Spinel Cobalt Ferrite Nanoparticles Research Articles

Metronidazole degradation mechanism by sono-photo-Fenton processes using a spinel ferrite cobalt on activated carbon catalyst

A heterogeneous catalyst was prepared by anchoring spinel cobalt ferrite nanoparticles on porous activated carbon (SCF@AC). The catalyst was tested to activate hydrogen peroxide (HP) in the Fenton degradation of metronidazole (MTZ). SCF nanoparticles were produced through the co-precipitation of iron and cobalt metal salts in an alkaline condition. Elemental mapping, physico-chemical, morphological, structural, and magnetic properties of the as-fabricated catalyst were analyzed utilizing EDX mapping, FESEM-EDS, TEM, BET, XRD, and VSM techniques. The porous structure of AC enhanced the catalytic activity of SCF by a significant decrease in the agglomeration of SCF nanoparticles. The effectiveness of SCF@AC in Fenton degradation improved substantially when UV light and ultrasound (US) irradiations were induced, most likely due to the strong synergistic effect between the catalyst and these irradiation sources. The photo-Fenton system was more efficient than the Fenton, sono-, and sono-photo-Fenton processes eliminating both MTZ and TOC. It was found that AC not only dispersed SCF nanoparticles and improved the stability of the catalyst, but also provided a high adsorption capacity of MTZ, resulting in a faster degradation. After 60 min of the photo-Fenton reaction, the elimination efficiencies of MTZ (30 mg L−1) and TOC were 97 and 42.1% under optimum operational conditions (pH = 3.0, HP = 4.0 mM, SCF@AC = 0.3 g L−1, and UV = 6 W). SCF@AC showed excellent stability with low leaching of metal ions during the reaction. Radical and non-radical (O2•–, HO•, and 1O2 species), alongside adsorption and photocatalysis mechanisms, were responsible for MTZ decontamination over the SCF@AC/HP/UV system. A comprehensive study on the HP activation mechanism and MTZ degradation pathway was obtained through scavenging tests. The findings demonstrate that SCF@AC is an effective, reusable, and environmentally sustainable catalyst for advanced oxidation processes that can effectively remove organic pollutants from wastewater. This study offers valuable insights into the feasibility of employing SCF@AC catalysts in Fenton-based processes for the degradation of MTZ.

Simple co-precipitation synthesis of activated carbon-cobalt ferrite (AC-CoFe2O4) nanocomposites: enhanced photocatalytic dye degradation and antimicrobial activity

Abstract In this present work, spinel cobalt ferrite nanoparticles (CoFe2O4 NPs) and activated carbon-CoFe2O4 nanocomposites (AC-CoFeO4 NCs) were synthesized by simple co-precipitation method and used for photocatalytic dye degradation (PCD) of rhodamine-B (Rh-B) dye. The antimicrobial study of the as-synthesized CoFe2O4 NPs was also performed. The as-synthesized CoFe2O4 NPs and AC-CoFe2O4 NCs were analyzed by ultraviolet spectroscopy (UV), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) studies, scanning electron spectroscopy (FE-SEM) techniques. Powder XRD analysis showed that the as-synthesized CoFeO4 NPs and AC-CoFeO4 NCs had average particle size of 18 nm and 46 nm, respectively. The FE-SEM showed that the CoFe2O4 samples have sphere like morphology and were well decorated on activated carbon in order to provide high surface area. AC-CoFe2O4 NCs have effectively used for the PCD of Rh-B dye with high efficiency. Furthermore, spinel CoFe2O4 NPs acted as a more effective antimicrobial agent against Gram-negative and Gram-positive bacterial strains. Moreover, AC-CoFe2O4 NCs can be used as the precursor materials for supercapacitor, sensors etc.

