Fe Foam Research Articles

Strategic Defect Engineering Enabled Efficient Oxygen Evolution Reaction in Reconstructed Metal‐Organic Frameworks

AbstractMetal‐organic frameworks (MOFs) have emerged as promising pre‐catalysts for oxygen evolution reaction (OER) due to their marvelous structural reconstruction process in strongly alkaline media. However, targeting design MOF structures to achieve excellent OER performance of reconstructed products is a challenge. Here, a strategic defect engineering is used to promote the OER performance of reconstructed products. Briefly, modified linkers with monocarboxylic acids (ferrocene carboxylic acid, FcCA) are incorporated into MOF (NiBDC‐FcCA), leading to its stepwise reconstruction into Fe‐doped Ni(OH)2 and NiOOH during the OER process, with the oxygen vacancy and strategic doping of metal Fe persisting throughout the multi‐step reconstruction. Benefiting from the synergistic interaction of oxygen vacancies and Fe doping, NiBDC‐FcCA delivers the extremely enhanced current density at 1.6 V versus reversible hydrogen electrode by ≈9 times compared with that of NiBDC. Moreover, the optimized NiBDC‐FcCA/Fe foam exhibits excellent OER catalytic activity and stability with a low overpotential of 250 mV at 200 mA cm−2 and negligible activity decay after 1200 h at 1 A cm−2. Density function theory calculations reveal that Fe doping weakens the interaction of oxygen intermediate with Ni sites, favoring the formation of OOH* to accelerate the OER process.

Enhancing Oxygen Activation Ability by Composite Interface Construction over a 2D Co3O4-Based Monolithic Catalyst for Toluene Oxidation.

Developing robust metal-based monolithic catalysts with efficient oxygen activation capacity is crucial for thermal catalytic treatment of volatile organic compound (VOC) pollution. Two-dimensional (2D) metal oxides are alternative thermal catalysts, but their traditional loading strategies on carriers still face challenges in practical applications. Herein, we propose a novel in situ molten salt-loading strategy that synchronously enables the construction of 2D Co3O4 and its growth on Fe foam for the first time to yield a unique monolithic catalyst named Co3O4/Fe-S. Compared to the Co3O4 nanocube-loaded Fe foam, Co3O4/Fe-S exhibits a significantly improved catalytic performance with a temperature reduction of 44 °C at 90% toluene conversion. Aberration-corrected scanning transmission electron microscopy and theoretical calculation suggest that Co3O4/Fe-S possesses abundant 2D Co3O4/Fe3O4 composite interfaces, which promote the construction of active sites (oxygen vacancy and Co3+) to boost oxygen activation and toluene chemisorption, thereby accelerating the transformation of reaction intermediates through Langmuir-Hinshelwood (L-H) and Mars-van Krevelen (MvK) mechanisms. Moreover, the growth mechanism reveals that 2D Co3O4/Fe3O4 composite interfaces are generated in situ in molten salt, inducing the growth of 2D Co3O4 onto the surface lattice of 2D Fe3O4. This study provides new insights into enhancing oxygen activation and opens an unprecedented avenue in preparing efficient monolithic catalysts for VOC oxidation.

Robust and efficient Iron-Based electrodes for hydrogen production from seawater at high current density above 1000 mA cm−2

The implementation of cheap iron-based catalysts for seawater electrolysis at high- current–density offers an economical and sustainable solution for industrial hydrogen production in near future. However, Fe-based electrodes suffer from poor intrinsic activity and corrosion resistance in seawater, resulting in unsatisfactory seawater splitting performance. Here, we reported the scale-up fabrication of whole-Fe-based electrodes (NiFe-X (X = O, P) NAs/Fe foam) by facile soaking-phosphating. Surface active layers exhibit enhanced corrosion resistance compared to bare Fe foam, and trace Ni modification lowers reaction energy barriers of cathodic NiFeP and in-situ generated anodic NiFeOOH, respectively. Thus, NiFe-P||NiFe-O pair only requires 1.93 V to deliver 3000 mA cm−2 at 6 M KOH, 60 °C for overall seawater splitting, and works stably for 200 h at 1000 mA cm−2. Furthermore, NiFe-X (X = O, P) NAs/Fe foam show impressive adaptation to fresh water/tap water/seawater and all kinds of renewable energies, presenting excellent flexibility for various environmental applications and scenarios.

