NiFe2O4 Nanosheets Research Articles

Magnetic field-assisted vertically aligned NiFe2O4 nanosheets in composite solid polymer electrolytes for advanced all solid-state lithium metal batteries

Two-dimensional materials (2D Ms) as fillers have been applied in polyethylene oxide (PEO)-based electrolyte to enhance the low ionic conductivity and poor interface compatibility. However, the randomly dispersed fillers in PEO matrix result in anisotropy of Li+ transportation and insufficent ionic conductivity. Herein, NiFe2O4 (NFO) nanosheets are firstly introduced in polymer matrix to form vertically aligned NFO-PEO (ANFO-PEO) composite solid-state electrolytes (CSEs) through magnetic field-assisted alignment strategy. The vertically aligned NFO/PEO interface in CSEs can construct oriented Li+ transport channels and maximize the utilization of high in-plane conductivity. Meanwhile, the NFO nanosheets with abundant oxygen vacancies could effectively anchor TFSI− to promote the dissociation of Li salts. Furthermore, the optimized Li+ transport flux in CSEs enables homogeneous Li deposition and effectively mitigates the growth of dendrites. Owing to the synergistic effects, the ANFO-PEO CSEs exhibit high ionic conductivity (9.16 × 10−4 S cm−1 at 60 °C) and stable potential window up to 5.0 V vs Li/Li+. Therefore, LiFePO4 in the full cell and pouch cell with ANFO-PEO CSEs could deliver excellent cycling performance (92.78 % capacity retention after 1000 cycles at 0.5C; 96.88 % capacity retention after 105 cycles at 0.1C).

Multiple strategies regulating the d-band center of Ni2P/NiFe2O4 @N-GTs hierarchical nanoarchitecture as efficient electrocatalyst for overall water splitting

The rational design of highly active electrocatalysts for water electrolysis remains challenging for green hydrogen utilization. Herein, guided by the correlation between the electroactivity and the d-band center (Ed), a novel hierarchical nanoarchitecture (Ni2P/NiFe2O4-VO@N-GTs) was fabricated, in which, Ni2P nanoparticles are grown on the oxygen vacancy-rich NiFe2O4 nanosheet arrays anchoring on N-doping graphene tubes. The results reveal that the multiple strategies including the vacancies and heterogeneous interface construction effectively induce the charge redistribution, and further adjust the Ed to the appropriate energy level, which endows the optimal balance between the adsorption and desorption ability of the catalyst to reaction intermediates, thus leading to the conspicuous electrocatalytic activity. Additionally, the hierarchical nanoarchitecture contributes to the exposure of more active sites, the efficiency of electron transfer, and the release of generated gas. Hence, Ni2P/NiFe2O4-VO@N-GTs presents superior bifunctional activity, especially a low overpotential of 194 mV at 10 mA cm−2 for OER. The corresponding overall water electrolyzer owns a lower cell voltage and long-term durability with continuously operating over 330 h at 100 mA cm−2, outperforming the most reported bifunctional electrocatalysts. This work presents an effective pathway for regulating the Ed through multiple strategies to improve the catalytic performance of catalysts.

Rapid synthesis of Mn-doped NiFe2O4 nanosheet arrays for high-performance hybrid supercapacitors

This research presents an innovative approach to the in-situ fabrication of Mn-doped NiFe2O4 (Mn-NiFe2O4) nanosheet arrays directly on nickel foam substrates. The formation of precursors on the nickel foam substrates is achieved through spontaneous corrosion, followed by a thermal treatment to form the Mn-NiFe2O4 nanosheet arrays. The material's structure and morphology were thoroughly examined, revealing that the addition of Mn transforms the nanoporous structure on the nickel foam into a nanosheet structure. The average thickness of the nanosheets is 30 nm, and their primary composition is Mn-doped NiFe2O4. The resulting highly porous structure of these nanosheets provides numerous active sites and effective electron and ion diffusion channels, thereby increasing charge density and mechanical stability. Electrochemical assays show that the areal-specific capacity of the synthesized electrode material reaches 4.34 C cm−2 (areal-specific capacitance is 8.68 F cm−2) at 1 mA cm−2. Notably, the constructed hybrid supercapacitor achieves a power density of 544 µW cm−2 at an energy density of 390 µWh cm−2. Furthermore, capacitance retention is 95.2% after 5000 charging cycles. Additionally, the assembled device delivers robust and sustained energy output for LED displays and electric toy cars. This method streamlines the production flow of electrode materials, reducing energy consumption while significantly enhancing the areal capacitance of supercapacitors. The assembled hybrid supercapacitor structure diagram and the assembled devices provide power sources for electric toy cars and LED displays.

