NiFe LDH Research Articles

Elucidating the Influence of Intercalated Anions in NiFe LDH on the Electrocatalytic Behavior of OER: A Kinetic Study

AbstractThe oxygen evolution reaction (OER) as one half‐cell reaction of electrochemical water splitting has a fundamental impact on water splitting efficiency and thus on the competitiveness of electrochemically generated hydrogen in the energy market. Nickel‐iron layered double hydroxides (NiFe LDH) are among the most promising electrocatalysts for efficient OER under alkaline conditions. Despite intensive research, correlations of the material properties and the resulting kinetically limiting surface processes are poorly investigated. This work focuses on the kinetic behavior of NiFe LDH catalysts containing different anions in the basal spacing in alkaline OER. Steady‐state Tafel plots, impedance measurements as well as reaction order plots were used to elucidate differences in the catalytic performance. All catalysts showed a dual Tafel behavior and fractional reaction orders. For kinetic modelling, the physisorbed hydrogen peroxide mechanism and Temkin adsorption model were adopted to fit experimental data. Our study showed that the intercalated anions affect the kinetics of rate determining steps. The hypophosphite intercalated LDH possessed the highest OER activity and the first step as rate determining. While for both carbonate and borate intercalated NiFe LDH, the second step proved to be rate determining in the low Tafel region, while the first step was found to be rate‐limiting in the high Tafel region.

Electrochemical investigation on naproxen sensing and steady-state diffusion analysis using Ni-Fe layered double hydroxide modified gold electrode

Naproxen, a nonsteroidal anti-inflammatory drug commonly used to treat various types of arthritis, including osteoarthritis, juvenile arthritis, and rheumatoid arthritis, has been associated with serious gastrointestinal and kidney complications. To address this issue, a long-lasting electrochemical sensor capable of sensitively and rapidly detecting naproxen has been developed. The sensor was fabricated by electrodepositing nickel–iron layered double hydroxide (NiFe LDH) on the surface of gold electrode, utilizing ferric nitrate and nickel nitrate as precursors. The NiFe LDH thin film serves as an efficient sensing platform for naproxen determination, and its electrochemical performance was characterized using differential pulse voltammetry and amperometry. Impressively, the developed naproxen sensor boasts a wide dynamic detection range (1–307 μM) and a remarkably low limit of detection of 0.32 μM. Additionally, the NiFe LDH/Au electrode exhibited long-term operational stability of 28 days, rapid response time (<80 s), excellent selectivity, and good reproducibility (1.89% RSD). In addition, Hermite wavelet was employed to formulate the relationship between the steady-state concentration of naproxen and the distance from the electrode's surface. With these impressive attributes, the NiFe LDH modified Au electrode is a promising candidate for the development of a long-lasting and reliable naproxen sensor.

Kinetically accelerated oxygen evolution reaction in metallic (oxy)hydroxides enabled by Cr-dopant and heterostructure

Efficient water-splitting is an underpinning technology for producing hydrogen in high-purity and enabling hydrogen economy, but it suffers from the sluggish kinetics of anodic oxygen evolution reaction (OER). Cost-efficient transition metals-based oxides/hydroxides, particularly NiFe-based double hydroxides (NiFe LDHs), have been deemed as promising OER electrocatalysts in alkaline electrolytes. However, their electrocatalytic performance still waits to be substantially optimized. Herein, we demonstrate the tremendously enhanced OER activity of NiFe LDH via a developed coupling strategies of intrinsic chromium (Cr) doping and external heterojunction engineering. Relying on the heterostructure, an in-built electric field is proved and thus the charge transfer kinetic is substantially accelerated. Remarkably, the synergistic surface electron modulation, explicitly revealed by theoretical calculation and experimental analysis, elucidates that the upward d-band center of Fe sites after doping Cr accounts for the much-enhanced OER activity, being inherited when combining with CuO substrate, while the increased empty d orbital of Ni sites after introducing CuO part interprets the activation of initially nonactive Ni sites. As a result, a low OER overpotential of 210 mV (at 10 mA cm−2) and excellent durability are achieved for Cr-NiFe LDH@CuO catalyst. Furthermore, the resultant alkaline electrolyzer also displays outstanding activity (requires a low voltage of 1.56 V at 100 mA cm−2) and good durability.

