Wasp-waisted behavior in magnetic hysteresis curves of CoFe<sub>2</sub>O<sub>4</sub> nanopowder at a low temperature: experimental evidence and theoretical approach

Alves, Tibério Magno de Lima; Amorim, B.; Morales, Marco A.; Bezerra, C. G.; Medeiros, S.N. de; Gastelois, Pedro Lana; Fernandez-Outon, L.E.; Macedo, W. A. A.

doi:10.1039/c6ra28727a

Cited by 96 publications

(51 citation statements)

References 32 publications

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“…3(c)), two spin-orbit doublets Fe 2p 3/2 (709.47 eV for B-sites and 710.55 eV for A-sites) and Fe 2p 1/2 (723.67 eV for B-sites and 725.86 eV for A-sites) were observed for Fe 3+ ions in the ferrite photocatalyst. The peaks at 718.42 eV, 723.67 eV, and 731.87 eV were satellite peaks 24 . The peak position of Fe 2p 3/2 B-sites and Fe 2p 1/2 B-sites coincided with the peak positions of Fe 2+ species 25 , indicating that Fe 2+ /Fe 3+ ions could occupy the octahedral sites.…”

Section: Resultsmentioning

confidence: 97%

Photocatalytic Degradation of Organic Pollutants over MFe2O4 (M = Co, Ni, Cu, Zn) Nanoparticles at Neutral pH

Gupta

Ghaffari

Kim

et al. 2020

Sci Rep

154

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in this study, we report a surfactant-mediated synthesis of ferrites (Mfe 2 o 4 : M = co, ni, cu, Zn) using the co-precipitation-oxidation method. The band gap calculated from UV-Visible diffuse reflectance spectra were found in the range of 1.11-1.81 eV. These ferrite nanocatalysts were studied for the photocatalytic degradation of multiple organic dyes in a 32 W UV-C/H 2 o 2 system. All the four ferrites showed an excellent dye degradation rate in the range of 2.065-2.417 min −1 at neutral pH. in the optimized condition, NiF was found to degrade 89%, 92%, 93%, and 78% of methylene blue, methyl orange, bromo green, and methyl red, respectively within 1 min of UV-irradiation. A 40% TOC removal was recorded after 5 min of degradation reaction, which increased to 60% after 50 min. Mechanism elucidated by scavenger studies and fluorescence spectroscopy revealed that • oH and holes were the primary reactive radicals responsible for the degradation process. ferrite photocatalysts showed an insignificant performance loss in seven consecutive cycles. The photocatalyst was found efficient in the presence of a high concentration of salts. thus, it was concluded that these photocatalysts are highly suitable for the remediation of dye-contaminated wastewater. The ever-increasing population, coupled with rapid urbanization and industrialization, have deteriorated the quality of life. Excessive contamination of water bodies could be a severe threat to both human beings and other life forms. Organic dyes are considered as one of the major pollutants discharged into the environment by textile, printing, food, and leather industries 1. Though a large segment of these synthetic dyes is non-toxic or less toxic, their presence in water increases the oxygen demand, which in turn affects aquatic animals 2. Among the dyes consumed in industries, up to 70% belong to azo dye family (those with azo-functional group "-N = N-"). Azo dyes have genotoxic, mutagenic, and carcinogenic effects on living beings 3. Some of the azo dyes are known to be carcinogenic in the non-cleaved state, and for many of the azo dyes, their cleaved products such as benzidine are known to induce tumors 4. Conventional biological, chemical, and physical methods like adsorption 5,6 , chemical precipitation 7 , and microbial degradation 8 have been established for the remediation of dye-contaminated wastewater. The practical application of these processes suffers due to high operational cost, sludge production, or formation of secondary pollutants. For a complete or partial degradation of organic dyes (into non-toxic byproducts), degradation by adopting the photocatalytic process is one of the viable options. In recent years, advanced oxidation processes based on the generation of highly reactive hydroxyl radicals have gained momentum for the degradation of toxic organic pollutants 9. Though the Fenton process is easier to operate, it suffers badly due to a slow regeneration of Fe 2+ ions 10. Thus, the ultraviolet radiation or electrochemical method is generally cou...

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Section: Resultsmentioning

confidence: 97%

Photocatalytic Degradation of Organic Pollutants over MFe2O4 (M = Co, Ni, Cu, Zn) Nanoparticles at Neutral pH

Gupta

Ghaffari

Kim

et al. 2020

Sci Rep

154

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“…SAED pattern ( Figure S3C, SI) of Fe 0.2 Ni 1.8 OH exhibited diffraction rings of (015), (018), (211) and (113) planes which were also observed in XRD pattern. Figure S4 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 of 711.55 eV, 713.97 eV, 719.18 eV, 725.78 eV, 711.55 eV and 719.18 eV should be related to Fe 3 + , [26,27] while others were related to Fe 2 + . [28,29] The amount of Fe 3 + was about 46.8% ( Figure S4A, SI).…”

Section: Characterization Of Fe X Ni Y Oh/egsimentioning

confidence: 98%

Self‐Supportive NiFe hydroxide with High Electrocatalytic Activity for Oxygen and Hydrogen Evolution Reaction

