Amount Of Fe Doping Research Articles

Facile modified polyol synthesis of FeCo nanoparticles with oxyhydroxide surface layer as efficient oxygen evolution reaction electrocatalysts

The oxygen evolution reaction (OER) at anode requires high overpotential and is still challenging. The metallic core-oxyhydroxide layer structure is an efficient method to lower an overpotential. We synthesized Fe rich FeCo core-Co rich FeCo oxyhydroxide layer with a different particle size of 173 nm, 225 nm, and 387 nm (FeCo 173, 225, 387) through a difference in the reduction rate of Fe/Co precursors using facile modified polyol synthesis. To investigate the effect of conductivity, CoFe2O4 nanoparticles of 80–130 nm were synthesized. Among samples, FeCo 173 showed remarkable catalytic performance of 316 mV at a current density of 10 mA/cm2 in 0.1 M KOH compared to RuO2 (408 mV), FeCo 225 (323 mV), FeCo 387 (334 mV), CoFe2O4 (382 mV). Moreover, FeCo 173 showed good stability for 60,000 s while RuO2 showed a gradual increase in overpotential to maintain 10 mA/cm2 after 15,000 s in chronopotentiometry. The excellent performance was attributed to Fe-rich metallic core, a small amount of Fe doping into CoOOH, and the synergic effect between the active site of Co rich FeCoOOH and conductive Fe rich metallic core. Following this result, it shows that the use of such FeCo electrodes has advantages in the production of hydrogen via electrochemical water oxidation.

Influence of Fe3+ ion doping on the luminescence emission behavior and photocatalytic activity of Fe3+, Eu3+-codoped TiO2 thin films

Abstract Thin films of Fe3+ doped TiO2:0.01Eu3+ nanoparticles were coated by sol-gel spin coating technique on glass substrates. The studies carried out by using X-ray Diffractometer, SEM-EDX, HRTEM, spectroscopic ellipsometer, Raman, EPR, UV–Vis, and fluorescence spectrometer techniques. The crystalline structure and phase formation of Fe doped TiO2:0.01Eu3+ nanoparticles were investigated using X-ray Diffractometer. The HRTEM pictures of 3%, and 5% Fe doped TiO2:0.01Eu3+ films confirmed that the particle size is about 11 nm and 9.5 nm respectively. Raman spectroscopy was used to study the phase identification and vibrational modes present in Fe, Eu codoped TiO2 films. The band gap declined with cumulative amount of Fe3+. The EPR analysis endorses that the Fe3+ ions are successfully doped in the lattice of Titania by replacing Ti4+ ions and formation of oxygen vacancies and Ti3+ sites. With 393 nm excitation, the Fe doped TiO2:0.01Eu3+ nanoparticles show characteristic photoluminescence in the visible range. The strong luminescence emission at 614 nm is related to the 5D0 → 7F2 ED transition. The emission peak intensity declined with an increase in the amount of Fe3+. J–O and radiative parameters of Fe doped TiO2:0.01Eu3+ films obtained from the emission spectra. These nanophosphor films having significant CIE chromaticity coordinate (x, y) values with high color purity might have potential applications in solid-state display devices. The photocatalytic activity (PCA) of Fe, Eu codoped TiO2 nanostructured films were estimated using decolorization of methylene blue (MB) and methyl orange (MO). Fe, Eu codoped TiO2 films exhibit strong photocatalytic performance than undoped and single doped TiO2 films. The degradation efficiencies significantly increase with an increase in Fe3+ doping concentration reached maximum at 3%Fe doping and then reduces gradually at high concentrations due to the formation of recombination centers for charge carriers at a higher amount of Fe doping.

