NiFe Foam Research Articles

In-situ growth strategy to synthesize porous nano-coral-like structure OER catalyst based on nife foam alloy substrate

The preparation of alloy-based catalysts is an effective approach to simplify the catalyst synthesis process for electrocatalysis. The oxygen evolution reaction (OER) is considered a key step in water splitting. By incorporating interface engineering design, electronic state optimization, and heteroatom doping, the electrocatalytic performance can be enhanced. In this study, a simple method was used to activate the NiFe foam (NIF) alloy substrate by acid etching, followed by in-situ S-doping of Cr via a hydrothermal method to synthesize S-Cr0.6@NiFe/NIF catalyst material. Its outstanding porous nanocoral-like structure not only provides abundant active sites but also exhibits superior catalytic water splitting performance, demonstrating superhydrophilic and superaerophobic characteristics. At a current density of 10 mA cm−2, only 262 mV overpotential is required to drive the OER (under basic conditions of 1 M KOH), with a low Tafel slope (71.6 mV dec−1) and a large electrochemical active surface area (ECSA = 85.25 cm2). After 80 hours of OER test, the current density of S-Cr0.6@NiFe/NIF shows negligible change. This study provides an attractive, effective, and feasible method for the in-situ growth design of alloy-based catalysts.

Stable selenium nickel-iron electrocatalyst for oxygen evolution reaction in alkaline and natural seawater

The development of efficient and stable catalysts for oxygen evolution reaction (OER) in seawater presents a major challenge for hydrogen production through water electrolysis. In this work, we present a stable NiFe foam catalyst with a Se-doped Ni/Fe oxide surface prepared through a combination of chemical vapor deposition and electrochemical exfoliation. This method effectively modifies the surface of the commercial NiFe foam to a rough and stable Se-doped Ni/Fe oxide surface, displaying exceptional OER performance in both freshwater and seawater with more than 54 days stability in natural seawater. Characterizations reveal Ni-Se doped Fe oxide surface, with subsurface layers consisting of Ni alloyed with a moderate concentration of Fe, optimizes the adsorption free energy of oxygen-containing intermediates. Our results demonstrate a surface engineering approach to activate NiFe foam as a robust OER catalyst for seawater electrolysis, which is beneficial for the hydrogen economy and for the environment.

Surface Engineered Ni-Fe Foam As a Bi-Functional Electrode for Water Electrolysis in Alkaline Media

Using fossil fuels as a main source of energy has resulted in various environmentally hazardous effects, including global warming, climate change, and environmental pollution. Consequently, the development of a sustainable and clean source of energy became of urgent need. Water electrolysis has captured considerable attention as the main technology of hydrogen fuel production. It is particularly enticing due to its eco-friendliness and sustainability. Self-supported electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) have prominent roles in water electrolysis. Growing self-supported metal oxides, hydroxides1, phosphates2, sulfides3, etc. that possess high electrical conductivity, electrocatalytic activity, and structural stability have attracted attention lately. FeNi-based catalysts are considered one of the most promising electrocatalysts for water electrolysis in alkaline solutions. However, improving their catalytic activity and stability is one of the research targets before further practical applications. Nickel foam is widely used as a self-supported electrocatalyst due to its high surface area, low cost, and exceptional catalytic activity, with several studies focused on the deposition of nickel-iron materials on nickel foam for the development of a bifunctional catalyst for water electrolysis4. However, very few studies used NiFe mesh or foam to grow a self-supported catalyst material5.In this study, surface-engineered NiFe foam electrodes were developed by facile control of the Ni/Fe surface ratio via chemical leaching and oxidation with NaOH and NaClO4 followed by electrochemical activation, aiming to design a bifunctional electrocatalyst for both OER and HER. Results revealed that varying the ratios of NaOH and NaClO4 induced significant alterations to the surface composition (different Ni/Fe), and hence the active sites for OER and HER. The physicochemical and structural properties of the NiFe foam were characterized using glancing angle X-ray diffraction (GAXRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM). Further, the catalytic activity of the modified electrode was assessed utilizing cyclic voltammetry, linear sweep voltammetry, chronopotentiometry, and electrochemical impedance spectroscopy. References F. Dionigi and P. Strasser, Advanced Energy Materials, 6, 1600621 (2016).Y. Yu et al., Journal of Colloid and Interface Science, 607, 1091–1102 (2022).A. Shankar, R. Elakkiya, and G. Maduraiveeran, New J. Chem., 44, 5071–5078 (2020).H.-S. Hu, S. Si, R.-J. Liu, C.-B. Wang, and Y.-Y. Feng, International Journal of Energy Research, 44, 9222–9232 (2020).C. Sun et al., ACS Appl. Energy Mater., 4, 8791–8800 (2021).