Guo

Pan

et al. 2019

ChemistrySelect

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Here, a facile method to prepare low‐cost self‐supportive NiFe hydroxide on etching galvanized sheet iron (EGSI) (FexNiyOOH/EGSI) for electrochemical water splitting was proposed for the first time. The EGSI was firstly treated in Fe2+, Ni2+ and urea mixture to obtain FexNiyOH/EGSI and then were further transformed into FexNiyOOH/EGSI by the electrooxidation in NaOH solution. SEM results indicated various morphologies including nanoflowers, nanosheets and cubes could be obtained depending on the ratio of Fe2+ and Ni2+. Raman spectra, XRD and electrochemical results indicated that the NiOOH was produced in electrooxidation process, which improved its catalytic activity of OER remarkably. Besides, modest Fe‐doping could make it achieve better catalytic activity because Fe‐doping could alter the redox properties of NiFe hydroxide to result in low overpotential. As a result, the FexNiyOOH/EGSI presented good OER and HER performances. The optimum Fe1.5Ni0.5OOH/EGSI as cathode and Fe0.2Ni1.8OOH/EGSI as anode were applied for water splitting, achieving a current density of 10 mA cm‐2 at 1.69 V, indicating that it could work at a lower potential.

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“…As seen, two characteristic peaks of Co 2p3/2 at around 779.2 and 781.5 eV were due to the Co 2+ in B-sites and Co 2+ in A-sites with the corresponding shake-up satellite peaks at 784.9 and 789.7 eV [30][31][32][33]. Similarly, the Fe 2p3/2 spectrum shown in Figure 5e is composed of two characteristic peaks at 709.4 and 710.8 eV, assigned to Fe 3+ at B-sites and Fe 3+ at A-sites along with shake-up satellites at 714.8 and 717.7 eV respectively [50][51][52][53][54][55]. Moreover, fitting peaks of O 1s reveal peaks at 529.6 and 530.8 eV, which coincide with the lattice oxygen and chemisorbed oxygen species, respectively, as displayed in Figure 5f [46,54].…”

Section: Resultsmentioning

confidence: 98%

Ultrasonically Induced Sulfur-Doped Carbon Nitride/Cobalt Ferrite Nanocomposite for Efficient Sonocatalytic Removal of Organic Dyes

et al. 2020

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The sulfur-doped carbon nitride/cobalt ferrite nanocomposite (SCN/CoFe2O4) was prepared via ultrasonication and studied for the sonocatalytic degradation of wastewater organic dye pollutants including methylene blue, rhodamine B, and Congo red. The X-ray photoelectron spectroscopy confirmed the presence and atomic ratios of S, C, N, Co, Fe, and O elements and their corresponding bonds with Co2+ and Fe3+ cations. The nanocomposite was found to have aggregated nanoparticles on a sheet-like structure. The bandgap energy was estimated to be 1.85 eV. For the sonocatalytic degradation of 25-ppm methylene blue at 20 kHz, 1 W and 50% amplitude, the best operating condition was determined to be 1 g/L of catalyst dosage and 4 vol % of hydrogen peroxide loading. Under this condition, the sonocatalytic removal efficiency was the highest at 96% within a reaction period of 20 min. SCN/CoFe2O4 outperformed SCN and CoFe2O4 by 2.2 and 6.8 times, respectively. The SCN/CoFe2O4 nanocomposite was also found to have good reusability with a drop of only 7% after the fifth cycle. However, the degradation efficiencies were low when tested with rhodamine B and Congo red due to difference in dye sizes, structural compositions, and electric charges.

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Wasp-waisted behavior in magnetic hysteresis curves of CoFe₂O₄ nanopowder at a low temperature: experimental evidence and theoretical approach

Abstract: We theoretically and experimentally investigated wasp-waisted magnetic hysteresis curves at a low temperature for CoFe2O4 nanopowders.

Cited by 96 publications

References 32 publications

Photocatalytic Degradation of Organic Pollutants over MFe2O4 (M = Co, Ni, Cu, Zn) Nanoparticles at Neutral pH

Photocatalytic Degradation of Organic Pollutants over MFe2O4 (M = Co, Ni, Cu, Zn) Nanoparticles at Neutral pH

Self‐Supportive NiFe hydroxide with High Electrocatalytic Activity for Oxygen and Hydrogen Evolution Reaction

Ultrasonically Induced Sulfur-Doped Carbon Nitride/Cobalt Ferrite Nanocomposite for Efficient Sonocatalytic Removal of Organic Dyes

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Wasp-waisted behavior in magnetic hysteresis curves of CoFe2O4 nanopowder at a low temperature: experimental evidence and theoretical approach

Abstract: We theoretically and experimentally investigated wasp-waisted magnetic hysteresis curves at a low temperature for CoFe2O4 nanopowders.

Cited by 96 publications

References 32 publications

Photocatalytic Degradation of Organic Pollutants over MFe2O4 (M = Co, Ni, Cu, Zn) Nanoparticles at Neutral pH

Photocatalytic Degradation of Organic Pollutants over MFe2O4 (M = Co, Ni, Cu, Zn) Nanoparticles at Neutral pH

Self‐Supportive NiFe hydroxide with High Electrocatalytic Activity for Oxygen and Hydrogen Evolution Reaction

Ultrasonically Induced Sulfur-Doped Carbon Nitride/Cobalt Ferrite Nanocomposite for Efficient Sonocatalytic Removal of Organic Dyes

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Wasp-waisted behavior in magnetic hysteresis curves of CoFe₂O₄ nanopowder at a low temperature: experimental evidence and theoretical approach