Fe-doped NiO Research Articles

Novel Fe doped NiO-based electrode material for photoactivated catalyst and supercapacitor application

Pure NiO and Fe-doped NiO NPs were prepared using coprecipitation synthesis for potential usage in supercapacitors and photocatalytic degradation of MB dye. The synthesized materials such as NiO, Fe1%NiO, Fe3%NiO, Fe5%NiO, and Fe7%NiO are efficient photocatalysts. Different characterization techniques like XRD, SEM, EDX, PL, and UVVis spectroscopy were used to examine synthesized nanomaterial. In order to improve the photocatalytic activity, the optical properties of prepared nanoparticles were enhanced by adding Fe into NiO. The optimal sample Fe5%NiO with bandgap 3.21 eV led to the degradation of 95 % of MB dye during the time interval of 120 min. The optimal catalyst's high ratio of surface-to-volume provides many active sites to degrade the pollutant. Cyclic test and reusability were also performed to check the stability of the optimum catalyst. To study the capacitive properties CV, GCD, and EIS techniques were utilized. The greatest specific capacitance of the 5 % Fe-doped NiO is equivalent to 1200 F/g, suggesting a significant increase above other reported materials based on NiO. These nanostructures showed good charging-discharging retention. The high capacitance of these nanostructures has shown that they have potential use in supercapacitors. This study will be helpful for manufacturing innovation.

Improved electrochemical performance of the iron-doped NiO nanoparticles at varying calcination temperatures and examination of their supercapacitor applications

The scientific community is interested in increasing oxide electrochemical characteristics for supercapacitor applications. The present research explores the development of supercapacitor electrodes using Fe-doped NiO nanoparticles synthesised via chemical co-precipitation method with varied calcination temperatures (350, 550, and 750 °C). The key innovation of the work lies in the systematic investigation of the effects of calcination temperature on the electrochemical properties and structural characteristics of the Fe-doped NiO nanoparticles. X-ray diffraction (XRD) analysis revealed a trend of increasing crystallite size with rising temperatures, and optical studies indicated a decreasing trend in the energy band gap from 3.67 eV to 3.23 eV. Fourier transform infrared (FTIR) spectroscopy confirmed the metal-oxygen bond in the molecules. Scanning electron microscopy (SEM) and High-Resolution Transmission Electron Microscopy (HR-TEM) analysis showed the mesoporous spherical morphology of the nanoparticles. Energy-dispersive X-ray spectroscopy (EDX) ensured the samples' elemental composition purity. Brunauer–Emmett–Teller (BET) shows a specific surface area of around 180.8 m2/g was obtained for Fe-doped NiO nanoparticles at 350 °C. Electrochemical tests demonstrated that the Fe-doped NiO electrodes, especially calcined at 350 °C, exhibit superior specific capacitance values (635 F/g) and impressive cycle stability with 93.29 % capacitance retention after 5000 cycles. The present demonstrates the potential of optimizing calcination temperatures to enhance the electrochemical performance and stability of Fe-doped NiO supercapacitor electrodes, marking a significant advancement in supercapacitor technology.

Fe-doped NiO nanoparticles: Microscopic and spectroscopic characterizations

Ni1−xFexO single phase nanoparticles, synthesized by lyophilization and heat treatment, were characterized by microscopic and spectroscopic techniques searching for evidence of a core-shell structure. Transmission electron microscopy, X-ray photoelectron spectroscopy, and more extensively Mössbauer spectroscopy were applied in this study. Consistent with structural and magnetic analyses previously reported, these findings support the plausibility of a core-shell structure in Ni1−xFexO nanoparticles. The shell was found to be very thin and more iron-rich than the core. The core has a lower iron concentration than the nominal overall concentration. The nanoparticles were not completely magnetized at room temperature, but below 200 °C the iron moments froze almost completely.

Unraveling the Role of Particle Size and Nanostructuring on the Oxygen Evolution Activity of Fe-Doped NiO.

