Search Results (108)

Sulfion oxidation reaction (SOR) has great potential in replacing oxygen evolution reaction (OER) and boosting highly efficient hydrogen evolution. The development of highly active and stable SOR electrocatalysts is crucial for assisting hydrogen production with low energy consumption. In this work, multiphase NiCoFe-based layered double hydroxide (namely NiCoFe-LDH) has been synthesized via a facile seed-assisted heterogeneous nucleation method. Benefiting from its unique microsized hydrangea-like structure and synergistic active phases, the catalyst delivers substantial catalytic interfaces and reactive centers for SOR. Consequently, NiCoFe-LDH electrode achieves a remarkably low potential of 0.381 V at 10 mA cm⁻² in 1 M KOH + 0.1 M Na₂S, representing a significant reduction of 0.98 V compared to conventional OER. Notably, under harsh industrial conditions (6 M KOH + 0.1 M Na₂S, 80 °C), the electrolysis system based on NiCoFe-LDH||NF pair exhibits a cell potential of only 0.71 V at 100 mA cm⁻², which shows a greater decreasing amplitude of 1.05 V compared with that of traditional OER/HER systems. Meanwhile, the NiCoFe-LDH||NF couple could maintain operational stability for 100 h without obvious potential fluctuation, as well as possessing a lower energy consumption of 1.42 kWh m⁻³ H₂. Multiphase eletrocatalysis for SOR could indeed produce hydrogen with low-energy consumption. Full article

This study investigates the influence of divalent metals—(Mg(II), Co(II), and Ni(II)) in layered double hydroxides (LDHs), with a constant trivalent Fe(III) component—on the decoloration of crystal violet and methyl blue dyes via a Fenton-type oxidation reaction. The catalysts, synthesized by co-precipitation and hydrothermal treatment, were tested in both hydroxide and oxide forms under varying agitation conditions (0 and 280 rpm). A 2² × 3 factorial design was used to analyze the effect of the divalent metal type, catalyst phase, and stirring. The Mg/Fe oxide, with the highest BET surface area (144 m²/g) and crystallite size (59.7 nm), showed superior performance—achieving up to 98% decoloration of crystal violet and 97% of methyl blue within 1 h. The kinetic analysis revealed pseudo-second-order and pseudo-first-order fits for crystal violet and methyl blue, respectively. These findings suggest that LDH-based catalysts provide a fast, low-cost, and effective option for dye removal in aqueous systems. Full article

A novel catalyst with a metal sulfide/hydroxide heterostructure was prepared by introducing sulfur ions into NiMnFe layered hydroxide by a simple hydrothermal method, using a series of characterization methods and electrochemical tests to explore the optimal sulfur ion doping amount. The XPS results show that the introduction of sulfur ions leads to a change in metal electron delocalization, which is conducive to the OER procedure. The newly formed metal sulfide can not only improve the conductivity of NiMnFe LDH/NF electrode materials but also enhance the intrinsic catalytic activity of the materials. The electrochemical performance indicated that the S₂-NiMnFe LDH/NF catalyst required only 205 mV overpotential to provide a current density of 10 mA⁻², and the Tafel slope was only 45.79 mV dec⁻¹. In addition, the large turnover frequency value (1.2614 S⁻¹) reflects the excellent intrinsic activity of the novel catalytic material. Full article

With the continuous consumption of fossil energy and the related environmental problems, clean energy, especially the hydrogen energy-derived water electrolysis, has attracted wide attention. However, as a result of the high energy consumption of water electrolysis and the limitations of single-function catalysts, there is an urgent need for cheap and simple-to-make bifunctional catalysts. In this work, based on the NiFe-LDH that is usually used for OER (Oxygen Evolution Reaction), doping of heteroatoms was carried out and a bifunctional catalyst could be then prepared using biomass as the carbon source. The preparation of catalyst precursors and in situ reduction were performed through the coupling process of hydrothermal and pyrolysis to enhance the electrolytic activity of the catalyst. Results showed that the overpotentials required to reach a current density of 10 mA·cm⁻² for the HER and OER processes were 305.2 mV and 310.4 mV, respectively, which are superior to the commercial catalysts. In the subsequent characterization, the structural characteristics of the catalyst support and their structure–activity correlation with active metals were systematically investigated by TEM, XRD, and XPS analysis, providing mechanistic insights into the catalytic behavior. The basic catalytic mechanisms of HER and OER were also obtained: the HER process was due to the formation of a Ni₃Fe alloy structure during catalyst preparation, which changed the electronic structure of the catalyst, while the OER process was induced by the formation of a NiOOH intermediate. The research results are expected to provide new ideas and data support for the preparation of bifunctional catalysts. Full article

