Transition Metal-based Catalysts Research Articles

The effect of different vulcanization reagents on the synthesis of NiFeS and the performance test of seawater electrolysis

Hydrogen energy, as the most promising new energy for sustainable development, has aroused wide concern of researcher in the field of energy chemical industry. Among the many hydrogen generation approaches, electric water splitting for producing H2 is considered to be a simple and environmentally friendly method. Transition metal-based catalysts have become an important field in alkaline seawater electrolysis due to their high abundance and superior catalytic performance. Therefore, NiFeS (Ni3S2@FeS) was in-situ generated on nickel foam through a simple two-step hydrothermal approach in this paper. NiFeS/NF catalysts synthesized by three vulcanization reagents (Na2S·9H2O, CH3CSNH2, CH4N2S) were characterized and compared by a series of electrochemical tests. It is worth noting that for the first time, different vulcanization reagents were used to explore the activity of the same catalyst in seawater splitting and urea splitting. It was found that the NiFeS catalyst synthesized by Na2S·9H2O (Ni3S2@FeS-1/NF) had better oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performance and good stability in alkaline seawater. The overpotential required for the OER with Ni3S2@FeS-1/NF electrode in alkaline seawater (1 M KOH + seawater electrolyte) is 290 mV at the 10 mA cm-2, and 92 mV for the hydrogen evolution reaction at the 10 mA cm-2. It is found that the NiFeS catalyst obtained by vulcanization of NiFe-LDH not only has high activity and conductivity, but also can effectively inhibit Cl- corrosion. Ni3S2@FeS-1/NF catalyst has a unique cluster rosette nanosheet array structure, which can present more catalytic reaction centres, accelerate the electron transfer rate and promote electrochemistry performance. The work proposes a novel way to explore the effect of different synthesis methods of the same composition on the performance of electrolytic seawater.

The Effect of Saccharin on SnNi Alloy: the Electrodeposition and its Electrocatalytic Activity in Ethanol Oxidation Reaction

The development of Direct Ethanol Fuel Cell (DEFC) has attracted much attention, as alternative energy sources due to its various advantages. However, among its various advantages, DEFC has several problems, such as the kinetics of the ethanol oxidation reaction. Transition metal-based catalysts such as nickel and tin are considered as potential catalysts for DEFC due to their oxophilic properties that can improve catalytic activity. In this study, the effect of saccharin on SnNi bimetallic alloy catalyst synthesized by electrodeposition method on copper wire substrate was investigated. SnNi samples were characterized by several techniques, including X-ray diffraction, Scanning electron microscopy, and energi dispersive X-ray spectrocopy. Saccharin addition had a significant effect on the morphology, crystallite size, and composition of the catalyst. The presence of saccharin causes the formation of more uniform particles and has a smaller size. The sample with the addition of saccharin had a smaller charge transfer resistance value 4.82 Ω, lower tafel slope by 115 mV/dec, and show higher jf/jb ratio by 0.55. Furthermore, as the current density decreases, the SnNi catalyst with saccharin has a slow decrease rate and higher stability than the SnNi catalyst without saccharin.

CO2 methanation: a bibliometric analysis and review of activated carbon-based materials (2014–24)

Abstract This study highlights the significant potential of activated carbon (AC)-based materials in environmental remediation and energy production, particularly in converting carbon dioxide (CO2) and hydrogen (H2) into methane (CH4) and water (H2O) using transition metal-based catalysts. It emphasizes the role of porous AC in waste reduction and resource utilization, examining various applications of CO2 and evaluating environmental impacts. The research explores commercialization opportunities and specifically investigates CO2 methanation using AC-based materials. Using bibliometric analyses of 4196 articles from the Web of Science database, the study identifies a growing research interest in porous AC-related CO2 methanation from 2014 to 2024. The top three journals in this field are Environment Development and Sustainability, Biomass Conversion and Biorefinery, and Journal of Environment Science and Pollution. However, there is limited inter-institutional collaboration in this field, suggesting room for development towards commercializing sustainable CH4 production pathways. CH4 is highlighted as a crucial intermediate in industrial processes, and research directions are identified through co-occurring author keywords analysis. The study suggests the need for a comprehensive approach integrating AC materials into carbon-neutral energy processes while addressing the potential adverse effects of AC nanoparticles on biological and environmental factors. Ultimately, it clarifies the potential uses and commercialization prospects for porous AC materials, especially in conjunction with carbon capture and utilization technologies, promoting sustainable practices in energy production and environmental management.