Nickel-based oxides and oxyhydroxide catalysts exhibit state-of-the-art activity for the sluggish oxygen evolution reaction (OER) under alkaline conditions. A widely employed strategy to increase the gravimetric activity of the catalyst is to increase the active surface area via nanostructuring or decrease the particle size. However, the fundamental understanding about how tuning these parameters influences the density of oxidized species and their reaction kinetics remains unclear. Here, we use solution combustion synthesis, a low-cost and scalable approach, to synthesize a series of Fe0.1Ni0.9O samples from different precursor salts. Based on the precursor salt, the nanoparticle size can be changed significantly from ∼2.5 to ∼37 nm. The OER activity at pH 13 trends inversely with the particle size. Using operando time-resolved optical spectroscopy, we quantify the density of oxidized species as a function of potential and demonstrate that the OER kinetics exhibits a second-order dependence on the density of these species, suggesting that the OER mechanism relies on O-O coupling between neighboring oxidized species. With the decreasing particle size, the density of species accumulated is found to increase, and their intrinsic reactivity for the OER is found to decrease, attributed to the stronger binding of *O species (i.e., a cathodic shift of species energetics). This signifies that the high apparent OER activity per geometric area of the smaller nanoparticles is driven by their ability to accumulate a larger density of oxidized species. This study not only experimentally disentangles the influence of the density of oxidized species and intrinsic kinetics on the overall rate of the OER but also highlights the importance of tuning these parameters independently to develop more active OER catalysts.

Electronic Structure Modulation Via Iron-Incorporated NiO to Boost Urea Oxidation/Oxygen Evolution Reaction.

The urea-assisted water splitting not only enables a reduction in energy consumption during hydrogen production but also addresses the issue of environmental pollution caused by urea. Doping heterogeneous atoms in Ni-based electrocatalysts is considered an efficient means for regulating the electronic structure of Ni sites in catalytic processes. However, the current methodologies for synthesizing heteroatom-doped Ni-based electrocatalysts exhibit certain limitations, including intricate experimental procedures, prolonged reaction durations, and low product yield. Herein, Fe-doped NiO electrocatalysts were successfully synthesized using a rapid and facile solution combustion method, enabling the synthesis of 1.1107 g within a mere 5 min. The incorporation of iron atoms facilitates the modulation of the electronic environment around Ni atoms, generating a substantial decrease in the Gibbs free energy of intermediate species for the Fe-NiO catalyst. This modification promotes efficient cleavage of C-N bonds and consequently enhances the catalytic performance of UOR. Benefiting from the tunability of the electronic environment around the active sites and its efficient electron transfer, Fe-NiO electrocatalysts only needs 1.334 V to achieve 50 mA cm-2 during UOR. Moreover, Fe-NiO catalysts were integrated into a dual electrode urea electrolytic system, requiring only 1.43 V of cell voltage at 10 mA cm-2.

Magnetic properties of Fe-doped NiO nanoparticles

Undoped and Fe-doped NiO nanoparticles were successfully synthesized using a lyophilization method and systematically characterized through magnetization techniques over a wide temperature range, with varying intensity and frequency of the applied magnetic fields. The Ni1-xFexO nanoparticles can be described by a core-shell model, which reveals that Fe doping enhances exchange interactions in correlation with nanoparticle size reduction. The nanoparticles exhibit a superparamagnetic blocking transition, primarily attributed to their cores, at temperatures ranging from above room temperature to low temperatures, depending on the Fe-doping level and sample synthesis temperature. The nanoparticle shells also exhibit a transition at low temperatures, in this case to a cluster-glass-like state, caused by the dipolar magnetic interactions between the net magnetic moments of the clusters. Their freezing temperature shifts to higher temperatures as the Fe-doping level increases. The existence of an exchange bias interaction was observed, thus validating the core-shell model proposed.

High efficiency toluene sensor based on iron-doped nickel oxide triple-shell microspheres with high moisture resistance

This paper provides a simple one-step synthesis of Fe-doped NiO triple-shell layer microsphere structures for toluene gas detection. The 2 at% Fe-doped NiO sensor has excellent sensing ability for toluene gas, with high response (36–100 ppm), low detection limits (100 ppb), fast response and recovery time (2/20 s). Moreover, the sensor demonstrates excellent moisture resistance, with satisfactory response to toluene even in conditions of 99 % relative humidity (34.1–100 ppm). To further investigate the adsorption properties of the sensor, a density functional theory (DFT) approach was employed, and the sensing mechanism of the NiO sensor was discussed detailly. Analysis of the results suggests that Fe-doped NiO triple-shell layer microspheres represent a promising approach for the design of high-performance toluene gas sensors.