Study on the effects of cadmium and chromium substitution in hydrothermally-synthesized spinel cobalt ferrite nanoparticles

Study on the effects of cadmium and chromium substitution in hydrothermally-synthesized spinel cobalt ferrite nanoparticles

An Efficient One-Pot Synthesis of Octahydroquinazolinone Derivatives Using Magnetic Cobalt Ferrite Catalyst

In this work, octahydroquinazolinone derivatives were synthesized using magnetic cobalt ferrite nanoparticles using oxalate precursor method. The XRD pattern and IR spectrum confirmed the formation of single segment cubic spinel cobalt ferrite. The average size of the crystallites was determined to be 26.599 nm, while the lattice constant was found to be 8.365 Å. A fine spherical CoFe2O4 particles with some quantity of aggregation may be observed within the SEM and TEM images. Nano spinel cobalt ferrite nanoparticles is a easily synthesized, non-toxic, less expensive, effortlessly magnetically recoverable and green catalyst for the synthesis of octahydroquinazolinone derivatives through the condensation of aromatic aldehydes with urea or thiourea and dimedone. The advantages of this technique are quick reaction time, ease of product isolation and high yields.

Reduced Graphene Oxide-Modified Spinel Cobalt Ferrite Nanocomposite: Synthesis, Characterization, and Its Superior Adsorption Performance for Dyes and Heavy Metals.

This work is dedicated to the synthesis, characterization, and adsorption performance of reduced graphene oxide-modified spinel cobalt ferrite nanoparticles. The as-synthesized reduced graphene oxide cobalt ferrite (RGCF) nanocomposite has been characterized using FTIR spectroscopy, FESEM coupled with EDXS, XRD, HRTEM, zeta potential, and vibrating sample magnetometer (VSM) measurements. FESEM proves the particle size in the range of 10 nm. FESEM, EDX, TEM, FTIR, and XPS analyses provide the proof of successful incorporation of rGO sheets with cobalt ferrite nanoparticles. The crystallinity and spinel phase of cobalt ferrite nanoparticles have been shown by XRD results. The saturation magnetization (M s) was measured as 23.62 emu/g, proving the superparamagnetic behavior of RGCF. The adsorption abilities of the synthesized nanocomposite have been tested using cationic crystal violet (CV) and brilliant green (BG) and anionic methyl orange (MO) and Congo red (CR) dyes. The adsorption trend for MO, CR, BG, and As(V) follows RGCF > rGO > CF at neutral pH. Adsorption studies have been accomplished by optimizing parameters like pH (2-8), adsorbent dose (1-3 mg/25 mL), initial concentration (10-200 mg/L), and contact time at constant room temperature (RT). To further investigate the sorption behavior, isotherm, kinetics, and thermodynamic studies have been conducted. Langmuir isotherm and pseudo-second-order kinetic models suited better for the adsorption of dyes and heavy metals. The maximum adsorption capacities (q m) obtained have been found as 1666.7, 1000, 416.6, and 222.2 mg/g for MO, CR, BG, and As, respectively, with operational parameters such as T = 298.15 K; RGCF dose: 1 mg for MO and 1.5 mg each for CR, BG, and As. Thus, the RGCF nanocomposite was found to be an excellent adsorbent for the removal of dyes and heavy metals.

Impact of Sm3+ and Er3+ Cations on the Structural, Optical, and Magnetic Traits of Spinel Cobalt Ferrite Nanoparticles: Comparison Investigation.