Dynamic Fe-O-Cu induced electronic structure modulation on CuOx electrode for selective electrocatalytic oxidation of glycerol

Electrocatalytic glycerol oxidation reaction to produce high-value organic chemicals has research significance for managing the overproduction of glycerol and handling the energy crisis. Herein, a copper-based self-supporting catalytic electrode with a dynamic Fe-O-Cu optimized coordination (Fe-CuOx/CF) was prepared. The oxygen-bridged asymmetric coordination structure (Fe-O-Cu) optimized the electronic configuration and promoted the formation of the crucial intermediate species. After Fe was embedded in the lattice of copper oxides, a remarkable enhancement in the adsorption capacity of OH- and glycerol was confirmed. As a result, Fe-CuOx/CF exhibited an excellent production capacity of formate, with high faradaic efficiency and selectivity values of 93.65 % and 95.10 %. Concurrent production of formate and high purity hydrogen was achieved in the double-electrode flow electrolyzer. This work provides guiding significance for the optimization of the catalytic coordination and the design of high-efficiency transition metal-based catalysts for electrooxidation of biomass platform molecules.

C3N4/Se-CNTs as Advanced Metal-Free Catalysts for the Photoassisted Electrocatalytic Oxygen Evolution Reaction.

Photoassisted electrocatalysis is a frontier direction of electrocatalysis for promoting energy conversion. In this work, a metal-free C3N4/Se-CNTs is reported as a novel catalyst for photoassisted electrocatalytic oxygen evolution reaction (OER). C3N4 has an appropriate bandgap, high specific surface area, and long-term stability. CNTs can modulate the electronic environment of C3N4 by strong π-π interaction and greatly enhance the separation efficiency of photogenerated carriers. The distributed Se nanoparticles in CNTs can further increase the charge transfer ability. As a metal-free catalyst, the C3N4/Se-CNTs exhibits an overpotential of 231 mV at a current density of 10 mA cm-2 and a small Tafel slope of 52 mV dec-1 under illumination, which ranks among the best catalysts for photoassisted OER performance, surpassing most noble and transition metal-based catalysts. The result demonstrates the great potential of C3N4-based catalysts in the photoassisted OER process and provides a new perspective to explore the excellent metal-free OER catalysts.

Atomically dispersed ruthenium single-atom alloy catalysts enabling efficient iodide oxidation reaction electrolysis in acidic media

Single-atom catalysts exhibit immense potential across diverse reactions, yet their synthesis and stability in acidic environments pose significant challenges. Herein, we introduce a facile one-step hydrothermal approach to fabricate Ru single-atom alloy catalysts (Ru SAAC) through the reaction of Ru and Ti precursors, followed by annealing in an argon atmosphere. Analysis via extended X-ray absorption fine structure spectroscopy and aberration-corrected scanning transmission electron microscopy confirms the atomically dispersed Ru alloy catalyst anchored on a TiO2 support. Remarkably, Ru SAAC demonstrates exceptional electrocatalytic performance in the iodide oxidation reaction (IOR), achieving a benchmark current density of 10 mA/cm2 at a mere voltage of 0.64 V in acidic conditions within a three-electrode electrolyzer setup. Surpassing nanoscale Ru/TiO2 and RuO2/TiO2 counterparts, Ru SAAC exhibits the highest voltage efficiency (84.4%), lowest Tafel slope (36 mV/dec), and lowest overpotential (100 mV) under identical experimental conditions. This method enables facile control over Ru morphology. It enhances the kinetics and thermodynamic favorability of Ru SAAC in acidic media, opening avenues for synthesizing diverse transition metal-based single-alloy catalysts for varied applications.

Manipulation of d-Orbital Electron Configurations in Nonplanar Fe-Based Electrocatalysts for Efficient Oxygen Reduction.

Manipulation of the spin state holds great promise to improve the electrochemical activity of transition metal-based catalysts. However, the underlying relationship between the nonplanar metal coordination environment and spin states remains to be explored. Herein, we report the precise regulation of nonplanar Fe atomic d-orbital energy level into an irregular tetrahedral crystal field configuration by introducing P atoms. With the increase of P coordination number, the spin magnetic moment decreases linearly from 3.8 μB to 0.2 μB, and the high spin content decreases linearly from 31% to 5%. Significantly, a volcanic curve between the spin states of Fe-based catalysts (Fe-NxPy) and oxygen reduction reaction (ORR) activity has been unequivocally established based on the thermodynamic results. Thus, the Fe-N3P1 catalyst with a 19% medium spin state experimentally exhibits the optimal reaction activity with a high half-wave potential of 0.92 V. These findings indicate that regulating electron spin moments through coordination engineering is a promising catalyst design strategy, providing important insights into spin catalysis.