Synthesis and Characterizations of Fe-Doped NiO Nanoparticles and Their Potential Photocatalytic Dye Degradation Activities

Recently, the preparation of smart multifunctional hybrid nanoparticles has captured significant interest in versatile areas, including medicine, environment, and food, due to their enhanced physicochemical properties. The present study focuses on the synthesis of Fe-doped NiO nanoparticles by the coprecipitation method using the sources of nickel (II) acetate tetrahydrate and iron (III) nitrate nonahydrate. The prepared Fe-doped NiO nanoparticles are characterized by X-ray diffraction, Fourier transform infrared spectroscopy, UV–visible spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy, and X-ray photon spectroscopic analysis. The XRD results clearly confirm the face-centered cubic structure and polycrystalline nature of the synthesized Fe-NiO nanoparticles. The Tauc plot analysis revealed that the bandgap energy of the Fe-doped NiO nanoparticles decreased with the increasing concentration of the Fe dopant from 2% to 8%. The XPS analysis of the samples exhibited the existence of elements, including Fe, Ni, and O, with the absence of any surplus compounds. The FE-SEM and TEM analyses proved the formation of nanostructured Fe-NiO with few spherical and mostly unevenly shaped particles. Further, the photocatalytic efficiency of the prepared Fe-doped NiO nanoparticles were identified by using the cationic dye rhodamine B (Rh-B). The photocatalytic results proved the 8% of Fe doped with NiO nanoparticles achieved 99% of Rh-B degradation within 40 min of visible-light irradiation. Hence, the results of the present study exemplified the Fe-doped NiO nanoparticles have acted as a noticeable photocatalyst to degrade the Rh-B dye.

Fe-doped NiO nanoarray interlayer-modified Pd/Ni foam cathode for enhanced electrocatalytic hydrodechlorination

Electrocatalytic hydrodechlorination (ECH) is a promising technology that efficiently removes persistent chlorinated organic contaminants from water. Herein, a Fe-doped NiO nanoarray interlayer-modified Pd/Ni foam (Pd/Fe-NiO/NF) was synthesized as an efficient cathode catalyst for ECH of 2,4-dichlorophenoxyacetic acid (2,4-D). Results revealed that the grown Fe-NiO nanoarray on nickel foam increased the electrochemically active surface area of the electrode and improved the dispersion of catalytically active Pd nanoparticles (Pd NPs). More importantly, introducing the Fe-NiO interlayer facilitated water ionization (Volmer reaction) and atomic H* generation, which afforded the anchored Pd NPs more atomic H* for the ECH process. Compared with the conventional Pd/NF electrode, the 2,4-D dechlorination efficiency of Pd/Fe-NiO/NF was enhanced to 100% within 90 min, and its Pd requirement was reduced by 76.7%. In addition, Pd/Fe-NiO/NF exhibited excellent reusability and stability during six consecutive cycles. This study proposes a feasible strategy for designing effective dechlorination electrocatalysts with less precious metals.

Composition-controlled chemical bath deposition of Fe-doped NiO microflowers for boosting oxygen evolution reaction

Water electrolysis for green hydrogen production is gaining tremendous attention in the quest towards sustainable energy sources. At the heart of water splitting technology are the electrocatalysts, which facilitate the two half-cell reactions, i.e., the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), with the latter being the most thermodynamically uphill. Herein, we managed to fabricate Ni1-xFexO microflowers (μFs) with varying % of Fe doping (0 < x < 0.36) via an easy chemical bath deposition (CBD) method. The as-synthesized μFs drop-casted on graphene paper (GP) are then applied as electrocatalysts for OER. Compared to contrast catalysts, the electrocatalyst with xFe = 0.1 exhibits a lower overpotential of 297 mV at a current density of 10 mA cm−2, Tafel slope of 44 mV dec−1 and unprecedented turnover frequency of 4.6 s−1 at 300 mV. It is believed that this remarkable electrochemical performance mainly stems from the synergistic effects of Ni and Fe species, working in harmony to enhance charge transfer kinetics and intrinsic activity of the catalyst. This work provides a promising avenue for developing cost-effective and highly active electrocatalysts as advanced electrodes for energy related applications.

High-Performance N-Butanol Gas Sensor Based on Iron-Doped Metal-Organic Framework-Derived Nickel Oxide and DFT Study.

In this study, a straightforward two-step hydrothermal process was used to synthesize Fe-doped NiO nanomaterials. A number of characterization approaches were employed to explore the structure and morphology of the synthesized Fe-doped NiO. The as-prepared samples were multi-layered flower-like structures formed by nanoparticles, according to scanning electron microscopy and transmission electron microscopy studies. The findings of the study on gas sensing performance showed that the response of the 1.5 at % Fe-NiO sensor was nearly 100 times greater than that of the pure NiO sensor, and the lower limit of detection was greatly decreased (50 ppb). The 1.5 at % Fe-NiO sensor exhibited superior sensing performance for n-butanol. The incorporation of an appropriate amount of Fe into the NiO lattice modified the carrier concentration, which is the primary cause of the increased sensor performance of an appropriate amount of Fe-doped NiO. In addition, the density functional theory calculation method based on the first-principles theory was used to study the adsorption performance and electronic behavior of pure NiO and 1.5 at % Fe-NiO for n-butanol. The calculated results were consistent with the experimental results.

