Fe Foam Research Articles

Formation of NiFe-MOF nanosheets on Fe foam to achieve advanced electrocatalytic oxygen evolution.

2D bimetal metal organic frameworks (MOFs) are recognized as one of the most promising electrocatalysts for the oxygen evolution reaction (OER). Herein, a facile approach was proposed to construct NiFe-MOF nanosheets on Fe foam (FF). As a self-supporting electrode, the NiFe-MOF/FF electrode shows impressive electrocatalytic OER performance. Specifically, it exhibits an ultra-low overpotential of 216 mV to reach a current density of 50 mA cm-2, and outstanding stability (beyond 50 h at 200 mA cm-2). The excellent performances of NiFe-MOF/FF arise from the highly exposed active centers, the excellent conductivity, and the synergy effect between Ni and Fe. This research provides a promising strategy for the synthesis of multi-metal MOFs as high-efficiency electrocatalysts.

Evolution of directionally freeze-cast Fe2O3 and Fe2O3+NiO green bodies during reduction and sintering to create lamellar Fe and Fe-20Ni foams

Directional freeze-casting (FC) of powder suspensions followed by freeze-drying and sintering is a versatile and scalable processing route for creating metallic foams with highly elongated pores. Because of the high propensity for oxidation of metal powders, the use of precursor oxide powders is studied here with an additional step of H2-reduction of oxides to metal before sintering. However, the large volume shrinkage due to oxide reduction causes foam deformations, making it difficult to optimize the FC parameters to obtain a particular foam structure. We use quasi in situ X-ray microtomography to analyze the three-dimensional structural evolution of directionally freeze-cast, lamellar Fe2O3 and Fe2O3+NiO green bodies as they are reduced by H2 at 725 °C to Fe and Fe-20Ni (at%), respectively, and sintered at 900 °C. These temperature and gas conditions result in sequential reduction and sintering steps that can be individually analyzed. Foam porosity, pore width, lamellae thickness, and macroscopic shrinkage are quantified by image analysis. Oxide green body structures match typical FC relationships: porosity increases with decreasing powder content in the FC suspension, and the lamellae spacing period, or FC wavelength, decreases with increasing freezing velocity. Upon H2-reduction, lamellae in Fe foams buckle due to mismatch stresses from spatially-inhomogeneous reduction rates, leading to anisotropic deformation. Buckling is absent in Fe-20Ni foams due to the faster reduction kinetics of Ni/NiO that lead to more spatially uniform reduction. Reduction is responsible for 73–86% of the total volumetric shrinkage, with sintering causing the remaining shrinkage, which is nearly isotropic for all foams. The observed relationships between FC parameters, green body and metal foam structure can help guide the design and optimization of metal foams for specific technological applications.

PH-responsive smart superwetting Fe foam for efficient in situ on-demand oil/water separation

Confronted with the increasing oily wastewater and oil leakage accidents, it is urgent to seek effective strategies to separate water/oil mixtures or clean spilt oil. In particular, the superwetting materials with special selective permeability have shown advantages in separating oil/water mixtures. Herein, Fe foams with switchable wettability were successfully fabricated via electrodeposition method and modification of mixed thiols. The smart Fe foam with pH-responsive wettability possessed selective separation performance for variety oil/water mixtures. In air, the superhydrophobic/superoleophilic foam worked in the oil-removing mode could allow the heavy oil to completely penetrate only by gravity, while retaining the water. After alkaline treatments, the water could spontaneously permeate through the superhydrophilic/underwater superoleophobic foam while preventing light oil from passing, belonging to the water-removing mode. After ten separation cycles, the separation efficiency of various oil/water mixtures still maintained not less than 98.5%. In addition, it also could achieve non-contact, remote control for oil–water separation. Meanwhile, the smart Fe foam possessed good mechanical durability, long-term stability and heat resistance. It is expected to provide a potential simple route to handle oil spills under various conditions and situations, which also is beneficial to expand the application of smart surface.

Ultra-long KFeS2 nanowires grown on Fe foam as a high-performance anode for aqueous solid-state energy storage

A high-performance anode for aqueous solid-state energy storage is fabricated using ultra-long KFeS2 nanowires grown on Fe foam. The assembled solid-state battery exhibits enhanced specific areal capacity, high-rate capability, and long-term cycling stability.

