excellent specific charge capacity of 490 mAh g−1 even after 400 cycles. Therefore, these superior electrochemical properties confirm the potential applicability in high-performance and stable Li-ion batteries.

Iron Cobalt Phosphonate Derived Heteroatom Doped Metal Oxides as Superior Electrocatalysts for Water Oxidation Reaction

AbstractThe development of low cost‐effective and highly efficient heterogeneous electrocatalysts is most appreciable in the research community. A newly designed microporous organic‐inorganic hybrid iron cobalt phosphonate (FeCoDPAM) is synthesized using diphenylphosphinamide as an organophosphorus ligand through a hydrothermal pathway without any template. To synthesize N, P‐codoped bimetallic oxides (NP/FeCoO350, NP/FeCoO550, and NP/FeCoO750), the as‐synthesized material FeCoDPAM has undergone pyrolysis at three different temperatures, i. e., 350, 550, 750 °C, respectively. The high specific surface area and a regular microporous array of N, P‐codoped iron cobalt oxide (NP/FeCoO350) material provide excellent oxygen evolution reaction (OER) activity. The NP/FeCoO350 material catalyzes OER with the overpotential of 331 mV at a current density of 10 mAcm−2 and Tafel slope of 56.7 mV dec−1 in 1.0 M KOH solution. The inclusion of iron in the cobalt phosphonate framework can change the electronic structure, and electron transfer can be feasible to the d‐orbital of cobalt. Due to the doping of heteroatoms such as N and P into the bimetallic oxide matrix, a synergistic effect can occur, which is the driving force for the efficient electrocatalytic OER activity. Also, the FeCoO350 displays stability with outstanding oxidative current up to 50 h time in chronoamperometry measurement.

Consecutive engineering of anodic graphene supported cobalt monoxide composite and cathodic nanosized lithium cobalt oxide materials with improved lithium-ion storage performances

Downsizing the electrochemically active materials in both cathodic and anodic electrodes commonly brings about enhanced lithium-ion storage performances. It is particularly meaningful to explore simplified and effective strategies for exploiting nanosized electrode materials in the advanced lithium-ion batteries. In this work, the spontaneous reaction between few-layered graphene oxide (GO) and metallic cobalt (Co) foils in mild hydrothermal condition is for the first time employed to synthesize a reduced graphene oxide (RGO) supported nanosized cobalt monoxide (CoO) anode material (CoO@RGO). Furthermore, the CoO@RGO sample is converted to nanosized lithium cobalt oxide cathode material (LiCoO2, LCO) by taking the advantages of the self-templated effect. As a result, both the CoO@RGO anode and the LCO cathode exhibit inspiring lithium-ion storage properties. In half-cells, the CoO@RGO sample maintains a reversible capacity of 740.6 mAh·g−1 after 300 cycles at the current density of 1000 mA·g−1 while the LCO sample delivers a reversible capacity of 109.1 mAh·g−1 after 100 cycles at the current density of 100 mA·g−1. In the CoO@RGO//LCO full-cells, the CoO@RGO sample delivers a reversible capacity of 553.9 mAh·g−1 after 50 cycles at the current density of 200 mA·g−1. The reasons for superior electrochemical behaviors of the samples have been revealed, and the strategy in this work can be considered to be straightforward and effective for engineering both anode and cathode materials for lithium-ion batteries.

Cobalt Nanocube Electrocatalysts Comprising Sub-Nanometer Oxide-Phosphide Hetero-Interface for Highly Efficient Water Electrolysis