Cr-doped tri-metallic nano prism catalyst for efficient alkaline and seawater splitting

Electrochemical water splitting is one of the most promising methods for sustainable production of green hydrogen. The oxygen evolution reaction (OER) is a crucial step in the process of water splitting. However, it exhibits sluggish kinetics and requires a significant overpotential for functioning at reasonable reactionrates. The efficiency of the reaction can be enhanced by reducing the overpotential, lowering the energy barrier, and using an effective electrocatalyst. Transition metal-basedcatalysts are well studied for this purpose. Specially, nickel–cobalt (Ni-Co) based catalysts have been regarded as the best OER electrocatalysts. Therefore, several studies have been carried out to enhance the electrocatalytic efficiency of Ni-Co catalysts. While mixing other transition metals with Ni-Co is a straightforward and reliable method to improve the OER activity of Ni-Co catalysts, there is still a need for a thorough examination of the design of Ni-Co catalysts with various additional elements. Seawater electrolysis, which utilizes abundant water resources that constitute over 97% of the world’s water, is highly appealing for sustainable energy production. To achieve commercial feasibility, scientists are striving to solve challenges, such as corrosion resistance, highoverpotential, and the need for efficient and durable electrocatalysts.In this study, we fabricated a transition metal-based trimetallic catalyst (CNF), consisting of cobalt (Co), nickel (Ni), and iron (Fe). Furthermore, CNF was doped with chromium (Cr-doped CNF) and tested for the OER in alkaline freshwater and alkaline seawater. Our Cr-doped trimetallic CNF catalyst demonstrates exceptional performance in both seawater and freshwater, with overpotential of 320 mV and 280 mV at 10 mA cm−2 current density, making it a promising candidate for large-scale, sustainable hydrogen production.

P-Block Aluminum Single-Atom Catalyst for Electrocatalytic CO2 Reduction with High Intrinsic Activity.

Atomically dispersed transition metal sites on nitrogen-doped carbon catalysts hold great potential for the electrochemical CO2 reduction reaction (CO2RR) to CO due to their encouraging selectivity. However, their intrinsic activity is restricted by the hurdle of the high energy barrier of either *COOH formation or *CO desorption due to the scaling relationship. Herein, we discover a p-block aluminum single-atom catalyst (Al-NC) featuring an Al-N4 site that enables disentangling this hurdle, which endows a moderate reaction kinetic barrier for *COOH formation and *CO desorption, as validated by in situ attenuated total reflection infrared spectroscopy and theoretical simulations. As a result, the developed Al-NC shows a CO Faradaic efficiency (FECO) of up to 98.76% at -0.65 V vs RHE and an intrinsic catalytic turnover frequency of 3.60 s-1 at -0.99 V vs RHE, exceeding those of the state-of-the-art Ni-NC and Fe-NC counterparts. Moreover, it also delivers a partial CO current of 309 mA·cm-2 at 93.65% FECO and 605 mA at >85% FECO in a flow cell and membrane electrode assembly (MEA), respectively. Strikingly, when using low-concentration CO2 (30%) as the feedstock, this catalyst can still deliver a partial CO current of 240 mA at >80% FECO in the MEA. Considering the earth-abundant character of the Al element and the high intrinsic activity of the Al-NC catalyst, it is a promising alternative to today's transition metal-based single-atom catalysts.

Fine regulation of self-supporting metal phosphonates for improved overall water splitting

The exploration of high-performance water electrolysis catalysts is crucial for the development of hydrogen energy and the alleviation of increasingly serious environmental problems. Transition metal phosphonates are very promising electrocatalysts. In this work, a new nickel phosphonate has been synthesized and successfully developed into high-performance electrocatalyst through in-situ growth on nickel foam (NF), introduction of iron, and adjustment of Ni:Fe mole ratio. It is revealed that NiFe12 and NIFe13 exhibit the best OER (η10: 268 mV vs. RHE; Tafel slope: 54 mV dec−1) and HER (η10: 172 mV vs. RHE; Tafel slope: 77 mV dec−1) catalytic activity under optimized conditions, respectively, with fast reaction kinetics and long-term durability. The water electrolysis device assembled with them can drive a current density of 10 mA cm−2 at low voltage (1.68 V) with long-term durability, demonstrating promising application prospects. This work has important reference significance for the development of transition metal-based water electrolysis catalysts.