Promoting electrocatalytic water oxidation through tungsten-modulated oxygen vacancies on hierarchical FeNi-layered double hydroxide

With growing demand for renewable energy to protect the environment, it is urgent to develop prominent and robust catalysts toward oxygen evolution reaction (OER) through a facile procedure to reduce energy consumption. However, the limited intrinsic activity of anodic electrocatalysts hinders the wide application of water splitting electrolyzers. To promote the electronic property of the anodic electrodes, enhancing the concentration of oxygen vacancies in electrocatalysts could effectively modulate the intrinsic electronic states and significantly accelerate the charge transfer ability of the electrocatalysts. Herein, a series of hierarchical FeNiW-layered double hydroxide (FeNiW-LDH) in situ growth on Fe foam are prepared via W doping into FeNi-LDH by an electrochemical corrosion engineering strategy. Remarkably, by virtue of excellent electronic conductivity and two-dimensional lamellar configuration, the representative FeNiW-LDH exhibits outstanding electrochemical activity for water oxidation with a low overpotential ( η 10 = 202 mV) and a small Tafel slope (55.7 mV dec –1 ). FeNiW-LDH could also maintain stability for 120 h at 300 mA cm –2 . Moreover, FeNiW-LDH in situ growth on Fe foam with a larger area (16 × 23 cm 2 ) could be successfully prepared under laboratory conditions, which could facilitate the laboratory-made catalyst moving toward industrialization. The doping W into FeNi-LDH could significantly enhance the concentration of oxygen vacancies, which was proved by electron paramagnetic spectroscopy. In addition, theoretical calculations also demonstrated the oxygen vacancies efficiently tune the intrinsic electronic structure of FeNi-LDH and optimize the intermediates adsorption energy, accelerating the OER reaction kinetics. A ternary FeNiW-LDH with abundant oxygen vacancies exhibited excellent performance for OER. • W doping increased concentration of oxygen vacancies in FeNi-LDH. • FeNiW-LDH exhibited a low overpotential and excellent stability for OER. • Large area of FeNiW-LDH electrode could be prepared under laboratory conditions. • DFT revealed oxygen vacancies in FeNiW-LDH reduced energy barrier.

Three-dimensional self-supported iron-doped nickel sulfides for sustainable overall water splitting

In this short communication, a three-dimensional (3D) iron-doped nickel sulfides catalyst supported was successfully prepared on commercial Ni–Fe foam through one-step heat sulfurization, and its electrocatalytic performance for water splitting in 1 M KOH was investigated. In a symmetric two-electrode system assembled by the prepared electrocatalyst, an ultralow cell voltage of 1.46 V was required to drive 10 mA cm−2, which was much lower than that of the symmetric two-electrode system assembled by bare Ni foam, bare Ni–Fe foam, or nickel sulfides without iron doping. The iron-doped nickel sulfides had desirable stability for overall water splitting, and the electrocatalytic performance showed no significant degradation during long-term durability test (70 h at 10 mA cm−2). The 3D porous structure of Ni–Fe foam, the in-situ growth of catalyst, and the combined iron doping effects contributed to the outstanding performance of our prepared catalyst for overall water splitting.

One‐Pot Route for Fe@Poly(styrene‐co‐divinylbenzene) Foam with Robust Physical/Chemical Stability and Remote Magnetic Driven Capacity for Oil Removal

AbstractMagnetic and superhydrophobic materials with robust physical/chemical stability for controllable and remote magnetic driven capacity for oil removal under harsh environments are meaningful for oil–water separation but still a challenge. Herein, an alternative strategy to address this challenge is demonstrated by decorating poly(styrene‐co‐divinylbenzene) (PSDVB) on Fe foam via one‐pot solvothermal method. Different from previous magnetic and superhydrophobic materials, Fe foam is chosen to replace Fe3O4 nanomaterials. Thus, complicated preparation procedures and the high cost for Fe3O4 nanomaterials can be avoided. Additionally, PSDVB coating provides the whole foam with robust physical/chemical stabilities: i) the surface wettability can be maintained after 50 abrasion cycles or exposed in humid air (relative humidity: 90%) for 14 days, and ii) the surface wettability does not change under different pH solutions (3 < pH < 12) or highly salty solution (NaCl 10 wt%) for 6 h. Besides, outstanding separation efficiency (>99.9%), high durability (>70 times), and excellent oil flux (16 963–75 156 L m−2 h−1) can be realized under gravity. Most importantly, the foam continuously removes oil from confine place (on water surface or under water) under magnetic driven force.

