Fe Doping Research Articles

Selective oxidation behavior based on iron-doped MOF derived carbon-based catalysts: Active site regulation and degradation mechanism analysis

Selective removal of target organic pollutants in complex water quality of municipal sewage is extremely important for the deep treatment of water quality. Here, energetic MOF and Fe-MOF are doped in electrostatic spinning process to adjust the structure and composition of the catalysts, active oxygen species (ROSs), realizing the selective removal of organic pollutants. Non-azo and azo pollutants are selected as target pollutants. Catalysts PCFe-8 with Fe nanoclusters, EPCFe-8 with Fe-Nx, and EPC-8 without Fe doping are used to activate peroxymonosulfate (PMS) for degrading pollutants. The results show that the PCFe-8/PMS system can produce the most SO4− and exhibit superior removal of azo pollutants, whereas the degradation behavior of non-azo pollutants is more inclined to occur in the EPCFe-8/PMS system and the EPC-8/PMS system. This work provides a reference for elucidating the relationship between catalyst structure and components, types of ROSs, and selective degradation of pollutants.

Ultrasonic enhanced liquid-liquid interfacial reaction for improving the synthesis of Iron-doped carbon dots (Fe-CDs) for achieving superior photocatalytic performance

The precise and controllable preparation of carbon nanomaterials under mild conditions poses a great challenge, especially for metal-catalysed multiphase preparation. This work proposes an efficient method that utilizing high-density ultrasound to enhance the liquid-liquid interfacial reaction system. Iron-doped carbon dots (Fe-CDs) are successfully synthesized in such a normal temperature and atmospheric-pressure reaction condition. It is shown that transient cavitation provides a high-temperature and high-pressure microenvironment for the preparation of Fe-CDs. Moreover, the size of the reactant droplets is reduced from 200.0 ± 17.3 μm to 8.1 ± 2.9 μm owing to the acoustic flow and cavitation effects, which increases the specific surface area of the two reacting phases and improves the mass transfer coefficient by more than 252.0 %. As a result, the yield increases by more than an order of magnitude (from 0.7 ± 0.1 % to 11.9 ± 0.2 %) and the Fe doping rate reaches 20.9 %. The photocatalytic oxidation conversion of 1,4-Dihydropyridine (1,4-DHP) using the obtained Fe-CDs is as high as 98.2 %. This research gives a new approach for the efficient and safe production of Fe-CDs, which is promising for industrial applications.

First-principles calculation on electronic properties of hydrogen evolution reaction of Ni-based electrode surfaces with different monatomic doping

At present, the hydrogen evolution reaction (HER) of Ni-based electrode has an important influence on water electrolysis hydrogen production technology, involving complex electrochemical process of electrode. In this project, Materials Studio (MS) software was used to design and construct Ni-based electrode surface (NES) models with monatomic Mo, Co, Fe, Cr doping, and the NES models attached 1 H atom and 2H atoms were denoted as the NES-H models and NES-2H model, respectively. Then the first-principles calculation was carried out.The results showed that the doping of different atoms can effectively change the work function of the pure Ni. In the charge transfer process of the four NES-2H models, the distance between the two H atoms is most affected by Mo doping, and they leave the Ni electrode surface as a single H ion, respectively, while the effect on Co, Fe and Cr doping is relatively consistent, and they leave the Ni electrode surface with H2 molecules, respectively. The doping of four single atoms changes the distance of valence band (VB) top and conduction band (CB) bottom from Fermi level in NES, NES-H and NES-2H models, and affects the HER, in which Mo doping has the greatest effect. The TDOS of the above models is mainly derived from the PDOS of the d orbitals of the doped atoms and Ni atoms. The results will provide a theoretical basis for the research and development of Ni-based electrode materials in HER.