Ru nanocrystals modified porous FeOOH nanostructures with open 3D interconnected architecture supported on NiFe foam as high‐performance electrocatalyst for oxygen evolution reaction and electrocatalytic urea oxidation

The construction of binder-free electrodes with well-defined three-dimensional (3D) morphology and optimized electronic structure represents an efficient strategy for the design of high-performance electrocatalysts for the development of efficient green hydrogen technologies. Herein, Ru nanocrystals were modified on 3D interconnected porous FeOOH nanostructures with open network-like frameworks on NiFe foam (Ru/FeOOH@NFF), which were used as an efficient electrocatalyst. In this study, a 3D interconnected porous FeOOH with an open network structure was first electrodeposited on NiFe foam and served as the support for the in-situ modification of Ru nanocrystals. Subsequently, the Ru nanocrystals and abundant oxygen vacancies were simultaneously incorporated into the FeOOH matrix via the adsorption-reduction method, which involved NaBH4 reduction. The Ru/FeOOH@NFF electrocatalyst shows a large specific surface area, abundant oxygen vacancies, and modulated electronic structure, which collectively result in a significant enhancement of catalytic properties with respect to the oxygen evolution reaction (OER) and urea oxidation reaction (UOR). The Ru/FeOOH@NFF catalyst exhibits an outstanding OER performance, requiring a low overpotential (360 mV) at 200 mA cm−2 with a small Tafel slope (58 mV dec-1). Meanwhile, the Ru/FeOOH@NFF catalyst demonstrates more efficient UOR activity for achieving 200 mA cm−2 at a lower overpotential of 272 mV. Furthermore, an overall urea electrolysis cell using the Ru/FeOOH@NFF as the anode and Pt as the cathode (Ru/FeOOH@NFF||Pt) reveals a cell voltage of 1.478 V at 10 mA cm−2 and a prominent durability (120 h at 50 mA cm−2). This work will provide a valuable understanding of the construction of high-performance electrocatalysts with 3D microstructure for promoting urea-assisted water electrolysis.

Vanadium-Doped Heterogeneous Bimetallic Phosphides Derived from Layered Double Hydroxides for Saline Water Splitting.

The development of energy- and time-saving synthetic methods to prepare bifunctional and high stability catalysts are vital for overall water splitting. Here, V-doped nickel-iron hydroxide precursor by etching NiFe foam (NFF) at room temperature with dual chloride solution ("NaCl-VCl3"), is obtained then phosphating to obtain V-Ni2P-FeP/NFF as efficient bifunctional (oxygen/hydrogen exchange reaction, OER/HER) electrocatalysts, denoted as NFF(V, Na)-P. The NFF(V, Na)-P requires only 185 and 117 mV overpotentials to reach 10 mA cm-2 for OER and HER. When used as a catalyst for water splitting in a full cell, it can be stably sustained for more than 1000 h in alkaline brine electrolysis at both current densities of 100 and 500 mA cm-2. In situ Raman analyses and density functional theory (DFT) show that the V-doping-induced surface remodeling generates hydroxyl oxides as the true catalytic active centers, which not only enhances the reaction kinetics, but also reduces the free energy change in the rate-determining step. This work provides a cost-effective substrate self-derivation method to convert commercial NFF into a powerful catalyst for electrolytic brine, offering a unique route to the development of efficient electrocatalysts for saline water splitting.