Ag engineered NiFe-LDH/NiFe2O4 Mott-Schottky heterojunction electrocatalyst for highly efficient oxygen evolution and urea oxidation reactions

Efficient and durable electrocatalysts with sufficient active sites and high intrinsic activity are essential for advancing energy-saving hydrogen production technology. In this study, a Mott-Schottky heterojunction electrocatalyst with Ag nanoparticles in-situ grown on NiFe layered double hydroxides (NiFe-LDH)/NiFe2O4 nanosheets (Ag@NiFe-LDH/NiFe2O4) were designed and successfully synthesized through a hydrothermal process and subsequent spontaneous redox reaction. The in-situ growth of metallic Ag on semiconducting NiFe-LDH/NiFe2O4 triggers a strong electron interaction across the Mott-Schottky interface, leading to a significant increase in both the intrinsic catalytic activity and the electrochemical active surface area of the heterojunction electrocatalyst. As a result, the Ag@NiFe-LDH/NiFe2O4 demonstrates impressive oxygen evolution reaction (OER) performance in alkaline KOH solution, achieving a low overpotential of 249 mV at 100 mA cm−2 and a Tafel slope of 42.79 mV dec−1. When the self-supported Ag@NiFe-LDH/NiFe2O4 is coupled with the Pt/C electrocatalyst, the alkaline electrolyzer reaches a current density of 10 mA cm−2 at a cell voltage of only 1.460 V. Furthermore, X-ray photoelectron spectroscopy and in-situ Raman analysis reveal that the Ni(Fe)OOH is the possible active phase for OER in the catalyst. In addition, when employed for UOR catalysis, the Ag@NiFe-LDH/NiFe2O4 also displays intriguing activity with an ultralow potential of 1.389 V at 50 mA cm−2. This work may shed light on the rational design of multiple-phase heterogeneous electrocatalysts and demonstrate the significance of interface engineering in enhancing catalytic performance.

Hydrochar-Supported NiFe2O4Nanosheets with a Tailored Microstructure for Enhanced CO2Photoreduction to Syngas.

Constructing high-efficiency composite photocatalysts with enhanced charge transfer and a rapid surface catalytic reaction has recently received significant attention. Herein, a hydrochar-mediated NiFe2O4 nanosheet (C/NFO) composite was rationally constructed by a simple hydrothermal method. Intimate interface contacts and chemical interactions between hydrochar and NFO were formed. The prepared C/NFO samples exhibited remarkable visible-light-driven catalytic CO2 reduction properties under mild reaction conditions with Ru(bpy)32+ sensitization. As the optimized sample, 16%-C/NFO achieved a 4-fold enhancement of CO production (17.49 μmol/h) compared with that of pure NFO. The C/NFO samples demonstrated good activity and structural stability in the CO2 photoreduction system. The carbon source of CO derived from CO2 was verified through isotopic labeling experiments using 13CO2. In situ photoluminescence and electrochemical characterizations confirmed the role of electron transfer intermediates of C/NFO. The synergistic effect of the nanosheet-like structure of NFO, combined with the surface functional groups of hydrochar, facilitated an exceptionally high rate of charge transfer and exposed abundant active adsorption sites for CO2, thereby promoting the efficient separation of photogenerated charge carriers and enhancing photocatalytic activity for CO2 reduction. This study presents a promising strategy for the rational design of hydrochar coupled with transition metal compound catalysts for efficient CO2 photoreduction.

