NiFe-LDH Nanosheets Research Articles

Enhancing Electrocatalytic Water Oxidation of NiFe-LDH Nanosheets via Bismuth-Induced Electronic Structure Engineering.

The design and synthesis of high-efficiency electrocatalysts are of great practical significance in electrocatalytic water splitting, specifically in accelerating the slow oxygen evolution reaction (OER). Herein, a self-supported bismuth-doped NiFe layered double hydroxide (LDH) nanosheet array for water splitting was successfully constructed on nickel foam by a one-step hydrothermal strategy. Benefiting from the abundant active sites of two-dimensional nanosheets and electronic effect of Bi-doped NiFe LDH, the optimal Bi0.2NiFe LDH electrocatalyst exhibits excellent OER performance in basic media. It only requires an overpotential of 255 mV to drive 50 mA cm-2 and a low Tafel slope of 57.49 mV dec-1. The calculation of density functional theory (DFT) further shows that the incorporation of Bi into NiFe LDH could obviously overcome the step of H2O adsorption during OER progress. This work provides a simple and effective strategy for improving the electrocatalytic performance of NiFe LDHs, which is of great practical significance.

Integration of surficial oxygen vacancies and interfacial two-dimensional NiFe-layered double hydroxide nanosheets onto bismuth vanadate photoanode for boosted photoelectrochemical water splitting

Considering its outstanding cost-to-efficiency ratio, N-type bismuth vanadate (BiVO4) is an ideal photoanode for photoelectrochemical (PEC) water splitting. Nevertheless, the widespread application of BiVO4 is being hindered commercially by innate challenges such as its poor carrier mobility, short hole diffusion length, and sluggish oxidation chemistry. Herein, we report the unique integration of surficial oxygen vacancies (Ovac) in conjunction with two-dimensional (2D) nickel-iron (NiFe) layered double hydroxide (LDH) nanosheets onto pristine BiVO4 photoanode to tweak the charge transfer kinetics during water splitting. The introduction of oxygen vacancies efficiently modulates band energetics, amplifies light absorption, and augments the carrier density. Concurrently, the 2D NiFe-LDH nanosheets play a dual role by facilitating interfacial hole transfer, thereby reducing excessive defect states, and serving as a protective layer against photocorrosion, ultimately resulting in a notable improvement in solar-driven water oxidation efficiency. The results of PEC water-splitting experiments demonstrate that the BiVO4 photoanode enriched with surficial oxygen vacancies and NiFe-LDH (BiVO4:Ovac/NiFe-LDH) achieved a photocurrent density of 2.92 mA cm−2 with ∼3-fold enhancement compared with a pristine BiVO4 photoanode. The engineered BiVO4 system yielded an impressive photoconversion efficiency of 1.29 %, charge separation efficiency (ηsep) > 40 %, and charge transport efficiency (ηtrans) > 35 %, clearly evidencing a boost in the charge dynamics of pristine BiVO4. Furthermore, during long-term stability testing, BiVO4:Ovac/NiFe-LDH retained 91 % of its initial photocurrent density for ∼20 h without any significant deterioration. This work sheds light on the role of integrating surface and interface engineering tactics for enhancing photo-induced charge transport in BiVO4, thereby providing efficient and stable PEC water splitting.

NiFe-LDH nanosheets anchored on Fe, N decorated carbon nanofibers as efficient bifunctional electrocatalysts for long-term rechargeable Zn-air batteries

NiFe-LDH nanosheets anchored on Fe, N decorated carbon nanofibers as efficient bifunctional electrocatalysts for long-term rechargeable Zn-air batteries

Constructing built-in electric field in 3D core-shell p-n heterostructure of NiFe-LDH nanosheets modified Cr-doped Ni3S2 nanofibers for efficient and stable oxygen evolution reaction