Metal doped layered MgB2 nanoparticles as novel electrocatalysts for water splitting

Growing environmental problems along with the galloping rate of population growth have raised an unprecedented challenge to look for an ever-lasting alternative source of energy for fossil fuels. The eternal quest for sustainable energy production strategies has culminated in the electrocatalytic water splitting process integrated with renewable energy resources. The successful accomplishment of this process is thoroughly subject to competent, earth-abundant, and low-cost electrocatalysts to drive the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), preferably, in the same electrolyte. The present contribution has been dedicated to studying the synthesis, characterization, and electrochemical properties of newfangled electrocatalysts with the formal composition of Mg1−xTMxB2 (x = 0.025, 0.05, and 0.1; TM (transition metal) = Fe and Co) primarily in HER as well as OER under 1 M KOH medium. The electrochemical tests revealed that among all the metal-doped MgB2 catalysts, Mg0.95Co0.05B2 has the best HER performance showing an overpotential of 470 mV at − 10 mA cm−2 and a Tafel slope of 80 mV dec−1 on account of its high purity and fast electron transport. Further investigation shed some light on the fact that Fe concentration and overpotential for HER have adverse relation meaning that the highest amount of Fe doping (x = 0.1) displayed the lowest overpotential. This contribution introduces not only highly competent electrocatalysts composed of low-cost precursors for the water-splitting process but also a facile scalable method for the assembly of highly porous electrodes paving the way for further stunning developments in the field.

Sunlight-driven degradation of diethyl phthalate via magnetically modified biochar catalysts in water: Internal electron transfer mechanism

This study presents a one-step synthetic approach for magnetic biochar (MBC) photo-degradation of diethyl phthalate (DEP). The results showed that MBC exhibited better catalytic property for DEP degradation than BC, and its catalytic performance was influenced by the amount of Fe doping. Electron paramagnetic resonance (EPR), quenching experiments, and chemical probe studies confirmed the presence of persistent free radicals (PFRs), hydroxyl radicals (·OH), and superoxide anion radical (·O2−) in both of BC and MBC. Solar light promoted the formation of PFRs in BC system, which transferred electrons to oxygen to form ·O2−, thus yielding ·OH. On the other hand, electron transfer occurred between PFRs and Fe3+ for MBC, Fe2+ played an important role in activation of O2 and ·O2− production. Subsequently, photo-Fenton reaction was primarily responsible for ·OH formation. This work compared the different generation pathways for ROS between BC and MBC and provides new insight into the possible mediatory roles of BC in O2 activation under solar light by transition metals.

High-precision regulation synthesis of Fe-doped Co2P nanorod bundles as efficient electrocatalysts for hydrogen evolution in all-pH range and seawater

Abstract The hydrogen evolution reaction (HER) via water electrolysis has gained immense research attention. Seawater electrolysis provides great opportunities for sustainable energy production, but is extremely challenging. Transition metal phosphides are promising candidate electrocatalysts. Herein, we prepared a novel Fe–Co2P bundle of nanorods (BNRs) for catalyzing the HER in seawater electrolysis and over the entire pH range. Cobalt phosphides with different crystal phases and morphologies were obtained by varying the Fe doping amount. The Co:Fe molar ratio of 1:0.5 was found to be optimum. The Fe doping improved the HER performance of Co2P over the entire pH range by providing favorable electronic properties and morphology, lattice distortion, and special coordination environment. The Fe-Co2P BNRs showed higher catalytic activity than 20% Pt/C in seawater at high potentials. The density functional theory calculations revealed that the Fe doping reduced the hydrogen binding strength of Co2P to efficiently accelerate the HER kinetics and produce a favorable charge density. This study provides valuable insights into the design and development of high-efficiency HER catalysts for large-scale seawater electrolysis.

Influence of Fe-doping amounts on magnetocaloric properties of Gd-based amorphous microfibers

