Cobaltite Spinel Research Articles

Catalytic performance of FeCo2O4 spinel cobaltite for degradation of ethylparaben in a peroxymonosulfate activation process: Response surface optimization, reaction kinetics and cost estimation

The presence of cosmetics and personal care products in water resources has become an increasing concern for environment due to their toxicity and persistence in aquatic medium. Peroxymonosulfate mediated advanced oxidation methods have a great potential for the efficient removal of complex organic compounds due to the generation of highly reactive radicals with high oxidation ability. Iron cobaltite, FeCo2O4 catalyst was used as a peroxymonosulfate (PMS) activator for the degradation of ethylparaben which was selected as a model personal care product ingredient. Paraben degradation was modelled and the optimum operating parameters were determined by using Box-Behnken design. The ethylparaben degradation efficiency was calculated as 94.6 % under the optimized conditions which were determined as 0.9 g/L FeCo2O4 loading, pH 6.15, and 0.26 g/L PMS dosage. The ethylparaben degradation reaction followed second-order reaction kinetics. The activation energy was evaluated as 40.1 kJ/mol. Quenching radical tests showed that the dominant reactive species were hydroxyl radicals. Toxicity of the treated samples in terms of L. sativum growth inhibition was evaluated as 1.5 %. The total cost of the treatment including the operating and the amortization costs was calculated as 0.91 €/L.

Ag-doped MgCo2O4/MXene composite: Tailoring the electrochemical properties via 2D layered material for next generation supercapacitor study

The major concern of the modern era is to conserve and store energy for future use because of the continuous depletion of natural resources. Spinel cobaltites have attracted a lot of attention to be studied in the energy storage and conversion arena because of their prospective applications and excellent electrochemical performance. Achieving excellent chemo-mechanically robust electrode materials requires creative structural design and effective multicomponent strategy implementation. Herein, MgCo2O4 (MC) and Ag-MgCo2O4 (AMC) were fabricated by hydrothermal treatment. Further, Ag-MgCo2O4 (AMC) coupling with MXene sheets was accomplished by ultrasonication treatment. After structural, morphological, functional, and compositional analyses, prepared materials were studied for supercapacitor measurements. AMC/MXene exhibited remarkable outcomes because of Ag ions insertion into the spinel oxide structure, providing electron transport paths by creating voids and interfacial contact between the electrolyte and available active sites, and 2D MXene layers boosting the transportation of ions during the charging and discharging stages. The specific capacitance at 1 Ag−1 was found to be 1722 Fg−1 for AMC/MXene. The bulk (solution) resistance Rs was found to be the lowest 0.63 Ω for AMC/MXene among other fabricated materials in this study. Hence, developing AMC/MXene offers an advanced method to build high-performance 2D electrode materials with hybrid structures for energy storage applications.

Synthesis and characterization of nickel cobaltite–supported film for hexavalent chromium photocatalytic reduction

ABSTRACT Hexavalent chromium (Cr(VI)) is a prevalent and highly toxic pollutant, posing a serious threat to human health and ecosystems. This study addresses this issue by exploring the photocatalytic reduction of Cr(VI) using hydrothermally synthesized nickel cobaltite (NiCo2O4) spinel–supported films. The research fills the gap for efficient visible light photocatalytic materials for Cr(VI) reduction, with the aim to synthesize, characterize, and assess NiCo2O4-supported films’ photocatalytic activity. Synthesis was achieved via a hydrothermal method on fluorine-doped tin oxide (FTO) and titanium dioxide (TiO2) over FTO substrate. The films were characterized using several techniques and their photocatalytic activity was tested under UV-A and visible light, with Cr(VI) concentration monitored periodically up to 240 min. The NiCo2O4/TiO2 film demonstrated superior photoreduction performance under both UV and visible light radiation compared to TiO2 and NiCo2O4, achieving photoreduction of Cr(VI) by 76% under UV light with a rate constant of 5.79 × 10−3 min−1 and 60% under visible light with a rate constant of 4.74 × 10−3 min−1. In conclusion, hydrothermally synthesized NiCo2O4/TiO2 film shows promising photocatalytic performance for Cr(VI) reduction, marking a significant advancement in photocatalysis and water treatment technologies. Future research will focus on stability assessment, synthesis process optimization, and real-world water treatment application.