Co9S8@NiFe-LDH Bifunctional Electrocatalysts as High-Efficiency Cathodes for Zn–Air Batteries

Exploring new cathodes with high-energy storage is a key issue for zinc–air batteries. Herein, a multidimensional free-standing cathode catalyst consisting of Co9S8 nanorods loaded with NiFe-LDH nanosheets (Co9S8@NiFe-LDH) was constructed. Co9S8@NiFe-LDH not only provides a conductive backbone for fast electron/ion transfer but also has abundant active sites to accelerate the oxygen reduction/evolution reaction (ORR/OER). Co9S8 nanorods with high ORR activity and good electrical conductivity were grown in situ on carbon cloth, and NiFe LDH nanorods were successfully loaded on the surface of Co9S8nanorods. Benefiting from such a delicate structural design, the OER potential of Co9S8@NiFe-LDH is 1.62 V at 10 mA cm–2, which is slightly higher than the OER potential of 1.61 V for the commercial noble metal RuO2, indicating its excellent OER activity close to that of noble metal catalysts. The prepared zinc–air cell based on the Co9S8@NiFe-LDH cathode has an ideal specific capacity of 780.5 mAh g–1 at 10 mA cm–2, a high power density of 148 mW cm–2 at 180 mA cm–2, and a good 200 h cycle stability. Therefore, this work paves the way for catalyst design and promotes the development of multidimensional composite-structured cathode materials for zinc–air batteries.

Layered double hydroxides as a robust catalyst for water oxidation through strong substrate-catalytic layer interaction

Electrochemical preparation of hydrogen permits a way to meet our energy and environmental issues, but the anodic reaction is kinetically slow and thus is the bottleneck in the overall water splitting. Achieving cost-effective electrocatalysts represents a big challenge for practical water oxidation. Herein, We report the tuning of the local electron structure of nickel-iron layered double hydroxides (NiFe LDH) by achieving a highly coupled interface between active sites and the current collector. Our developed NiFe-LDH/Fe catalysts as the anode can provide 10 mA cm−2 at 1.455 V vs. RHE with a Tafel slope of only 32.7 mV dec−1. Simultaneously, the catalyst has high catalytic stability. Combined with the X-ray photoelectron spectroscopy and density functional theory calculation, the coupling interface between the substrate and catalytic layer can effectively regulate the electron density of the Fe sites, which is the main reason for the high catalytic ability of the layered double hydroxide catalyst.

Starch modified NiFe layered double hydroxide composites for better adsorption and photocatalytic removal of reactive dye and piroxicam-20 drug.

One of the most omnipresent problems to the environment is the efficient removal of textile dyes and non-steroidal drugs from wastewater. For this purpose, renewable, sustainable, and biodegradable biopolymers are used. In this study, starch (S) modified NiFe-layered double hydroxide (LDH) composites were successfully synthesized by the co-precipitation method and have been examined as a catalyst for the effective adsorption of reactive blue 19 dye, reactive orange 16 dye, and piroxicam-20 NSAID from wastewater and photocatalytic degradation of reactive red 120 dye. The physicochemical properties of the prepared catalyst were assessed by XRD, FTIR, HRTEM, FE-SEM, DLS, ZETA, and BET. The coarser and more porous micrographs are shown in FESEM, indicating the homogeneous dispersion of layered double hydroxide on starch polymer chains. The S/NiFe-LDH composites have a slightly greater SBET (6.736m2/g) than NiFe LDH (4.78m2/g). The S/NiFe-LDH composite shows remarkable ability in the removal of reactive dyes. The band gap value of NiFe LDH, S/NiFe LDH (0.5:1), and S/NiFe LDH (1:1) composites was calculated as 2.28eV, 1.80eV, and 1.74eV, respectively. The qmax assessed from Langmuir isotherm for removal of piroxicam-20 drug, reactive blue 19 dye, and reactive orange 16 was 2840mg/g, 149.47mg/g, and 182.4mg/g, respectively. The activated chemical adsorption without product desorption is predicted by the Elovich kinetic model. With reactive red 120 dye, S/NiFe-LDH shows photocatalytic degradation within 3h of irradiation of visible light with 90% removal efficiency and follows a pseudo-first-order kinetic model. The scavenging experiment confirms the involvement of electrons and holes in photocatalytic degradation. With a little decline in adsorption capacity up to five cycles, starch/NiFe LDH was easily regenerated. So, the suitable adsorbent required for wastewater treatment is nanocomposites of LDHs and starch as they enhance the chemical and physical attributes of the composite structure with greater absorption capabilities.