Modification of Corroded Metal (Ni or Fe) Foam for High‐Performance Rechargeable Alkaline Ni/Fe Batteries

AbstractAqueous rechargeable Ni/Fe batteries with low cost and high safety have attracted tremendous attention for large‐scale energy storage. However, their application is limited by the poor conductivity and cycle performance of electrode materials. Herein, one high‐performance Ni/Fe battery with binder‐free electrodes is successfully designed and fabricated. Both of cathode and anode are initially synthesized by in‐situ corrosion process. Then, the cathode is treated by electrochemical activation (NiO‐NiF2/NF). The smooth nanoparticles transform into porous nanospheres, increasing the electrochemical activity. The anode is decorated with carbon and Bi2S3 (C@Fe‐based/Bi/FF), which can enhance the conductivity and overcome hydrogen evolution reaction. The rate capacity and the cyclic stability are promoted evidently. We assemble the Ni/Fe battery based on C@Fe‐based/Bi/FF anode and NiO‐NiF2/NF cathode, exhibiting a high energy density of 75.72 mWh cm−3 at a power density of 136.30 mW cm−3, and two batteries in series also can lighten a red LED.

Effects of pore morphology on the cyclical oxidation/reduction of iron foams created via camphene-based freeze casting

Solid-oxide iron-air batteries have potential for applications in large-scale energy storage systems, but their storage materials, iron and iron oxides, have limited cycle life due to powder sintering and choking of gas flow. To address this issue, Fe foams are synthesized with either equiaxed or directional dendritic pore structures by camphene-based freeze casting of Fe2O3 powders, followed by H2 reduction to Fe and sintering. For each pore architecture, Fe foams are created with three different initial porosities, ranging from 47 to 63 vol %, and are then cycled at 800 °C under alternating oxidation (via H2O) and reduction (via H2) conditions. The redox-cycled foams are examined by optical microscopy, scanning electron microscopy, and synchrotron X-ray tomography to assess the evolution of their porosity driven by the redox volume changes, sintering, and micropore formation via the Kirkendall effect. After 5 redox cycles, the Fe foams have lost the majority (39 ± 2 vol %) of their initial porosity.

Turning Waste into Treasure: Regulating the Oxygen Corrosion on Fe Foam for Efficient Electrocatalysis.

Iron corrosion causes a great damage to the economy due to the function attenuation of iron-based devices. However, the corrosion products can be used as active materials for some electrocatalytic reactions, such as oxygen evolution reaction (OER). Herein, the oxygen corrosion on Fe foams (FF) to synthesize effective self-supporting electrocatalysts for OER, leading to "turning waste into treasure," is regulated. A dual chloride aqueous system of "NaCl-NiCl2 " is employed to tailor the structures and OER properties of corrosion layers. The corrosion behaviors identify that Cl- anions serve as accelerators for oxygen corrosion, while Ni2+ cations guarantee the uniform growth of corrosion layers owing to the appeared chemical plating. The synergistic effect of "NaCl-NiCl2 " generates one of the highest OER activities that only an overpotential of 212 mV is required to achieve 100 mA cm-2 in 1.0 m KOH solution. The as-prepared catalyst also exhibits excellent durability over 168 h (one week) at 100 mA cm-2 and promising application for overall water splitting. Specially, a large self-supporting electrode (9 × 10 cm2 ) is successfully synthesized via this cost-effective and easily scale-up approach. By combining with corrosion science, this work provides a significant stepping stone in exploring high-performance OER electrocatalysts.

Organic Small Molecule Activates Transition Metal Foam for Efficient Oxygen Evolution Reaction.

Developing low-cost, highly efficient, and durable electrocatalysts for oxygen evolution reaction (OER) is essential for the practical application of electrochemical water splitting. Herein, it is discovered that organic small molecule (hexabromobenzene, HBB) can activate commercial transition metal (Ni, Fe, and NiFe) foam by directly evolving metal nanomeshes embedded in graphene-like films (M-NM@G) through a facile Br-induced solid-phase migration process. Systematic investigations indicate that HBB can conformally generate graphene-like network on bulk metal foam substrate via the cleavage of CBr bonds and the formation of CC linkage. Simultaneously, the cleaved CBr fragments can efficiently extract metal atoms from bulk substrate, in situ producing transition metal nanomeshes embedded in the graphene-like films. As a result, such functional nanostructure can serve as an efficient OER electrocatalyst with a low overpotential and excellent long-term stability. Specifically, the overpotential at 100 mA cm-2 is only 208 mV for NiFe-NM@G, ranking the top-tier OER electrocatalysts. This work demonstrates an intriguing general strategy for directly transforming bulk transition metals into nanostructured functional electrocatalysts via the interaction with organic small molecules, opening up opportunities for bridging the application of organic small molecules in energy technologies.