Tuning the composition of manganese cobaltite spinel with tungsten for enhanced energy storage performance

The development of efficient and innovative energy storage devices is a necessity of the hour. Emerging nanomaterials possessing tungsten are believed to have unique physicochemical properties and their application could be extended over a wide spectrum as nanocomposite electrodes for effective high voltage energy storage applications. In the present work, a one-step hydrothermal process has been employed to prepare Tungsten (W) doped spinel oxide MnWxCo2–2xO4 (MWCO) nanostructures, where x varies from 0.01 to 0.05. The spectroscopic characterization studies proved spherical subunits embedded onto nanosheets formed by W doped bimetallic oxide with a crystalline phase. On employing the synthesized material in asymmetric supercapacitor application, it was inferred that W doping had a notable effect on the electrochemical performance. The optimized doping ratio (x=0.03) revealed an appreciable specific capacitance of 91 F g−1 at the current of 0.5 A g−1, with a retention in the capacitance of more than 80 % even after 10000 GCD cycles. Remarkable specific energy (3.17 Wh kg−1) and specific power (98 W kg−1) were also noted. Hence, the material synthesized in this study by our facile method is thought to be highly suitable as an electrode for high-performance energy storage applications.

Excellent electrochemical performance of N and Mn doped NiCo2O4 functional nanostructures: an effective approach for symmetric supercapacitor application

In supercapacitors (SCs), cobaltite spinel is considered as an excellent electrode material because it is abundant on earth, cost-effective, and theoretically capable of achieving high capacitance values. However, there are number of factors that prevent spinel cobaltite from achieving its maximum theoretical specific capacitance, including low electrical conductivity, insufficient active sites, and slow charge transport. For these reasons, it is necessary to simplify the structural and compositional design to overcome these limitations. An efficient solvothermal method followed by pyrolysis was successfully used to shape NiCo2O4 nanoflowers doped with N (Nitrogen) and Mn (Manganese). In addition to increasing the ion diffusion resistance and charge transfer resistance, N and Mn-doped NiCo2O4 provides an electrical conductivity system. The optimized N, Co, and Mn4 (NCoMn4) nanoflowers (4 wt% Mn-doped NiCo2O4) exhibits maximum specific capacitance of 269Fg−1 at 1Ag−1 current density with an exceptional retention of capacitance 92% after 5,000 uninterrupted cycles in the Na2SO4 media. The electrokinetic analysis of NCoMn4 further indicates that overall charge is stored predominantly through capacitance, as compared with other electrodes. It is also worth noting that the as-fabricated symmetric supercapacitor delivers the maximum energy density of 36.11 Whkg−1 at a power density of 1.04 kWkg−1 at 1 Ag−1 current density. This work opens a new path to develop hybrid electrodes for enhanced supercapacitor applications and will specify an efficient method for improving the charge transfer capability.

Effect of cerium substitution on structural, optical, electrical transport and magnetic properties of spinel cobaltite synthesized through citrate-nitrate method

Effect of cerium substitution on structural, optical, electrical transport and magnetic properties of spinel cobaltite synthesized through citrate-nitrate method

Correction to: Effect of cerium substitution on structural, optical, electrical transport and magnetic properties of spinel cobaltite synthesized through citrate–nitrate method

Correction to: Effect of cerium substitution on structural, optical, electrical transport and magnetic properties of spinel cobaltite synthesized through citrate–nitrate method

Chestnut-like Molybdenum-Doped Nickel Cobaltite Spinel Oxide Nanoparticles Grown on Ni Foam as the Electrocatalyst for the Hydrogen Evolution Reaction

Chestnut-like Molybdenum-Doped Nickel Cobaltite Spinel Oxide Nanoparticles Grown on Ni Foam as the Electrocatalyst for the Hydrogen Evolution Reaction

Investigation of Zn-to-Co Chemometric Ratio in Zinc Cobaltite Spinel as Battery-Type Superior Redox-Active Electrodes for Hybrid Supercapacitors: Density Functional Theory Analysis

Investigation of Zn-to-Co Chemometric Ratio in Zinc Cobaltite Spinel as Battery-Type Superior Redox-Active Electrodes for Hybrid Supercapacitors: Density Functional Theory Analysis

Phytotoxic and electrochemical properties of mixed Cu-Ni cobaltite nanoflowers: Environmental and energy storage applications