Hydrogen production from electrochemical water splitting is known as an eco-friendly energy conversion process, which has drawn attention for a few decades. Typically, the water electrolysis is divided into PEM and AEM electrolysis where acidic and alkaline electrolyte are used, respectively. In case of PEM water electrolysis, the acidic water splitting reveals critical drawback of poor counterpart OER efficiency. For this reason, AEM water electrolysis in alkaline condition has huge advantages in high efficiency of full cell owing to the lower overpotential for oxygen evolving anode, and accessibility of using transition metal-based materials for each anode and cathode. However, alkaline HER is 2-3 orders of magnitude slower than acidic HER due to the lack of proton nearby the surface.Thus, it is necessary to find highly efficient alkaline HER electrocatalysts for the future commercialization of AEM electrolyzer.Herein, by phosphidation of 10 nm Co3O4 nanocube (CO) loaded on nickel foam (NF) substrate, unique heterojunction interface of CoP and Co3O4 within 10 nanometers were realized, which converged both the excellent electrocatalytic performance of CoP and high stability of Co3O4. Unique sub-nanometer oxide-phosphide heterojunction was discovered via inverse fast fourier transform (IFFT), which confirmed the phase transition alongside the particle, while maintaining its nanocube morphology. X-ray photoelectron spectroscopy (XPS) was brought out to further confirm the co-exsistence of cobalt oxide and phosphide materials with respect to the chemical structure.Experimental investigations revealed the excellent water splitting activity of the hybrid-phosphidated Co3O4 (H-PCO) catalyst, only requiring an overpotential of 162, 171 and 395 mV to reach 100 mA cm-2, each for acidic HER, alkaline HER, and alkaline OER, respectively. H-PCO/PNF showed excellent stability over 20 hours under various working conditions, which was superior to that of conventionally fabricated CoP catalysts. Such outstanding alkaline water electrolysis performance and stability stems from the evolution of new active sites are expected at the interface because the interface has different chemical and electronic structures compared to bulk materials. In addition, the scalability of the electrocatalyst was demonstrated where a 34.56 cm-2 catalyst foam was uniformly fabricated As a result, all 15 points of as-prepared H-PCO electrode showed negligible distribution of the overpotentials at 100 mA cm-2, and the large unit-cell scale measurement showed remarkably improved HER performance compared to bare Ni foam. Applicability of the electrocatalyst was demonstrated by the construction of unbiased PV-EC water splitting system, where a high STH efficiency of 11.5% over 100 hours was achieved with the help of Si solar cells.In conclusion, we developed water splitting electrode containing hybrid interface of cobalt oxide and phosphide in sub-10 nm cube structure. The hybrid structure of H-PCO comprising sub-nanometer hetero-interface between cobalt oxide and phosphide evoluted synergetic effect that greatly improved either HER performance, pH indenpendency, or long-term stability, which outperformed single CO and CoP electrodes. We believe our rationally designed hetero-interfacial electrocatalyst can outperform previously established electrocatalysts via its high efficiency, versatility, and scalability.

Substitutional effects of Ni on thermoelectric properties of cobalt spinels to yield more than 10-fold increase in the thermoelectric figure of merit

The low thermoelectric figure of merit, ZT, is severely limiting the wide practical applications of thermoelectric materials. In this research theoretical calculations were performed on Ni substituted cobalt oxide (Co3O4) semiconductor materials to identify the qualitative trend of thermoelectric properties due to substitutions. Ni substitutions were made in the tetrahedral sites of 56 atom Co3O4 super cell. With the increasing Ni substitution, the band gap near the Fermi region started to close, from 0.337 eV for pure Co3O4 to 0 eV with Ni+2 substitutions in the tetrahedral sites of Co3O4, thereby showing an increasing metallic behavior which is also evident from the electrical conductance calculations. To calculate band structure, Seebeck coefficient, electrical conductance and thermal conductance due to electrons, first principles based density functional theory, DFT, combined with non-equilibrium Green's function method for two-probe systems were used. To calculate the lattice thermal conductance, reverse non-equilibrium molecular dynamics was used. The calculated Seebeck coefficients were 720 μV/K for pure Co3O4 and decreased exponentially to 35 μV/K for Co2NiO4, where the qualitative trend aligned very well with the available experimental data for Ni substituted cobalt oxide materials. These calculated properties assisted in calculating the theoretical thermoelectric figure of merit, and to qualitatively assess the effect of doping on the overall performance. Improved thermoelectric properties such as low thermal conductance and high Seebeck coefficient for low Nickel substitutions (12.5% of tetrahedral sites represented with Ni0·125Co2·875O4), was observed which yielded a 10-fold increase in thermoelectric figure of merit, ZT, in comparison to pure Co3O4 at 300 K. Additionally, the effect of Nickel substitutions on the p-type behavior was presented and discussed in this research article.

Exchanging Anion in CuCo-Carbonate Double Hydroxide for Faradaic Supercapacitors: A Case Study.