Tailoring Ni 3d orbitals in Ni-Fe/Ni foam heterostructures for enhanced H* adsorption and boosted electrocatalytic nitrate reduction performance

The electrochemical nitrate (NO3−) reduction (ENR) in wastewater, a promising remediation strategy, is often impeded by the essential use of costly noble metals. This study introduces an innovative non-noble Ni-Fe/Ni foam cathode fabricated via one-step electrodeposition technique. Efficient nitrate removal (99.4 %) was achieved with the selectivity of 83.6 % to NH3. The exceptional performance can be ascribed to the augmented active sites and the synergistic interaction between Ni and Fe. The leftward shift of the 3d orbitals density of Ni and the elevation of density at the Fermi level on Ni foam heterostructures, consequent to Fe doping, enhance the adsorption of H*. The addition of reactive chlorine species, generated through anodizing in Cl− mediated system, further improves N2 selectivity by oxidizing intermediate NH4+ product. The coupled anodic oxidation method employed herein achieves nearly 100 % removal efficiency of total nitrogen (TN) for initial concentration of 100 mg/L within 180 min, under the conditions of 1.5 g/L Cl− concentration and a current density of 25 mA cm−2. The findings underscore the potential of the Ni-Fe/Ni foam cathode within a Cl− mediated electrocatalytic framework for nitrate wastewater treatment, providing novel insights into the design of cathode catalysts and anodic coupling strategies for efficient TN removal.

Antibacterial efficacy of Rumex dentatus leaf extract-enriched zinc oxide and iron doped zinc nanoparticles: a comparative study

In the current investigation, zinc oxide (ZnO) nanoparticles and Fe-doped ZnO nanoparticles were sustainably synthesized utilizing an extract derived from the Rumex dentatus plant through a green synthesis approach. The Scanning electron microscope (SEM), X-ray diffraction (XRD), Energy-dispersive x-ray spectroscopy (EDX), Ultra-violet visible spectroscopy (UV–vis) spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and Thermogravimetric analysis (TGA) techniques were used to examine the compositional, morphological, optical, and thermal properties of both samples. The doping of iron into ZnO NPs has significantly influenced their properties. The analysis firmly established that both ZnO NPs and Fe-doped ZnO NPs have hexagonal wurtzite structures and spherical shapes by XRD and SEM. The EDX analysis suggests that iron atoms have been successfully integrated into the ZnO lattice. The change in color observed during the reaction indicated the formation of nanoparticles. The UV–vis peaks at 364 nm and 314 nm confirmed the presence of ZnO NPs and Fe-doped ZnO NPs, respectively. The band gap of ZnO NPs by Fe dopant displayed a narrowing effect. This indicates that adding iron ions to ZnO NPs offers a control band gap. The thermal study TGA revealed that Fe-doped ZnO NPs remain stable when heated up to 600 °C. The antibacterial efficacy of ZnO NPs and Fe-doped ZnO NPs was evaluated against several bacterial strains. The evaluation is based on the zone of inhibition (ZOI). Both samples exhibited excellent antibacterial properties as compared to conventional pharmaceutical agents. These results suggest that synthesizing nanoparticles through plant-based methods is a promising approach to creating versatile and environmentally friendly biomedical products.

Enhancement the linear/nonlinear optical and magnetic properties of ZnCo2O4 nanostructures through Ni/Fe dual doping

Nano Zn0.9Ni0.1Co2-xFexO4 samples were prepared using the hydrothermal procedure in order to enhance the functional characteristics of ZnCo2O4 sample. The structural and microstructural parameters of the prepared samples were determined through Rietveld and FTIR analyses. The morphologies and compositions of the samples were examined by SEM and EDS techniques. Upon Ni2+ doping, the bandgap energy of nano ZnCo2O4 decreased from 2.22 eV to 3.61 eV–2.18 eV and 3.51 eV. Doping with Fe caused a slight decrease in bandgap energy for x = 0.05, then an increase for a higher content of Fe. Several empirical equations were used to determine the refractive index from the corresponding obtained optical energy gap values. As the Fe content rose to 5 %, the value of refractive index and nonlinear optical parameters increased; thereafter, it declined with additional Fe doping. The photoluminescence technique was used to analyze defects and processes of charge carrier recombination in the samples. ZnCo2O4 sample exhibits paramagnetic performance. With the addition of Ni to ZnCo2O4, the magnetic characteristics of the sample became superparamagnetic. Samples doped with Ni and various quantities of Fe exhibit a weak ferromagnetic behavior. The effect of doping on the magnetic transition, coercivity, saturation magnetization and remanent magnetization was explored.