Low-temperature dechlorination methods for pyrolysis oil of municipal plastic waste

Pyrolysis oil produced from municipal plastic waste can be utilized as fuel and various valuable chemicals as an alternative to petroleum. However, pyrolysis oil usually contains a relatively high concentration of chlorinated compounds, obstructing its utilization in the chemical industry. The present research reveals that pyrolysis oil contains inorganic chlorine and organochlorine compounds, and differentiated approaches should be considered to remove Cl from covalent and ionic chlorine linkages. Transition metal-based ZSM-5 catalysts showed remarkable dechlorination performance via mild C-Cl cracking of 1-chlorooctane and 4-chlorotoluene at 180 °C or below. The neutralization method of mixing pyrolysis oil with an alkaline solution quickly eliminated ionic chlorine from inorganic chlorine compounds, reducing Cl concentrations by up to 70 % at temperature below 40 °C. Based on the different dechlorinating pathways, an ideal combination of these two methods was suggested to enhance chlorine removal efficiency from pyrolysis oil.

Exploration of cobalt-based spinel oxide nanocatalysts MCo2O4 (M = Mn, Fe, Co, Ni, Cu, Zn) for glucose electrochemical sensing: NiCo2O4 exhibits largest Faradaic current

In traditional glucose sensing, glucose undergoes an enzyme-catalyzed oxidation reaction (GOR) on the electrode, causing electron transfer and generating a Faradaic current, which allows for quantitative glucose concentration analysis by measuring the current. Replacing enzymes with transition metal-based catalysts for glucose electrochemical sensing is a promising approach. As an extension of the study of spinel oxide Co3O4 for glucose electrochemical sensing, a series of cobalt-based spinel oxide nanocatalysts, MCo2O4 (M = Mn, Fe, Co, Ni, Cu, Zn), were prepared and studied. Their electrocatalytic oxidation activities for 3 mM glucose in 0.1 M KOH electrolyte solution (pH = 13) at potentials of 0.5 ∼ 0.6 V (vs Hg/HgO) are in the order: NiCo2O4 > CuCo2O4 > MnCo2O4 > Co3O4 > FeCo2O4 > ZnCo2O4, the Faradic current by NiCo2O4 is more than three times that of Co3O4. When NiCo2O4 is loaded onto a carbon cloth electrode for glucose electrochemical sensing, it exhibits high linear sensitivity and stability. Furthermore, theoretical calculations revealed that the high electrocatalytic oxidation activity of NiCo2O4 for glucose is due to its effective reduction of the Gibbs free energy barrier for the desorption of intermediates to form glucose oxidation product. Finally, it is proposed that the electrocatalytic oxidation activities of MCo2O4 (M = Mn, Fe, Co, Ni, Cu, and Zn) towards glucose exhibit a “volcano plot” relationship with their d-band centers. This offers valuable guidance into using the d-band center as a descriptor to screen effective glucose electrocatalysts for glucose sensing and potentially other applications.

Highly efficient Co-added Ni/CeO2 catalyst for co-production of hydrogen and carbon nanotubes by methane decomposition

The catalytic decomposition of methane (CDM) is a hydrogen and nanostructured carbon production process with minimal CO2 emission. Among the transition metal-based catalysts (e.g. Ni, Fe, Co, etc.), Ni-based catalysts are most widely studied due to the higher catalytic activity in decomposing methane. However, the limited lifespan of the catalyst makes it unsuitable for practical applications. Effective methane decomposition catalysts should be designed to optimize both reaction efficiency and catalyst lifetime. A Ni/CeO2 catalyst, developed in previous studies, Co was added to promote low-temperature (< 700 °C) activity manipulating the redox property of Co. Among the prepared catalysts with varying Ni:Co ratio, the methane conversion rate of the Ni8Co2/CeO2 catalyst was approximately twice that of the Ni10/CeO2 catalyst, confirming its excellent low-temperature activity. The reaction rate of Ni8Co2/CeO2 catalyst was 4.38 mmol/min∙gcat at 600 °C with WHSV of 36 L/gcat∙h. In terms of characteristics of carbon products, Raman spectroscopy analysis revealed that the carbon grown on the catalyst surface exhibited high crystallinity, with D-G band ratio (ID/IG) of 1.01. The fresh and used catalyst samples were characterized by TEM, XPS, XAS, and other methods to analyze the parameters affecting catalytic activity.