Herein, the flower-like mixed Cu-Ni cobaltite spinels Cu1−xNixCo2O4 (x = 0, 0.05, 0.15, and 0.25) were successfully synthesized via simple hydrothermal approach followed by annealing process. Copper cobaltite flowers were characterized using XPS, XRD, FT-IR, SEM, TEM, EDAX, BET, and UV–Vis analysis. The photodegradation efficiency (PDE) of the cobaltite photocatalysts was determined by the degradation of rhodamine 6 G (Rh6G), methylene green (MG), and mixed dye effluents (Rh6G+MG, 1:1 v/v) upon visible-light radiation. The PDE of the CNC 3 catalyst was found to be 90%, 83%, and 86% for degradation of Rh6G, MG, and mixed dye effluents, respectively, and it retained 87% of photocatalytic efficiency even after four cycles. The phytotoxic analysis of control, untreated, and treated Rh6G dye solutions was examined in Phaseolus vulgaris for real-time applications. The electrochemical characteristic was investigated by CV, GCD, and EIS. The CNC 3 electrode showed excellent electrochemical performance (315 Fg−1 at 0.5 Ag−1), and the capacity reached 93% of its initial capacitance after 3000 cycles. The b values of oxidative and reductive currents were determined to be 0.67 and 0.68, respectively. The capacitance contribution was 56% at 10 mVs−1, indicating a mixture of surface capacitive and diffusion controlled behavior in charge/discharge processes. The two-electrode symmetric cell was fabricated using CNC 3 as the positive and negative electrodes for real-life applications. CNC 3 cell delivered a significant energy density (13.47 Wh/kg) and a power density (251.01 W/kg) at 0.5 Ag−1.

Multilayer coatings based on cerium oxide and manganese cobaltite spinel for Crofer22APU SOC interconnects

The application of protective coatings on stainless-steel interconnects can improve the durability of the metallic component in Solid Oxide Cell devices. In this work, we explored the possibility of producing multilayered coatings based on cerium oxide deposited by electrolytic deposition and manganese cobaltite spinel deposited by electrophoretic deposition. Obtained coatings were oxidized at 850 °C in air for 1000 h and the oxidation rate was calculated in the range of 10-14 g2cm-4s−1. The morphological evolution of the oxide scale and the coating system after oxidation revealed that the ceria particles were located at the boundaries between the grains of the reaction layer and those of the MCO coating, as assessed by FESEM and TEM characterizations.

Electrochemically enhanced wetting of 3YSZ and Mn1.5Co1.5O4 by Ag−CuO and their application in flash joining

Ag−CuO is a widely used air braze sealant for joining ceramic electrolytes and stainless-steel interconnects in solid oxide fuel cells (SOFCs). Balancing the amount of CuO in a braze is challenging because it enhances wettability and also aggravates steel surface degradation. Manganese cobaltite spinel (MCO) is widely used as a protective coating for SOFC steel interconnects. Therefore, we herein propose a strategy for enhancing the wetting of an Ag−CuO alloy with a low concentration of CuO (4 mol%) on 3 mol% yttria-stabilized zirconia (3YSZ) and MCO by applying a direct current to the 3YSZ/Ag−CuO/MCO system. It was discovered that the wetting of 3YSZ improved regardless of the current polarity; however, the wetting of MCO was selectively improved by the current flowing from MCO to 3YSZ. The underlying mechanisms are discussed based on the current-induced interfacial electrochemical reactions and dissolution. Furthermore, the flash joining of 3YSZ to MCO-coated Crofer22APU was achieved, and an optimized shear strength of 62 ± 11 MPa was obtained. A correlation between the interfacial microstructure, mechanical properties, current polarity and current intensity was also established.

Magnetic and elastic properties of spinels oxides XCo2O4 (X=Tc and Si): Ab initio study

In this article we have studied, the structural, electronic, magnetic and elastic properties of two spinels XCo2O4 (X=Tc and Si) for the first time using the full potential linearized augmented Plane wave method within the framework of density functional theory (DFT) considering different approximations for the exchange and correlation potential. The computed structural parameters of these compounds with GGA are consistent with experimental values. Moreover for the improvement of electronic and magnetic characteristics of these compounds, we have also adopted the GGA+U formalism for better results. From the study of electronic band profiles, one can predict that XCo2O4 (X=Tc and Si) compounds are metallic in nature. The crystal fields splitting (CFC) and the curie temperature of these compounds were also presented. Spin polarized optimization and total magnetic moments of XCo2O4 (X=Tc and Si) type spinels compounds depicts their ferromagnetic nature. From the elastic properties of XCo2O4 (X=Tc and Si) we conclude that both compounds are elastically stable and ductile. Ferromagnetic nature of XCo2O4 (X=Tc and Si) predicts the importance of these cobaltite spinels in spintronic.