Combustion Growth of NiFe Layered Double Hydroxide for Efficient and Durable Oxygen Evolution Reaction.

NiFe layered double hydroxide (LDH) with abundant heterostructures represents a state-of-the-art electrocatalyst for the alkaline oxygen evolution reaction (OER). Herein, NiFe LDH/Fe2O3 nanosheet arrays have been fabricated by facile combustion of corrosion-engineered NiFe foam (NFF). The in situ grown, self-supported electrocatalyst exhibited a low overpotential of 248 mV for the OER at 50 mA cm-2, a small Tafel slope of 31 mV dec-1, and excellent durability over 100 h under the industrial benchmarking 500 mA cm-2 current density. A balanced Ni and Fe composition under optimal corrosion and combustion contributed to the desirable electrochemical properties. Comprehensive ex-situ analyses and operando characterizations including Fourier-transformed alternating current voltammetry (FTACV) and in situ Raman demonstrate the beneficial role of modulated interfacial electron transfer, dynamic atomic structural transformation to NiOOH, and the high-valence active metal sites. This study provides a low-cost and easy-to-expand way to synthesize efficient and durable electrocatalysts.

Interface Engineering of Mo‐doped Ni2P/FexP‐V Multiheterostructure for Efficient Dual‐pH Hydrogen Evolution and Overall Water Splitting

AbstractDeveloping highly effective transition metal‐based bifunctional electrocatalysts remains a tremendously challenging task for large‐scale overall water splitting. Herein, a multiheterostructured Mo‐doped Ni2P/FexP electrocatalyst on NiFe foam with P vacancy (denoted as Mo─Ni2P/FexP‐V/NFF) is developed to serve as an efficient dual‐pH electrocatalyst. Due to the synergistic effect of multiple strategies (heteroatom doping, heterointerface, and P vacancy), the Mo─Ni2P/FexP‐V/NFF possesses remarkable hydrogen evolution reaction (HER) catalytic activity in alkaline/acidic and excellent oxygen evolution reaction (OER) in alkaline media, along with encouraging durability. The mechanisms of improved electrocatalytic activity combining multicharacterizations and density functional theory (DFT) calculations are elucidated. Specifically, X‐ray absorption fine structure experimental analysis confirms that the Mo doping can optimize the electronic structure of electrocatalyst. In situ Raman spectroscopy demonstrates that the evolved oxyhydroxides are the real active substances for the OER. DFT calculations reveal that the conductivity of as‐prepared samples can be enhanced through multiple strategy synergy. Moreover, in the HER process, multiple strategies can not only reduce the hydrogen binding energy to near zero but also enhance the H2O dissociation and *OH desorption. In the OER process, DFT calculations also verify that Mo doping and interface engineering can optimize the adsorption of the rate‐determining step, achieving the lowest theoretical overpotential.

Facile synthesis of amorphous/crystalline Ni-Fe thiophenedicarboxylate coordination polymer nanobelts for efficient water oxidation