Deep eutectic solvent-induced controllable synthesis of bifunctional Ni–Fe–P catalysts for electrochemical water splitting

Developing electrocatalysts with excellent activity, high stability, and low cost is vital for large-scale hydrogen production through electrochemical water splitting. Herein, a bifunctional Ni–Fe–P catalyst in situ grown on Fe foam (Ni–Fe–P/FF) is developed by a simple one-step solvothermal process in the deep eutectic solvent (DES) of ethylene glycol and choline chloride (named Ethaline). The unique solvent environment of Ethaline assisted with the regulating effect of the introduced Fe(III) ions shows an essential role in governing the preparation process. The developed Ni–Fe–P/FF acts as the efficient bifunctional electrocatalyst for water splitting in 1.0 M KOH, requiring overpotentials of 82 mV (229 mV) and 263 mV (370 mV) to deliver 10 mA cm−2 (100 mA cm−2) for oxygen and hydrogen evolution reactions, respectively. Furthermore, the self-supported catalyst-assembled electrolyzer also exhibits good catalytic performance with a low voltage of 1.83 V to drive 100 mA cm−2 and good stability over 100 h. This work offers a facile approach to fabricating high-performance bifunctional Ni–Fe–P electrocatalysts to catalyze water splitting.

Construction of honeycomb-like hematite superstructure on Fe foam and their application in Fischer–Tropsch synthesis

Construction of honeycomb-like hematite superstructure on Fe foam and their application in Fischer–Tropsch synthesis

Construction of nickel iron sulfide at ambient temperature on Fe foam for high-current overall water splitting

The development of non-precious metal overall water splitting electrocatalysts under high current density is of utmost importance in feasible water splitting technology.

Bioactive Fe Foam for Degradable Bone Graft Cages

Fe foams when combined with a proper surface coating can be effectively used as a biodegradable metal with improved biocompatibility and bioactivity. Herein, Fe foams prepared via powder metallurgy route coated with two different bioactive coatings namely polyvinyl alcohol (PVA)/bioglass (BG) and polylactic acid (PLA)/BG are investigated. The effect of hydrophilic PVA and hydrophobic PLA, in conjunction with BG, has been examined. The study of biomineralization, degradation, and weight loss of the composite‐coated material over a period of 28 days is compared with that of the uncoated Fe foam samples in simulated body fluid. The composite coatings on the Fe foam effectively tailor the degradation with enhanced biomineralization. The composite‐coated material exhibits viability toward the L929 fibroblast cell line. The work reveals the great potential of Fe foams to be used as a biodegradable metallic material for temporary implant applications such as bone graft cages.

Outstanding oxygen evolution reaction properties released at the interface of NiMoO4 and FeNi layer double hydroxide heterostructures

For the alkaline oxygen evolution reaction (OER), FeNi layered double hydroxide (FeNi LDH) exhibits good activity and stability. For the sake of saving freshwater, the use of abundant seawater as an electrolyte poses new requirements for its OER performance. A novel method was designed based on a corrosion reaction to convert commercial Fe foam into a high-performance OER catalyst (FeNiM), which consisted of FeNi LDH layers and NiMoO4 nanoparticles modified on its surface. FeNiM exhibited excellent OER activity, only requiring an overpotential of 250 mV to achieve a current density of 100 mA cm−2. Experimental results indicated that the heterostructures formed by NiMoO4 and FeNi LDH was conducive to exposing active sites, promoting the adsorption of active intermediates, and generating highly active oxyhydroxides. In addition, the heterostructure was beneficial to stabilizing the electrode surface structure and inhibiting seawater corrosion. Therefore, FeNiM could maintain high current density activity in both alkaline freshwater and alkaline seawater, which only required low overpotentials of 326 mV and 304 mV to achieve a high current density of 1500 mA cm−2, respectively. This catalyst preparation method has the advantages of economic efficiency, industrial compatibility, and significantly promoting the development of green hydrogen economy and industrial seawater desalination.

Carbon encapsulated FeS nanosheet-nanoribbon interwoven sandwich structure as efficient sodium-ion battery anodes

Carbon encapsulation and optimization of nanoparticle structure are key strategies in the development of battery electrode materials. Herein, we report a simple, one step chemical vapor deposition-like method to synthesize carbon encapsulated sandwich structured nanosheets/nanoribbons of ferrous sulphide (FeS@C NSRs) as a high performance sodium-ion battery anode material. The structurally advantageous FeS@C NSRs arises from heating Fe foam in the presence of a sulphur-containing resin, which supplies both the sulphur and carbon for the reaction. FeS@C NSRs maintains a high capacity of 582.8 mAh g−1 at 0.1 A g−1 for 120 cycles and a high rate capability of 270 mAh g−1 at 10 A g−1 for 2500 cycles. The impressive cycling performance results from fast electron and ion transfer with low structural strain on the bulk material. Furthermore, in situ Raman spectroscopy and XRD also reveal evidence that FeS@C NSRs cycles via a fully reversible conversion reaction pathway facilitated by the C–S–Fe bond. The efficient synthesis method could also be explored to produce other carbon coated transition metal sulphides for electrochemical applications.

