NiFe Layered Double Hydroxide Research Articles

Functional coupling hole transport and extraction units over BiVO4 for efficient solar-to-hydrogen conversion

Photoelectrochemical (PEC) water splitting based on BiVO4 nanostructures is largely limited by the fast recombination of charge carriers and the low oxygen evolution reaction (OER) kinetics. To enhance PEC performance of BiVO4, combining hole transport units and hole extraction units is a simple and effective methods. In this work, Co3O4 and NiFe layered double hydroxide (NiFe-LDH) were coupled to promote bulk-phase charge separation and solid–liquid interface transfer, which accelerated OER kinetics on surface of target photoanodes. Moreover, p-n heterojunction between BiVO4 and Co3O4 suppressed charge recombination and promoted charge transfer, resulting in an effectively enhanced photocurrent density and applied bias photon to current efficiency (ABPE). To facilitate involvement of photogenerated holes in OER, BiVO4/Co3O4 electrodes are coated with NiFe-LDH as a hole extraction layer using a straightforward chemical bath deposition (CBD) technique. Successful fabrication of NiFe-LDH with rich oxygen vacancies significantly improves transport of charge carriers and provides many activity sites on the electrode surface. The optimized BiVO4/Co3O4/NiFe-LDH photoanode displayed a photocurrent density of 5.41 mA cm−2 at 1.23 VRHE with an ABPE of 1.08 % at 0.86 VRHE under light. These values are approximately 4.66 and 8.30 times higher than those of BiVO4 photoanodes. This study presents a powerful approach to enhance charge separation and transport in BiVO4-based photoanodes by functionally coupling hole transport and extraction units, thereby enabling efficient solar-to-hydrogen conversion.

TiO2 nanorod arrays modified by NiFe-layered double hydroxide nanosheets for boosting photoelectrochemical water splitting

TiO2 nanorod arrays modified by NiFe-layered double hydroxide nanosheets for boosting photoelectrochemical water splitting

Low-Spin Fe3+ Evoked by Multiple Defects with Optimal Intermediate Adsorption Attaining Unparalleled Performance in Water Oxidation.

Electrocatalytic water splitting is long constrained by the sluggish kinetics of anodic oxygen evolution reaction (OER), and rational spin-state manipulation holds great promise to break through this bottleneck. Low-spin Fe3+ (LS, t2g 5eg 0) species are identified as highly active sites for OER in theory, whereas it is still a formidable challenge to construct experimentally. Herein, a new strategy is demonstrated for the effective construction of LS Fe3+ in NiFe-layered double hydroxide (NiFe-LDH) by introducing multiple defects, which induce coordination unsaturation over Fe sites and thus enlarge their d orbital splitting energy. The as-obtained catalyst exhibits extraordinary OER performance with an ultra-low overpotential of 244 mV at the industrially required current density of 500 mA cm-2, which is 110 mV lower than that of the conventional NiFe-LDH with high-spin Fe3+ (HS, t2g 3eg 2) and superior to most previously reported NiFe-based catalysts. Comprehensive experimental and theoretical studies reveal that LS Fe3+ configuration effectively reduces the adsorption strength of the O* intermediate compared with that of the HS case, thereby altering the rate-determining step from (O* → OOH*) to (OH* → O*) of OER and lowering its reaction energy barrier. This work paves a new avenue for developing efficient spin-dependent electrocatalysts for OER and beyond.

Activation of Hidden Catalytic Sites in 2D Basal Plane via p–n Heterojunction Interface Engineering Toward Efficient Oxygen Evolution Reaction

AbstractNonprecious metal‐based 2D materials have shown promising electrocatalytic activity toward the oxygen evolution reaction (OER). However, the catalytically active sites of 2D materials are mainly presented at the edge, and most of their basal planes are still catalytically inactive, which turns into a significant drawback on the catalytic efficiency. Here, a novel p–n heterojunction strategy is suggested that generates active sites on the basal plane of 2D NiFe‐layered double hydroxide (NiFe‐LDH). The n‐type NiFe‐LDH is first grown on a nickel foam (NF) substrate, and p‐type Co3O4 nanocubes are deposited through a simple dip‐coating method to fabricate a Co3O4/NiFe‐LDH@NF p–n heterojunction electrode. As a result, electron transfer is induced at the interface of p‐type Co3O4 and n‐type NiFe‐LDH, which consequently promotes oxidation of the inert Ni2+ state to a more catalytically active Ni3+ state on the inert basal plane of NiFe‐LDH. As‐prepared Co3O4/NiFe‐LDH@NF electrodes obtained enhanced OER performance showing a high current density of 100 mA cm−2 at 1.48 V (vs RHE) which outperforms that of pristine NiFe‐LDH@NF. The utilization of the p–n junction concept will disclose a new strategy for modifying the electronic structure of the catalytically inactive basal plane and stimulating its electrocatalytic activity.