Octahedron-Shaped Nano FeCo2O4 Phase Materials: Wet Chemical Synthesis and Characterization Studies

Background: Amongst the different spinel cobaltites investigated to date, the FeCo2O4 phase has been relatively less studied in detail despite the potential applications in several areas. As the nanostructured spinels are sensitive to the processing conditions, we have extended our research interest in FeCo2O4 phase materials. Objective: The objective of this study is (i) to synthesize the FeCo2O4 nanomaterials by different approaches using different precursors and (ii) to investigate the structural, thermal, optical, and microstructural properties of different materials by various characterization techniques. Methods: Different approaches such as hexamine-assisted combustion synthesis, co-precipitation, and solvothermal methods were employed to obtain FeCo2O4 nanomaterials using different precursors. Results: The XRD pattern of the as-prepared product of the solvothermal method is significantly different from other processed as-prepared products. The annealed FeCo2O4 materials obtained by coprecipitation using nitrates and/or chlorides showed nearly a single phase of FeCo2O4 nanomaterials. Conclusion: The phase formation of FeCo2O4 materials is sensitive to the presently employed synthesis conditions. The XRD patterns confirmed the deficient crystalline nature of the as-prepared materials produced by sol-gel combustion and co-precipitation methods. The annealed materials obtained by the co-precipitation using nitrates and chlorides showed nearly a single FeCo2O4 phase. The observed particle sizes of the FeCo2O4 phase materials are octahedral shaped with different sizes of 89 to 344 nm. The optical property studied using the FT-IR technique shows IR bands at 500 ~ 630 cm-1.

Probing the electrocatalytic activity of hierarchically mesoporous M-Co3O4 (M = Ni, Zn, and Mn) with branched pattern for oxygen evolution reaction

The large-scale production of hydrogen energy from the electrolysis of water requires earth-abundant and highly efficient oxygen evolution electrocatalysts. Cation substitution in spinel cobaltite is an efficient approach to tune electronic structure and improve their electrocatalytic activity towards oxygen evolution reaction (OER). In this article, for the first time, we have prepared hierarchically nanostructured Mn, Ni and Zn doped Co3O4 having a branching pattern via a simple hydrothermal and calcination method, and the same was used as an electrocatalyst for OER. Different methods confirmed the doping of transition metal ions. The result of structural characterization shows the formation of pure phase samples without impurity. The tetrahedral and octahedral functional groups were explained by FTIR spectroscopy, confirming the formation of a spinel structure. Ni-doped Co3O4 showed an excellent OER performance with a current density of 10 mA/cm2 at an overpotential of 380 mV in 1 M KOH and a Tafel slope of 63.19 mV/dec in alkaline media. The detailed study unveiled that the large surface area, hierarchically nanostructured branching pattern with porous structure, presence of a high amount of oxygen vacancy and the synergistic effect of Ni and Co are beneficial for increased OER activity and stability of Ni-Co3O4.

Phosphate ions functionalized spinel iron cobaltite derived from metal organic framework gel for high-performance asymmetric supercapacitors

Spinel iron cobaltite (FeCo2O4) with high theoretical capacity is a promising positive electrode material for building high-performance supercapacitors. However, its inherent poor conductivity and deficient electrochemical active sites hinder the improvement of its electrochemical kinetics behavior. Herein, phosphate ions modified FeCo2O4 is obtained in the presence of oxygen vacancies (P-FeCo2O4-x) by a simple metal organic framework gel-derived strategy. Phosphate ions added on the surface of P-FeCo2O4-x greatly enhances its surface activity, thus prompting the faster charge storage kinetics of the electrode material. Due to its ample electrochemical active sites and rapid ion diffusion and electron mobility, the optimized P-FeCo2O4-x electrode delivers a superior specific capacity of 1568.8 F g−1 (784.4 C g−1) at a current density of 1 A/g and has an excellent cycling stability with 93.3 % initial capacity retention ratio after 5000 cycles. More impressively, the assembled asymmetric supercapacitor consisting of P-FeCo2O4-x and activated carbon which act as positive and negative electrode materials, respectively displays a favorable energy density of 60.2 Wh kg−1 at a power density of 800 W kg−1 and has a long cycling lifespan. These results demonstrate the potential importance of modifying the surface of spinel cobaltite with phosphate ions and incorporating oxygen defects in it as a facile strategy for enhancing the electrochemical kinetics of electrode materials.