SILAR-engineered ZnO thin films: exploring the impact of Ni, Co, and Fe dopants on structural, optical, and electronic properties

SILAR-engineered ZnO thin films: exploring the impact of Ni, Co, and Fe dopants on structural, optical, and electronic properties

Retraction Note: Influence of Fe doping on the photocatalytic dye degradation and H2 evolution properties of BiVO4 thin films under visible-light irradiation

Retraction Note: Influence of Fe doping on the photocatalytic dye degradation and H2 evolution properties of BiVO4 thin films under visible-light irradiation

The intermediate valence state Mo5+ in Fe doping La2(MoO4)3 boosting electrochemical nitrogen reduction

NH3 is considered as an ideal fuel for fuel cells to achieve zero carbon emissions due to its high energy density (at liquefaction) and carbon-free properties. The zero-carbon clean electrocatalytic nitrogen reduction reaction (NRR) is one of the alternative routes for NH3 synthesis. The efficiency of NRR is restricted by the high stability of N N and the slow reaction rate. In this study, La2(MoO4)3 (LaMo), and x%Fe doping-LaMo (x = 3, 5, 7, and 10) are synthesized via a hydrothermal method. The strong electron-donating ability of Fe converts a part of Mo6+ to Mo5+ and Mo4+ improving the electronic environment. The presence of Mo5+, an intermediate valence state, facilitates the oxidation and reduction reactions and establishes rapid electron transport channels. The electron transport of Mo6+↔e−Mo5+ is easier than Mo6+↔2e−Mo4+. Furthermore, the Mo5+ activates N2 and enhances N2 adsorption, boosting the NRR performance. Importantly, the content of Mo5+ exhibits a positive correlation with NH3 yield rate (R2 = 0.89), and Faradaic efficiency (FE, R2 = 0.95). Consequently, the 5%Fe–LaMo exhibits the highest Mo5+ percentage (75.9 %) and NRR performance (NH3 yield rate:30.4 μg h−1 mgcat−1, FE: 3.6 %). Thus, this study proposes a method to enhance the NRR performance by element doping with strong electron-donating ability to regulate the Mo5+ percentage.

Improved thermodynamic properties of (Sc, V, Ti, Fe, Mn, Co, and Ni) doped NaBH4 for hydrogen storage: First-principal calculation

Sodium borohydride (NaBH4) shows promise as a hydrogen storage option, but its substantial thermodynamic stability limits its practical application. Enhancing NaBH4 by introducing transition metals is an effective approach to enhance its hydrogen-related characteristics. Nevertheless, even with the most successful additives, the temperatures needed for hydrogen release remain too elevated, exceeding 400 °C, which hinders its practical utility. Using first-principles density functional, we have investigated the potential of sodium borohydride as a hydrogen-based fuel source. Our focus has been on the stable α-phase NaBH4 structure with space group symmetry F-43m (216), aiming to understand the impact of 3d transition metal (Sc, V, Ti, Fe, Mn, Co, and Ni) doping on the structural, electronic, and dehydrogenation properties of the NaBH4 system. Furthermore, the heat of formation and desorption temperature values obtained align with the stability and volumetric capacity criteria set by the U.S. Department of Energy (DOE). Our findings indicate that doping transition metals at the Na site weakens the B–H bonds, thereby enhancing the dehydrogenation performance. Among the various systems studied, those doped with Sc and Ti exhibit the most favorable dehydrogenation properties.