The effects of trace Fe-doping on the magnetic and magnetocaloric performances of Gd-based metallic microfibers were systematically and detailedly investigated in this article. Experimental results indicated that the Gd-based microfibers prepared by the rotated-dipping process are uniform and continuous, with typically amorphous structure characteristics and favorable thermal stability. Curie temperature TC of Gd-based amorphous microfibers increases with the rising of Fe content, and the TC of GdAlCoFe3 microfibers is the highest at 128.7 K (relatively increased by 15.3 K than before doping). Among the general magnetic performance indicators, the saturation magnetization Ms of GdAlCoFe2 microfibers reaches a peak at 264.04 emu/g. Furthermore, the values of magnetocaloric performance indexes of Gd-based amorphous microfibers increase firstly and then decrease with the rising of Fe-doping amount. When the external magnetic field Hex = 50,000 Oe, the maximum magnetic entropy change -ΔSmmax, refrigeration capacity RC and relative cooling power RCP of GdAlCoFe1 microfibers are 10.33 J/kg·K, 748.22 J/kg and 1006.90 J/kg, which increased by 0.07 times, 0.13 times and 0.16 times, respectively than before Fe-doping (namely -ΔSmmax = 9.68 J/kg·K, RC = 663.79 J/kg, RCP = 871.73 J/kg). From the perspective of microstructural changes, Fe-doping results in the formation tendency of atomic clusters and nanocrystals in micro-regions, the orderly orientation of atoms appears, and the magnetic anisotropy increases accordingly. In addition, the 3d electron layer of the doped Fe element in Gd-Al-Co-Fe quaternary alloy system enhances the RKKY indirectly exchange coupling interaction and changes the state of magnetic entropy, which in turn leads to an increase in Curie temperature and an improvement in magnetocaloric performance. Since RC and RCP are the main indicators in engineering applications, the GdAlCoFe1 amorphous microfibers can be selected as a low-temperature magnetic refrigeration working medium to provide technical guarantee for the application of magnetic refrigeration technology.

Design of co-symbiotic FexMnyO catalysts for NO reduction by CO

FexMnyO catalyst with different Fe content was prepared by ethylene glycol solvent-thermal method, and the CO-SCR activity of FexMnyO catalyst was tested to investigate the influence of Fe doping amount on the activity of manganese based catalyst.

High-performance porous carbon catalysts doped by iron and nitrogen for degradation of bisphenol F via peroxymonosulfate activation

Fabrication of high-performance, cost-effective and environmentally friendly carbocatalysts for environmental remediation is still a challenge. In this study, a series of iron and nitrogen co-doped porous carbon catalysts (Fe-N/C) were prepared through pyrolysis of Fe-doped zeolitic imidazolate framework-8. The catalytic performance of the Fe-N/C was evaluated for the degradation of bisphenol F via peroxymonosulfate (PMS) activation. Fe-N/C at appropriate Fe doping (0.5–5.0%) possessed hierarchically porous architecture with abundant micro- and meso-pores, rich defects, enhanced N doping and conductivity. Compared with N/C, Fe-N/C retained original polyhedral morphology and the particle size could be tuned by controlling Fe doping amount. An optimized catalyst, 1.0%Fe-N/C was obtained, which exhibited superior catalytic activity for the degradation of bisphenol F. The rate constant was 34.0 and 6.1 times of that for N/C and benchmark catalyst Co3O4, respectively. More importantly, the 1.0%Fe-N/C-PMS system was not affected by pH and common water components, and had high selectivity of organic contaminants. The mechanism of PMS activation by 1.0%Fe-N/C was examined with chemical, electrochemical and physical analyses (chemical probes, solvent exchange, ESR spectra and radical trapping). The results indicated that singlet oxygen was proved as the primary reactive species responsible for the degradation. Furthermore, Fe-Nx, pyridinic/graphitic N and structural defects were possible catalytically active sites. This study provides a new insight for development of high-performance carbocatalysts toward environmental remediation.

Structural, Optical and Magnetic Properties of ZnS Co-doped with Cd and Fe

Cd and Fe co-doped nano ZnS samples (Zn0.75−xFexCd0.25S) are prepared by thermolysis method. The effect of Fe doping content on the structural parameters, infrared absorption bands and the energy gap of Zn0.75Cd0.25S are investigated using Rietveld analysis for synchrotron X-ray diffraction data, Fourier transform infrared and UV–Vis spectroscopy. The energy gap first decreases upon doping then it increases with further Fe-doping. The photoluminescence spectroscopy reveals that the emitted colors for Zn0.75−xFexCd0.25S are dependent on the excitation wavelengths and the amount of Fe-doping. Magnetization measurements indicate that Zn0.75Cd0.25S possess a diamagnetic behavior while Zn0.55Fe0.2Cd0.25S exhibits a weak ferromagnetic nature with small coercivity and saturation magnetization obtain from the law of approach to saturation.