Enhanced OER Performance by Cu Substituted Spinel Cobalt Oxide

Cobaltite spinel oxides (CuCo2O4), which show electrocatalytic activity for oxygen evolution reaction (OER), are readily synthesized using a facile hydrothermal method, with a stationary ratio, uniform flower-like mesopores morphology, and high crystallinity. We have carried out first-principles calculations on the mechanism of the reaction pathway and the Gibbs free energy diagram of CuCo2O4 structures using density functional theory and purely confirmed by experimental results. This catalyst performed an outstanding OER performance with an overpotential 230 mV at 10 mA cm−2 in 1 M KOH, which was close to IrO2 with an overpotential 190 mV at 10 mA cm−2. This work provides a facile method for electrocatalytic oxygen production with enhanced conductivity and enhanced OER by replacing cobalt with copper.Graphical Abstract

Effect of the synthesis method on the MnCo2O4 towards the photocatalytic production of H2

Abstract In the present work, manganese cobaltite (MnCo2O4) spinel (MCO) was synthetized by Pechini and hydrothermal method, characterized and photocatalytically evaluated toward H2 production through water splitting under visible-light irradiation. Characterization consisted in Thermogravimetry analysis (TGA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy, scattering transmission electronic microscopy, BET surface area, UV-Vis spectroscopy, cyclic voltammetry, Hall effect, and photoluminescence. The MCO were evaluated as photocatalyst using an artificial visible light lamp and monitored by gas chromatography. XRD analysis found a pure spinel phase MCO. The surface area was ∼5 m2·g−1 for the MCO synthetized by Pechini and increased to 155 m2·g−1 with the hydrothermal method with acetates as precursors. The Pechini MCO showed higher carrier mobility but the fastest recombination. Photocatalytic evaluation of the MCOs showed that the highest photocatalytic activity generated was 12 μmol H2/gcat at 8 h with the MCO obtained by hydrothermal method with the acetates.

Microwave absorption properties of ZnCo2O4 and MnCo2O4 powders synthesized by oxalate-assisted hydrothermal method

Zinc and manganese spinel cobaltites were prepared by hydrothermal method using oxalic acid as precipitant. The structural, microstructural, and magnetic and microwave absorption properties were analyzed by various characterization methods. The ZnCo2O4 nanoparticles were arranged as lamellar-like morphology, while the MnCo2O4 powders were composed of the large octahedral particles. The ZnCo2O4 powders showed the ferromagnetic behavior with the higher magnetization of 3 emu/g at 15 kOe than that of the MnCo2O4 powders (1.5 emu/g). The ZnCo2O4 powders had the better microwave absorption performances, including a minimum reflection loss of −40 dB and an effective absorption bandwidth of 3.6 GHz in Ku band at a matching thickness of 1.6 mm. However, the MnCo2O4 powders absorbed a great fraction (60%) of X band at a matching thickness of 2.4 mm with a minimum reflection loss of −43 dB.

Electrochemical Characteristics of Nanosized Cu, Ni, and Zn Cobaltite Spinel Materials

For a long time, transition metal oxide systems have been considered well explored materials in heterogeneous catalysis. Amongst, the spinel-type oxides, materials such as cobaltites (Co3O4) received significant attention, owing to their use in many industrial applications. In the present study, nanosized Cu, Ni, and Zn cobaltite spinel oxides were synthesized by a simple hydrothermal method. Physicochemical characterization of the synthesized materials was performed utilizing XRD, HRTEM, CO2-TPD, and XPS techniques. The textural characteristics (BET-surface area, pore size, etc.) of samples were determined from N2 physisorption measurements at −196 °C. The CO2-electrocatalytic reduction was selected as a model reaction to evaluate the electrochemical performance of the synthesized spinel cobaltites. For Ni, Cu, and Zn spinel materials, hydrogen was produced as the main product at the whole potential, along with other products, such as CO and HCOOH. Despite the advantages, the catalytic electrochemical CO2 reduction performance of spinel cobaltite catalysts is still far from adequate, which is principally ascribed to the low number of active sites combined with poor electrical conductivity.