Rational Design of Cost-Effective Metal-Doped ZrO2 for Oxygen Evolution Reaction

HighlightsSurface energy and surface Pourbaix diagram reveal that ZrO2 (1¯11\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\overline{1 }11$$\\end{document}) is the most thermodynamically stable facet and is preferentially occupied by HO* at the equilibrium potential of oxygen evolution reaction (OER).Microkinetic modeling analyzed the OER activity of 40 single-metal doped ZrO2 and identified 16 metals exhibit improved catalytic activity, with Rh and Fe dopants showing the remarkable improvement.Thermodynamic free energy diagrams, density of states analysis, and ab initio molecular dynamics simulations further confirm that Fe–ZrO2 and Rh–ZrO2 are highly promising catalysts for OER, showcasing low ΔG for the rate-determining step, high conductivity, and exceptional stability.

Effect of doping TiO2 with Fe on the loading of a natural extract

This study explores the relationship between Fe doping in TiO2 nanoparticles and their capacity to load a natural citrus extract. Synthesized TiO2 (T) and TiO2-Fe (TF) nanoparticles were characterized using XRD patterns, N2 physisorption, UV–Vis and FTIR spectroscopy, and electron microscopy. Fe doping induced shifts in X-ray diffraction patterns and broadened absorption bands in UV–Vis spectra, reflecting changes in crystal structure and electronic transitions. BET analysis revealed increased surface area with Fe doping. Loading of the natural citrus extract was confirmed by FTIR. SEM and TEM images displayed slight morphological changes and a reduced nanoparticle size after Fe doping. Finally, Fe doped TiO2 demonstrated an improvement in loading ability with loading values up to 82.4%.

Transition metal (Fe, Co, Ni)-doped cuprous oxide nanowire arrays as self-supporting catalysts for electrocatalytic CO2 reduction reaction to ethylene

The transition metal (Fe, Co, Ni)-doped cuprous oxide (Cu2O) nanowire arrays on Cu mesh (CM) (M-Cu2O@CM, M = Fe, Co, Ni) are successfully synthesized for the electrocatalytic CO2 reduction reaction (CO2RR) to ethylene (C2H4) through the simple calcination and impregnation-exchange methods. Systematic characterizations have demonstrated that the Ni/Co doping in Cu2O@CM is conducive to stabilizing the Cu+ sites due to the electron transfer from Cu2O to Ni/Co, while the Fe doping has the opposite effect. Consequently, they show the different electrocatalytic performances of Ni-Cu2O@CM > Co-Cu2O@CM > Cu2O@CM > Fe-Cu2O@CM for CO2RR to C2H4 in an H-cell. Among them, Ni-Cu2O@CM exhibits the ∼2.0-fold faradaic efficiency for C2H4 (58.2 % vs. 28.7 %) and the ∼2.5-fold current density (−37.6 vs. −15.0 mA·cm−2) at −1.1 V vs. RHE, as compared with Cu2O@CM. Further experiments reveal that during the electrocatalytic CO2RR, the Ni-Cu2O@CM can generate more *CO, which promotes the C–C coupling reaction. The activity of Co-Cu2O@CM is lower than Ni-Cu2O@CM because of the strong adsorption of *COOH, while the Fe-Cu2O@CM even exhibits a lower activity than Cu2O@CM. This work provides an insight into the effect of transition metal-doped Cu2O array on the electrocatalytic CO2RR to C2H4 products.