A systematic synthetic method involving the anion exchange process was designed and developed to fabricate the superior functioning three-dimensional (3-D) urchin-architectured copper cobalt oxide (CuCo2O4; CCO) and copper cobalt sulfide (CuCo2S4; CCS) electrode materials from copper-cobalt carbonate double hydroxide [(CuCo)2(CO3)(OH)2; CCH]. The effective tuning of chemical, crystalline, and morphological properties was achieved during the derivatization process of CCH, based on the anion exchange effect and phase transformation without altering the 3-D spatial assembly. Benefiting from morphological and structural advantages, CCO and CCS exhibited superior electrochemical activity with capacity values of 1508 and 2502 C g-1 at 10 A g-1 to CCH (1182 C g-1 at 10 A g-1). The thermal treatment of CCH has generated a highly porous nature in nanospikes of 3-D urchin CCO structures, which purveys betterment in electrochemical phenomena than pristine smooth-surfaced CCH. Meanwhile, the sulfurization reaction induced the anion effect to a greater extent in the CCS morphology, resulting in hierarchical 3-D urchins formed by 1-D nanospikes constituting coaxially swirled 2-D nanosheets with high exposure of active sites, specific surface areas, and 3-D electron/ion transportation channels. The asymmetric supercapacitor was constructed with a superior CCS electrode as a cathode and an activated carbon electrode as an anode, showing a high specific capacity of 287.35 C g-1 at 7 A g-1 and durability for 5000 cycles with 94.2% retention at a high current density of 30 A g-1. The ultrahigh energy and power density of 135.3 W h kg-1 (10 A g-1) and 44.35 kW kg-1 (30 A g-1) were harvested during the PC device performance. Our finding proposes an idea about the importance of anions and phase transformation as a versatile tool for engineering high-functioning electrode materials and their endeavor toward overwhelming the major demerit of SCs by aggrandizing the energy density value and rate performance.

Li[Ni0.6Mn0.2Co0.2]O2 Made From Crystalline Rock Salt Oxide Precursors

Layered lithium nickel manganese cobalt oxide or NMC type cathode materials dominate the lithium-ion battery market. However, the production of their precursor involves the use of large amounts of water and can create waste. All-dry synthesis methods are attractive as they are potentially cheaper and greener. However, it remains a challenge to achieve atomic scale mixing of the precursor elements by dry methods. Here, we report an alternative route to achieve atomic scale mixing by employing thermal interdiffusion to produce a phase pure rock salt structure precursor for NMC cathode materials, which can significantly shorten the preparation time and may further reduce cost. The complications and applicability of using a thermally synthesized precursor to make layered cathode material are presented in detail.

Highly Efficient Electrochemical Sensing of Acetaminophen by Cobalt Oxide-Embedded Nitrogen-Doped Hollow Carbon Spheres.

With respect to sensor application investigations, hollow mesoporous carbon sphere-based materials of the spinel type of cobalt oxide (Co3O4) and heteroatom-doped materials are gaining popularity. In this contribution, dopamine hydrochloride (DA) and cobalt phthalocyanine (CoPc) precursors were employed to construct a highly homogeneous Co3O4-embedded N-doped hollow carbon sphere (Co3O4@NHCS) by a straightforward one-step polymerization procedure. The resulting Co3O4@NHCS materials may effectively tune the surface area, defect sites, and doping amount of N and Co elements by altering the loading amount of CoPc. The relatively high surface area, greater spherical wall thickness, enriched defect sites, and better extent of N and Co sites are all visible in the best 200 mg loaded Co3O4@NHCS-2 material. This leads to significant improvement in pyridine and graphitic N site concentrations, which offers exceptional electrochemical performance. Electrochemical analysis was used to study the electrocatalytic activity of Co3O4@NHCSs towards the sensing of pharmacologically active significant compounds (acetaminophen). Excellent sensor properties include the linear range (0.001-0.2 and 1.0-8.0 mM), sensitivity, limit of detection (0.07 and 0.11 μM), and selectivity in the modified Co3O4@NHCSs/GCE. The authentic sample (acetaminophen tablet) produces a satisfactory result when used practically.

Effect of lithium ion on the separation of electrode materials in spent lithium ion batteries using froth flotation

There is an urgent need to develop a recycling process for spent Lithium-Ion Batteries (LIBs). Amongst the various recycling technologies proposed, froth flotation is considered a cost-effective candidate for the separation of graphite from the lithium metal oxides due to the hydrophobic nature of graphite. However, experimental studies have identified that soluble lithium has a significant impact on the separation efficiency.Two series of experiments were undertaken to understand the influence of lithium ions. The first used a semi-synthetic mixture of spent anode and pure cathode material based on lithium nickel manganese cobalt oxide (LiNi0.33Mn0.33Co0.33O2) or NMC-111 cathode material. The second used mixed samples of spent lithium ion batteries of the same composition. Both the separation efficiency and the flotation kinetics are reported. The soluble lithium concentration is shown to have a significant impact on both. However, if the spent battery material is washed to reduce the lithium ion concentration, the flotation efficiency and kinetics are similar with the graphite recovery exceeding 90% and the graphite grade exceeding 84% in a single flotation stage.