In this study, we investigated a comparison of the structure, morphology, optic, and magnetic (room temperature (RT)) features of Er3+ and Sm3+ codoped CoFe2O4 (CoErSm) nanospinel ferrite (NSFs) (x ≤ 0.05) synthesized via hydrothermal (H-CoErSm NSFs) and sonochemical (S-CoErSm NSFs) approaches. The formation of all products via both synthesis methods has been validated by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM), along with energy-dispersive X-ray (EDX) and transmission electron microscopy (TEM) techniques. The single phase of the spinel structure (except for the Hyd sample with x = 0.03) was evidenced by XRD analysis. The DXRD (crystallite size) values of H-CoErSm and S-CoErSm NSFs are in the 10–14.7 and 10–16 nm ranges, respectively. TEM analysis presented the cubic morphology of all products. A UV–visible percent diffuse reflectance (DR %) study was performed on all products, and Eg (direct optical energy band gap) values varying in the 1.32–1.48 eV range were projected from the Tauc plots. The data of RT magnetization demonstrated that all prepared samples are ferromagnetic in nature. M–H data revealed that rising the contents of cosubstituent elements (Sm3+ and Er3+ ions) caused an increase in Ms (saturation magnetization) and Hc (coercive field) in comparison to pristine samples. Although concentration dependence is significant (x > 0.02), no strict regularity (roughly fluctuating) has been ruled out in Ms values for doped samples prepared via the hydrothermal method. However, sonochemically prepared samples demonstrated that Ms values increase with increasing x up to x = 0.04 and then decrease with the further rise in cosubstituent Sm3+ and Er3+ ions. The calculated values of Ms and Hc were found to be greater in H-CoErSm NSFs compared to those in S-CoErSm NSFs. The present investigation established that the distribution of cations and the variation in crystallite/particle sizes are efficient to control the intrinsic properties of all samples.

Magnetically Recyclable Heterogeneous Cobalt Ferrite Catalyst for the Direct N‐Alkylation of (Hetero)aryl Amines with Alcohols

AbstractHerein we report the use of spinel cobalt ferrite nanoparticles as an efficient and selective catalyst for the mono N‐alkylation of aryl and hetero aryl amines with various aromatic and aliphatic alcohols. Based on our experiments, the optimum condition for good to excellent yield were observed with alcohol (1.0 mmol), aniline (1.2 mmol), KOH (0.5 equiv), and CoFe2O4 nanocatalyst (10 mol%) in toluene at 130 °C in 24 hours. Further control experiment studies revealed that the reaction does not proceed in the absence of the catalyst or a strong base. This magnetically recyclable nanocatalyst does not require any ligands and is easily synthesized at low temperature. The reutilization of the recovered catalyst in a fresh reaction gave good to excellent yield. The experiment results strongly suggest a borrowing hydrogen pathway for N‐alkylation under our standard conditions. The utility of these nanocatalysts was also demonstrated for the dehydrogenative synthesis of heterocycles like indole and quinolines.

Effect of rosemary extract on the microstructure, phase evolution, and magnetic behavior of cobalt ferrite nanoparticles and its application on anti-cancer drug delivery

Cobalt ferrite nanoparticles (CFO NPs) were synthesized by a modified sol-gel method using Fe(NO3)3.9 H2O and Co(NO3)2·6H2O as the sources of Fe 3+ and Co 2+ in presence of different volumes of rosemary extract and sucrose as gel agent, chelating agent and non-magnetic elements such as calcium and magnesium ions. The prepared nanoparticles were characterized via X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FT-IR), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM). The X-ray diffraction results confirmed that the sample prepared with 5 mL rosemary extract has single-phase spinel cobalt ferrite nanoparticles with a cubic crystal structure at 750 °C for 3 h (S1 sample). The average crystallite size was calculated about 33 nm using the Debye–Scherrer equation. Scanning electron microscopy also exposed that the prepared nanoparticles have a cubic morphology. Besides, the magnetic properties of the as-synthesized nanoparticles (S1 sample) indicated the highest saturated magnetization of 64 emu.g−1 as compared to other samples. The nanoparticles were then coated with tripolyphosphate (TPP) and chitosan polymer (Cs) to be applied as a carrier for drug delivery CoFe2O4-TPP-Cs (CFO-TPP-CS). The antioxidant doxorubicin (DOX) drug was then covered on the surface of the nanoparticles, and its drug release (CFO-TPP–CS–DOX) from the substrate of coated nanoparticles containing doxorubicin was evaluated at different pH levels. The coated CFO nanoparticles with tripolyphosphate (TPP) –Chitosan (Cs) sample indicated the biocompatibility and non-toxic nature of CFO-TPP- Cs NPs. Meanwhile, the CFO-TPP–CS–DOX nanosystem showed good death percentage of the breast cell cancer line (MCF-7 cell) in an acidic medium.

