NiFe Layered Double Hydroxide Research Articles

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

Coordination Stabilization of Fe by Porphyrin‐Intercalated NiFe‐LDH Under Industrial‐Level Alkaline Conditions for Long‐Term Electrocatalytic Water Oxidation

AbstractThe durable and economic electrocatalysts with high current density under industrial alkaline conditions are critical for advancing the industrial production of hydrogen energy by water electrolysis. The industrial highly alkaline electrolyte exacerbates the Fe dissolution of NiFe layered double hydroxide (NiFe‐LDH), leading to the dramatic degradation of stability and activity. The NiFe‐LDH intercalated Tetrakis(4‐carboxyphenyl)porphyrin (TCPP) (NiFe‐TCPP), 1,4,7,10‐Tetraazacyclododecane‐1,4,7,10‐tetraacetic acid (DOTA) (NiFe‐DOTA) and CO32− (NiFe‐CO3) are fabricated respectively for electrocatalytic water oxidation under industrial alkaline conditions. In 10 m KOH, compared to NiFe‐DOTA (335.0 mV) and NiFe‐CO3 (499.2 mV), the resultant NiFe‐TCPP exhibits the lowest overpotentials of 290.2 mV at 1000 mA cm−2. The NiFe‐TCPP also operates continuously for 1000 h at 500 mA cm−2 with near‐zero attenuation. The theoretical and experimental studies reveal that the strong coordination between conjugated carboxylate ligand TCPP and Fe of the laminate inhibits the Fe leaching by increasing the dissolution energy barriers to 4.29 eV and improving the self‐healing ability, thus enhancing the stability. Furthermore, the charge redistribution induced by the strong coordination optimizes the d‐band centers (‐2.81 eV) and decreases the reaction energy barriers (1.47 eV), thereby increasing the catalytic 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 is evaluated using linear sweep voltammetry (LSV), which demonstrates a significant reduction in the OER overpotential from 320 mV to 240 mV at a current density of 100 mA cm‐2. X‐ray photoelectron spectroscopy (XPS) and X‐ray absorption spectrum (XAS) indicate that the distribution of nickel valence states showed no significant difference between two samples, yet the NiFe‐LDH‐CA has a significantly 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.

Key roles of surface Cr in the NiFe layered double hydroxides for an efficient oxygen evolution reaction via adaptive reconfiguration

Cr doping is a new strategy to enhance the OER (Oxygen Evolution Reaction) performance of NiFe-LDH (NiFe-Layered Double Hydroxides) by optimizing surface states and offering a scalable production process. However, as an additive element, Cr itself has weak OER performance, so its promotion on the Ni- and Fe-active site by electron perturbation and structural stabilization in NiFeCr-LDH has been the focus. Herein, a one-step hydrothermal method is used to incorporate Cr into NiFe-LDH, systematically investigating the relationship between Cr content and the material's microstructure. The results of physical characterization show that Cr ion plays a leading role in the electron perturbation Ni/Fe-active center, which causes the increasing of Fe3+ and Ni3+ content. Furthermore, variations in Cr content resulted in the lattice stretching and morphology evolving synchronously. The optimized NiFeCr-LDH exhibited significantly enhanced OER activity and durability compared to undoped NiFe-LDH and outperformed commercial RuO2 catalysts. Additionally, a microstructure comparison was made between the initial- and long-term used-NiFeCr-LDH. The findings reveal that the material's distinctive structural evolution behavior confers it with exceptional self-adaptability to the OER reaction, which results in a consistent enhancement of activity lasting up to 12 h during long-term I-t test showing a new idea for the design of high performance NiFeCr-LDH.

Partially amorphous NiFe layered double hydroxides enabling highly-efficiency oxygen evolution reaction at high current density

Layered double hydroxide (LDH) serves as an innovative catalyst for water electrolysis, showcasing outstanding performance in the oxygen evolution reaction (OER) under alkaline conditions. However, it faces challenges due to its low electrical conductivity and limited accessibility to active sites. In this work, the flexibility advantages of disordered amorphous and ordered crystals in NiFe LDH were combined to improve OER performance and maintain long-term stability. This combination induces a variety of effects, including improving the intrinsic activity, changing the OER mechanism from adsorb evolution mechanism (AEM) to lattice oxygen mechanism (LOM), and promoting the reaction kinetics of the catalyst. Moreover, the porous structure of NiFe LDH can efficiently alleviate the issue of local acidic environment induced by prolonged OER reaction, satisfying the criteria for long-term stability. Therefore, the NiFe-2.0 LDH catalyst only requires an ultralow overpotential of 189 mV at a current density of 10 mA cm−2 with Tafel slope of 43 mV dec−1. More importantly, the catalyst not only displays excellent electrocatalytic activity with an overpotential of 289 mV but also represents an outstanding stability over 80 h at an ultra-high current density of 1 A cm−2. This study provides a promising strategy for optimizing the catalytic activity and stability of catalyst at ampere current density, which is expected to achieve commercial applications.

PTFE as a Multifunctional Binder for High-Current-Density Oxygen Evolution.

Binder plays a crucial role in constructing high-performance electrodes for water electrolysis. While most research has been focused on advancing electrocatalysts, the application of binders in electrode design has yet to be fully explored. Herein, the in situ incorporation of polytetrafluoroethylene (PTFE) as a multifunctional binder, which increases electrochemical active sites, enhances mass transfer, and strengthens the mechanical and chemical robustness of oxygen evolution reaction (OER) electrodes, is reported. The NiFe-LDH@PTFE/NF electrode prepared by co-deposition of PTFE with NiFe-layered double hydroxide onto nickel foam demonstrates exceptional long-term stability with a minimal potential decay rate of 0.034mV h-1 at 500mA cm-2 for 1000 h. The alkaline water electrolyzer utilizing NiFe-LDH@PTFE/NF requires only 1.584V at 500mA cm-2 and sustains high energy efficiency over 1000 h under industrial operating conditions. This work opens a new path for stabilizing active sites to obtain durable electrodes for OER as well as other electrocatalytic systems.