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%.

Controlling the electronic structure of Fe-MOF electrocatalyst for enhanced water splitting and urea oxidation: A plasma-assisted approach

The design of high-performance electrocatalysts for water splitting and urea oxidation reactions requires effective regulation of their electronic structure and electrochemical surface area (ECSA). In this study, we developed an in-situ grown Fe-MOF electrocatalyst on Fe foam (FF) by using a combination of easy hydrothermal synthesis and advanced plasma technology (Fe-MOF/FF). By varying the plasma treatment time, we could tailor the surface morphology and electronic structure of the Fe-MOF/FF microrods. Meanwhile, density functional theory (DFT) calculations investigated the catalytic mechanism, revealing that plasma-treated Fe-MOF/FF has a lower energy barrier for water splitting and H* adsorption during the HER process, and higher catalytic activity for UOR. Additionally, the electronic density of optimized Fe-MOF/FF is significantly expanded near the Fermi level. Remarkably, our catalysts achieved exceptional activity in both water splitting and urea electrolysis, requiring only 1.54 V and 1.472 V, respectively, at 10 mA cm−2, with excellent stability. Our findings highlight the potential of plasma technology as a powerful tool for developing multifunctional electrocatalysts for clean energy and industrial wastewater treatment applications.

Poly lauryl methacrylate modified superhydrophobic Fe foam, with excellent stability and magnetic oil/water separation ability

With the acceleration of the industrial process, oil-water separation is an urgent problem for oil spill accidents and wastewater treatments. Exploiting superhydrophobic materials applied in harsh environments and remote drives remains a significant challenge in solving oil moisture problems. An alternative strategy to solve this problem has been demonstrated by decorating poly lauryl methacrylate (LMA) on Fe foam via the solution polymerization method. The as-prepared Fe foam possesses good superhydrophobicity (>150°) under broad pH (1 < pH < 12) and a wide temperature range (−55°C-180 °C). Furthermore, outstanding separation efficiency (>99.1%), high cycle stability (>50 times), and high oil flux (63.7–114.6 kL m−2 h−1) against diverse oil/water mixtures can be realized under gravity. Interestingly, oil harvesting capacity above or beneath the water can be realized by remote magnetic driving as well.

Sintering inhibition enables hierarchical porosity with extreme resistance to degradation during redox cycling of Fe-Mo foams

High-temperature (800 ºC) steam-hydrogen redox cycling, relevant to grid-scale energy storage, is studied for iron-based freeze-cast lamellar foams. In contrast to previously studied Fe, Fe-Ni, and Fe-Co foams that rapidly degrade, Fe-25Mo foams feature a much-enhanced structural damage resistance. Utilizing in-situ x-ray diffraction, microscopy, and x-ray tomography, strong sintering inhibition is observed in Fe-Mo foams, creating a hierarchically porous lamellar structure. This leads to (i) wide channels between lamellae, enabling high macroscopic porosity (∼78%) which can accommodate gas flow as well as volumetric expansion without lamellar contact, and (ii) microporosity within lamellae, providing additional free volume to accommodate expansion during oxidation, limiting both swelling of the lamellae and the formation of Kirkendall pores. These combined effects enable a near-complete reversibility of the microstructure during cycling, preventing damage produced via internal lamellar buckling, cracking, contacting and sintering, with a remarkably high porosity (65%) remaining after 50 consecutive redox cycles.