Designing and creating effective, dependable, and conveniently accessible electrocatalysts for the oxygen evolution process is necessary to increase the efficiency of hydrogen production by water electrolysis. In this study, utilizing hydrothermal and electrodeposition methods, we have successfully synthesized a unique 3D Cr-Ni3S2 @NiFe-LDH/NF core-shell p-n heterostructure with a built-in electric field for use as an oxygen evolution reaction (OER) electrocatalyst. By constructing a built-in electric field into the p-n junction, the electronic state of the NiFe-LDH surface can be modified, resulting in an increase in hole concentration and enhanced adsorption of hydroxyl groups from the electrolyte. This facilitates OER reaction kinetics and improves electrocatalytic performance. The Cr-Ni3S2 @NiFe-LDH/NF-120 electrocatalyst exhibits a low overpotential of only 190 mV at a current density of 10 mA cm−2, with a Tafel slope of 33.4 mV dec−1. Remarkably, the overpotential is low, remaining at just 270 mV even at 100 mA cm−2. By operating continuously for 40 h at room temperature in a 1.0 M KOH solution while maintaining a current density of 100 mA cm−2, the exceptional stability was demonstrated. Our research provides a solid framework for the creation of extremely stable and effective 3D core-shell heterojunction electrocatalysts, which can greatly improve OER performance.

Core–shell heterostructure engineering of CoP nanowires coupled NiFe LDH nanosheets for highly efficient water/seawater oxidation

Searching for efficient nonprecious metal-based catalysts toward oxygen evolution reaction (OER) are of significance for seawater electrolysis. Herein, a core–shell-structured hybrid of cobalt phosphide nanowires@NiFe layered double hydroxide nanosheets grown on conductive nickel foam (CoP@NiFe LDH/NF) is prepared by a feasible approach at low temperature. The charming structure can provide numerous phosphide/hydroxide heterogenous interfaces, expose abundant active sites, and boost electron/mass transfer, synergistically enhancing catalytic OER activity. When employed as an electrocatalyst toward the OER, the resultant CoP@NiFe LDH/NF only requires a small overpotential of 287 mV to provide 300 mA/cm2 current density as well as long-time durability in 1.0 mol/L KOH seawater. The regulation of electronic states and surface reconstruction synergistically contribute to highly efficient seawater oxidation. This work provides an opportunity to construct efficient and inexpensive electrocatalysts for hydrogen production.

Defective Nickel–Iron Layered Double Hydroxide for Enhanced Photocatalytic NO Oxidation with Significant Alleviation of NO2 Production

Photocatalysis offers a sustainable means for the oxidative removal of low concentrations of NOx (NO, NO2, N2O, N2O5, etc.) from the atmosphere. Layered double hydroxides (LDHs) are promising candidate photocatalysts owing to their unique layered and tunable chemical structures and abundant surface hydroxide (OH−) moieties, which are hydroxyl radical (OH) precursors. However, the practical applications of LDHs are limited by their poor charge-separation ability and insufficient active sites. Herein, we developed a facile N2H4-driven etching approach to introduce dual Ni2+ and OH− vacancies (Niv and OHv, respectively) into NiFe-LDH nanosheets (hereafter referred to as NiFe-LDH-et) to facilitate improved charge-carrier separation and active Lewis acidic site (Fe3+ and Ni2+ exposed at OHv) formation. In contrast to inert pristine LDH, NiFe-LDH-et actively removed NO under visible-light illumination. Specifically, Ni76Fe24-LDH-et etched with 1.50 mmol·L−1 N2H4 solution removed 32.8% of the NO in continuously flowing air (NO feed concentration: ∼500 parts per billion (ppb)) under visible-light illumination, thereby outperforming most reported catalysts. Experimental and theoretical data revealed that the dual vacancies promoted the production of reactive oxygen species (O2− and OH) and the adsorption of NO on the LDH. In situ spectroscopy demonstrated that NO was preferentially adsorbed at Lewis acidic sites, particularly exposed Fe3+ sites, converted into NO+, and subsequently oxidized to NO3− without the notable formation of the more toxic intermediate NO2, thereby alleviating risks associated with its production and emission.