Boosting photocatalytic degradation of RhB via interfacial electronic effects between Fe-based ionic liquid and g-C3N4

The Fe-based ionic liquid doped g-C3N4 (FeCN) photocatalyst was firstly prepared base on ultrathin g-C3N4 obtained by multiple calcination method with a metal-based reactive ionic liquid [Omim]FeCl4 for the degradation of Rhodamine B (RhB). Experimental results revealed that Fe3+ species were doped into the framework of g-C3N4. The effect of the amount of Fe-doping on the catalytic activity was performed. The result showed that the FeCN could effectively degrade RhB under the condition of visible light irradiation. The photocurrent analysis showed that the incorporation of Fe3+ into g-C3N4 material could accelerate the separation of the photogenerated carriers significantly. At the same time, the reactive species generated during the photodegradation process were tested by radicals trapping experiments and electron spin resonance (ESR). It was proposed that the synergistic effect of O2•− and ·OH contributed to degrade RhB efficiently.

Residual Fe enhances the activity of BiOCl hierarchical nanostructure for hydrogen peroxide activation

BiOCl hierarchical nanostructures with trace amount of Fe doping (∼1 wt%) have been successfully prepared via a facile one-step room temperature method, which exhibits enhanced photocatalytic activity for the degradation of methyl blue (MB) under visible light irradiation. It is found that the photocatalysis of the Fe-doped BiOCl undergoes a hydroxyl radicals dominated photo-Fenton process. XRD, XPS and EDS data reveals that the doped Fe ions exist in the lattice of BiOCl by replacing the Bi atoms. The presence of Fe not only extends the solar energy response of the material from 350 to 600 nm by creating a new energy level in the forbidden band of BiOCl, but also alters the chemical state of the surface, resulting in the electron flowing favorably to H2O2 rather than oxygen molecular in aqueous solution.

In-situ Fe-doped g-C3N4 heterogeneous catalyst via photocatalysis-Fenton reaction with enriched photocatalytic performance for removal of complex wastewater

In this work, an in-situ Fe-doped g-C3N4 catalyst was synthesized by thermal shrinkage polymerization. A heterogeneous photocatalysis-Fenton system was formed with the addition of H2O2 under visible irradiation and exhibited excellent and recyclable removal performance for refractory contaminants such as: phenol, bisphenol A, 2, 4-dichlorophenol and coking wastewater, which was due to the formation of σ-π bonds via Fe and N element in the triazine ring skeleton of Fe-g-C3N4. The electrons generated can be quickly transferred to Fe3+ to form Fe2+ under the interaction of the chemical bond. The efficiency of photoelectron separation was accelerated, and OH radicals were quickly generated with the reaction between Fe2+ and H2O2. Specifically, the recycling of Fe can be achieved in the heterogeneous system, which avoids the problems for the recycling and secondary pollution of Fe ions in homogeneous Fenton reaction. Parameters such as Fe doping amount, hydrogen peroxide concentration, pH value, catalyst concentration, and complex wastewater (coking wastewater) were optimized. The degradation of coking wastewater were also performed, and the chemical oxygen demand (COD) and total organic carbon (TOC) values for 300 ml coking wastewater could be reduced from 64.6 and 25.3 mg/L to 22.8 and 12.3 mg/L in 60 min, respectively. These results demonstrate photocatalysis-Fenton reaction with Fe-g-C3N4 catalyst is promising for environmental remediation.