The oxygen evolution reaction (OER) is a complex four-electron transfer process that poses a significant challenge to the efficient production of hydrogen through water splitting. However, developing non-noble metal electrocatalyst with excellent OER performance is still a big challenge. Herein, we propose a new strategy for the in-situ growth of two-dimensional amorphous/crystalline thiophene-based Ni-Fe metal–organic frameworks (MOFs) using Ni-Fe foam (NFF) as metal source and current collector, and thiophene-2,5-dicarboxylic acid (TDC) as corrosion agent and ligand. TDC was ionized at high temperature to produce H+ ions that etch NFF to release Ni2+ and Fe2+ ions, which were coordinated with TDC to in situ synthesize two-dimensional Ni-Fe thiophenedicarboxylate coordination polymer (NiFe-TDC) nanobelts on NFF. The unique structure and synergistic effect of Ni and Fe ions of NiFe-TDC0.05 result in the excellent OER performance with an overpotential of 224 and 256 mV at current densities of 10 and 100 mA cm−2, respectively, and it can run stably for 100 h at a current density of 100 mA cm−2, indicating the outstanding stability. Furthermore, NiFe-TDC0.05 remains the excellent OER performance with an extremely low potential of 196 and 271 mV at current densities of 10 and 100 mA cm−2 in seawater with 1 mol L-1 (M) KOH, respectively. The assembled NiFe-TDC0.05 || Pt/C water electrolysis cell achieves a current density of 100 mA cm−2 at a low voltage of 1.78 V. The work provides a new method to prepare two dimensional MOFs for efficient water oxidation.

Room‐Temperature, Meter‐Scale Synthesis of Heazlewoodite‐Based Nanoarray Electrodes for Alkaline Water Electrolysis

AbstractAlkaline water electrolysis is among the most promising technologies to massively produce green hydrogen. Developing highly‐active and durable electrodes to catalyze the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) is of primary importance. Here a facile, room‐temperature synthetic route is presented to access heazlewoodite phase (Ni, Fe)3S2 nanosheet arrays supported on NiFe foam (NFF), whose production can be easily scaled up to meter size per batch operation. The (Ni, Fe)3S2/NFF electrode can serve as a high‐performance electrocatalyst for both HER and OER in alkaline media, and remains highly stable for over 1000 h at 100 mA cm−2 current densities. When working as HER electrocatalyst, (Ni, Fe)3S2 is confirmed as catalytic phase that provides a high density of efficient active sites (e.g., Ni─Ni and Ni─Fe bridge sites). During electrochemical OER testing, (Ni, Fe)3S2 nanosheets totally transform into γ‐(Fe, Ni)OOH as active catalytic phase for OER. As a consequence, the (Ni, Fe)3S2/NFF can be used to integrate into an alkaline electrolyzer as both the cathode and anode, and to give an excellent catalytic performance (600 mA cm−2 @1.93 V), which is better than the alkaline electrolyzer based on commercial Raney Ni electrodes.

Bifunctional Substrates: In‐situ Ni, Fe co‐doped Cobalt Carbonate Hydroxides for Overall Water Splitting

AbstractDeveloping highly efficient and stable electrocatalysts with large current densities for hydrogen and oxygen evolution is still challenging. Herein, Ni and Fe co‐doped cobalt carbonate hydroxide catalysts were designed in situ on the three‐dimensional porous NiFe foam through a facile one‐step hydrothermal strategy. Inductively coupled plasma atomic emission spectrum, transmission electron microscopy‐element mapping, X‐ray photoelectron spectroscopy, and DFT calculations demonstrate that the three‐dimensional NiFe foam substrate not only serves as the porous substrate, which enhances the exposed number of active sites, but also enhances the intrinsic activities of single active sites via introducing Ni and Fe dopants in the cobalt carbonate hydroxide catalyst during the hydrothermal process. The obtained hybrid electrocatalyst can be employed as a highly efficient and stable bifunctional electrocatalyst for the oxygen and hydrogen evolution reactions, with overpotentials of 340 mV and 371 mV at 1000 mA cm−2, respectively. In addition, tests in an alkaline electrolyzer revealed that the current density could reach 1000 mA cm−2 at a voltage of 2 V and maintain stable operation for 100 h.

One-step hydrothermal synthesis of a Ni3S2-FeMoO4 nanowire-nanosheet heterostructure array for synergistically boosted oxygen evolution reaction.