Iron-doped nickel oxide as a potential biosensor of urea determination via voltammetry

Biosensor made from metal oxide is reported to be useful for sensing urea levels in the human body, NiO nanoparticles have successfully been utilized to make urea biosensors. Ni-based electrodes are favorable for making a low-cost urea biosensor. Fe-doped NiO nanoparticles were prepared by the sol-gel method. Different concentrations of Iron doping were done in NiO and its sensing response was measured. XRD characterization was performed to determine the material's structure, phase purity, and crystallinity. Also, this characterization showed that the NiO compound is pure and single phase with a cubic structure. CV, time response FTIR, and UV–Visible spectroscopy were performed on the pure and Fe-doped NiO samples. The CV curve of a Fe-doped NiO-modified electrode in the presence of urea showed an excellent electrochemical response. Furthermore, it was also observed that with the increase in Fe doping, the sensing response and absorption properties of the samples were enhanced.

Probing into the physicochemical consequences of pristine and X0.06Ni0.94O (X = Co, Fe, Cu) nanoparticles for bactericidal, antifungal and hemolytic competency

Nano-scaled transition metal oxides are massively gaining an exciting horizon of research interest among material scientists by triggering scientific attention due to its prime advancements in physico-chemical, magneto-optical, electro-chemical, bio-medical and bio-compatible characteristics. The current work highlights the fabrication and formalisation of pure and X0.06Ni0.94O (X = Co, Fe, Cu) nanoparticles via bottom-up sol-gel pathway employing citric acid as the gelling factor. The crystallite size evaluated from X-Ray Diffraction (XRD) analysis decreased with respect to doping were estimated by successive systems among which Halder-Wagner (H-W) and Wagner-Agua (W-A) approach delivered prime results. Fourier Transform Infra-Red (FTIR) spectroscopy analysis regulated at room temperature in the mid infrared frequency continuum 400–4000 cm−1 confirmed the cubic conformation and the presence of predicted functional groups in the as-synthesized nanoparticles. The bandgap energy calculated from Ultra Violet-visible (UV–vis) spectroscopy is found to decrease for Co-NiO and Cu-NiO nanoparticles and increased for Fe doped NiO nanoparticles in comparison with the bandgap of pure NPs reasoned out by the Burstein-Moss shift. The device dependent parameter Urbach energy, and other pivotal optical parameters crucial in the fabrication of optoelectronic devices were evaluated. Surface morphological features and porous network of doped nanoparticles were investigated from Scanning Electron Microscopy (SEM) technique. Energy Dispersive X-ray (EDX) spectra ascertained the molecular matrix array and elemental composition in synthesized samples. The surface area measured from Brunauer-Emmett-Teller (BET) analysis revealed higher surface area (42 m2/g) for Fe-doped NiO nanoparticles than other counterparts. The thermal decomposition and stability of the pure and doped samples were analysed by Thermo-Gravimetric (TG) studies. The fundamental kinetic and thermodynamic parameters such as entropy, enthalpy, activation and Gibb’s free energy were elucidated through six different models viz., Coats-Redfern (CR), Piloyan-Novikava (PN), Horowitz-Metzger (HM), Van-Krevelen (VK), MacCallum-Tanner (MT) and Broido methods. Vibrating Sample Magnetometer (VSM) analysis coupled with the Law of Approach to Saturation (LAS) operandi extracted two critical magnetic criteria and the saturation magnetization is noticed to reduce with doping. The antibacterial and antifungal efficacies of the as-synthesized NPs were deeply discussed by portraying the nanoparticles-microbes interface. Iron and copper doped nickel oxide nanoparticles encountered favorable antimicrobial activity against pathogenic organisms. Furthermore, the bio-compatibility nature of the NPs was examined through hemolytic activity and the samples exhibited non-toxic behavior towards human cells till 50 μg/ml.