Enhance the Proportion of Fe3+ in NiFe-Layered Double Hydroxides by utilizing Citric Acid to Improve the Efficiency and Durability of the Oxygen Evolution Reaction.

NiFe-layered double hydroxides (NiFe-LDH) are a type of catalyst known for their exceptional catalytic performance during the oxygen evolution reaction (OER). In this study, citric acid was incorporated into the synthesis process of NiFe-LDH, resulting in the NiFe-LDH-CA catalyst with superior OER performance. The catalytic efficacy was evaluated using linear sweep voltammetry (LSV), which demonstrated a significant reduction in the overpotential for OER from 320 mV to 240 mV at a current density of 100 mA cm-2. X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) indicate that the distribution of nickel valence states showed no significant difference between two samples. However, the NiFe-LDH-CA exhibits a markedly higher proportion of Fe3+ ions in its iron content. In-situ Raman spectroscopes reveal that Fe3+ broadens the redox potential of nickel and Pourbaix diagrams indicate that higher Fe3+ levels could facilitate the interaction with oxygen active sites. Based on the analysis of test data, we propose a hypothesis that the high proportion of Fe3+ in catalysts may accelerate the oxygen evolution process by modulating the redox potential of nickel and engaging with reactive oxygen species. This provides valuable insights into how to improve the reaction rate of nickel-based catalysts.

Activation of Persulfate by NiFe-Layered Double Hydroxides Toward Efficient Degradation of Doxycycline in Water

In recent years, the excessive use and improper disposal of antibiotics have led to their pervasive presence in the environment, resulting in significant antibiotic pollution. To address this pressing issue, the present study synthesized nickel–iron-layered double hydroxides (NiFe-LDHs) with varying molar ratios using a hydrothermal method, employing these LDHs as catalysts for the oxidative degradation of doxycycline, with peroxymonosulfate (PMS) serving as the oxidant. X-ray diffraction analysis confirmed that the synthesized NiFe-LDHs exhibited a hexagonal crystal structure characteristic of layered double hydroxides. Experimental results demonstrated that the catalytic efficiency of NiFe-LDHs increased with both the dosage of the catalyst and the concentration of PMS, achieving a high degradation efficiency for doxycycline at a catalyst concentration of 0.5 g/L. Furthermore, the catalytic performance was notably effective across a range of pH conditions, with the highest degradation efficiency being observed at a Ni–Fe molar ratio of 3:1. The activation of PMS by NiFe-LDHs for the catalytic degradation of pollutants primarily occurs through singlet oxygen (1O2), superoxide radicals (O2−·), and sulfate radicals (SO4−·). The study also proposed three potential degradation pathways for doxycycline, indicating that the final degradation products have lower environmental toxicity. This research offers novel approaches and methodologies for the treatment of antibiotic-contaminated wastewater.

Continuous lattice oxygen participation of NiFe stack anode for Sustainable water Splitting

Non-noble anode catalysts exhibit insufficient activity and stability for anion exchange membrane water electrolysis (AEMWE). Accordingly, we propose an electrolyte additive strategy involving NiFe-layered double hydroxide. In situ Raman spectroscopy and 18O isotope labeling experiments reveal that Fe ions in the electrolyte change the oxygen evolution reaction mechanism from adsorbate evolution to the lattice oxygen participation mechanism (LOM). These Fe ions continuously refill Fe vacancies owing to facile metal dissolution via the LOM. In a unit cell, we achieve an excellent cell voltage of 1.73 V and energy conversion efficiency (ECE) of 69.4 % at 3.0 A cm−2, meeting the target set by the U.S. Department of Energy (1.80 V and 69.0 % ECE). Our optimized membrane electrode assembly enhances the cell activity (1.567 V at 1.0 A cm−2; ECE = 76.5 %) and stability (0.125 mVcell h−1 at 0.5 A cm−2 for 500 h) with a 100 cm2 AEMWE stack.