Heterogeneous interface engineering of cationic vacancy defects layered double hydroxides and molybdenum-nickel-based selenium compounds to facilitate overall water splitting

Constructing non-uniform interfaces of noble-metal-free electroactive materials is vital for the rapid kinetics and high ion/electron transfer rate towards overall water splitting. Herein, we propose a strategy to combine the cationic vacancy defects NiFe-LDH (VNFL) nanosheets with MoNiSe nanowires to design heterogeneous structures (MoNiSe@VNFL) grown on Ni foam (NF) for enhancement of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalytic activity. Density flooding theory (DFT) calculations show that the electron transfer rate can be optimized by tuning electron dissipation and aggregation at the active site around the d-band centers near the Fermi energy level. As anticipated, even at a current density of 10 mA cm−2, the HER and OER occurring in these catalysts exhibit remarkable activity, with an rather low overpotentials of 27 mV, 200 mV and a Faradaic efficiency (FE) of almost 100 %. Notably, merely the cell overpotential of 1.56 V effectively propels a 10 mA cm−2 current density in the two-electrode architecture, as well with remarkable long-term stability for the water splitting, disclosing its potential in reduce the cost for large-scale industrial application.

Surface reconstruction of NiFe layered double hydroxides by S2- corrosion for efficient oxygen evolution

Nickel-iron layered double hydroxides (NiFe LDH) are subject to surface reconstruction by the applied anodic potential in alkaline media, and the reconstructed metal hydroxyl oxides are often considered to be the actual active material for oxygen evolution reaction (OER), so how to facilitate surface reconstruction is crucial for their performance. In this paper, the surface reconstruction of NiFe LDH nanosheets was successfully induced by S2- corrosion using rapid wet chemical engineering without affecting their crystal structure and nanomorphology; Notably, the NiOOH species formed on the corroded S-NiFe LDH/NF surface participate in the OER process as active species. The electrochemical measurements show that S-NiFe LDH/NF has a low overpotential of 250 mV and a Tafel slope of 26.3 mV dec -1 at 50 mA cm−2. This work provides a simple activation strategy for the surface reconstruction of NiFe LDH, which is an important reference for the design of advanced catalysts.

GQD@NiFe-LDH Nanosheets for Photocatalytic Activity towards Textile Dye Degradation via Lattice Contraction.

The functionalized NiFe-LDH with photosensitized GQDs were synthesized through the hydrothermal route by differing the amount of GQDs solution and studied its efficacy towards the mineralization of textile dyes under visible light. The synthesized samples were characterized by XRD, FESEM, HRTEM, DRUV-Vis, RAMAN, XPS, and BET. The combined effect of the hexagonal carbon lattice in GQD and open layered porous structure of NiFe-LDH nanosheets results in the contraction of the lattice. Different reactive and conventional dyes were taken as representative dyes to evaluate the activity of the as-synthesized photocatalysts. The enhanced electron absorption/donor effect between GQDs and NiFe-LDH, and the growth of oxygen-bridged Ni/Fe-C moieties enable the composite to exhibit better photocatalytic activity. Both photocatalytic activity and characterization results confirmed that the GQD@NiFe-LDH nanocomposite heterostructure synthesized at 160 °C by taking 10 mL of GQDs aqueous solution named GNFLDH10 has a higher degree of crystallinity and has the best photocatalytic efficiency compared to other reported visible light catalysts. Specifically, the above optimized GQD@NiFe-LDH photocatalyst is capable of photo-mineralizing 50 ppm of Reactive Green in 20 min, Reactive Red in 20 min, and Congo Red in 25 min respectively following a direct Z-scheme mechanism with substantial reusability.

Hierarchical MoN@NiFe-LDH Heterostructure Nanowire Array for Highly Efficient Electrocatalytic Hydrogen Evolution.

The slow charge transfer and high energy barrier are the key restrictions of cost-effective electrocatalysts for hydrogen production. A hierarchical heterostructure of MoN@NiFe-layered double hydroxides (LDH) is developed, with NiFe-LDH nanosheets supported on MoN nanowire arrays. The as-prepared MoN@NiFe-LDH exhibits a remarkably high performance on hydrogen production in alkaline medium, which is close to the benchmark Pt/C. The theoretical computations indicate that MoN@NiFe-LDH has a metallic character inherited from MoN, which gives rise to the promoted charge transfer. Furthermore, the adsorption intensity of intermediates on MoN@NiFe-LDH is optimized and thereby the energy barrier is diminished. This work demonstrates the significance of constructing heterostructure for boosting the charge transfer and reducing the energy barrier, which can shed light on the development of highly efficient and low-cost electrocatalyst for hydrogen production.