Boosting photoelectrocatalytic oxygen evolution activity of BiVO4 photoanodes via caffeic acid bridged to NiFeOOH

Bismuth vanadate (BiVO4) is a promising n-type photoanode material for photoelectrochemical (PEC) water splitting. However, its activity is impeded by poor charge carrier transport and sluggish oxygen evolution kinetics. In this study, we reports a Fe doping and caffeic acid (CA)/NiFeOOH (NiFe) modification with BiVO4 photoanode (NiFe/CA/Fe-BiVO4) to enhance the PEC water oxidation performance and stability. The modified BiVO4 demonstrates significant advantages in promoting the PEC performance and stability. Specifically, Fe doping via in-situ electro-deposition results in smaller crystal sizes, larger specific surface areas, and more exposed active sites. Furthermore, co-catalyst NiFe connects with Fe-BiVO4 through CA bridge facilitates a more uniform self-assembly distribution of NiFe on BiVO4 surface. The NiFe/CA/Fe-BiVO4 exhibits an excellent photocurrent density of 6.2 mA/cm2 at 1.23 VRHEand demonstrates good stability at 0.8 VRHE. In addition, the composite photoanode shows a high applied bias photon-to-current efficiency (ABPE) value of 2.15% at 0.65 VRHE. EPR and in-situ FTIR confirm the generation of superoxide active species (O2- and ·O2-) during the PEC water oxidation reaction.

Rich oxygen vacancies mediated metal-insulator transition materials toward ultrasensitive sensing and energy conversion

Regulating structural phase transitions of metal insulator transition (MIT) correlated materials is an ideal approach to modulate their properties. However, due to phase transition hysteresis, ultrasensitive electron transition is difficult to achieve. Here, we develop a convenient method via Fe ions surface doping-induced oxygen vacancies (OVs) at the Ti3O5 surface to enable ultrasensitive electronic transitions. The Fe doping promotes the formation of free electrons, which is attributed to the reduced bandwidth, making it relatively easy for valence band electrons to leap to the conduction band. The formation of OVs increase the electron concentration and enhance the electronic conductivity (2.49×10−4 S/cm) at low temperatures, resulting in an ultrasensitive sensing over a wide temperature range before metal insulator transition. This unique property facilitates its application in fire warning with ultrasensitive sensing (response time 0.63 s, and response temperature 150 °C) and good durability. Moreover, the as-obtained MIT correlated material with rich-OVs structure exhibits excellent oxygen sensing and photothermal conversion properties. These results offer a novel design for MIT correlated materials and provide an innovative insight for modulating their multifunctional properties.

Self-supporting nanosheet electrode for efficient oxygen evolution in a wide pH range: engineering electronic structure of Co3O4 by Fe doping

Self-supporting nanosheet electrode for efficient oxygen evolution in a wide pH range: engineering electronic structure of Co3O4 by Fe doping

SiO2 and Fe cation synergistically modify the LaMnO3 NTC thermistors with high stability

SiO2 insulator and Fe2O3 dopant was simultaneously used to modify the crystalline phase, morphology and electric properties of LaMnO3 ceramics. Results show that there are several merits after modification. On the one hand, the addition of SiO2 is demonstrated to have multifunction to the LaMn1-xFexO3 (0 ≤ x ≤ 0.5) (LMFO) ceramics. After adding SiO2, the surface of LMFO ceramics tend to be flat, the degree of densification increases, the porosity decreases, and the pores almost disappear. Meanwhile, the resistance drift rate of LaMnO3 with SiO2 is reduced and the aging stability is improved. In addition, the crystalline structure of LMFO ceramics transform from hexagonal perovskite phase (x ≤ 0.2) to cubic perovskite phase (x ≥ 0.25) along with the Fe-doping contents increase. Moreover, the grain size decreases and the grain boundaries increase with the increase of Fe content. X-ray photoelectron spectroscopy (XPS) spectra show that both the Mn4+/Mn3+ ratio and the oxygen vacancy concentration decrease with increasing Fe content. Resistivity ρ25°C raised from 2.84 Ω cm to 65.38 Ω cm, and material constant B25/50 increased from 139.36 K to 1751.78 K. Fe doping significantly improves the stability of LMFO ceramics, and the minimum value of resistance drift rate is 0.168 % after aging at 125 °C for 500 h. The above results confirm that the SiO2 modified LMFO ceramic is a high stability negative temperature coefficient (NTC) thermistor.