Efficient electrocatalyst for solar-driven electrolytic water splitting: Phosphorus (P) and niobium (Nb) co-doped NiFe2O4 nanosheet

In the context of hydrogen production through water electrolysis, the development of efficient and stable electrocatalysts is of paramount importance. However, the creation of cost-effective electrocatalysts poses a significant challenge. In this study, a P and Nb co-doped NiFe2O4 nanosheet is designed and grown on Fe foam (referred to as P, Nb-NiFe2O4/FF). The P, Nb-NiFe2O4/FF exhibits a distinctive crystalline/amorphous heterostructure, and the co-doping of P and Nb in the material leads to the exposure of additional catalytic active sites, optimization of the electronic structure, and enhancement of charge conductivity. Additionally, the P, Nb-NiFe2O4/FF possesses a superhydrophilic surface for the enhancement of charge/mass transfer at interface and a superaerophobic surface, facilitating the efficient release of gas. The P, Nb-NiFe2O4/FF demonstrates remarkable oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) activities, achieving overpotential as low as 247 mV and 127 mV, respectively, to attain the current density response of 100 mA cm−2. Based on the high bifunctional activities, the P, Nb-NiFe2O4/FF requires only a working voltage of 1.56 V to obtain the current density of 10 mA cm−2 in overall water splitting. Furthermore, the overall water splitting device of P, Nb-NiFe2O4/FF is integrated with a commercial solar cell to simulate a solar-powered water splitting system, resulting in as superior solar-to-hydrogen conversion efficiency of 15.11%.

Preferential Adsorption of Ethylene Oxide on Fe and Chlorine on Ni Enabled Scalable Electrosynthesis of Ethylene Chlorohydrin

AbstractIndustrial manufacturing of ethylene chlorohydrin (ECH) critically requires excess corrosive hydrochloric acid or hypochlorous acid with dealing with massive by‐products and wastes. Here we report a green and efficient electrosynthesis of ECH from ethylene oxide (EO) with NaCl over a NiFe2O4nanosheet anode. Theoretical results suggest that EO and Cl preferentially adsorb on Fe and Ni sites, respectively, collaboratively promoting the ECH synthesis. A Cl radical‐mediated ring‐opening process is proposed and confirmed, and the key Cl and carbon radical species are identified by high‐resolution mass spectrometry. This strategy can enable scalable electrosynthesis of 185.1 mmol of ECH in 1 h with 92.5 % yield at a 55 mA cm−2current density. Furthermore, a series of other chloro‐ and bromoethanols with good to high yields and paired synthesis of ECH and 4‐amino‐3,6‐dichloropyridine‐2‐carboxylicacid via respectively loading and unloading Cl are achieved, showing the promising potential of this strategy.

Preferential Adsorption of Ethylene Oxide on Fe and Chlorine on Ni Enabled Scalable Electrosynthesis of Ethylene Chlorohydrin.

Industrial manufacturing of ethylene chlorohydrin (ECH) critically requires excess corrosive hydrochloric acid or hypochlorous acid with dealing with massive by-products and wastes. Here we report a green and efficient electrosynthesis of ECH from ethylene oxide (EO) with NaCl over a NiFe2 O4 nanosheet anode. Theoretical results suggest that EO and Cl preferentially adsorb on Fe and Ni sites, respectively, collaboratively promoting the ECH synthesis. A Cl radical-mediated ring-opening process is proposed and confirmed, and the key Cl and carbon radical species are identified by high-resolution mass spectrometry. This strategy can enable scalable electrosynthesis of 185.1 mmol of ECH in 1 h with 92.5 % yield at a 55 mA cm-2 current density. Furthermore, a series of other chloro- and bromoethanols with good to high yields and paired synthesis of ECH and 4-amino-3,6-dichloropyridine-2-carboxylicacid via respectively loading and unloading Cl are achieved, showing the promising potential of this strategy.

Enrichment of sulfur-oxidizing bacteria using S-doped NiFe2O4 nanosheets as the anode in microbial fuel cell enhances power production and sulfur recovery