Composite material of NiFe-LDH nanosheets and CoP nanowires for efficient oxygen evolution reaction

Composite material of NiFe-LDH nanosheets and CoP nanowires for efficient oxygen evolution reaction

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.

Cu2S Nanorods Decorated with NiFe-Layered Double Hydroxide Nanosheets as Bifunctional Electrocatalysts for Hydrogen Evolution in Alkaline Saline Water/Seawater

The progress of highly efficient and stable nonprecious metallic-based electrocatalysts for the hydrogen evolution reaction (HER) in saline water/seawater is of great importance for the mass-scale production of hydrogen energy. Herein, a nanostructured NiFe-LDH/Cu2S heterostructure is constructed by growing NiFe-LDH nanosheets onto Cu2S nanorods. This heterostructure possesses exceptional HER performances with η10 = 36 mV (η10 indicates the overpotential at a current density of 10 mA cm2) and worked stably over 100 h in alkaline saline water. Moreover, the heterojunction catalyst acts as a bifunctional electrocatalyst for the anode and cathode, achieving a cell voltage of η10 = 1.463 V, which is superior to many reported electrocatalysts. The improvement of catalytic performance of NiFe-LDH/Cu2S can be ascribed to the charge redistribution on the heterointerface that accelerates the dissociation process caused by the formation of Ni with low electron cloud density. Moreover, the obtained covalent S–O bonds are beneficial to the adsorption of H*. In addition, NiFe-LDH/Cu2S also exhibits considerable catalytic performances in seawater electrolytes, delivering a cell voltage of η10 = 1.483 V with a stability of 27 h. We present a promising bifunctional electrocatalyst for water electrolysis in alkaline saline water/seawater which may find wide applications in the area of hydrogen energy.

In Situ Synthesis of NiFeLDH/A-CBp from Pyrolytic Carbon as High-Performance Oxygen Evolution Reaction Catalyst for Water Splitting and Zinc Hydrometallurgy.

Nickel-iron-layered double hydroxide (NiFeLDH) is one of the promising catalysts for the oxygen evolution reaction (OER) in alkaline electrolytes, but its conductivity limits its large-scale application. The focus of current work is to explore low-cost, conductive substrates for large-scale production and combine them with NiFeLDH to improve its conductivity. In this work, purified and activated pyrolytic carbon black (CBp) is combined with NiFeLDH to form an NiFeLDH/A-CBp catalyst for OER. CBp not only improves the conductivity of the catalyst but also greatly reduces the size of NiFeLDH nanosheets to increase the activated surface area. In addition, ascorbic acid (AA) is introduced to enhance the coupling between NiFeLDH and A-CBp, which can be evidenced by the increase of Fe-O-Ni peak intensity in FTIR measurement. Thus, a lower overvoltage of 227 mV and larger active surface area of 43.26 mF·cm-2 are achieved in 1 M KOH solution for NiFeLDH/A-CBp. In addition, NiFeLDH/A-CBp shows good catalytic performance and stability as the anode catalyst for water splitting and Zn electrowinning in alkaline electrolytes. In Zn electrowinning with NiFeLDH/A-CBp, the low cell voltage of 2.08 V at 1000 A·m-2 results in lower energy consumption of 1.78 kW h/KgZn, which is nearly half of the 3.40 kW h/KgZn of industrial electrowinning. This work demonstrates the new application of high-value-added CBp in hydrogen production from electrolytic water and zinc hydrometallurgy to realize the recycling of waste carbon resources and reduce the consumption of fossil resources.