Significant improvement in the structural, microstructural, and room-temperature magnetic properties of Fe-doped NiO nanoparticles prepared by the solution combustion method

Significant improvement in the structural, microstructural, and room-temperature magnetic properties of Fe-doped NiO nanoparticles prepared by the solution combustion method

Ni3+-enriched nickel-based electrocatalysts for superior electrocatalytic water oxidation

A good understanding of the strategy to improve the reconstruction process and catalytic mechanism of non-noble transition metal electrocatalysts in the oxygen evolution reaction (OER) is crucial to achieving high-efficiency and energy-saving hydrogen production because it is considered the rate-determining step in water splitting. In this work, Fe-doped NiO nanosheet arrays are prepared on carbon cloth (Fe/NiO/CC) by a simple solution method and subsequent sonication. The Fe dopants facilitate energy-efficient and rapid surface reconstruction, activate more Ni3+ species, and generate more oxygen vacancies to enable fast and efficient OER. As a result, an overpotential of merely 288 mV is required for a current density of 100 mA cm−2 by the Fe/NiO/CC electrocatalyst and a small Tafel slope of 72.6 mV dec−1 is observed in the alkaline electrolyte. Based on density-functional theory calculation, the difference in the bonding and charge redistribution in NiO caused by Fe dopants modulates the electronic structure and coordination unequally, consequently increasing the number of active sites and enhancing the intrinsic catalytic activity as well. The results provide a deeper understanding of how heteroatom doping modulates the intrinsic activity of active atoms in transition metal-based electrocatalysts and reveal the role in reconstruction in electrocatalytic OER.

High-frequency ultrasonic pyrolysis of 200 nm ultrafine Fe-doped NiO hollow spheres for efficient oxygen evolution catalysis

High-frequency ultrasonic pyrolysis (3 MHz) was developed to prepare ultrafine Fe-doped NiO porous hollow spheres ∼200 nm. The material showed a low overpotential of 288 mV for a current density of 10 mA cm−2 as oxygen evolution reaction catalyst.

Synthesis of Fe-doped NiO nanosheets on carbon cloth for improved catalytic performance in Li–O2 batteries

The substitution of Ni2+ in NiO with Fe3+ can significantly improve the cycling stability and discharge/recharge capacities of Li–O2 batteries.

Triple captured iron by defect abundant NiO for efficient water oxidation

Fe-doped NiO host (Fe–NiMoO4@NiO-30) with a large surface area is designed to achieve the triple capture of Fe via adjustable surface reconstruction and impregnation to optimize the OER activity and durability of bimetallic NiFe hydroxides.

Hydrothermal preparation of iron doped nickel oxide for electrochemical sensing of urea

This study is devoted to the synthesis of iron-doped nickel oxide nanomaterials with the help of the hydrothermal technique, to study the effect of different dopant concentrations on the structural, morphological, and Direct current properties. Various testing has been performed on the materials for their utilization in some potential chemical applications. X-ray study showed that the material is pure single phased NiO. A cubic crystalline structure was shown by pure NiO Morphology and was analyzed by SEM revealed oval/spherical crystallites of Fe-doped NiO samples where concentration was much low i.e., 2%. The materials showed unsymmetrical morphology when dopant concentration was increased (4% to 8%). Doped NiO material (8%) was utilized to modify the glassy carbon electrode (GCE) for electrochemical sensing of various chemical analytes. The results show that as-synthesized material exhibits a good sensing response towards urea (CH4N2O) detection with high selectivity and sensitivity as compared to different interfering compounds.

Synergistic effects of α-Fe2O3 nanoparticles and Fe-doping on gas-sensing performance of NiO nanowires and interface mechanism

High surface area nickel oxide nanowires (NiO NWs), Fe-doped NiO NWs and α-Fe2O3/Fe-doped NiO NWs were synthesized with nanocasting pathway, and then the morphology, microstructure and components of all samples were characterized with XRD, TEM, EDS, UV–vis spectra and nitrogen adsorption–desorption isotherms. Owing to the uniform mesoporous template, all samples with the same diameter exhibit the similar mesoporous-structures. The loaded α-Fe2O3 nanoparticles should exist in mesoporous channels between Fe-doped NiO NWs to form heterogeneous contact at the interface of n-type α-Fe2O3 nanoparticles and p-type NiO NWs. The gas-sensing results indicate that Fe-dopant and α-Fe2O3-loading both improve the gas-sensing performance of NiO NWs sensors. α-Fe2O3/Fe-doped NiO NWs sensors presented the highest response to 100 ppm ethanol gas (55.264) compared with Fe-doped NiO NWs (24.617) and NiO NWs sensors (3.189). The donor Fe-dopant increases the ground state resistance and the absorbed oxygen content in air. α-Fe2O3 nanoparticles in electron depletion region result in the increasing resistance in ethanol gas and decreasing resistance in air. In this way, α-Fe2O3/Fe-doped NiO NWs sensor presents the excellent gas-sensing performance due to the formation of heterogeneous contact at the interface.