Sublayer-Sulfur-Vacancy-Induced Charge Redistribution of FeCuS Nanoflower Awakening Alkaline Hydrogen Evolution.

Advancing the progress of sustainable and green energy technologies requires the improvement of valid electrocatalysts for the hydrogen evolution reaction (HER). Reconfiguring charge distribution through heteroatom doping-induced vacancy serves as an effective approach to implement high performance for HER catalysts. Here, we successfully fabricated Fe-doped CuS (FeCuS) with the sublayer sulfur vacancy to judge its HER performance and dissect the activity origins. Density functional theory calculation further elucidates that the primary factor contributing to the heightened HER activity is that the sublayer sulfur vacancies awaken the charge redistribution. In addition to effectively decreasing the energy barrier associated with the Volmer step, it modulates the adsorption/desorption capacity of H*. As a result, its intrinsic activity for the HER has significantly increased. Concretely, the obtained FeCuS displays an excellent catalytic performance, whose Tafel slope is only 59 mV dec-1 and the overpotential (at 10 mA cm-2) is as low as 71 mV in an alkaline environment, surpassing the majority of previously documented catalysts in scientific literature. This work shows that the construction of sublayer sulfur vacancies by Fe doping can achieve the charge redistribution and precise tuning of electronic structure; thereby, the inert CuS can be transformed into highly efficient electrocatalysts.

Crystal Structure Regulation of CoSe2 Induced by Fe Dopant for Promoted Surface Reconstitution toward Energetic Oxygen Evolution Reaction.

Most nonoxide catalysts based on transition metal elements will inevitably change their primitive phases under anodic oxidation conditions in alkaline media. Establishing a relationship between the bulk phase and surface evolution is imperative to reveal the intrinsic catalytic active sites. In this work, it is demonstrated that the introduction of Fe facilitates the phase transition of orthorhombic CoSe2 into its cubic counterpart and then accelerates the Co-Fe hydroxide layer generation on the surface during electrocatalytic oxygen evolution reaction (OER). As a result, the Fe-doped cubic CoSe2 catalyst exhibits a significantly enhanced activity with a considerable overpotential decrease of 79.9 and 66.9 mV to deliver 10 mA·cm-2 accompanied by a Tafel slope of 48.0 mV·dec-1 toward OER when compared to orthorhombic CoSe2 and Fe-doped orthorhombic CoSe2, respectively. Density functional theory (DFT) calculations reveal that the introduction of Fe on the surface hydroxide layers will tune electron density around Co atoms and raise the d-band center. These findings will provide deep insights into the surface reconstitution of the OER electrocatalysts based on transition metal elements.

Enhanced CO2 methanation activity of Ni-Rutile-based catalyst by tuning the metal−support interaction with Fe doping

CO2 methanation is an effective way for CO2 recycling, and nickel-based catalysts have attracted much attention in this field due to their excellent CH4 selectivity and cost-effectiveness; however, their applications are limited by their suboptimal catalytic activity. In this work, the catalytic activity of Ni-rutile-based catalysts was increased by almost an order of magnitude simply by doping the rutile with Fe. Series characterizations show that three factors that mainly contributed to the improved catalytic performance of the Ni/Fe-Rutile, which are the reduction of the Ni size, the increase of the basic sites, and the inhibition of the encapsulation of the Ni particles by the support. With Fe doping, the OH and oxygen vacancies on the rutile surface were reduced, which made the support difficult to reduce and thus suppressed the encapsulation of Ni by the support. As a result, the number of exposed active sites on the Ni/Fe-Rutile which with a smaller Ni size was further successfully increased, and the catalytic activity was significantly improved. This study provides new ideas for the design of activity-enhanced supported catalysts from the perspective of tuning the metal-support interaction and may be applicable to other reducible oxide-supported metal catalysts.