Electrocatalytic performance of cobalt oxide and hybrid composite thin films of cobalt Oxide@Polyaniline for oxygen evolution reaction

Water splitting is the process in which oxygen evolution reaction is prominent. This can be done by the most affordable technique using an electric field (electrochemical method). Keeping this in mind, we have synthesized novel hybrid composite thin films of Co3O4@PANI, to overcome the deficient electrochemical performance of solo Co3O4. The electrocatalytic performance of cobalt oxide and hybrid composite material for oxygen evolution reaction is studied. Cobalt oxide is deposited by the SILAR method, and hybrid composite material is prepared via different methods like electrochemical deposition and SILAR. Morphology, charge transfer resistance, and phase of material are studied with Scanning Electron Microscopy (SEM), Electrochemical Impedance Spectroscopy (EIS) and X-ray diffraction (XRD) respectively. The hybrid composite Co3O4@PANI electrocatalyst manifests high catalytic activity with 258 mV overpotential at 10 mA cm−2 current while solo Co3O4 shows deficient catalytic activity with 323 mV overpotential at 10 mA cm−2 which is examined by Linear swap voltammetry (LSV) and 16.28 mV dec-1 is Tafel slope. This hybrid combination also shows excellent stability for 10 hrs for OER in 1 M NaOH.

Improving Performance of Regenerated Cathode Materials from Aged Lithium-Ion Batteries By Forming Nano-Coatings

Lithium-ion batteries (LIBs) have emerged as the battery of choice for rapidly growing markets in electric vehicles (EVs) and grid electricity storage. This spurs a great demand for lithium, graphite, cobalt, and nickel that could outstrip the supply of virgin materials. Thus, there is an enormous interest in the development of new sustainable technologies for recycling and recovery of valuable materials from secondary resources, especially from used lithium-ion batteries. Compared to conventional high-temperature pyrometallurgical or hydrometallurgical methods, direct recycling of LIBs is a more desirable approach because it can directly regenerate the cathode materials by relithiation without destroying the LIB compounds. Additionally, direct recycling is a comparatively low-cost and less resource-intensive method of recovering LIB materials.However, completely regenerating the full capacity and long-term performance of the original materials is still particularly challenging. For instance, the cathode materials are often coated with a nanometer-thick protecting layer, which is engineered to reduce the degrading effect on the cathode from direct contact with the electrolyte. The long-term charge-discharge cycling causes damage to this coating layer, and thus it needs to be repaired in order to recover the material performance. To address this challenge, we have developed a novel process that can regenerate and upgrade cathode materials from aged lithium-ion batteries, as well as create a new coating layer to improve the performance of the cathode materials. In this presentation, we will provide a case study to show the performance improvement of recycled lithium cobalt oxide (LCO) materials by forming an alumina coating layer on the surface. By controlling the thickness and sintering temperature, this surface alumina coating can be an effective way to improve the stability and cyclability of recycled LCO cathode materials. Material characterization by XPS, SEM, STEM, and XRD helps to reveal the structure and composition of the surface alumina coating layer, and provides insights into the healing and protective roles of this layer for recycled LCO particles.

Optimization of Ascorbic Acid Contents in Preparation of Cobalt Oxide for Highest Oxygen Evolution Activity

The activity of the cobalt oxide (Co3O4) material towards the oxygen evolution reaction is governed by cobalt oxidation states present at the surface. The fabrication methodology decides the concentration of Co+2 and Co+3 at the Co3O4 surface. We used ascorbic acid as a fuel (reductant) for cobalt oxide synthesis. On the variation of the precursor ratio (cobalt nitrate to ascorbic acid) 1:0.5, 1:1, 1:2, and 1:4, the Co+3 and Co+2 content at the surface increases and decreases, while the oxygen vacancy decreases with increasing the ascorbic acid content. The combined effect of oxygen vacancy with Co+2 and Co+3 contents shows the maxima activity for 1:1 sample. Further, low oxygen vacancy with moderate Co+2 and Co+3 contents show low activity compared to the 1:1 sample. Also, high oxygen vacancy with low Co+2 and Co+3 contents show low activity compared to the 1:1 sample. Thus, high Co+2 and Co+3 contents with moderate oxygen vacancy give the highest activity towards the oxygen evolution reaction. The Tafel analysis further supports the above with the help of the Tafel slope. The Tafel slope of the 1:1 sample shows 55.12 mV/dec. Finally, the impedance analysis supports the above by showing the lowest value for the adsorption resistance of the 1:1 sample. Thus, the above study showed that at the ascorbic acid's optimized value, the cobalt oxide showed the highest activity via the moderate oxygen vacancy and highest Co+2 and Co+3 content.