Insights into performance and mechanism of CuCo2O4/MXene composite as an efficient peroxymonosulfate activator for p-nitrophenol degradation

The slow redox cycle during oxidation and the toxicity risk due to leaching of metal ions greatly hinder the practical application of transition metal-based catalysts in advanced oxidation processes. In this study, a novel layered-structured CuCo2O4/MXene composite was prepared by self-assembling CuCo2O4 spinel with two-dimensional MXene and used as a heterogeneous catalyst based on peroxymonosulfate (PMS) activation for the oxidative degradation of p-nitrophenol (4-NP). Benefiting from its unique structure, the degradation efficiency of 4-NP by CuCo2O4/MXene-activated PMS was close to 100 % within 10 min at the initial pH 7.0. Quenching experiments and electron paramagnetic resonance demonstrated that both radical (SO4•- and •OH) and non-radical (1O2) pathways were involved in the degradation of 4-NP. X-ray photoelectron spectroscopy analysis showed that the introduction of MXene could significantly promote the efficient redox cycling of Cu2+/Cu+ and Co3+/Co2+ on the catalyst surface, thus providing a continuous driving force for the PMS activation. More importantly, CuCo2O4/MXene exhibited good ionic interference resistance, high stability and low metal ion leaching rate, suggesting its potential practical application. This work not only demonstrates that CuCo2O4/MXene is a promising catalyst for the degradation of organic pollutants by PMS activation, but also provides a new idea for the development of efficient PMS-activated catalysts for pollutant degradation.

Peroxymonosulfate activation by CoO@C catalyst from integrated recycling of spent lithium-ion battery: Performance and mechanism

Developing low-cost, highly active transition metal-based catalysts for peroxymonosulfate (PMS) activation is essential but remains challenging. Herein, we proposed a novel “waste-to-energy” strategy to derive an effective PMS activator (CoO@C) by integrally utilizing the abundant Co content in the cathodes and the defective structure of anode graphite from spent lithium-ion batteries (LIBs). The CoO@C/PMS system could completely degrade atrazine (ATZ) within 15 min, along with a robust resilience to coexisting substrate and a wide pH range of 5.0–11.0. Through quenching experiments and electron paramagnetic resonance (EPR), •OH was identified as the primary reactive oxygen species (ROS) responsible for ATZ degradation. Furthermore, electron transfer between the catalyst and PMS was examined via density functional theory (DFT) calculations to elucidate the activation mechanism. The Fukui index pinpointed the vulnerable sites of ATZ, offering insights into the possible degradation pathways along with UHPLC-MS analysis. Furthermore, CoO@C was fixed on a polyethersulfone (PES) membrane for continuous degradation of ATZ, which maintained a degradation efficiency exceeding 90 % after treating 6 L of wastewater. This research provided valuable insights into the preparation of metal-based catalysts for advanced oxidation processes and achieved the sustainable utilization of spent LIBs.

Turning Solid Waste into Catalysts: A Path for Environmental Solutions.

Waste, often overlooked, stands out as a prime source of valuable products, meeting the demand for natural resources. In the face of environmental challenges, this study explores the crucial role of waste-derived catalysts in sustainable practices, emphasizing the transformative potential of solid waste materials. Carbon-based catalysts sourced from agricultural, municipal, and industrial waste streams can be transformed into activated carbon, biochar, and hydrochar which are extensively used adsorbents. Furthermore, the paper also highlights the potential of transition metal-based catalysts derived from spent batteries, electronic waste, and industrial byproducts, showcasing their efficacy in environmental remediation processes. Calcium-based catalysts originating from food waste, including seashells, eggshells, bones, as well as industrial and construction waste also find an extensive application in biodiesel production, providing a comprehensive overview of their promising role in sustainable and eco-friendly practices. From mitigating pollutants to recovering valuable resources, waste-derived catalysts exhibit a versatile role in addressing waste management challenges and promoting resource sustainability. By transforming waste into valuable catalysts, this study champions a paradigm shift towards a more sustainable and resource-efficient future.