In this paper, we use the facile approach for preparing novel, low-cost, efficient electrocatalysts for electrocatalytic water splitting. Interfacial engineering can significantly enhance the intrinsic performance of electrocatalysts. Herein, self-supporting FeOOH/NiFe-layered double hydroxide (LDH) nanosheet arrays were synthesized via hydrothermal and impregnation methods. The resulting FeOOH/NiFe-LDH can provide more active regions, which provide more active regions for co-reaction to proceed and accelerates electron transmit processes. Additionally, the amorphous FeOOH provides abundant active sites with low coordination, leading to excellent activity. The FeOOH/NiFe-LDH demonstrates remarkable two half-reaction electrocatalytic activity, along with excellent overpotentials of 168 mV (OER) and 155 mV (HER). This research introduces a sophisticated and scalable methodology for the creation of remarkably efficient and resilient alkaline conditions specifically designed for the HER and OER. Full article

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

Ferrate (Fe(VI)), an emerging green oxidant and disinfectant in water treatment, faces challenges due to its limited reaction efficiency stemming from a highly electron-deficient state. To address this, we designed NiFe-Layered Double Hydroxides (NiFe-LDHs) with different spin states to enhance electron transfer efficiency in Fe(VI)-mediated advanced oxidation processes (AOPs). We hypothesized that fine-tuning the spin state of NiFe-LDHs could optimize the balance between adsorption capabilities and electronic structure regulation. Our experiments revealed that intermediate-spin NiFeLDH-1, with a magnetic moment of 0.67 μB, exhibited the best catalytic performance, achieving 100% phenol removal. The NiFeLDH-x/Fe(VI) system demonstrated a significant synergistic enhancement in degradation efficiency. In addition, NiFeLDH-1 showed excellent performance in stability and continuous flow experiments. This study unveils a novel correlation between spin polarization and catalytic efficiency, offering insights into the optimization of electrocatalysts for Fe(VI)-mediated AOPs. The findings suggest that spin state modulation is a promising strategy to enhance the electrocatalytic activity and stability of non-noble metal catalysts. Full article

The development of bifunctional air electrodes with high activity and durability is essential for advancing flexible zinc–air batteries. Herein, a hierarchical electrode structure is designed by growing N-doped carbon nanotubes (CNTs) on copper foam, where CNTs serve as highly active oxygen reduction reaction (ORR) sites. The controlled deposition of NiFeCo-layered double hydroxide (LDH) nanosheets, optimized to maintain ORR activity while enhancing oxygen evolution reaction (OER) performance, enables a finely tuned bifunctional catalyst. This architecture achieves outstanding electrochemical properties, requiring only 0.897 V vs. RHE and 1.446 V vs. RHE to reach 10 mA cm⁻² in 1 M KOH, thereby minimizing overpotentials. When implemented as an air electrode in a quasi-solid-state zinc–air battery, the system demonstrates remarkable cycling stability, sustaining performance for over 300 h. Furthermore, a 16 cm² pouch-type zinc–air battery delivers a high discharge capacity of 0.62 Ah, highlighting the scalability of this design. This work presents a robust and scalable strategy for developing high-performance bifunctional air electrodes, offering a promising route for next-generation flexible energy storage systems. 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

Electrochemical water splitting is a feasible and effective method for attaining hydrogen, offering a mechanism for renewable energy solutions to combat the world’s energy crises due to the scarcity of fossil fuels. Evidently, the viability and stability of the electrocatalysts are fundamental to the electrochemical water-splitting process. However, the net efficiency of this process is noticeably hindered by the kinetic drawbacks related to the OER. Hence, NiFe LDH has been widely used as a highly efficient OER and HER catalyst material due to its unique nanostructure, tunable composition, and favorable electronic structure. This review offers a systematic analysis of the latest progress in the fabrication of functional NiFe LDH catalysts and associated fabrication strategies, structure optimizations, and performance improvements. Special emphasis is given to understanding the role of nanostructure engineering in increasing active site accessibility, enhancing the effectiveness of subsequent electron transfer, and boosting the intrinsic catalytic activity for HER and OER. Moreover, we discuss the influence of doping, defects, and the formation of heterostructures with other materials on the OER and HER activities of NiFe LDHs. Additional accounts of basic structures and the OER and HER catalytic activities are provided, along with an enhanced theoretical understanding based on DFT studies on the NiFe LDH. Moreover, the limitations and potential developments of the work focus on the need for existing synthesis approaches, the stability of the NiFe LDH catalysts, and their insertion into working electrochemical processes. This review is a comprehensive analysis of the current state of research and developments in the use of NiFe LDH catalysts for the electrochemical water-splitting process to foster improved development of sustainable hydrogen sources in the future. Full article