Poly(3-thiophenemalonic acid) Modified NiFe Layered Double Hydroxide Electrocatalyst for Stable Seawater Oxidation at an Ampere-Scale Current Density

Poly(3-thiophenemalonic acid) Modified NiFe Layered Double Hydroxide Electrocatalyst for Stable Seawater Oxidation at an Ampere-Scale Current Density

Engineering Lattice Oxygen Regeneration of NiFe Layered Double Hydroxide Enhances Oxygen Evolution Catalysis Durability

The lattice oxygen mechanism (LOM) endows NiFe layered double hydroxide (NiFe‐LDH) with superior oxygen evolution reaction (OER) activity, yet the frequent evolution and sluggish regeneration of lattice oxygen intensify the dissolution of active species. Herein, we overcome this challenge by constructing the NiFe hydroxide/Ni4Mo alloy (NiFe‐LDH/Ni4Mo) heterojunction electrocatalyst, featuring the Ni4Mo alloy as the oxygen pump to provide oxygenous intermediates and electrons for NiFe‐LDH. The released lattice oxygen can be timely offset by the oxygenous species during the LOM process, balancing the regeneration of lattice oxygen and assuring the enhancement of the durability. In consequence, the durability of NiFe‐LDH is significantly enhanced after the modification of Ni4Mo with an impressively durability for over 60 h, much longer than that of NiFe‐LDH counterpart with only 10 h. In‐situ spectra and first‐principle simulations reveal that the adsorption of OH− is significantly strengthened owing to the introduction of Ni4Mo, ensuring the rapid regeneration of lattice oxygen. Moreover, NiFe‐LDH/Ni4Mo‐based anion exchange membrane water electrolyzer (AEMWE) presents an impressive durability for over 150 h at 100 mA cm−2. The oxygen pump strategy opens opportunities to balance the evolution and regeneration of lattice oxygen, enhancing the durability of efficient OER catalysts.

Engineering Lattice Oxygen Regeneration of NiFe Layered Double Hydroxide Enhances Oxygen Evolution Catalysis Durability.

The lattice oxygen mechanism (LOM) endows NiFe layered double hydroxide (NiFe-LDH) with superior oxygen evolution reaction (OER) activity, yet the frequent evolution and sluggish regeneration of lattice oxygen intensify the dissolution of active species. Herein, we overcome this challenge by constructing the NiFe hydroxide/Ni4Mo alloy (NiFe-LDH/Ni4Mo) heterojunction electrocatalyst, featuring the Ni4Mo alloy as the oxygen pump to provide oxygenous intermediates and electrons for NiFe-LDH. The released lattice oxygen can be timely offset by the oxygenous species during the LOM process, balancing the regeneration of lattice oxygen and assuring the enhancement of the durability. In consequence, the durability of NiFe-LDH is significantly enhanced after the modification of Ni4Mo with an impressively durability for over 60 h, much longer than that of NiFe-LDH counterpart with only 10 h. In-situ spectra and first-principle simulations reveal that the adsorption of OH- is significantly strengthened owing to the introduction of Ni4Mo, ensuring the rapid regeneration of lattice oxygen. Moreover, NiFe-LDH/Ni4Mo-based anion exchange membrane water electrolyzer (AEMWE) presents an impressive durability for over 150 h at 100 mA cm-2. The oxygen pump strategy opens opportunities to balance the evolution and regeneration of lattice oxygen, enhancing the durability of efficient OER catalysts.

Dual Cocatalytic Sites Synergize NiFe Layered Double Hydroxide to Boost Oxygen Evolution Reaction in Anion Exchange Membrane Water Electrolyzer

AbstractNickel‐iron layered double hydroxide (LDH) is a promising cost‐efficient catalyst to replace noble metals for alkaline oxygen evolution reaction (OER), yet its intrinsic activity under high current density conditions is not satisfactory, which greatly constrains the industrial application of NiFe LDH catalysts. Herein, a new class of integrated Co and W co‐doped NiFe LDH catalysts is reported with dual cocatalytic sites for alkaline OER catalysis. The optimized Co2.8, W3.8‐NiFe LDH integrated catalyst has superior alkaline OER activity (255 mV@1000 mA cm−2) and excellent catalytic stability (200 h@500 mA cm−2). The turnover frequency value of Co2.8, W3.8‐NiFe LDH can reach 4.02 s−1 at 1.49 V versus RHE, which is 9.6 times higher than that of NiFe LDH and superior to the noble metal catalysts. Moreover, it can achieve 1.0 A cm−2 at 1.86 V and maintain 300‐h stable operation in anion exchange membrane water electrolyzer. Theoretical and experimental studies indicate that W sites promote the *OH adsorption and Co sites favor protons desorption of OH*. These dual cocatalytic sites jointly promote *O coverage, effectively accelerating alkaline OER kinetic.