Constructing multiple heterogeneous interfaces in porous bimetallic FeNi3/C and CoNi/C flowers towards brilliant electromagnetic wave absorption performance

Construction of materials with multiple interfaces has always been a significant research direction to the high-performance electromagnetic wave (EMW) absorption materials. Here, the composites, consisted of three-dimensional (3D) flower-like NiFe layered double hydroxide (LDH) and regular dodecahedron CoNi-MOF, are synthesized at the first time, and their electromagnetic absorption capacity can be efficaciously improved by altering the proportion of NiFe-LDH (NFL) and CoNi-MOF. Benefiting from the suitable ratio of constituents, at a matching thickness of 2.29 mm, the minimum reflection loss (RLmin) of Z@NFL-2 is −61.87 dB, and the effective absorption bandwidth (EAB, RLmin < −10 dB) is reach up to 6.1 GHz. Especially, Z@NFL-4 can obtain a large EAB of 7.23 GHz (10.77–18 GHz) at a thickness of only 2.06 mm. Amazingly, under the far domain circumstance, the lowest radar cross-section acreage can accomplish −44.72 dB m2. The remarkable EMW absorption performance is mainly attributed to the collaborative effect of abundant electrical-magnetic loss mechanism, and remarkable impedance matching characteristics. Therefore, this work furnishes a fresh idea for exploring the application of LDH-based materials in electromagnetic wave absorption filed.

Optimizing electronic structure of NiFe LDH with Mn-doping and Fe0.64Ni0.36 alloy for alkaline water oxidation under industrial current density

Optimizing electronic structure of NiFe LDH with Mn-doping and Fe0.64Ni0.36 alloy for alkaline water oxidation under industrial current density

Te-doped NiFe2O4 stabilized by amorphous carbon layers derived from one-step topological transitions of NiFe LDHs with significantly enhanced oxygen evolution reaction

Constructing efficient oxygen evolution reaction (OER) electrocatalysts that can stably operate under high temperatures and strong alkaline conditions still faces great challenges for industrial hydrogen production from water electrolysis. Herein, a self-supported tellurium (Te)-doped spinel NiFe2O4 with a carbon-stabilized nanosheet structure anodic catalyst on nickel foam (NF) (Te-NiFe2O4@C/NF) is successfully synthesized by calcination of a layered double hydroxide precursor (NiFe LDH). Benefiting from Te doping as well as coupling with the amorphous carbon layer and the unique superhydrophilic/aerophobic surface property, which provides efficient mass transport channels and rapid electron transport, the optimized Te-NiFe2O4@C/NF requires an overpotential of 220 mV to achieve a current density of 10 mA cm−2 for the OER in 1 M KOH at 25 ℃. Furthermore, an extremely low overpotential of 180 mV is required to achieve 500 mA cm−2 in 6 M KOH at 80 ℃ and maintains superior stability over 60 h under such harsh quasi-industrial conditions. Density functional theory calculations further reveal that Te doping can effectively modulate the local electronic environment of the Ni and Fe sites, which optimizes the intermediate (*OH) adsorption and facilitates the OER kinetics. This work may open up opportunities to explore efficient electrocatalysts for scalable hydrogen production.

Electronic modulation with Pt-incorporated NiFe layered double hydroxide for ultrastable overall water splitting at 1000 mA cm−2

Achieving large current density is crucial to the practical application of large-scale hydrogen production by water splitting, but it is hindered by sluggish and unstable catalysts. Herein, a Pt-induced NiFe layered double hydroxide (Pt-NiFe LDH) nanosheet is synthesized for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). It affords 10 mA cm–2 at overpotentials of only 198 mV and 36 mV for OER and HER, respectively. Impressively, an alkali-electrolyzer (Pt-NiFe LDH || Pt-NiFe LDH) exhibits a stable cell voltage of 1.887 V to deliver a current density of 1000 mA cm–2 over 3000 h. The introduction of Pt modulates the electronic structure on the surface of NiFe LDH by charging redistribution at the interface and decreasing the Gibbs free energy change (ΔG) for the potential determining step (from *O to *OOH) during OER. This work provides a facile strategy for developing catalysts for large current density water splitting.