Microbial fuel cells (MFCs) have great promise for power generation by oxidizing organic wastewater, yet the challenge to realize high efficiency in simultaneous energy production and resource recovery remains. In this study, we designed a novel MFC anode by synthesizing S-doped NiFe2O4 nanosheet arrays on carbon cloth (S10-NiFe2O4@CC) to build a three-dimensional (3D) hierarchically porous structure, with the aim to regulate the microbial community of sulfur-cycling microbes in order to enhance power production and elemental sulfur (S0) recovery. The S10-NiFe2O4@CC anode obtained a faster start-up time of 2 d and the highest power density of 4.5 W/m2 in acetate-fed and mixed bacteria-based MFCs. More importantly, sulfide removal efficiency (98.3 %) (initial concentration of 50 mg/L S2−) could be achieved within 3 d and sulfur (S8) could be produced. Microbial community analysis revealed that the S10-NiFe2O4@CC anode markedly enriched sulfur-oxidizing bacteria (SOB) and promoted enrichment of SOB and sulfate-reducing bacteria (SRB) in the bulk solution as well, leading to the enhancement of power generation and S0 recovery. This study shows how carefully designing and optimizing the composition and structure of the anode can lead to the enrichment of a multifunctional microbiota with excellent potential for sulfide removal and resource recovery.

S-Doped NiFe2O4 Nanosheets Regulated Microbial Community of Suspension for Constructing High Electroactive Consortia.

Iron-based nanomaterials (NMs) are increasingly used to promote extracellular electron transfer (EET) for energy production in bioelectrochemical systems (BESs). However, the composition and roles of planktonic bacteria in the solution regulated by iron-based NMs have rarely been taken into account. Herein, the changes of the microbial community in the solution by S-doped NiFe2O4 anodes have been demonstrated and used for constructing electroactive consortia on normal carbon cloth anodes, which could achieve the same level of electricity generation as NMs-mediated biofilm, as indicated by the significantly high voltage response (0.64 V) and power density (3.5 W m−2), whereas with different microbial diversity and connections. Network analysis showed that the introduction of iron-based NMs made Geobacter positively interact with f_Rhodocyclaceae, improving the competitiveness of the consortium (Geobacter and f_Rhodocyclaceae). Additionally, planktonic bacteria regulated by S-doped anode alone cannot hinder the stimulation of Geobacter by electricity and acetate, while the assistance of lining biofilm enhanced the cooperation of sulfur-oxidizing bacteria (SOB) and fermentative bacteria (FB), thus promoting the electroactivity of microbial consortia. This study reveals the effect of S-doped NiFe2O4 NMs on the network of microbial communities in MFCs and highlights the importance of globality of microbial community, which provides a feasible solution for the safer and more economical environmental applications of NMs.

Regulating Sulfate-Reducing and Sulfur-Oxidizing Bacteria Via S-Doped Nife2o4 Nanosheets as Microbial Fuel Cell Anode for Simultaneous Enhancement of Sulfur and Energy Recovery

Regulating Sulfate-Reducing and Sulfur-Oxidizing Bacteria Via S-Doped Nife2o4 Nanosheets as Microbial Fuel Cell Anode for Simultaneous Enhancement of Sulfur and Energy Recovery

Magnetic g-C3N4/NiFe2O4 composite with enhanced activity on photocatalytic disinfection of Aspergillus flavus

Aspergillus flavus can cause crop loss and produce mycotoxin that bring serious threats to human health. The large usage of chemical pesticides or fungicides might cause environmental problems and fungal resistance. Therefore, developing the novel, low possibility of resistance and pro-environment way to control and reduce this fungi is meaningful. Herein, an efficient, environmental-friendly and photocatalytic method to disinfect Aspergillus flavus was demonstrated on magnetic and Z-schematic composites. The composites were composed of rhombic NiFe2O4 nanosheets and g-C3N4 nanosized sheets, and 0.2 g-C3N4/NiFe2O4 (mass ratio) showed the excellent activity with above 90% disinfection rate under 90 min visible light irradiation. The efficient disinfection activities were ascribed to the favorable charges separation, well photoelectric properties and suitable band structure. It was found that the •O2− and •OH were the main active radical species in photocatalytic disinfection. The attack of these species could cause the destruction of fungal cell structure and the leakage of intracellular contents as proved by the fluorescence staining of spores, biological scanning electron microscope and the detection of extracellular protein and DNA. Moreover, the composites also showed high photocatalytic disinfection activity of Aspergillus flavus on peanuts, which can reduce aflatoxin B1 from 315.21 µg kg−1 to 18.50 µg kg−1. This efficient method might be considered as a potential way to control the contamination of Aspergillus flavus, and as a reference to the mitigation of other pathogenic fungi in future.