A Green Solvent-Free Approach Synthesis for Rational Designing of a NiFe-Layered Double Hydroxide [NiFe-LDH] Electrocatalyst for Hydrogen Generation

A Green Solvent-Free Approach Synthesis for Rational Designing of a NiFe-Layered Double Hydroxide [NiFe-LDH] Electrocatalyst for Hydrogen Generation

Synchronous interlayer and surface engineering of NiFe layered double hydroxides by functional ligands for boosting oxygen evolution reaction

NiFe layered double hydroxides (LDHs) are among the most advanced electrocatalysts for oxygen evolution reaction (OER), but their catalytic activity and long-term working stability still need to be highly boosted for practical applications. Herein, an innovative strategy that combines anion intercalation/deintercalation and surface coordination is developed, which simultaneously realizes the modification of the interlay and surface properties of the NiFe LDHs by ethylenediaminetetraacetate (EDTA) and trisodium citrate (TSC). The intercalation/deintercalation of the anions engineers the interlay structure, while the surface metal-ligand coordination tunes the surface properties. Both the EDTA- and TSC-engineered NiFe LDHs exhibit highly enhanced catalytic performance, showing an overpotential of 204 and 233 mV, respectively at 10 mA cm-2 in 1.0 M KOH. The remarkable catalytic performance of the EDTA-engineered NiFe LDHs is due to the combined effect of the intercalation/deintercalation and the surface metal-EDTA coordination, while the surface TSC coordination only shows limited promoting effect on catalytic activity. In addition, the EDTA-engineered NiFe LDHs demonstrate good working stability at 100 mA cm-2.

Ultrafast Room-Temperature Synthesis of Phosphate-Intercalated NiFe Layered Double Hydroxides for High-Performance Alkaline Seawater Oxidation.

Quick and easy synthetic methods and highly efficient catalytic performance are equally important to anodic oxygen evolution reaction (OER) electrocatalysts for alkaline seawater electrolysis. Herein, we report a facile one-step route to in situ growing PO43- intercalated NiFe layered double hydroxides (NiFe-LDH) on Ni foam (denoted as NiFe-P/NF) by a room-temperature immersion for several minutes. This ultrafast approach transforms the NF surface into a rough PO43- intercalated NiFe-LDH overlayer, which demonstrates outstanding OER performance in both alkaline simulated and natural seawaters owing to good hydrophilic interface and the electrostatic repulsion of PO43- against Cl- anions. Density functional theory calculations reveal that the intercalated PO43- can not only promote electron transfer but also prevent Cl- from entering the interlayer and simultaneously inhibit the migration of Cl- over the NiFe-LDH surface. In alkaline simulated and natural seawater electrolytes, NiFe-P/NF needs low overpotentials of 248 and 298 mV to achieve a current density of 100 mA cm-2, respectively. NiFe-P/NF can stably run over 42 h in an alkaline high-salty electrolyte (1 M KOH + 2.5 M NaCl) at 250 mA cm-2, more than 70 times that of NiFe/NF (0.6 h), emphasizing the critical role of the intercalated PO43- anions on the excellent durability. This study offers a new strategy to modify commercial NF to prepare efficient and stable OER catalysts for seawater electrolysis.

The Construction of Face-to-Face Combination between NiFe-layered Double Hydroxide Nanosheets and Monolayer rGO for Efficient Water Splitting and Oxygen Reduction.

Developing cost-effective and efficient electrocatalysts is essential for advancing a green energy future. Herein, a NiFe-layered double hydroxide loaded on reduced graphene oxide (NiFe-LDHs@rGO) hybrid was synthesized using a straightforward three-step process involving exfoliation tearing, electrostatic self-assembly, and chemical reduction. The face-to-face packing and ultrathin exfoliation enable strong heterogeneous interactions, fully harnessing the potential of these complementary two-dimensional counterparts. Consequently, the resultant catalyst displays outstanding oxygen evolution reaction (OER) catalytic activity and stability, whose overpotential is as low as 241 mV at 30 mA cm-2 and 255 mV at 50 mA cm-2 with a low Tafel slope of 62.1 mV dec-1. Both the experimental results and density functional theory (DFT) calculations reveal that the face-to-face assembly strengthens the electronic interactions between NiFe-LDHs and rGO, which effectively modulates the d-band center of Ni and Fesites and improves the reaction kinetics for OER. Moreover, the resultant NiFe-LDHs@rGO hybrids exhibit excellent multifunctional catalytic performance. Its hydrogen evolution reaction (HER) activity is endowed by Fe-site of NiFe-LDHs and defect states rGO and achieves a low voltage of 1.68 V to drive a current density of 10 mA cm-2 for overall water splitting. The face-to-face heteroassembly also imparts NiFe-LDHs@rGO with superior oxygen reduction reaction (ORR) activity, with a half-wave potential of 0.70 V and a limiting current density of 4.2 mA cm-2. Its ORR primarily follows a four-electron transfer pathway with a minor contribution from a two-electron process. This study establishes the groundwork for optimizing two-dimensional heterogeneous interfaces in LDH@carbon-based materials for advanced energy conversion.