Synergetic regulation of CeO2 modification and (W2O7)2- intercalation on NiFe-LDH for high-performance large-current seawater electrooxidation

Four-electron process and the interference of Cl- make sluggish kinetics on oxygen evolution reaction (OER) for seawater electrolysis. Herein, NiFe LDH grown on NiFe-foam with CeO2 modification and (W2O7)2- intercalation was synthesized by one-step hydrothermal method. It only needs 353.8 and 386.7 mV to achieve a large current density of 1000 mA·cm−2 in 1 M KOH and alkaline natural seawater, respectively. The catalytic material can stand 100 h with a retention of 98.1% at 1000 mA·cm−2 in alkaline natural seawater. Experiments and theoretical calculations confirm that the state-of-the-art OER activity comes from the introduced CeO2 with optimized adsorption energy of intermediates. The improved stability and selectivity in seawater can be ascribed to the preferential adsorption of Ni and Fe with higher valence on OH- based on hard and soft acid based (HSAB) principle by (W2O7)2- intercalation. This work provides a viable approach to develop efficient catalytic material for large-current seawater electrolysis.

Bifunctional reduced graphene oxide/polyelectrolyte/NiFe layered double hydroxide composites for efficient catalyzed dephosphorylation and 4-nitrophenol reduction

Dephosphorylation that separates phosphate groups from substrates is a significant reaction for both living organisms and environmental protection. Meanwhile, 4-nitrophenol (4-NP) is known to be a popular organic compound used for pesticides production, which is genotoxic and carcinogenic to humans and animals. Herein, we have developed a bifunctional catalyst that can be used for simultaneous dephosphorylation and 4-nitrophenol (4-NP) reduction when para-nitrophenyl phosphate (p-NPP) serves as the model compound. This bifunctional catalyst was obtained by in-situ growth of NiFe layered double hydroxide on the reduced graphene oxide/polyelectrolytes assembly nanolayers (denoted as rGP3.5/NiFe LDH). The results demonstrate that the rGP3.5/NiFe LDH can activate dephosphorylation of p-NPP at 20 °C and the catalytic efficiency increases significantly with increasing temperature in the range of 20 °C to 90 °C. Moreover, by-product 4-NP formed through p-NPP dephosphorylation is further fully converted to 4-aminophenol by the rGP3.5/NiFe LDH within 15 min. As far as we know, this is the first example for both dephosphorylation and 4-NP reduction through NiFe LDH as bifunctional catalysts, which paves the way for the development of multiple potential applications for NiFe LDH.

Interface strong-coupled 3D Mo-NiS@Ni-Fe LDH flower-cluster as exceptionally efficient electrocatalyst for water splitting in wide pH range

It is crucial to create a bifunctional catalyst with high efficiency and low cost for electrochemical water splitting under alkaline and neutral pH conditions. This study investigated the in-situ creation of ultrafine Mo-NiS and NiFe LDH nanosheets as an effective and stable electrocatalyst with a three-dimensional (3D) flower-cluster hierarchical structure (Mo-NiS@NiFe LDH). The strong interfacial connection between Mo-NiS and NiFe LDH enhances the formation of metal higher chemical states in the material, optimizes the electronic structure, increases OH– adsorption capacity improves electron transfer/mass diffusion, and promotes O2/H2 gas release. As a result, at 10 mA cm−2, Mo-NiS@NiFe LDH/NF demonstrates the outstanding bifunctional electrocatalytic activity of just 107 mV (HER, hydrogen evolution reaction) and 184 mV (hydrogen evolution reaction) (OER, oxygen evolution reaction). The catalytic performance is remarkably stable after 72 h of continuous operation in 1 M KOH at high current densities (300 mA cm−2). More interestingly, in the overall water splitting system, the cell voltages for anode and cathode in both alkaline and neutral electrolytes for Mo-NiS@NiFe LDH/NF are only 1.54 V (alkaline) and 2.06 V (neutral) at 10 mA cm−2. These results demonstrated that the bifunctional electrocatalyst design concept is a viable solution for water splitting in both alkaline and neutral systems.