Accelerated oxygen evolution kinetics on nickel–iron diselenide nanotubes by modulating electronic structure

Development of cost-effective, highly active and durable electrocatalysts is highly demanded for oxygen evolution reaction (OER), which is an indispensable process involved in water splitting cells and metal-air batteries. Here, we accelerate the sluggish OER kinetics by controlling the morphology and engineering electronic structure of FexNi1-xSe2 catalysts. FexNi1-xSe2 nanotubes with tunable stoichiometry were fabricated through the removal of sacrificial templates (Cu2O nanowires) and subsequent low-temperature selenization process. By precise tuning of Fe doping amount in FexNi1-xSe2 nanotubes, the optimized Fe0.125Ni0.875Se2 nanotubes show a low overpotential of 253 mV at a current density of 10 mA cm−2, a small Tafel slope of 49 mV dec−1, and superior durability. By combining analysis of the experimental results with density-functional-theory (DFT) simulations, we reveal that the in-situ formed amorphous hydroxyl group layers on the surface of Fe0.125Ni0.875Se2 (Fe0.125Ni0.875Se2–OH) enable highly efficient oxygen evolution catalysis. The Fe dopant can achieve a near-optimal adsorption energy for OER intermediates (OH*, O*, and OOH*) on the oxidized surface of Fe0.125Ni0.875Se2–OH, which is responsible to the enhanced OER performance of Fe0.125Ni0.875Se2. This work paves a new way for exploring low cost and highly active OER electrocatalysts based on ternary metal selenides with hollow structure.

Structural, Dielectric and Impedance Spectroscopic Studies on Fe Doped BaTiO3

Compositions with x=0.03, 0.05 and 0.10 are synthesized in the syst em BaFexTi1–xO3 using conventional solid state reaction method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). XRD patterns reveal the coexistence of tetragonal and hexagonal phases which are strongly affected by the level of Fe doping. The hexagonal phase increases with increasing x, being maximum for x=0.10. SEM images show the presence of agglomerated grains which increase in size with amount of Fe doping. SEM for x=0.10 shows mostly rod-like or rectangular grains indicating predominantly hexagonal phase. Dielectric and impedance measurements have been carried out in the frequency range 20 Hz-1 MHz as a function of temperature (300-650 K). The samples with x=0.03 and 0.05 exhibit diffuse phase transition. Using complex impedance analysis equivalent circuit models have been developed which represent the data well and successfully separate out the contributions of tetragonal phase, hexagonal phase, grain boundaries and electrodes.

Electrochemical performance of FexMn1−x-based metal–organic frameworks as electrode materials for supercapacitors

We use Fe as dopant in the metal–organic framework (MOF) of [(CH3)2NH2]Mn(HCOO)3, and four crystals were obtained with hydrothermal method according to the doping ratio: [(CH3)2NH2]Mn(HCOO)3, [(CH3)2NH2]Fe0.1Mn0.9(HCOO)3, [(CH3)2NH2]Fe0.2Mn0.8(HCOO)3 and [(CH3)2NH2]Fe0.3Mn0.7(HCOO)3. And their electrochemical properties were studied by measuring cyclic voltammetry, galvanostatic charge–discharge and electrochemical impendence spectrum. The results showed that the sample of [(CH3)2NH2]Fe0.1Mn0.9(HCOO)3 performed the highest specific electrical capacity of 167.95 F g−1 at a current density of 0.01 A g−1. This work suggests that a small amount of Fe doping can improve the electrochemical performance of MOFs-based supercapacitors.

Effects of Fe doping on photoluminescent and magnetic properties of CaTiO3:Eu3+

In this work, photoluminescent and ferromagnetic bifunctional properties were found in Fe-doped CaTiO3:Eu3+ ceramic materials synthesized via ceramic sintering method. With appropriate amount of Fe doping in CaTiO3:Eu3+ ceramic, both photoluminescent intensities and magnetization strength of samples increase. When doping content of Fe is 0.05 mol%, the ceramic has optimal photoluminescent intensity. After 0.05 mol% Fe-doped CaTiO3:Eu3+ ceramic material experiences 0.15 T external magnetic treatment for 12 h, main red emission at 615 nm ([5D0→7F2]) increases ~80%, and 593 nm emission ([5D0→7F1]) increases ~109%. This study is helpful for understanding effects of Fe doping on photoluminescent and magnetic properties of CaTiO3:Eu3+ ceramic and provides valuable reference for effects of Fe impurities on photoluminescent and magnetic properties of other materials.

