Search Results (19)

The oxygen evolution reaction (OER) is pivotal in hydrogen production via water electrolysis, yet its sluggish kinetics, stemming from the four-electron transfer process, remain a major obstacle, with overpotential reduction being critical for enhancing efficiency. This work addresses this challenge by developing a novel approach to stabilize and activate non-precious metal catalysts for OER. Specifically, we synthesized a three-dimensional flake NiFe-LDH/ZIF-L composite catalyst on a flexible nickel foam (NF) substrate through a room temperature soaking and hydrothermal method, leveraging the mesoporous structure of ZIF-L to increase the specific surface area and optimizing electron transfer pathways via interfacial regulation. Continuous linear sweep voltammetry (LSV) scanning induced structural self-reconstruction, forming highly active NiOOH species enriched with oxygen vacancies, which significantly boosted catalytic performance. Experimental results demonstrate an overpotential of only 221 mV at 10 mA cm⁻² and a Tafel slope of 56.3 mV dec⁻¹, alongside remarkable stability, attributed to the catalyst’s hierarchical nanostructure that accelerates mass diffusion and charge transfer. The innovation lies in the synergistic effect of the mesoporous ZIF-L structure and interfacial regulation, which collectively enhance the catalyst’s activity and durability, offering a promising strategy for advancing large-scale water electrolysis hydrogen production technology. Full article

Transition metal oxides (TMOs) are considered to be highly promising materials for supercapacitor electrodes due to their low cost, multiple convertible valence states, and excellent electrochemical properties. However, inherent limitations, including restricted specific surface area and low electrical conductivity, have largely restricted their application in supercapacitors. In this paper, core–shell heterostructures of nickel–iron layered double hydroxide (NiFe-LDH) nanosheets uniformly grown on CuCo₂O₄ nanoneedles were synthesized by hydrothermal and calcination methods. It is found that the novel core–shell structure of CuCo₂O₄@NiFe-LDH improves the electrical conductivity of the electrode materials and optimizes the charge transport path. Under the synergistic effect of the two components and the core–shell heterostructure, the CuCo₂O₄@NiFe-LDH electrode achieves an ultra-high specific capacity of 323.4 mAh g⁻¹ at 1 A g⁻¹. And the capacity retention after 10,000 cycles at 10 A g⁻¹ is 90.66%. In addition, the assembled CuCo₂O₄@NiFe-LDH//RGO asymmetric supercapacitor device achieved a considerable energy density (68.7 Wh kg⁻¹ at 856.3 W kg⁻¹). It also has 89.36% capacity retention after 10,000 cycles at 10 A g⁻¹. These properties indicate the great potential application of CuCo₂O₄@NiFe-LDH in the field of high-performance supercapacitors. Full article

The construction of high-performance catalysts for overall water splitting (OWS) is crucial. Nickel–iron-layered double hydroxide (NiFe LDH) is a promising catalyst for OWS. However, the slow kinetics of the HER under alkaline conditions seriously hinder the application of NiFe LDH in OWS. This work presents a strategy to optimize OWS performance by adjusting the entropy of multi-metallic LDH. Quaternary NiFeCrCo LDH was constructed, which exhibited remarkable OWS activity. The OER and HER of NiFeCrCo LDH were stable for 100 h and 80 h, respectively. The OWS activity of NiFeCrCo LDH//NiFeCrCo LDH only required 1.42 V to reach 10 mA cm⁻², and 100 mA cm⁻² required 1.54 V. Under simulated seawater conditions, NiFeCrCo LDH//NiFeCrCo LDH required 1.57 V to reach 10 mA cm⁻² and 1.71 V to reach 100 mA cm⁻². The introduction of Co into the structure induced Cr to provide more electrons to Fe, which regulated the electronic state of NiFeCrCo LDH. The appropriate electronic state of the structure is essential for the remarkable performance of OWS. This work proposes a new strategy to achieve excellent OWS performance through entropy-increase engineering. Full article