Alloy Foam‐Derived Ni0.86Fe2.14O4 Hexagonal Plates as an Efficient Electrochemical Catalyst for the Oxygen Evolution Reaction

AbstractSynthesis of binary electrocatalysts from substrates is ideal for further integration of water‐splitting electrodes. The seamless growth of an electrocatalyst directly from an alloy substrate would provide excellent mechanical behavior and lower interface resistance. Herein, a three‐dimensional (3D) intertwined Ni0.86Fe2.14O4 hexagonal plate electrocatalyst as the active site for the oxygen evolution reaction (OER) was successfully prepared by seamless growth and direct synthesis on Ni−Fe foam (NFF) via a hydrothermal route. Ni0.86Fe2.14O4/NFF exhibited excellent OER electrochemical properties, achieving a low overpotential of 286 mV to reach a current density of 200 mA cm−2 and prominent electrochemical durability. The synergistic effect between Ni and Fe in Ni0.86Fe2.14O4 and the seamless connection between Ni0.86Fe2.14O4 and the substrate make main contribution to excellent OER activity for the electrode system. This synthesis strategy provides a route for the synthesis of binary metal‐oxide electrocatalysts from alloys, which can be extended to other binary electrocatalysts.

Finite Element Model for Coupled Diffusion and Elastoplastic Deformation during High-Temperature Oxidation of Fe to FeO

Solid-oxide iron-air batteries are an emerging technology for large-scale energy storage, but mechanical degradation of Fe-based storage materials limits battery lifetime. Experimental studies have revealed cycling degradation due to large volume changes during oxidation/reduction (via H2O/H2 at 800 °C), but degradation has not yet been correlated with the microstructural stress and strain evolution. Here, we implement a finite element model for oxidation of a Fe lamella to FeO (74% volumetric expansion), in a lamellar Fe foam designed for battery applications. Growth of FeO at the Fe/gas interface is coupled, via an oxidation reaction and solid-state diffusion, with the shrinkage rate of the Fe lamellar core. Using isotropic linear elasticity and plastic hardening, the model simulates deformation of a continuously growing FeO layer by dynamically switching “gas” elements into new “FeO” elements along a sharp FeO/gas interface. As oxidation progresses, the effective plastic strain and von Mises stress increase in FeO. Distribution of tensile and compressive stresses along the Fe/FeO interface are validated by oxidation theory and explain interface delamination, as observed during in operando X-ray tomography experiments. The model explains the superior stability of lamellar vs dendritic foam architectures and the improved redox lifetime of Fe-Ni foams.

In situ conversion of metal (Ni, Co or Fe) foams into metal sulfide (Ni3S2, Co9S8 or FeS) foams with surface grown N-doped carbon nanotube arrays as efficient superaerophobic electrocatalysts for overall water splitting

Metal (Ni, Co or Fe) foams can be in situ converted into metal sulfide (Ni3S2, Co9S8 or FeS) foams with surface grown N-doped carbon nanotube arrays, and work as efficient superaerophobic electrocatalysts for overall water splitting.

Fe–Ni foams self-heal during redox cycling via reversible formation/homogenization of a ductile Ni scaffold

Alloying Fe foams with Ni creates a self-healing effect of lamellar structure for extended high-temperature redox cycling via H2/H2O.

Self-supported iron-doping NiSe2 nanowrinkles as bifunctional electrocatalysts for electrochemical water splitting

Designing low-cost and efficient bifunctional electrocatalysts is a great challenge for the clean production of hydrogen energy in electrochemical water splitting. In this study, we reported the preparation of three-dimensional (3D) porous iron-doping NiSe2 nanowrinkles supported on commercial Ni–Fe foam through a facile method of oxalic immersion and subsequent selenization, and investigated the electrocatalytic performance of the catalyst for HER, OER and overall water splitting in alkaline solutions. To drive a current density of 10 mA cm−2, the overpotential is merely 145 mV for HER and 135 mV for OER, and a cell voltage of only 1.58 V is required for overall water splitting in a two-electrode system using the prepared electrocatalyst as both cathode and anode. Meanwhile, the iron-doping NiSe2 catalyst has desirable stability for HER, OER and overall water splitting, and its electrocatalytic performance shows negligible degradation during the durability test. The iron-doping effect, the unique porous nanowrinkle structure, and the in-situ growth of catalyst on the Ni–Fe foam are responsible for the excellent electrochemical performance of the prepared catalyst in water splitting. This work provides new insights for the design of non-noble transition metal chalcogenide catalysts with excellent electrocatalytic performance in overall water splitting.