Unraveling the Synergistic Mechanism of Bi‐Functional Nickel–Iron Phosphides Catalysts for Overall Water Splitting

AbstractNi–Fe bimetallic electrocatalysts are expected to replace existing precious metal catalysts for water splitting and achieve industrial applications due to their high intrinsic activity and low cost. However, the mechanism by which Ni and Fe species synergistically enhance catalytic activity remains obscure, which still needs further in‐depth study. In this study, a highly active bi‐functional electrocatalyst of Ni2P/FeP heterostructures is constructed on Fe foam (Ni2P/FeP‐FF), clearly illustrating the effect of Ni on Fe species for oxygen evolution reaction (OER) and revealing the true catalytic active phase for hydrogen evolution reaction (HER). The Ni2P/FeP‐FF only needs overpotentials of 217 and 42 mV to reach 10 mA cm−2 for OER and HER, respectively, exhibiting superior bi‐functional activity for overall water splitting. The Ni can elevate the strength of FeO on Ni2P/FeP‐FF surface and promote the formation of high‐valence FeOOH phase during OER, thus enhancing OER performance. Based on first‐principles calculations and Raman characterizations, the Ni2P/Ni(OH)2 heterojunction evolved from Ni2P/FeP is identified as the real high active phase for HER. This study not only builds a near‐commercial bifunctional electrocatalyst for overall water splitting, but also provides a deep insight for synergistic catalytic mechanism of Ni and Fe species.

Interface engineering and heterometal doping Co–Mo/FeS for oxygen evolution reaction

The sluggish kinetics of the oxygen evolution reaction (OER) limits the development of water electrolysis technology and the long-term efficiency of hydrogen energy production. In addition, it is important to evaluate the reconstruction performance of OER catalysts for actual water electrolysis. We created a self-supported electrode with FeS film coated Fe foam as a substrate, ordered resoluble molybdate (MoO42−) anions in interlayers, and Co-doped as a catalytically active phase for the OER. The catalyst is capable of electrochemical self-reconstruction (ECSR). With the dissolution of molybdate and sulfur ions, the catalyst surface cobalt iron oxide (CoFe2O4) forms an active amorphous FeCoOOH, which is favorable for alkaline OER. We realized the introduction of new active sites in the catalyst reconstruction process. Finally, the composite CoFeOx catalyst increased the specific surface area, promoted bubble transport, and enhanced electron mass transfer. The synergistic coupling effect of the catalyst makes it have excellent OER activity and stability. Remarkably, Co–Mo/FeS nanosheets afforded an electrocatalytic OER with a current density of 100 mA cm−2 at a low overpotential of 321 mV. These discoveries open up new opportunities for the application of doping and template-directed surface reconfiguration, which holds promise as an effective electrocatalyst for the OER.

Kinetics of oxidative bio-ethanol reforming over bimetallic structured catalysts

The core of this work is a comprehensive investigation of ethanol oxidative reforming kinetics over a Pt–Ni/CeO2–Al2O3 catalyst in the presence of fuel grade bioethanol, which has been very rarely investigated in the past. The developed kinetic model also included the formation of solid carbon. The results show that the reaction scheme involving ethylene and acetaldehyde formation from ethanol, their subsequent decomposition, methane oxidation as well as steam reforming and water gas shift reaction is able to assure a satisfactory fitting of the experimental data. Moreover, the above formulation, deposited on a porous support (Ni–Fe foam), was employed for a very long stability test (almost 400 h) and subjected to several oxidation-reduction cycles: at 600 °C, after 170 h of time-on-stream, a stable ethanol conversion of 95% and hydrogen yield of 35% were recorded, with near-zero carbon emission during its thermochemical conversion for energy generation.

Hybrid Heterostructure Ni3 N|NiFeP/FF Self-Supporting Electrode for High-Current-Density Alkaline Water Electrolysis.

Exploring earth-abundant and efficient electrocatalysts for oxygen evolution reaction (OER) is anurgent need and significant to water electrolysis. Although great achievements have been made, itisstill challenging to achieve industrial current density and stability. Herein, a hybrid heterostructure electrode based on Ni3 N and NiFeP over Fe foam substrate (Ni3 N|NiFeP/FF) is reported, along with 3D-interconnected hierarchical porous architecture, achieving the low overpotentials of 287, 178, and 290mV at 500mA cm-2 in 1m KOH, 30 wt% KOH, and alkaline simulated seawater, respectively, with excellent durability at 800mA cm-2 over 120h, which can satisfy the requirements of industrial water electrolysis. Here, the hybrid heterostructure can ensure the low energy barrier of the catalytic active sites, the 3D-interconnected hierarchical porous architecture can facilitate the fast mass/ions/electrons transformation, which contributes together to boost the superb water splitting performance. Furthermore, the COMSOL simulations confirm the multiple merits of the designed electrode during the water electrocatalysis. The present work provides a new strategy in the design and engineering of high-performance electrodes for industrial water electrolysis.