Nickel Iron Layered Double Hydroxide Nanostructures Composited with Carbonyl Iron Powder for Microwave Absorption

The specific nanostructure of the absorber is a key factor in improving the electromagnetic absorption performance. Herein, NiFe layered double hydroxide composited with carbonyl iron powder (LDH/CIP) was fabricated by a one-step hydrothermal synthesis process for the first time. By varying the morphology of the CIP template (spherical or flaky), the nanostructure of in situ grown LDH could be modulated, to optimize the electromagnetic wave absorption performance of LDH. The resultant NiFe/CIP synergistic composite has proved its excellent electromagnetic (EM) wave absorption performance with the minimum reflection loss (RLmin) of −96.5 dB and an effective absorption bandwidth (EAB) up to 7.6 GHz at the thickness of 8 mm. At a smaller thickness of 3 mm, the EAB value remains 7.2 GHz with the RLmin of −16.4 dB. Such an outstanding absorption capacity is primarily attributed to the magnetic loss of NiFe LDH, which is more significantly enhanced using CIP as the substrate. Moreover, the formation of nano-flower-like LDHs, which possess rich heterogeneous structural interfaces and specific surface area to induce the polarization relaxation of the absorber. Therefore, the established NiFe/CIP composite brings insights into the design of high-performance EM wave absorbers.

Cu-doped NiFe layered double hydroxide nanosheets on nickel foam as an effective and durable electrocatalyst for oxygen evolution reaction

Water splitting by electrolysis is an environmentally friendly and promising method to gain hydrogen energy. Since both oxygen evolution reaction (OER) process and hydrogen evolution reaction process of electrolysis are kinetically sluggish and need to overcome a large potential barrier, it is imperative, especially for the poor kinetic OER, to explore available electrocatalytic materials. Here, this paper proposed a preparation of copper-doped nickel–iron-layered double hydroxide (NiFeCu LDH) with sheet-like nanostructure arranged perpendicularly to nickel foam matrix (NiFeCu LDH/NF) through a facile hydrothermal process. Benefitting from the combination with nickel foam and doping with copper, the poor conductivity of pure NiFe LDH is remedied and the quantity of exposed catalytic active sites on the electrocatalyst is increased. Hence, the as-prepared NiFeCu LDH/NF possesses outstanding OER catalytic capacity in 1.0[Formula: see text]M KOH, and when applying a mere overpotential of 183[Formula: see text]mV, it can convey a current density of 10[Formula: see text]mA cm[Formula: see text]. Furthermore, both at 10 and 80[Formula: see text]mA cm[Formula: see text], this electrocatalyst could maintain long-term durability at least for 24[Formula: see text]h. In our preparation, a simple approach was applied to bolster the OER catalytic performance of electrocatalysts based on NiFe LDH.

Constructing microstructures in nickel-iron layered double hydroxide electrocatalysts by cobalt doping for efficient overall water splitting

The development of Ni–Fe layered double hydroxide (NiFe LDH) catalysts for overall water splitting (OWS) is urgently required. NiFe LDHs are promising catalysts for the oxygen evolution reaction (OER). However, their hydrogen evolution reaction (HER) performance is restricted by slow kinetics. The construction of multiple types of active sites to simultaneously optimise the OER and HER performance is significant for OWS using NiFe LDHs. Hence, a Co-doped NiFe LDH electrocatalyst with dislocations and stacking faults was designed to modulate the electronic structure and generate multiple types of activity sites. The Co0.03-NiFe0.97 LDH catalyst only required overpotentials of 280 (50 mA cm−2, OER) and 170 mV (10 mA cm−2, HER). However, it reached a current density of 50 mA cm−2 at 1.53 V during OWS. Co0.03-NiFe0.97 LDHs could be stabilised for 140 h at 1.52 V. Furthermore, Co0.03-NiFe0.97 LDHs exhibited a higher electrocatalytic activity than commercial Raney nickel and Pt/C||IrO2 under industrial conditions. The significant specific surface area, high conductivity, and unique microstructures are the major factors contributing to the excellent OWS performance. This study suggests an efficient strategy for introducing microstructures to fabricate catalysts with high activity for application in OWS.