Evidence of large exchange bias effect in single-phase spinel ferrite nanoparticles

Sm3+ doped spinel cobalt ferrite nanoparticles with a generic formula CoSmxFe2−xO4 (x = 0.00, 0.06, 0.12 and 0.18) were prepared using wet chemical co-precipitation technique. The structural, optical, magnetic and dielectric characteristics of the samples were investigated carefully. The phase purity and growth of spinel cubic structure was verified by room temperature x-ray diffractograms. Mean crystallite size was observed within the range of 6 nm to 15 nm as calculated from Scherrer’s formula. A blue shift in the indirect optical band gap was noticed with increasing Sm percentage as observed in UV–vis spectra due to the nanosize effect. Superparamagnetic nature at 300 K was detected for all Sm doped ferrite samples. Field cooled (150 kOe) M-H loops obtained at 5 K revealed a large amount of exchange bias field (≈4 kOe) together with high coercivity for the sample having smallest sized particles. Dielectric responses of all samples showed that the hopping of electrons was the fundamental charge conduction mechanism and grain boundaries play a crucial role in determining the dielectric properties.

Enhanced transport properties in Ce doped cobalt ferrites nanoparticles for resistive RAM applications

Abstracts Polycrystalline Cerium doped Cobalt ferrite with general formula CoFe x − 2 Ce x O 2 (X = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5) was synthesized by Co-precipitation method. The effect of Cerium substitution on the structural, dielectric, electrical and switching properties of spinel cobalt ferrite nanoparticles was studied. Formation of the spinel structure was confirmed by X-ray Diffraction (XRD) analysis. With increase in cerium content, secondary phase (CeO2) was also identified. The frequency dependent dielectric constant, AC electrical conductivity, dielectric loss, dielectric loss tangent and impedance was investigated in the frequency range of 20Hz–3MHz. Dielectric constant, AC conductivity and dielectric loss decreased with the addition of Cerium contents. From impedance study, the role of grains and grain boundaries with in prepared spinel ferrite nanoparticles was investigated. The values the activation energies and drift mobility are calculated from the DC electrical resistivity measurements. DC resistivity and hence, activation energy increases with increasing Cerium contents. Resistive switching properties were studied using current–voltage (I–V) measurements. All I–V curves in the current study exhibit a hysteresis loop-type behavior. Hysteresis loop-type trend confirm that resistive switching effect exist in Cerium doped Cobalt ferrites nanoparticles. Our study suggest that Cerium doped Cobalt ferrites have high potential for resistance switching memory devices like Resistive Random-Access Memory (ReRAM). Resistive switching mechanism in Cerium doped cobalt ferrites nanoparticles is also explained by available theoretical model.

Vanadium supported on spinel cobalt ferrite nanoparticles as an efficient and magnetically recoverable catalyst for oxidative degradation of methylene blue

Vanadium supported on spinel cobalt ferrite nanoparticles was synthesized and characterized using Fourier transform infrared spectroscopy, X‐ray diffraction, energy‐dispersive X‐ray analysis and transmission electron microscopy. For the first time, the prepared material was used for the catalytic degradation of methylene blue as an organic dye in the presence of hydrogen peroxide as a green oxidant and NaHCO3 as a co‐reagent at room temperature. The dependency of removal percentage on various parameters such as amount of catalyst, pH, reaction time and temperature and the effect of radical scavenging agents were studied. Finally, recoverability and reusability of the vanadium supported on spinel cobalt ferrite nanoparticles were investigated.