A key factor for boosting oxygen evolution reaction (OER) is the design of heterostructures with steerable defects and interfaces, which can optimize the surface electronic structures and achieve efficient water splitting to produce hydrogen fuel. Herein, we propose a novel one-step hydrothermal approach to fabricate hierarchical Ni3S2 nanowires with an S-doped FeMoO4 nanosheet heterostructure array in situ on Ni-Fe foam (NFF) as a self-standing electrode for synergistically boosted OER. The metalloid Ni3S2 nanowires with good conductivity support the FeMoO4 nanosheets and act as high-speed paths for the charge transfer. Numerous ultrathin S-doped FeMoO4 nanosheets are uniformly distributed on each Ni3S2 nanowire to form heterostructures with larger specific surface area and more revealable active sites, and a strong synergistic effect is created at the heterostructure interfaces to further promote the OER dynamics. Additionally, the NFF serves as the conductive support substrate and simultaneously provides the Ni and Fe sources for the self-growing Ni3S2-FeMoO4, leading to a structurally-integrated electrode with low contact resistance, fast mass transfer, and good stability. Therefore, the Ni3S2-FeMoO4/NFF electrode offers a low overpotential of 331 mV to achieve 500 mA cm-2 and long-term stability at 100 mA cm-2 level for more than 40 h. This work provides insight into the heterostructure of molybdate and sulfide, and a deep understanding of the significance of the synergism in OER operation.

The ultrafast reconfigurability and ultrahigh durability of an NiFe phosphide electrocatalyst with an Fe-rich surface induced by in situ acid corrosion for water oxidations

This work proposes an in situ acid corroding-phosphating strategy to build an Fe-rich layer-coated NiFe phosphide electrocatalyst on NiFe foam, which exhibits outstanding OER performances.

Immersion-Driven Structural Evolution of NiFeS Nanosheets for Efficient Water Splitting.

The development of low-cost, highly active, and stable electrocatalytic water-splitting catalysts is crucial to solving the current energy crisis and environmental pollution. Herein, a simple two-step conversion strategy is proposed to successfully prepare NiFeS nanosheet structure catalyst through the "immersion-sulfurization" strategy. The self-supported electrode can be prepared in large quantities due to its simple preparation process. As an active substance, NiFeS can grow directly on the NiFe foam substrate, avoiding the use of adhesives or conductive agents, and directly used as electrodes. The as-obtained NiFeS/NFF-300 displays efficient catalytic activity in electrocatalytic water splitting. The overpotential required for OER of the NiFeS/NFF-300 electrode at a current density of 10 mA cm-2 is 230 mV. The electrode underwent a stability test at 10 mA cm-2 for 24 h, and the overpotential remained essentially unchanged, demonstrating excellent stability. Moreover, NiFeS/NFF-300 exhibits considerable HER performances compared with NiFeC2O4/NFF and NiFe foam. The unique nanosheet structure and the presence of Niδ+ and Ni2+ formed by NiFe foam substrate on the NiFeS surface are responsible for its excellent electrocatalytic activity.

Highly efficient oxygen evolution catalysts prepared by bacteria Desulfovibrio caledoniensis and Pseudomonas stutzeri based on Ni-Fe foam

Oxygen evolution reaction (OER) has gained increasing attention among researchers due to its significance in energy conversion. However, the sluggish kinetics of the OER present notable challenges. In this work, we present an energy-efficient, cost-effective, widely applicable, and scaled-up biological preparation method to prepare OER catalytic materials with high activity and stability based on bacteria and inexpensive Ni-Fe foam under mild conditions. Anaerobic sulfate-reducing bacterium Desulfovibrio caledoniensis and aerobic Pseudomonas stutzeri are the typical microorganisms and the OER performance of their products is not clear. Electrochemical measurements show that the catalyst prepared via D. caledoniensis exhibits a low overpotential of only 247 mV to achieve 10 mA cm−2 and a low Tafel slope of 46 mV dec-1, while the catalyst prepared via P. stutzeri has an overpotential and Tafel slope of 259 mV and 71 mV dec-1, respectively. Therefore, these catalysts exhibit excellent catalytic activities. Furthermore, they have a good stability of more than 40 h at 10 mA cm−2 which is far superior to that of the majority of reported NiFe-based OER catalysts. This work shows new insights into the preparation and development of high-performance OER catalysts in mild conditions.