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. Full article

In recent years, there has been significant interest in transition-metal sulfides (TMSs) due to their economic affordability and excellent catalytic activity. Nevertheless, it is difficult for TMSs to achieve satisfactory performance due to problems such as low conductivity, limited catalytic activity, and inadequate stability. Therefore, a catalyst with a heterostructure constituted of a nickel–iron-layered double hydroxide, nickel sulfide, molybdenum disulfide, and cerium dioxide was designed. At the current density of 10 mA cm⁻² in an alkaline solution, the catalyst exhibits a HER overpotential of 116 mV. In addition, an overpotential of 235 mV@150 mA cm⁻² was displayed for OER. The catalyst showed a good retention rate (94.7% for HER, 98.6% for OER) after 160 h stability tests. The excellent electrochemical performance is attributed to the following points: 1. The self-supporting three-dimensional hierarchical structure provides abundant sites, fast ion diffusion channels, and electron transfer paths, and ensures structural stability. 2. The strong interfacial electron interaction between Ni₃S₂/MoS₂ heterojunction and NiFe-LDH improves the OER reaction kinetics. 3. The Ce³⁺ and oxygen vacancies in CeO₂ promote the dissociation of H₂O and promote the HER reaction kinetics. This approach paves the way for developing highly efficient electrocatalysts for various electrochemical applications. Full article

Developing high-performance and cost-competitive electrocatalysts have great significance for the massive commercial production of water-splitting hydrogen. Ni-based electrocatalysts display tremendous potential for electrocatalytic water splitting. Herein, we synthesize a novel NiFe-layered double hydroxide (LDH) electrocatalyst in nanosheets array on high-purity Ni foam. By adjusting the Ni/Fe ratio, the microstructure, and even the behavior of the electrocatalyst in the oxygen evolution reaction (OER), changes significantly. The as-obtained material shows a small overpotential of 223 mV at 10 mAcm⁻² as well as a low Tafel slope of 48.9 mV·dec⁻¹ in the 1 M KOH electrolyte. In addition, it can deliver good stability for at least 24 h of continuous working at 10 mAcm⁻². This work proposes a strategy for engineering catalysts and provides a method for the development of other Ni-based catalysts with excellent performance. Full article

NiFe-layered double hydroxides (NiFe-LDH) have been reported to possess exceptional oxygen evolution reaction (OER) activity. However, maintaining the stability of high activity over a long time remains a critical challenge that needs to be addressed for their practical application. Here, we report a custom-sized deep recombination of 2D graphene oxide with NiFe-LDH (NiFe-LDH/GO/NF) through a simple electrodeposition method that improves OER activity and achieves excellent stability. The excellent performance of the catalyst mainly comes from the three-phase interface and electron transport channel dredged by the three-dimensional structure constructed by the deep composite, which can not only significantly reduce its charge and electron transfer resistance, improving the material conductivity, but it also effectively increases the specific surface area, inhibits aggregation, and exposes rich active sites. In addition, GO with good conductivity not only supports NiFe-LDH well but also increases the heterogeneous interface, putting the NiFe-LDH/GO composites in close contact with Ni foam and increasing the electrocatalytic stability of the NiFe-LDH/GO/NF. The experimental results show that the overpotential of NiFe-LDH/20,000GO/NF is only 295 mV at a current density of 100 mA cm⁻²; the Tafel slope is 52 mV dec⁻¹, and the charge transfer resistance (Rct) is only 0.601 Ω in 1 M KOH. This indicates that GO has excellent potential to assist in constructing geometric and electronic structures of NiFe-LDH in long-term applications. Full article