Full spectrum solar hydrogen production by tandems of perovskite solar cells and photothermal enhanced electrocatalysts

Among various methods of hydrogen production, water splitting driven by perovskite solar cell (PSC) is highly desirable due to the abundance of solar energy and low material cost. The key to achieve higher solar-to-hydrogen (STH) conversion efficiency is to reduce the overpotential of water splitting and enhance the solar energy utilization of the system. Herein, we demonstrate a photothermal enhanced oxygen evolution reaction (OER) electrocatalyst by depositing NiFe layer double hydroxide (NiFe LDH) on a three-dimensional carbon nanotubes (CNTs) scaffold. The CNTs can serve double functions, first as a conductive support of the catalyst to effectively transport charge, second as a photon absorber to induce photothermal effect to enhance OER activity. The photothermal enhancement of OER is demonstrated with infrared irradiation, part of the solar spectrum that is normally wasted in a conventional photovoltaic-electrolysis water splitting system. Based on the superior OER activity and photothermal properties, an unbiased water splitting system is constructed by integrating a CNTs@NiFe LDH//Pt/C electrochemical cell (EC) with a semitransparent perovskite solar cell (ST-PSC) mini-module in tandem configuration. The ST-PSC module provides voltage to drive water splitting and transmits infrared light to the rear CNTs@NiFe LDH electrode to induce the photothermal effect. The integrated PSC-EC system improves the STH efficiency from 11.7% to 13.2% with assistance of the photothermal effect and demonstrates a new strategy to harvest the full spectrum of solar irradiation for hydrogen production.

Bifunctional Water Splitting Performance of NiFe LDH Improved by Pd2+ Doping

AbstractNobel metal doping is an effective strategy to enhance the catalytic activity of electrocatalysts. Herein, a novel bifunctional electrocatalyst based on NiFe layered double hydroxide with ultra‐low Pd2+ doping (NiFePd LDH) was constructed by a one‐step hydrothermal method, where the Pd2+ is introduced by PdCl42−. The results show that Ni2+ and Pd2+ species are concomitantly deposited, and the slow‐release introduction of Pd2+ improves the element uniform distribution and effectively affects the electronic structures of active species by inducing local defects and lattice distortions, which is beneficial for stimulating the catalytic activity of NiFePd LDH. Under the optimal hydrothermal time, NiFePd LDH‐3 h only requires OER/HER overpotentials of 270 mV at 50 mA cm−2/‐316 mV at −10 mA cm−2, respectively, whose Tafel slopes are only 69.3/135.8 mV dec−1. As a bifunctional catalyst, it achieves a low voltage of 1.74 V at 10 mA cm−2 for overall water splitting with excellent long‐term durability.

Active Surface Area and Intrinsic Catalytic Oxygen Evolution Reactivity of NiFe LDH at Reactive Electrode Potentials Using Capacitances

Determination of the electrochemically active surface area (ECSA) is essential in electrocatalysis to provide surface normalized intrinsic catalytic activity. Conventionally, ECSAs of metal oxides and hydroxides are estimated using double layer capacitance (Cdl) measured at nonfaradaic potential windows. However, in the case of Ni-based hydroxide catalysts for the oxygen evolution reaction (OER), the nonfaradaic potential region before the Ni(II) oxidation peak is nonconductive, which hinders accurate electrochemical measurements. To overcome this problem, in this work, we have investigated the use of electrochemical impedance spectroscopy (EIS) at reactive OER potentials to extract the capacitance that is hypothesized to arise due to reactive OER intermediates (O*, OH*, OOH*) adsorbed on the catalyst surface. This allowed the estimation of ECSA and intrinsic activity of NiFe layered double hydroxide (NiFe LDH), the most active, state-of-the-art OER electrocatalyst in alkaline media. We analyzed the OER adsorbates capacitance (Ca) on NiFe LDH and Ni(OH)2 at different electrode potentials and identified a suitable potential range for accurate ECSA evaluation. Finally, we validated our method and the choice of potential range through rigorous catalyst loading and support studies.

Facile topochemically prepared hierarchical Ni–Fe LDH nanoflowers for the electrochemical oxygen elution reaction

Ni–Fe LDHs prepared via topochemical method composed of co-precipitation of Ni2+ and Fe2+ by NH4HCO3 and oxidation intercalation showed good OER performance with overpotential low to 240 mV at 10 mA cm−2 and Tafel slope of 25 mV decade−1.