(General Student Poster Award Winner - 1st Place) Six Practices to Improve Alkaline Electrolyte Preparation

Alkaline electrolytes represent a critical component of electrochemical energy devices, including alkaline electrolyzers, fuel cells, supercapacitors, and alkaline batteries. In addition, these electrolytes define essential properties of electrocatalytic reactions, such as the oxygen evolution reaction (OER), the hydrogen evolution reaction (HER), and the oxygen reduction reaction (ORR). However, alkaline electrolyte concentrations and compositions are often considered trivial, resulting in misinterpretation of different phenomena and overestimating critical performance metrics. Thus, in an expanding field full of interdisciplinary research groups, there is an urgent need for standardized protocols designed to improve and evaluate the quality of alkaline electrolytes so that electrochemical energy systems can be objectively examined and compared.In this work, we propose a protocol composed of six steps to prepare, characterize and validate the quality of common alkaline electrolytes. By adapting well-established methods in the literature and validating additional features experimentally, we standardize six general practices: (1) proper alkaline electrolyte handling and preparation, (2) removal of Fe impurities, (3) alkali molarity standardization via pH titrations, (4) electrolyte composition analysis via inductively-coupled plasma mass spectrometry (ICP-MS), (5) statistical quality control assessment and (6) electrolyte validation through electrochemical aging of Ni electrodes in alkaline media. The effects of Fe incorporation for different alkaline electrolytes were examined using Ni and NiFe foam electrodes. Furthermore, ICP-MS measurements were complemented with prolonged cyclic voltammetry tests to confirm the effectiveness of the Fe purification procedure. We believe this work illustrates the importance of standardizing protocols and reporting reliable quality metrics to improve consistency and accuracy in electrochemistry. Furthermore, adopting the practices presented in this work would greatly benefit the evaluation and comparison of electrochemical energy materials and devices operating with alkaline electrolytes. Figure 1

The self-reconstruction of Co-modified bimetallic hydroxysulfide nanosheet arrays for efficient hydrazine assisted water splitting

Exploiting low-cost and bifunctional electrodes for the hydrogen evolution reaction (HER) and hydrazine hydrate oxidation (HzOR) is significant for the efficient generation of H2, but still some challenges remain. In this work, the in-situ growth of the Co-modified bimetallic hydroxysulfide (NiFeSOH) nanosheet arrays is realized by a simple aging method. The NiFe foam (NFF) is used as self-sacrificing Ni and Fe sources and happens coupling reaction with the surface-modified Co2+, resulting in the self-reconstruction of hydroxysulfide on NFF. Remarkably, the catalytic active sites and reaction kinetics are optimized by the introduction of Co centers, which endows the catalyst with greatly improved catalytic activity for both HER and HzOR. As a consequence, the Co–FeNiSOH/NFF sample shows low potentials toward HER (−0.266 V) and HzOR (0.355 V) at 100 mA cm−2 in an alkaline medium. In addition, the Co–FeNiSOH/NFF-based electrolyzer realizes small cell voltages of 0.26 V and 0.64 V at the current density of 10 mA cm−2 and 100 mA cm−2, respectively, that outperforms most reported hydroxide materials. Our work develops efficient bifunctional HER/HzOR electrodes, which may provide a promising way for the preparation of the other catalysts in H2 generation.