Straightforward Preparation of Fe-Based Electrocatalytic Films at Various Substrates for IrO2-like Water Oxidation Activity

Here, we report a cost-effective and easily accessible nanotextured iron oxide electrocatalyst, which behaves much better than the benchmark noble metal catalysts, such as IrO2, for oxygen evolution reaction (OER) catalysis. In a typical procedure, a magnetite electrocatalytic layer (Fe3O4-ECs) is deposited over high surface area three-dimensional substrates, such as Fe foam (FeF), stainless steel mesh (SS), and Ni foam (NiF), following a simple chemical vapor deposition process. As-prepared catalysts are thoroughly analyzed by various analytical techniques. Field emission scanning electron microscopy (FESEM) analysis shows conformal coatings of catalysts over all of the substrates; however, a continuous sheath of spherical nanostructures is shown to grow over FeF surfaces only. OER activities of all electrocatalytic layers were comparatively evaluated under similar electrochemical conditions in alkaline (1.0 M KOH) media. All of the catalysts employed here presented satisfactory OER activity. Interestingly, the samples prepared over FeF (Fe3O4-ECs/FeF) exhibit a comparatively significant OER activity, initiating OER and achieving current decade at an overpotential of just 160 and 180 mV, respectively. It further presents a low Tafel slope of 41 mV/dec, high exchange current density, mass activity, electrochemically active surface area (ECSA), and specific activity of 4.9 mA/cm2, 8750 mA/mg, 376.25 cm2, and 2.79 mA/cm2, respectively. Notably, Fe3O4-ECs/FeF also demonstrates strong long-term durability for an extensive OER process with its activity being retained for continuous 20 h and a high turnover frequency of 4.6 s–1 at an overpotential of 0.32 V. Thus, Fe3O4-ECs/FeF outperforms benchmark OER catalysts, including IrO2, NiO, and CoO, when studied under identical conditions. This distinct behavior among other catalysts may be ascribed to nanoscale morphological features and synergistic effects of Fe-based catalysts with underlying Fe support. Thus, this study facilitates the time-effective development of 3D low-cost electrocatalysts for efficient OER that may have commercial applicability.

Bimetallic Phosphide Heterostructure Coupled with Ultrathin Carbon Layer Boosting Overall Alkaline Water and Seawater Splitting.

Seawater electrolysis is promising for green hydrogen production but hindered by the sluggish reaction kinetics of both cathode and anode, as well as the detrimental chlorine chemistry environment. Herein, a self-supported bimetallic phosphide heterostructure electrode strongly coupled with an ultrathin carbon layer on Fe foam (C@CoP-FeP/FF) is constructed. When used as an electrode for the hydrogen and oxygen evolution reactions (HER/OER) in simulated seawater, the C@CoP-FeP/FF electrode shows overpotentials of 192mV and 297mV at 100mA cm-2 , respectively. Moreover, the C@CoP-FeP/FF electrode enables the overall simulated seawater splitting at the cell voltage of 1.73V to achieve 100mA cm-2 , and operate stably during 100h. The superior overall water and seawater splitting properties can be ascribed to the integrated architecture of CoP-FeP heterostructure, strongly coupled carbon protective layer, and self-supported porous current collector. The unique composites can not only provide enriched active sites, ensure prominent intrinsic activity, but also accelerate the electron transfer and mass diffusion. This work confirms the feasibility of an integration strategy for the manufacturing of a promising bifunctional electrode for water and seawater splitting.

Ambient Fast Synthesis of Superaerophobic/Superhydrophilic Electrode for Superior Electrocatalytic Water Oxidation

Developing cost‐effective and facile methods to synthesize efficient and stable electrocatalysts for large‐scale water splitting is highly desirable but remains a significant challenge. In this study, a facile ambient temperature synthesis of hierarchical nickel–iron (oxy)hydroxides nanosheets on iron foam (FF‐FN) with both superhydrophilicity and superaerophobicity is reported. Specifically, the as‐fabricated FF‐FN electrode demonstrates extraordinary oxygen evolution reaction (OER) activity with an ultralow overpotential of 195 mV at 10 mA cm−2 and a small Tafel slope of 34 mV dec−1 in alkaline media. Further theoretical investigation indicates that the involved lattice oxygen in nickel–iron‐based‐oxyhydroxide during electrochemical self‐reconstruction can significantly reduce the OER reaction overpotential via the dominated lattice oxygen mechanism. The rechargeable Zn–air battery assembled by directly using the as‐prepared FF‐FN as cathode displays remarkable cycling performance. It is believed that this work affords an economical approach to steer commercial Fe foam into robust electrocatalysts for sustainable energy conversion and storage systems.