Lithiophilic interface dynamic engineering to inhibit Li dendrite growth for intrinsically safe Li-metal batteries

Lithium (Li) metal is deemed as attractive anode due to its low electrochemical potential and high theoretical capacity. Nevertheless, the uncontrollable Li dendrite growth causes safety concern and battery failure, which severely impedes the commercialization of Li metal batteries (LMBs). Herein, 3D functional matrix comprising NiFe-layered-double-hydroxide nanosheet arrays (NiFe-LDH) evenly dispersed on acidified carbon cloth (NiFe-LDH@ACC) via hydrothermal method is designed to manipulate uniform Li electrodeposition morphology. Vertical NiFe-LDH nanosheets possess high accessible surface area to supply vast Li nucleation sites, thus effectively reducing the local current density and decreasing the nucleation energy barrier to suppress Li dendrites growth, which has been validated by simulation. Moreover, 3D structure of carbon cloth provides adequate space for storing Li metal, substantially abating volume fluctuation during repeated Li plating/stripping process. Consequently, the Li@NiFe-LDH@ACC electrode manifests ultra-long lifespan over 3500 h and low-voltage hysteresis in symmetric cells. Additionally, the full cell with limited Li@NiFe-LDH@ACC anode and commercial LiFePO4 cathode (mass loading: 8.35 mg cm−2) displays good rate capacity from 0.2 C to 5 C, and can steadily operate for 75 cycles at 2 C with a capacity of 131 mAh g−1, revealing the practical feasibility of the surface modification strategy for constructing advanced Li metal anode with high safety and appealing durability.

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.

Rh-doped ultrathin NiFeLDH nanosheets drive efficient photocatalytic water splitting

NiFeLDH (Layered double hydroxide) semiconductors are promising for harnessing light energy. The development of transition metal-based photocatalysts consisting of rhodium building blocks is not only beneficial for the separation and transfer of photo-generated carriers in photocatalytic reactions but also an effective means of widening the optical window of light absorption. In this report, a facile hydrothermal approach is employed in modulating NiFeLDH nanosheets arrays with optimal molar ratio of Rhodium (Rh) in LDH to engineer a robust hierarchical NiFeLDH-Rh photocatalytic system towords efficient hydrogen evolution reaction (HER) under visible light. In a systematic investigation, the NiFeLDH is grown on nickel foam and controlled doping of Rhodium led to fine-tuning of their electronic structure and efficient visible light-driven proton reduction system due to its multiple accessible active sites boosting the photocatalytic performance. Furthermore, the 2D hierarchical nanosheet arrays can speed up electron diffusion and assure fast electron/mass transfer while maintaining high photocatalytic stability. The NiFeLDH-Rh composite demonstrated an enhanced hydrogen generation rate of 2.09 mmolg−1h−1 (AQY = 6.1%). The photocurrent density and transient photocurrent curve show rapid charge transfer as well as the unique electron transfer paths through the contact surface, resulting in efficient charge separation. Moreover DFT and photoelectrochemical studies reveal higher HER activity due to the augmented electric field between Rh and NiFeLDH complex. This research offers a novel strategy and new insights into the investigation of highly active photocatalysts for overall water splitting.

Constructing Cation Vacancy Defects on NiFe-LDH Nanosheets for Efficient Oxygen Evolution Reaction

Active site exposure and intrinsic catalytic performance are considered important aspects of oxygen evolution reaction catalyst design. In this work, the coordination capacity of tributylphosphine is utilized to construct cationic vacancy defects on NiFe-LDH nanosheets. As-prepared defective NiFe-LDH nanosheets show not only the optimization of the exposure ability of the active site but also the intrinsic catalytic capacity is improved by construction of cationic vacancy defect to tune local electronic structure. The x-ray photoelectron spectroscopy results revealed that after reconstruction of the prepared d-NiFe-LDH, high-valence Ni and Fe can stably appear on the surface of the material. The presence of high-valence Ni and Fe is considered to be the main reason to improve the intrinsic catalytic capacity of catalysts. Finally, d-NiFe-LDH nanosheets show excellent catalytic performance (η 10 = 243 mV) and remarkable long-term stability.

Core–shell heterojunction engineering of Co3O4/NiFe LDH nanosheets as bifunctional electrocatalysts for efficient reduction of nitrite to ammonia

Core–shell Co3O4/NiFe LDH heterostructured nanosheets serve as remarkable NO2−RR and OER bifunctional electrocatalysts for high-efficiency and low-cost ammonia production.

Active-site-enriched Cu-doped Ni–Fe layered double hydroxide nanosheets for boosting the oxygen evolution reaction

In this study, porous Cu-doped NiFe-LDH nanosheets were synthesized through a cation exchange method, and exhibited highly competitive OER catalytic activity and stability.