Enhancing electrocatalytic nitrate/nitric oxide reduction to NH3 on two-dimensional p-block InSe monolayer via defect engineering

Electrochemical nitrate/nitric oxide (NO3−/NO) reduction to ammonia (NH3) is an environmentally friendly and sustainable strategy that mitigates pollutants while synthesizing value-added products NH3. Despite the prevalence of transition metal-based catalysts, the exploration of inexpensive two-dimensional (2D) p-block materials is needed in NH3 synthesis. Based on density functional theory calculations, we proposed an InSe monolayer with single Se vacancy as an outstanding catalyst for NO3RR and NORR. The catalyst exhibits exceptional catalytic performance, characterized by a low limiting potential comparable to that of most transition metal-based catalysts, and efficaciously suppresses the formation of competitive by-products. Successful adsorption and activation of NO3− and NO molecules are achieved, attributed to the charge rearrangement around the vacancy. The electronic structure analysis reveals that the enhancement of activity stems from the upward shift of the p-band center of unsaturated indium atoms. This work heralds a novel avenue for designing pure 2D p-block NH3 synthesis catalysts and sheds light on a deeper understanding of the catalytic mechanism at the electronic level.

Fe-Co co-doped 1D@2D carbon-based composite as an efficient catalyst for Zn-air batteries

A Fe-Co dual-metal co-doped nitrogen-containing carbon composite (FeCo-HNC) was prepared by adjusting the ratio of iron to cobalt as well as the pyrolysis temperature with the assistance of functionalized silica template. Fe1Co-HNC, which was made from 1D carbon nanotubes and 2D carbon nanosheets with a rich mesoporous structure, presented exceptional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalytic activity. The ORR half-wave potential is 0.86 V (vs. reversible hydrogen electrode, RHE), and the OER overpotential is 0.76 V at 10 mA cm−2 with the Fe1Co-HNC catalyst, which can be applied to zinc-air batteries with superior performance. It is worth noting that the zinc-air batteries with Fe1Co-HNC-1000 as the cathodic catalyst achieved the highest power density of 94.9 mW cm−2 under a current density of 159.8 mA cm−2. This method provides a promising strategy for fabricating efficient transition metal-based carbon catalysts.

Promising urea electrosynthesis by C-N coupling on copper-based single-atom alloys

Electrochemical synthesis of urea holds a significant importance in the energy landscape, however, the lack of efficient electrocatalysts is the main bottleneck. In this study, 40 single-atom alloys (SAAs) based on Cu(100) and Cu(111) surfaces have been systematically investigated as electrocatalysts for CO2 and N2 co-reduction to produce urea utilizing first-principles calculations. A promising single N and C coupling pathway is uncovered on Cu-based SAAs, besides conventional NCON, CO2, COOH, and CO pathways. CuHf(100) displays a high efficiency in N-N decomposition, C-N coupling, and low reaction limiting potential. Furthermore, CuHf(100) and CuSc(100) have been identified as superior electrocatalysts for efficient urea electrosynthesis. This work provides potential reaction mechanisms with specific single N species, but also a universal strategy for the surface engineering of transition metal-based catalysts in electrocatalytic urea synthesis reactions.

P-NiFe2O4/N-Doped Carbon Nanotubes/NiFe Multi-Phase Heterojunctions for Overall Water Splitting and Urea Electrolysis.

The design and construction of highly efficient electrocatalysts for overall water splitting and urea electrolysis are significantly important for promoting energy conversion and realizing green hydrogen production. In this work, we constructed a multi-phase heterojunction through a simple hydrothermal and phosphorization process. The P-doped NiFe2O4 (P-NiFe2O4) nanoparticles were uniformly anchored on the bamboo-like N-doped carbon nanotubes (NCNTs) grown via a NiFe-alloy autocatalysis. The electronic structure and coordination environment of active species were optimized by the synergistic action of P doping, well-dispersed ultrafine NiFe2O4, and NCNTs matrix with good conductivity, enhancing their quantity and activity for electrocatalysis. Consequently, the P-NiFe2O4/NCNTs/NiFe exhibits excellent HER and OER activities with an overpotential of 111 and 266 mV at 10 mA cm-2 in 1 M KOH, respectively. The symmetrical overall water-splitting cell using P-NiFe2O4/NCNTs/NiFe as both anode and cathode delivers 10 mA cm-2 at a voltage of 1.604 V in 1 M KOH. Notably, the two-electrode cell requires a low voltage of 1.467 V to achieve a current density of 10 mA cm-2 in 1 M KOH solution with 0.6 M urea. This designed catalysts display outstanding reaction kinetics and catalytic stability. This work provides useful guidance for applying transition metal-based catalysts for hydrogen production.