In-situ growth of hierarchically porous FeNi2S4/Ti3C2Tx nanosheets arrays on Ni-Fe foam for overall water splitting

Ti3C2Tx nanosheets arrays sandwiched with FeNi2S4 nanoparticles are in-situ grown on Ni-Fe foam (FeNi2S4-Ti3C2Tx@NFF) via a facile one-pot hydrothermal route. The as-prepared FeNi2S4-Ti3C2Tx@NFF exhibits simultaneously excellent catalytic activity towards oxygen and hydrogen evolution reactions with low overpotentials (136 and 97 mV at 10 mA cm-2, respectively) and superior stability. Moreover, a symmetrical electrolyzer utilizing FeNi2S4-Ti3C2Tx@NFF as the anode and cathode only requires 1.51 V for overall water splitting to reach 10 mA cm-2, and can continuously operate at 20 mA cm-2 for 100 h. The outstanding catalytic performance of the catalyst can be attributed to increased active sites in the well-dispersed FeNi2S4 nanoparticles, enhanced electronic conductivity due to introduction of Ti3C2Tx nanosheets, strong electronic coupling between Ti3C2Tx and FeNi2S4, improved mass transfer through the hierarchically porous structures and robust self-supporting configuration.

NiFe-LDH nanosheets with high activity in three dimensions on NiFe foam electrode for water oxidation

Water decomposition is the most promising system for developing renewable energy, but the sluggish kinetics of the oxygen evolution reaction (OER) is the key limiting factor. Recently, inorganic nanomaterials have been widely used as an effective catalyst for the stimulation of OER kinetics, for which the subsequent dispersion and the current collector are essential. We present a three-dimensional NiFe-layered double hydroxide (NiFe-LDH) synthesized by electrochemical corrosion, with increased electrochemical performance for electrocatalytic water splitting. Electrochemical measurements reveal that the NiFe-LDH has a lower Tafel slope of 46 mVˑdec−1 compared with the NiFe foam. The resulting electrode had a current density of 50 mAˑcm−2 and a remarkably low overpotential of 150 mV. Theoretical calculations and experimental observations showed and explained NiFe-LDH-90 electrode has high alkaline medium endurance, implying excellent OER electrocatalytic activity. The produced composite is expected to bring new insights into the design of foam electrocatalyst materials for OER.

Facile and rapid construction of NiFe-LDH foam with abundant oxygen vacancies as high-performance supercapacitor negative electrode

Herein, a high-performance supercapacitor negative electrode was constructed by soaking the NiFe foam in H2SO4 just for 5 min. Benefiting from the in-situ route, hierarchical porous structure and abundant oxygen vacancies, the obtained NiFe layered double hydroxide foam presented excellent capacitive performance (1.54F cm−2 at 5 mA cm−2). Furthermore, the assembled hybrid supercapacitor yielded a high energy density of 0.15 mWh cm−2 and an excellent cycle life with 86.7% capacitance retention even after 7000 cycles, which outperformed the previously reported asymmetric supercapacitors. This work definitely shed light on the possible industrialization of the negative electrode material.

Facile formation of Zn-incorporated NiFe layered double hydroxide as highly-efficient oxygen evolution catalyst

Electrochemical water splitting is the primary method to produce green hydrogen, which is considered an efficient alternative to fossil fuels for achieving carbon neutrality. For meeting the increasing market demand for green hydrogen, high-efficiency, low-cost, and large-scale electrocatalysts are crucial. In this study, we report a simple spontaneous corrosion and cyclic voltammetry (CV) activation method to fabricate Zn-incorporated NiFe layered double hydroxide (LDH) on commercial NiFe foam, which shows excellent oxygen evolution reaction (OER) performance. The electrocatalyst achieves an overpotential of 565 mV and outstanding stability of up to 112 h at 400 mA cm−2. The active layer for OER is shown to be β-NiFeOOH according to the results of in-situ Raman. Our findings suggest that the NiFe foam treated by simple spontaneous corrosion has promising industrial applications as a highly efficient OER catalyst.