Enhanced visible-light photocatalytic activity of Bi2O2CO3 nanoplates by Fe-doping in the degradation of rhodamine B

In this study, Fe-doped Bi2O2CO3 nanoplates were fabricated using a facile solvothermal approach. The successful substitution of Bi3+ by Fe3+ was identified by a shift in the (010) diffraction peak of Bi2O2CO3 at 2θ = 30.2°. A controllable amount of Fe doping in Bi2O2CO3 was utilized to gradually tailor the band gap energy from 3.39 eV to 2.68 eV, resulting in the absorption edge switched from ultraviolet light to visible-light region. Compared to the pure Bi2O2CO3, Fe-doped Bi2O2CO3 nanoplates exhibited an enhanced visible-light photocatalytic activity. With the gradual increase of Fe dopant amount, the photocatlytic activity of Fe-doped Bi2O2CO3 increased initially, and then slightly decreased. Further reactive species trapping experiments demonstrated that holes (h+) and superoxide anion radicals (O2−) played important roles in the photocatalytic oxidation.

Orthogonal design Fe, N co-doped TiO2/GF photo catalyst treatment of nitrobenzene wastewater.

Objective: to determine the optimum preparation conditions and the treatment effect of TiO2/GF photo catalyst by four factors and three horizontal orthogonal tests. Methods: the preparation of sol-gel immersion Fe, N total light catalyst, doping TiO2 / GF in homemade photo catalytic reactor, based on nitrobenzene degradation rate, design and discusses the calcination time, calcination temperature, Fe doping amount and N doping amount of light the influence of catalyst preparation and its physical and chemical properties. Results: the results showed that the main order of influence was: >Fe doping, >N doping, > calcination time; The catalytic activity of co-doped photo catalyst is better than that of single doped TiO2 catalyst. Conclusion: the best preparation conditions as follows: 2.5 h calcination time, calcination temperature 550 °C, Fe doping amount 0.5% (mass fraction) and N doping amount is 0.45% (mass fraction), deal with 40 mg/L of nitrobenzene degradation, nitrobenzene wastewater degradation rate was 86.5%. The catalyst can be reused.

Effect of transition metal oxidation state on crystal structure and magnetic ordering in frustrated ABaM4O7 systems (A= Y, Ca; M= Co, Fe): X-ray diffraction, soft X-ray absorption, and magnetization studies

We present X-ray diffraction patterns, soft Ca, Co, and Fe L2,3 absorption spectra, magnetic susceptibility, and temperature dependent magnetization measurements in order to characterize ABaM4O7 solid solutions A = Y, Ca; M = Co, Fe). Cobalt ions are in 2 + and high-spin 3 + oxidation states. In the iron-doped solid solutions, Fe ions were found to be trivalent. Doping with Fe ions leads to a decreasing amount of Co3+ ions. Magnetic properties of the studied samples showed a spin-glass behavior. Negative values of the Curie–Weiss temperatures indicated the predominance of antiferromagnetic exchange interactions. The freezing point of the magnetic moments is 51 K and does not vary with the amount of Fe doping.

Iron and carbon codoped WO3 with hierarchical walnut-like microstructure for highly sensitive and selective acetone sensor

Current metal-oxide-based sensing materials are confronted with several challenges, especially in sensitivity, selectivity and stability, for their application in the breath acetone analysis. Herein, hierarchical walnut-like Fe-C-codoped WO3 microspheres were synthesized and characterized by X-ray diffraction (XRD), Raman spectra, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The amount of Fe doping was optimized based on detecting the acetone responses dependent on the operating temperature. The sensor based on the optimal Fe-C-codoped WO3 (FW3) exhibited high response to acetone and very low responses to NH3, CO, toluene, methanol, ethanol and NO. The results indicate that the optimized material possesses high sensitivity and good selectivity toward acetone vapor. Besides, the FW3 sensor presented superior anti-interferential ability to various mixed-gas systems. More importantly, the responses of the sensor exhibited no obvious fluctuation over 12 weeks, implying good long-term stability of the synthesized material. We suggest that the phase, morphology and the increased number of oxygen vacancies induced by Fe doping are the underlying reason for the improved gas sensing performance of the Fe-C-codoped WO3 microspheres.