In this work, the performances of nickel iron layered double hydroxides (LDH) with the nitrate anion at the interlayer (NiFe-NO₃) for the manufacture of anodes for lithium-ion batteries have been tested before and after its sintering at different temperatures. After synthesis, the material was thermally analyzed in a range 30–1250 °C, showing a mass loss occurring in three different consecutive steps leading to a total mass decrease of ~30 mass%. Following thermogravimetric analysis (TGA), four samples were prepared by annealing at four different temperatures: one of the four did not undergo a thermal treatment (NiFe-0), while the remaining three were annealed at 250 °C, 360 °C, and 560 °C for 6 h (NiFe-250, NiFe-360, and NiFe-560). All materials where completely characterized via FE-SEM, PXRD, and FT-IR. The pristine LDH material showed some structural and compositional changes for growing temperatures, starting from the typical turbostratic hexagonal structure through a mixture of amorphous metal oxides and finally to the stoichiometric oxides FeNi₂O₄ and NiO. The as-obtained materials were mixed with carbon black (C65) and sodium alginate and tested as electrodes in Swagelok half cells in LP30 vs. metallic Li to perform CV and GCPL analysis. The electrochemical tests showed that the performances of NiFe-0, both in terms of stability and specific capacity, are not so different from the one of the NiFe-560, even if the Ni mass% in the former is lower than in the NiFe-560. This phenomenon could be explained by assuming a combined mechanism of reaction involving both intercalation and conversion. Full article

The electrocatalytic oxygen evolution reaction (OER) is an arduous step in water splitting due to its slow reaction rate and large overpotential. Herein, we synthesized glycerate-anion-intercalated nickel–iron glycerates (NiFeGs) using a one-step solvothermal reaction. We designed various NiFeGs by tuning the molar ratio between Ni and Fe to obtain Ni₄Fe₁G, Ni₃Fe₁G, Ni₃Fe₂G, and Ni₁Fe₁G, which we tested for their OER performance. We initially analyzed the catalytic performance of powder samples immobilized on glassy carbon electrodes using a binder. Ni₃Fe₂G outperformed the other NiFeG compositions, including NiFe layered double hydroxide (LDH). It exhibited an overpotential of 320 mV at a current density of 10 mA cm^–2 in an electrolytic solution of pH 14. We then synthesized carbon paper (CP)-modified Ni₃Fe₂G as a self-supported electrode (Ni₃Fe₂G/CP), and it exhibited a high current density (100 mA cm⁻²) at a low overpotential of 300 mV. The redox peak analysis for the NiFeGs revealed that the initial step of the OER is the formation of γ-NiOOH, which was further confirmed by a post-Raman analysis. We extensively analyzed the catalyst’s stability and lifetime, the nature of the active sites, and the role of the Fe content to enhance the OER performance. This work may provide the motivation to study metal-alkoxide-based efficient OER electrocatalysts that can be used for alkaline water electrolyzer applications. Full article

In a contemporary sustainable economy, innovation is a prerequisite to recycling waste into new efficient materials designed to minimize pollution and conserve non-renewable natural resources. Using an innovative approach to remediating metal-polluted water, in this study, eggshell waste was used to prepare two new low-cost nanoadsorbents for the retrieval of nickel from aqueous solutions. Scanning electron microscopy (SEM) results show that in the first eggshell–zeolite (EZ) adsorbent, the zeolite nanoparticles were loaded in the eggshell pores. The preparation for the second (iron(III) oxide-hydroxide)–eggshell–zeolite (FEZ) nanoadsorbent led to double functionalization of the eggshell base with the zeolite nanoparticles, upon simultaneous loading of the pores of the eggshell and zeolite surface with FeOOH particles. Structural modification of the eggshell led to a significant increase in the specific surface, as confirmed using BET analysis. These features enabled the composite EZ and FEZ to remove nickel from aqueous solutions with high performance and adsorption capacities of 321.1 mg/g and 287.9 mg/g, respectively. The results indicate that nickel adsorption on EZ and FEZ is a multimolecular layer, spontaneous, and endothermic process. Concomitantly, the desorption results reflect the high reusability of these two nanomaterials, collectively suggesting the use of waste in the design of new, low-cost, and highly efficient composite nanoadsorbents for environmental bioremediation. Full article