Surface Structure Engineering of Nanosheet-Assembled NiFe2O4 Fluffy Flowers for Gas Sensing.

In this work, we present a strategy to improve the gas-sensing performance of NiFe2O4 via a controllable annealing Ni/Fe precursor to fluffy NiFe2O4 nanosheet flowers. X-ray diffraction (XRD), a scanning electron microscope (SEM), nitrogen adsorption–desorption measurements and X-ray photoelectron spectroscopy (XPS) were used to characterize the crystal structure, morphology, specific surface area and surface structure. The gas-sensing performance was tested and the results demonstrate that the response was strongly influenced by the specific surface area and surface structure. The resultant NiFe2O4 nanosheet flowers with a heating rate of 8 °C min−1, which have a fluffier morphology and more oxygen vacancies in the surface, exhibited enhanced response and shortened response time toward ethanol. The easy approach facilitates the mass production of gas sensors based on bimetallic ferrites with high sensing performance via controlling the morphology and surface structure.

Nickel ferrite beehive-like nanosheets for binder-free and high-energy-storage supercapacitor electrodes

Herein, we present the facile growth of beehive-like NiFe2O4 nanosheets over Ni nanocones for shorter electron transport distances in supercapacitor electrodes. The electrodeposited ultrathin nanosheets provide excellent electrode–electrolyte interfacial areas, thereby enabling superior electrochemical performances. Notably, the deposition duration is tuned to achieve abundant energy storage sites and controlled cavities for adequate electrolytic ion diffusion. The synergy of these advantageous cavities and active sites of beehive-like NiFe2O4 nanosheets yields excellent stability with a capacitance retention of 95.3% after 10, 000 charging and discharging cycles of the nanosheet-based supercapacitor electrodes. At a high galvanostatic current rate of 5 A g−1, the capacitance was 483 F g−1. The optimal two-dimensional ultrathin NiFe2O4 beehive nanostructure exhibits immense potential for high-energy-storage supercapacitor electrodes, paired with the required pseudocapacitive characteristics.

Boosting the Oxygen Evolution Reaction Activity of NiFe2O4 Nanosheets by Phosphate Ion Functionalization.

Here, we demonstrate an effective strategy to constitutionally increase the conductivity and electrocatalytic property of NiFe2O4 by phosphate ion functionalization. The phosphate-ion-modified NiFe2O4 (P-NiFe2O4) nanosheets are readily grown on a carbon cloth by a simple hydrothermal method and followed by a phosphating process. The introduction of phosphate ions on the NiFe2O4 surface is highly beneficial for increasing the charge transport rate and electrocatalytic active sites. As a result, the as-prepared P-NiFe2O4 nanosheets show outstanding electrocatalytic activity toward oxygen evolution reaction (OER), with a low overpotential (231 mV at 10 mA/cm2) and Tafel slope (49 mV/dec). Furthermore, the P-NiFe2O4 electrode has a remarkable stability with no activity fading after 50 h. In addition, the as-fabricated water electrocatalysts exhibit excellent flexibility at the foldable state. These features make the phosphate-ion-functionalized NiFe2O4 electrodes open a new way to develop OER electrocatalysts with high electrochemical property.

Fabrication of uniform Ru-doped NiFe2O4 nanosheets as an efficient hydrogen evolution electrocatalyst.

Here we demonstrate the synthesis of uniform Ru-doped NiFe2O4 nanosheets with robust hydrogen evolution reaction (HER) activity in alkaline solution, with an extremely low overpotential of 18 mV versus a reversible hydrogen electrode (RHE) at a current density of 10 mA cm-2 and a Tafel slope of 27 mV dec-1.

One-pot in-situ synthesis of Ni(OH)2–NiFe2O4 nanosheet arrays on nickel foam as binder-free electrodes for supercapacitors

We present a facile and low-cost in-situ growth of Ni(OH)2–NiFe2O4 nanosheet arrays on nickel foams via one-pot hydrothermal process. Different amounts of Fe(NO3)3 solutions as the oxidant have been used to optimize morphology of the nanosheet arrays on nickel foams without any templates and nickel salts. The nanosheet arrays show excellent electrochemical stability as well as good electroconductivity. As an electrochemical electrode, it presents an optimized areal capacitance (1.434 F cm−2 at the current density of 1.0 mA cm−2) and excellent cycling stability (retaining 75.9% after 5000 cycles at 3.0 mA cm−2). This strategy holds great potential for low-cost and readily scalable production of high performance electrode materials for supercapacitors.