Advanced oxidation processes (AOPs) based on activated persulfate (PS) are gradually being employed in the treatment of novel pollutants. In this study, an efficient and reliable CoNiFe-layered double hydroxide (LDH) was prepared by a hydrothermal method, which could effectively activate peroxomonosulfate (PMS) and cause free sulfate radical (SO₄^•−) oxidation to decompose atrazine (ATZ). The degradation rate of ATZ was greater than 99% within 60 min at pH 7 when the initial concentration of ATZ was 10 mg·L⁻¹, and the dosages of PMS and activator were 0.6 mM and 80 mg·L⁻¹. The analysis of ATZ degradation confirmed the reusability of the activator and its strong structural stability. The generation of four free radicals was analyzed and confirmed, and the influence on the degradation reaction was SO₄^•− > O₂^•− > ¹O₂ > •OH. The analytical results showed that the metal ions reacted with HSO₅⁻ in PMS to cause an oxidation–reduction cycle change in the valence state of the metal ions and generated the primary factor affecting the degradation reaction—SO₄^•−. Nine degradation intermediates with reduced toxicity were detected and possible ATZ degradation pathways were deduced, thus confirming the activation mechanism of CoNiFe-LDH. Full article

Layered double hydroxides (LDHs) have potential applications for pollutant removal. Enhancing their pollutant removal ability by fully utilizing the synergistic effects of physical adsorption and chemical catalysis has received widespread attention. In this study, a high methyl orange (MO) removal capacity was achieved by utilizing the synergistic effects of physical adsorption and chemical catalysis of NiFe-LDH. wNiFe-LDH showed a significant removal amount of MO, up to 506.30 mg/g due to its reserving of the active surface to the largest extent. Experiment and molecular simulation clarified the high removal capacity derived from surface adsorption and the degradation ability of the active surface. The presence of more -OH groups on the surface enhanced the removal of MO, and the vacancies in the surface were beneficial for the formation of •O₂⁻ and contributed to the degradation of MO. As K₂S₂O₈ was introduced, the removal rate of MO improved to 100% from 60.67%. However, a deeper study showed that the degradation was incomplete, as K₂S₂O₈ inhibited the formation of •O₂⁻, and the active species in the system changed to holes. The degradation path of MO was also altered. Thus, this study gives new insight into the reactivity of the active surface of NiFe-LDH and affords a new path to preserve the active surface. Full article

Hydrogen plays a vital role in the global shift toward cleaner energy solutions, with water electrolysis standing out as one of the most promising techniques for generating hydrogen. Despite its potential, the oxygen evolution reaction (OER) involved in this process faces significant challenges, including high overpotentials and slow reaction rates, which underscore the need for advanced electrocatalytic materials to enhance efficiency. Noble metal catalysts are effective but expensive, so transition-metal-based electrocatalysts like nickel–cobalt layered double hydroxides (NiCo LDHs) have become promising alternatives. In this research, a series of NiCo LDH catalysts doped with Fe, Mn, Cu, and Zn were effectively produced using a one-step hydrothermal technique. Among the catalysts, the Fe-doped NiCo LDH exhibited OER activity, achieving a lower overpotential (289 mV) at a current density of 50 mA/cm², which was far better than the 450 mV of the undoped NiCo LDH. The Mn-, Cu-, and Zn-NiCo LDHs also exhibited lower overpotentials of 414 mV, 403 mV, and 357 mV, respectively, at this current density. The Fe-doped NiCo LDH had a 3D layered nanoflower structure, increasing the surface area for reactant adsorption. The electrochemically active surface area (ECSA), as indicated by the double-layer capacitance (C_dl), was larger in the doped samples. The C_dl value of the Fe-doped NiCo LDH was 3.72 mF/cm², significantly surpassing the 0.82 mF/cm² of the undoped NiCo LDH. These changes improved charge transfer and optimized reaction kinetics, enhancing the overall OER performance. This study offers significant contributions to the development of efficient electrocatalysts for the OER, advancing the understanding of key design principles for enhanced catalytic performance. Full article

Electrocatalytic water splitting is a critical approach for achieving carbon neutrality, playing an essential role in clean energy conversion. However, the slow kinetics of the oxygen evolution reaction (OER) remains a major bottleneck hindering energy conversion efficiency. Although noble metal catalysts (e.g., IrO₂ and RuO₂) show excellent catalytic activity, their high cost and scarcity limit their applicability in large-scale industrial processes. In this study, we introduce a novel electrocatalyst based on selenized NiFe-layered double hydroxides (NiFe-LDHs), synthesized via a simple hydrothermal method. Its key innovation lies in the selenization process, during which Ni atoms lose electrons to form selenides, while selenium (Se) gains electrons. This leads to a significant increase in the concentration of high-valent metal ions, enhances electronic mobility, and improves the structural stability of the catalyst through the formation of Ni-Se bonds. Experimental results show that selenized NiFe-LDHs exhibit excellent electrocatalytic performance in 1 M KOH alkaline solution. In the oxygen evolution reaction (OER), the catalyst achieved an ultra-low overpotential of 286 mV at a current density of 10 mA cm⁻², with a Tafel slope of 63.6 mV dec⁻¹. After 60 h of continuous testing, the catalyst showed almost no degradation, far outperforming conventional catalysts. These results highlight the potential of NiFe-LDH@selenized catalysts in large-scale industrial water electrolysis applications, providing an effective solution for efficient and sustainable clean energy production. Full article