Antibacterial, antibiofilm, and photocatalytic activities of metals-substituted spinel cobalt ferrite nanoparticles

This study reports the photocatalytic degradation of Methylene Blue (MB) dye (a class of dyestuffs that are resistant to biodegradation) under the influence of UV-light irradiation. Antibacterial and antibiofilm activities of ferrite nanoparticles (FO NPs) were examined against some pathogenic bacteria isolated from the medical operating room surfaces. In the same context, metals-substituted spinel cobalt ferrite nanoparticles with nominal composition [MxCo1-xFe2O4 NPs; (M = Zn, Cu, Mn; x = 0.0, 0.25, 0.5 and 0.75)] were synthesized by citrate sol-gel method. Also, the structures of the synthesized FO NPs were characterized by X-ray diffraction, and Williamson-Hall (WH) method was used to determine the crystallite size. The estimated specific surface area is found in the range from 37.99 to 107.05 m2/g, between the synthesized ferrites, Zn0.5Co0.5Fe2O4 NPs have average pore radius 1.84 nm and the pore volume was 0.136 ml/g. SEM images revealed that, the synthesized FO NPs have an unique pores and uniformly distribution, while EDX spectra shows the elemental composition for the synthesized FO NPs. The elastic properties of FO NPs have been estimated using FTIR data, whereas (M − H) hysteresis loops revealed that, by replacing cobalt ions with Zn, Cu, and Mn ions the magnetic behaviour changed from ferromagnetic to paramagnetic. Results obtained from the photocatalysis indicated that Mn0.75Co0.25Fe2O4 NPs (30.0 mg) were a promising photocatalyst achieving 96.0% removal of MB after 100 min of UV-light exposure in the alkaline solution. Antibacterial results showed that the most effective combination was Zn0.75Co0.25Fe2O4 NPs (20.0 ppm) displaying activity against Staphylococcus aureus, Enterococcus columbae, and Aerococcus viridians by 15.0, 13.0, and 12.0 mm ZOI, respectively. Additionally, Zn0.75Co0.25Fe2O4 NPs were active as antibiofilm factors producing activity by 63.7, 57.9, and 45.5% towards S. aureus, A. viridians, and E. columbae, respectively. Accordingly, Zn0.75Co0.25Fe2O4 and Mn0.75Co0.25Fe2O4 NPs can be utilized in industrial, biological and medical applications.

The effect of capping agents on the structural and magnetic properties of cobalt ferrite nanoparticles

Microwave-assisted co-precipitation method was adopted to analyze the effect of polyethylene glycol (PEG) and urea concentrations on the properties of cobalt ferrite nanoparticles (NPs). The average crystallite size of single phase cubic spinel cobalt ferrite NPs was controlled within 10–14 nm with the effect of PEG, urea and the combination of them. The transmission electron micrographs revealed that the morphology of cobalt ferrites was not significantly influenced by the different concentration of capping agents but almost uniform morphology with nearly narrow size distribution was obtained. The interaction of PEG and urea molecules on the surface of nanoparticles was mediated through –OH hydroxyl group affected the crystal growth rate. The possible interaction mechanism was proposed with the help of IR vibrational spectra. All the samples exhibited ferromagnetism at room temperature and it was found that the capping agents showed an effect on the magnetic properties. The maximum saturation magnetization of 58 emu/g was achieved when the urea of 60 mg was used and the maximum coercivity of 311 Oe was attained when the mixture of PEG (40 mg) and urea (20 mg) were used. Ultrafine and hydrophilic cobalt ferrite NPs that showed appreciable magnetic properties obtained in the present experimental procedure would be of great interest in various biomedical applications.