The oxygen evolution reaction (OER) plays a crucial role in hydrogen production through water electrolysis. However, the high overpotential and sluggish kinetics of the OER pose significant challenges. Layered double hydroxides (LDHs) have been widely used as highly active electrocatalysts to tackle these issues. To further enhance the catalytic activity of LDHs and optimize their composition and morphology, the rational design of highly efficient electrocatalysts is desirable. Considering the flexibility of heterogeneous structures in terms of their electronic structure and surface chemistry, this study employs a simple and effective hydrothermal synthesis method. By leveraging van der Waals (vdW) interactions, a heterostructure is constructed between nickel-iron bimetallic hydroxide (NiFe LDH) nanosheets and black phosphorene (BPene). The OER electrochemical test results demonstrate the superior electrocatalytic properties of the NiFe LDH/BPene heterostructure. The heterostructure exhibits remarkably low overpotential (180 mV) and Tafel slope (72.36 mV dec⁻¹) at a current density of 10 mA cm⁻². Furthermore, the stability test conducted for 30,000 s showed a current retention rate exceeding 93.00%. This work provides new perspectives into the electronic structure regulation of 2D heterostructures and highlights new avenues for tuning the electrocatalytic adsorption of emerging phosphorus-based materials. Full article

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/Kg_Zn, which is nearly half of the 3.40 kW h/Kg_Zn 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. Full article

The design of high-performance and low-cost oxygen evolution reaction (OER) electrocatalysts is crucial for environment friendly hydrogen production. Some transition metals have been proven to be good substitutes for noble metals due to their unique electronic structural characteristics and good electrocatalytic performances, with examples including nickel and cobalt, which are usually used to prepare OER electrocatalysts. In this work, we synthesized three-dimensional Ni-Co-Fe ternary layered double hydroxide nanosheet array electrocatalysts via hydrothermal process. Iron element was introduced into the Ni-Co based hydroxide. The ternary layered double hydroxide has a nanoarrays microstructure. Theoretical analysis confirms that by adjusting the ratio of Ni/Co/Fe, the microstructure of the catalyst changes significantly. Attributed to the special nanostructure, the catalysts show superior catalytic activities in oxygen evolution reaction (OER). The results show that a small overpotential of 222 mV at the current density of 20 mA·cm⁻² for the OER in 1.0 M KOH is acquired. A small Tafel slope of 61.22 mVdec⁻¹ and a maximum specific capacitance of 239 Fg⁻¹ are also obtained. Full article

Layered double hydroxides (LDHs) have been reported as one of the most effective materials for oxygen evolution reaction (OER) catalysts, which are prone to hydrolysis and oxidation under OER conditions. Metal–organic frameworks (MOFs) are porous materials with high crystallinity and internal surface area. The design of LDHs based on MOFs has attracted increasing attention owing to their high surface area, exposed catalysis sites, and fast charge/mass transport kinetics. Herein, we report a novel approach to fabricate a leaf-shaped iron-doped nickel–cobalt LDH (L-Fe-NiCoLDH) derived from a two-dimensional (2D) zeolitic imidazolate framework with a leaf-like morphology (ZIFL). Iron doping played a significant role in enhancing the specific surface area, affecting the OER performance. L-Fe-NiCoLDH showed high OER performance with an overpotential of 243 mV at 10 mA cm⁻² and high durability after 20 h. The design of LDHs based on the leaf morphology of MOFs offers tremendous potential for improving OER efficiency. Full article

Because of industrial water, many groundwater sources and other water bodies have a strongly acidic medium. Increased bacterial resistance against multiple antibiotics is one of the main challenges for the scientific society, especially those commonly found in wastewater. Special requirements and materials are needed to work with these severe conditions and treat this kind of water. In this trend, nanolayered structures were prepared and modified in different ways to obtain an optimum material for removing different kinds of heavy metals from water in severe conditions, alongside purifying water from a Gram-negative bacteria (E. coli), which is an indication for fecal pollution. An ultrasonic technique effectively achieved this dual target by producing nanolayered structures looking like nanotapes with dimensions of 25 nm. The maximum removal percentages of the heavy metals studied (i.e., iron (Fe), copper (Cu), chromium (Cr), nickel (Ni), and manganese (Mn)) were 85%, 79%, 68%, 63%, and 61%, respectively for one prepared structure. In addition, this nanostructure showed higher antimicrobial activity against the most common coliform bacterium, E. coli (inhibition zone up to 18.5 mm). This study introduces dual-functional material for removing different kinds of heavy metals from water in severe conditions and for treating wastewater for Gram-negative bacteria (E. coli). Full article