Innovative Catalytic Strategies: The Game - Changing Role of S - Doping in NiFe Layered Double Hydroxides (LDHs) for Superior Water Oxidation

Innovative Catalytic Strategies: The Game - Changing Role of S - Doping in NiFe Layered Double Hydroxides (LDHs) for Superior Water Oxidation

Oxygen evolution reaction of tellurium-incorporated nickel-iron layered double hydroxide microcrystals

Transition-metal-based layered double hydroxide (LDH) crystals have generated substantial interest as highly efficient oxygen evolution reaction (OER) catalysts because of their abundance, low cost, environmental friendliness, and favourable adsorption/desorption energies for intermittent reactants. However, the application of LDH crystals as high-performance electrocatalysts is frequently hindered by their sluggish electronic transport kinetics resulting from their intrinsically low conductivity. Herein, we report the effects of incorporating metalloids into transition metal LDH crystals on their electrocatalytic activity. In this study, tellurium (Te) incorporated NiFe (xTe-NiFe) LDH microcrystal, where x = 0.2, 0.4, 0.6 and 0.8, were grown on three-dimensional porous nickel foam using a facile solvothermal method. The electrocatalytic OER properties were analyzed using linear sweep voltammetry and electrochemical impedance spectroscopy. The amount of Te was found to play a crucial role in improving the catalytic activity of NiFe LDH. The optimum amount of Te (x) introduced into NiFe LDH was examined with respect to the OER performance.

In situ microbubble-mediated strategy for highly efficient anti-crude oil-fouling membrane with parallel nanosheet structure

Membrane fouling caused by highly viscous oils severely hampers the long-term application of oil–water separation membranes. In situ aeration, achieved by applying a voltage to the membrane to produce bubbles, can effectively reduce the adhesion of oil contaminants. Herein, the parallel NiFe-layered double hydroxide arrays were successfully constructed on Ni foam using a hydrothermal method. Compared with NF@NFLDH having randomly aligned nanosheet arrays, NF@NFLDH-P can produce more numerous micro-size bubbles. A substantial number of the microbubbles spontaneously coalesced with oil droplets, and the synergy of buoyancy and kinetic energy significantly hindered oil fouling on the NF@NFLDH-P membrane. Specifically, this microbubble–mediated anti-oil-fouling strategy substantially reduced the flux attenuation and maintained a high flux recovery ratio during long-term crude oil–water separation, exhibiting a great operational life. This study suggests an innovative way to design future anti-fouling membranes with bubble-mediated capabilities.

Tailoring Ni-Fe-B Electronic Effects in Layered Double Hydroxides for Enhanced Oxygen Evolution Activity.

NiFe layered double hydroxides (LDHs) are state-of-the-art catalysts for the oxygen evolution reaction (OER) in alkaline media, yet they still face significant overpotentials. Here, quantitative boron (B) doping is introduced in NiFe LDHs (ranging from 0% to 20.3%) to effectively tailor the Ni-Fe-B electronic interactions for enhanced OER performance. The co-hydrolysis synthesis approach synchronizes the hydrolysis rates of Ni and Fe precursors with the formation rate of B─O─M (M: Ni, Fe) bonds, ensuring precise B doping into the NiFe LDHs. It is demonstrated that B, as an electron-deficient element, acts as an "electron sink" at doping levels from 0% to 13.5%, facilitating the transition of Ni2+ to the active Ni3+δ, thereby accelerating OER kinetics. However, excessive B doping (13.5-20.3%) effectively generates oxygen vacancies in the LDHs, which increases electron density at Ni2+ sites and hinders their transition to Ni3+δ, thereby reducing OER activity. Optimal OER performance is achieved at a B doping level of 13.5%, with an overpotential of only 208mV to reach a current density of 500mA cm-2, placing it among the most effective OER catalysts to date. This Ni-Fe-B electronic engineering opens new avenues for developing highly efficient anode catalysts for water-splitting hydrogen production.

In Situ Growth of NiFe Layered Double Hydroxide Coating for the Corrosion Inhibition of 316 and 304 Stainless Steels in 3.5 wt.% NaCl Solution

In Situ Growth of NiFe Layered Double Hydroxide Coating for the Corrosion Inhibition of 316 and 304 Stainless Steels in 3.5 wt.% NaCl Solution