Cobalt ferrite nanoparticles with controlled composition-peroxymonosulfate mediated degradation of 2-phenylbenzimidazole-5-sulfonic acid

Magnetic spinel cobalt ferrite nanoparticles with variable composition (CoxFe3-xO4; x=0.1, 0.5, 0.7 and 1.0) were synthesized. The nanoparticles were characterized by various surface techniques. Average sizes and surface areas of ferrites were determined in the ranges of 11–34nm and 18.5–49.1m2/g, respectively. Surface analysis of the nanoparticles confirmed the spinel type structures in which Co(II) incorporated into the crystal lattice. The synthesized catalysts were used to dissociate peroxomonosulphate (PMS) into reactive sulfate radicals (SO4•−) and further into hydroxyl radicals (HO•) to degrade a target pollutant, 2-phenylbenzimidazole-5-sulfonic acid (PBSA) in absence of heat and light. As the molar ratio of cobalt (i.e., x) in the ferrite catalyst increased from 0.1 to 1.0, PBSA degradation enhanced from 24 to 75% in 240min. The removal of PBSA increased significantly with the increase in PMS concentration up to 0.1mM, followed by a decrease at PMS levels of >0.1mM. Nitrogen content in PBSA was mineralized by the cobalt ferrite-PMS system mostly into NO3− and NH4+ ions with minor formation of NO2−. Only 32% TOC removal was observed over a 240min reaction time, indicating carbon content in PBSA was not completely mineralized. A chemical probe method, based on free radical scavenging, revealed the contribution of both SO4•− and HO• species in PBSA degradation. Fifteen reaction intermediates were identified using LC/Q-TOF-ESI–MS analysis. Hydroxylation, elimination of sulfonate moiety, and ring cleavage processes were involved in the major degradation pathways. Catalyst reuse experiments demonstrated PBSA degradation efficiency either retained or increased with each subsequent reuse. The magnetic spinel Co-ferrite nanoparticles can be applied effectively to activate PMS without energy aiding for degrading harmful emerging organic contaminants in water.

Evaluation of humidity sensing properties of TMBHPET thin film embedded with spinel cobalt ferrite nanoparticles

In this study, we report the enhanced sensing parameters of previously reported TMBHPET-based humidity sensor. Significant improved sensing performance has been demonstrated by coupling of TMBHPET moisture sensing thin film with cobalt ferrite nanoparticles (synthesized by eco-benign ultrasonic method). The mean size of CoFe2O4 nanoparticles has been estimated to be ~ 6.5 nm. It is assumed that the thin film of organic–ceramic hybrid matrix (TMBHPET:CoFe2O4) is a potential candidate for humidity sensing utility by virtue of its high specific surface area and porous surface morphology (as evident from TEM, FESEM, and AFM images). The hybrid suspension has been drop-cast onto the glass substrate with preliminary deposited coplanar aluminum electrodes separated by 40 µm distance. The influence of humidity on the capacitance of the hybrid humidity sensor (Al/TMBHPET:CoFe2O4/Al) has been investigated at three different frequencies of the AC applied voltage (V rms ~ 1 V): 100 Hz, 1 kHz, and 10 kHz. It has been observed that at 100 Hz, under a humidity of 99 % RH, the capacitance of the sensor increased by 2.61 times, with respect to 30 % RH condition. The proposed sensor exhibits significantly improved sensitivity ~560 fF/ % RH at 100 Hz, which is nearly 7.5 times as high as that of pristine TMBHPET-based humidity sensor. Further, the capacitive sensor exhibits improved dynamic range (30–99 % RH), small hysteresis (~2.3 %), and relatively quicker response and recovery times (~12 s, 14 s, respectively). It is assumed that the humidity response of the sensor is associated with the diffusion kinetics of water vapors and doping of the semiconductor nanocomposite by water molecules.