A novel synthesis of non-aggregated spinel nickel ferrite nanosheets for developing non-enzymatic reactive oxygen species sensor in biological samples

Herein, the synthesis of novel non-aggregated spinel nickel ferrite, NiFe2O4 nanosheets (NiFe2O4 NSs) and its application towards the selective electrocatalytic reduction of hydrogen peroxide are described. Initially, NiFe2O4 NSs is synthesized by one-step hydrothermal approach, and numerous characterizations deliberately explain the compound's composition and structure. Finally, the NiFe2O4 NSs underwent direct non-enzymatic electrochemistry and succeeded, it as mimicking Horseradish Peroxidase properties. The significance of non-aggregated NiFe2O4 NSs together with good electrocatalytic properties leads the material to the platform for electrochemical sensors. Moreover, NiFe2O4 NSs is fabricated and validated as an enzyme-free biosensor for the sensitive detection of H2O2. The demonstrated sensor revealed excellent detection of H2O2 with the pico-molar detection limit (12.4 pM), and also it offered good analytical parameters with more extensive linear range and higher sensitivity. Likewise, the non-enzymatic biosensor annexes good durability, reproducibility, and selectivity towards the determination of H2O2. Due to the nourishing capacity of the prepared NiFe2O4 NSs, it is employed for the enzyme-free detection of H2O2 in human blood and rat brain serum samples.

2D Nanostructures of CoFe2O4 and NiFe2O4: Efficient Oxygen Evolution Catalyst

Development of cost-effective, efficient electrocatalyst for oxygen evolution reaction (OER) is a challenging issue as OER has sluggish reaction kinetics due to transfer of multi-electrons. In this study, a new strategy has been developed for the synthesis of 2D nanostructures of CoFe2O4 and NiFe2O4 following a wet-chemical route followed by calcination. Following this method nanoplates of CoFe2O4 and nanosheets of NiFe2O4 have been successfully synthesized. These interconnected 2D structures are very efficient for oxygen evolution reaction and it is observed that CoFe2O4 nanoplates and NiFe2O4 nanosheets are catalytically more active compared to nanocubes and nanobipyramids of CoFe2O4 and NiFe2O4. CoFe2O4 nanoplates require only 1.64 V vs. RHE for generating current density of 10 mA/cm2 whereas nanocubes of CoFe2O4 require 1.68 V vs. RHE. Similarly, NiFe2O4 nanosheets require 1.69 V to generate current density 10 mA/cm2 and NiFe2O4 nanobipyramids require 1.77 V vs. RHE to engender 10 mA/cm2 current density. 2D sheet or Plate-like structure with more exposed surface atoms faces more electrolyte to adsorb and react which results in higher electrocatalytic activity.

Metal Precursor Dependent Synthesis of NiFe2O4 Thin Films for High-Performance Flexible Symmetric Supercapacitor

Herein, we report the chemical synthesis of NiFe2O4 thin films forming nanosheet-, nanoflower-, and nanofeather-like morphologies using NiCl2·6H2O, Ni(NO3)2·6H2O, and NiSO4·6H2O nickel salt precursors, respectively, while using the same iron salt precursor. A nanostructure formation mechanism is proposed in detail using coordination chemistry theory. Interestingly, nanostructures of NiFe2O4 nanosheets revealed a maximum surface area of 47 m2 g–1, which was higher than those of nanoflowers and nanofeathers (25 and 11 m2 g–1). Similarly, the supercapacitive properties of the individual NiFe2O4 nanosheet-based electrode demonstrated maximum specific capacitance of 1139 F g–1, which is found to be better than that of NiFe2O4 nanoflowers (677 F g–1) and nanofeathers (435 F g–1) in 6 M KOH electrolyte. Furthermore, the symmetric device fabricated using NiFe2O4 nanosheet electrodes and PVA-KOH solid gel electrolyte shows higher specific capacitance of 236 F g–1 with 98% retention after 7000 cycles and higher spe...