In‐situ Growth of a Bimetallic Cobalt‐Nickel Organic Framework on Iron Foam: Achieving the Electron Modification on a Robust Self‐supported Oxygen Evolution Electrode

AbstractAs a clean energy source, hydrogen may be obtained via overall water splitting. However, the reaction is limited by the anodic oxygen evolution reaction (OER) in the catalytic field. In order to overcome the limitation in OER catalyst activity, this paper attempts to synthesize and develop a series of three‐dimensional metal‐organic frameworks (MOFs) electrocatalytic materials. The structure and morphology of bimetallic cobalt and nickel MOFs are characterized by FT‐IR, Raman, SEM, TEM, and XPS. It is found that the bimetallic cobalt and nickel MOFs have a columnar micro‐structure assembled by nanosheets. Further in‐situ growth on the iron (Fe) foam to prepare an integrated nanoarray self‐supported electrode did not significant change their micro‐structure. The obtained bimetal electrocatalysts exhibit significantly enhanced OER activity as compared to the single‐metal MOFs counterpart. The cobalt and nickel double‐doped materials in‐situ grown on Fe foam exhibited an excellent electrocatalytic activity and remarkable durability with a current density of 10 mA cm−2 in a 0.1 M KOH solution (with the overpotential of 264 mV and the Tafel slope of 54.3 mV dec−1). There is a significant improvement compared with the material on the glassy carbon electrode. The introduction of the bimetal species (Co and Ni) into the ordered MOFs provides a synergistic effect of the active centers resulting in an enhanced electron transfer and improved electrochemical performance. This work enriches the MOFs electrocatalytic electrode and pave the way for their practical applications.

A facile strategy toward hydrophobic–oleophilic 3D Fe foam for efficient oil–water separation

In this work, we present a hydrophobic–oleophilic Fe foam for oil–water separation. Hydrophobic–oleophilic Fe foam was fabricated simply through dip-coating with n-dodecyl mercaptan. The morphology, chemical composition and water contact angle of the Fe foam were characterized. The Fe foam could absorb a variety of oils, such as diesel, toluene, xylene, cyclohexane, dodecyl methacrylate, crude oil, 1,2-dichloroethane, hexane and chloroform, these oils could be underwater or on water surface, and it exhibited excellent durability, verified by the high separation efficiency (more than 98.8% for a cyclohexane–water mixture) after reusing for 48 times. Furthermore, oil collection with the Fe foam could be controlled remotely using external magnetic field, and the Fe foam displayed high flux, good anti-corrosion and wear resistance. The simple and low-cost fabrication method enabled the Fe foam to be a promising candidate for large-scale oil–water separation and for remotely controllable water purification.

Self-supported Ni2P nanosheets on low-cost three-dimensional Fe foam as a novel electrocatalyst for efficient water oxidation

Abstract Electrochemical water splitting into hydrogen and oxygen is a promising strategy for future renewable energy conversion devices. The oxygen evolution reaction (OER) is considered as the bottleneck reaction in an overall water splitting system because it involves 4e− and 4H+ transfer processes. Currently, it is highly desirable to explore low-cost alternative catalysts for OER at ambient conditions. Herein, we report for the first time that nickel phosphide (Ni2P) nanosheets can be facilely grown on Fe foam (FF) as an efficient electrocatalyst for OER with excellent durability and catalytic activity under alkaline conditions. To reach a current density of 10 mA/cm2, the Ni2P-FF catalyst required a low overpotential of only 198 mV for OER. The catalyst's high OER activity and durability were well maintained at a high current density. The required overpotentials were only 267 and 313 mV to achieve the current densities of 100 and 300 mA/cm2, respectively. The combination of low-cost Fe foam with Ni2P provides a promising low-cost catalyst for large-scale application of electrocatalytic water splitting.

Facile, cost-effective plasma synthesis of self-supportive FeSx on Fe foam for efficient electrochemical reduction of N2 under ambient conditions

A non-precious, self-supportive FeSx NRR electrocatalyst was synthesized by a simple H2S-plasma treatment on low-cost Fe foam, which shows a remarkable NH3 production rate of 4.13 × 10−10 mol s−1 cm−2 and a high faradaic efficiency of 17.6%.