Surface modified spinel cobalt ferrite nanoparticles for cationic dye removal: Kinetics and thermodynamics studies

Present study is an endeavour to explore adsorption potential cobalt ferrite nanoparticles which were synthesised by combustion method and its surface modification was done by a SDS surfactant to make it suitable for the removal of cationic dye. Characterization was carried through FTIR, SEM and XRD analysis. Batch adsorption studies were carried out for removal of crystal violet cationic dye by SDS coated cobalt ferrite. Various parameters like initial concentration (50–300mg/L), effect of contact time, adsorbent dose (0.1–0.5 gm/50mL), and pH (2–9) were studied at constant temperature. Equilibrium time for the adsorption process was found to be 2h. Adsorption percentage of dye increased with an increase in the adsorbent dose and amount of adsorption increased with an increase in initial dye concentration. Initial pH in the basic region exhibited better results as compared to acidic pH. Langmuir adsorption isotherm fitted better than Temkin followed by Freundlich and Dubinin-Raduskevich adsorption isotherms. Monolayer adsorption capacity was found to be 105mg/g which is comparable to other reported adsorbents. Adsorption followed Lagergren pseudo second order kinetics model better than Lagergren pseudo first order and Elovich models. Adsorption studies conducted at different temperatures (301–313K) indicated rise in adsorption with the increase in temperature. This implied that sorption phenomenon was endothermic in this case. Data was fitted to Van’t Hoff equation to study thermodynamics. Value of ΔH° was in the range of 23–88kJ/mol for different concentration which indicated that mechanism of adsorption was complex comprising of both physical and chemical adsorption.

Study on synthesis of superparamagnetic spinel cobalt ferrite nanoparticles as layered double hydroxides by co-precipitation method

Cobalt ferrite layered double hydroxide (LDH) nanoparticles with cubic structure were synthesized by the co-precipitation method: addition of NaOH solution to a solution of Co2+ and Fe3+. Formation of nanoparticles was confirmed by XRD, SEM, TEM, PSA, FT-IR, TGA, DSC, and magnetic characteristics were measured using VSM. Crystals produced by calcination at 900°C possessed high coercivity and pronounced physical and chemical stability. Nanoparticles of CoFe2O4 formed outer layers with poor crystallization on the surface of cobalt ferrite nanocrystals.

Study on synthesis of superparamagnetic spinel cobalt ferrite nanoparticles as layered double hydroxides by co-precipitation method

Study on synthesis of superparamagnetic spinel cobalt ferrite nanoparticles as layered double hydroxides by co-precipitation method

Electrochemical Properties of Spinel Cobalt Ferrite Nanoparticles with Sodium Alginate as Interactive Binder

AbstractWe introduce a process of making high‐capacity and rate‐capable metal‐ferrite‐based conversion anodes for lithium‐ion batteries. Cobalt ferrite (CoFe2O4) exhibits a discharge capacity that is two‐times higher compared to the state‐of‐the‐art graphite anode, but at the same time it shows high volume change (ca. 95 %) during conversion reaction with lithium in an electrochemical environment. This large volume expansion is responsible for the particle–particle and conductive‐carbon particles–active materials detachment, which leads to cyclic instability during subsequent cycles. As observed in our earlier work, any kind of weak or strong chemical interaction between active materials and binder is necessary to achieve excellent electrochemical performance in case of conversion or alloying reactions. To compare the electrochemical activity of CoFe2O4 nanoparticles against lithium, we use conventional polyvinylidene fluoride and sodium alginate binder to fabricate electrodes. Fourier‐transform infrared measurements reveal weak hydrogen‐bond formation between surface OH groups of CoFe2O4 and COOH groups of the alginate binder. Indentation tests further confirm the increased hardness of the alginate/CoFe2O4‐based electrode films. CoFe2O4–alginate–carbon anode exhibits a high specific capacity of 890 mAh g−1 at 0.1 C rate (91.4 mA g−1) after 50 charge–discharge cycles. Even at high rate cycling with current densities such as 18280 mA g−1 (20 C), the same electrode material exhibits a specific capacity of 470 mAh g−1, which is much higher than that of conventional graphite anode at the same electrochemical conditions.