Enhanced Supercapacitor Performance Using a Co3O4@Co3S4 Nanocomposite on Reduced Graphene Oxide/Ni Foam Electrodes

To avoid an enormous energy crisis in the not-too-distant future, it be emergent to establish high-performance energy storage devices such as supercapacitors. For this purpose, a three-dimensional (3D) heterostructure of Co₃O₄ and Co₃S₄ on nickel foam (NF) that is covered by reduced graphene oxide (rGO) has been prepared by following a facile multistep method. At first, rGO nanosheets are deposited on NF under mild hydrothermal conditions to increase the surface area. Subsequently, nanowalls of cobalt oxide are electro-deposited on rGO/Ni foam by applying cyclic-voltammetry (CV) under optimized conditions. Finally, for the synthesis of Co₃O₄@Co₃S₄ nanocomposite, the nanostructure of Co₃S₄ was fabricated from Co₃O₄ nanowalls on rGO/NF by following an ordinary hydrothermal process through the sulfurization for the electrochemical application. The samples are characterized by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The obtained sample delivers a high capacitance of 13.34 F cm⁻² (5651.24 F g⁻¹) at a current density of 6 mA cm⁻² compared to the Co₃O₄/rGO/NF electrode with a capacitance of 3.06 F cm⁻² (1230.77 F g⁻¹) at the same current density. The proposed electrode illustrates the superior electrochemical performance such as excellent specific energy density of 85.68 W h Kg⁻¹, specific power density of 6048.03 W kg⁻¹ and a superior cycling performance (86% after 1000 charge/discharge cycles at a scan rate of 5 mV s⁻¹). Finally, by using Co₃O₄ @Co₃S₄/rGO/NF and the activated carbon-based electrode as positive and negative electrodes, respectively, an asymmetric supercapacitor (ASC) device was assembled. The fabricated ASC provides an appropriate specific capacitance of 79.15 mF cm⁻² at the applied current density of 1 mA cm⁻², and delivered an energy density of 0.143 Wh kg⁻¹ at the power density of 5.42 W kg⁻¹.     

泡沫镍负载Fe2O3@Ni3S2纳米线网状结构电极的制备及其电催化析氧性能

通过两步水热法制备泡沫镍(NF)负载Fe_2O_3纳米粒子@Ni_3S_2纳米线网状结构电极(Fe_2O_3@Ni_3S_2/NF)。运用X射线衍射(XRD)、X射线光电子能谱(XPS)、透射电子显微镜(TEM)、N_2吸附-脱附测试等方法对电极材料的物相和微观结构特征等进行了表征。水热条件下原位表面化学刻蚀生成的Ni_3S_2纳米线与三维多孔NF基体间拥有强结合力和低界面电阻,Fe_2O_3粒子均匀分布在纳米线的表面。在1 mol·L~(-1)的KOH溶液中,运用线性扫描伏安测试(LSV)、计时电位法、电化学交流阻抗测试(EIS)等对电极的电催化析氧(OER)性能进行了测试。结果表明:在100 mA·cm~(-2)的超高电流密度下,Fe_2O_3@Ni_3S_2/NF电极的OER过电势仅为223 mV,比Ni_3S_2/NF材料的过电势降低了285 mV;经过10 h计时电位测试,性能保持率高达80%。     

Hierarchical FeCo2S4@FeNi2S4 Core/Shell Nanostructures on Ni Foam for High-Performance Supercapacitors

The design of electrode materials with rational core/shell structures is promising for improving the electrochemical properties of supercapacitors. Hence, hierarchical FeCo₂S₄@FeNi₂S₄ core/shell nanostructures on Ni foam were fabricated by a simple hydrothermal method. Owing to their structure and synergistic effect, they deliver an excellent specific capacitance of 2393 F g⁻¹ at 1 A g⁻¹ and long cycle lifespan as positive electrode materials. An asymmetric supercapacitor device with FeCo₂S₄@FeNi₂S₄ as positive electrode and graphene as negative electrode exhibited a specific capacitance of 133.2 F g⁻¹ at 1 A g⁻¹ and a high energy density of 47.37 W h kg⁻¹ at a power density of 800 W kg⁻¹. Moreover, the device showed remarkable cycling stability with 87.0 % specific-capacitance retention after 5000 cycles at 2 A g⁻¹. These results demonstrate that the hierarchical FeCo₂S₄@FeNi₂S₄ core/shell structures have great potential in the field of electrochemical energy storage.     

The Core/Shell Structure P Doped MoS2@Ni3S2 Nanorods Array for High Current Density Hydrogen Evolution in Alkaline and Acidic Electrolyte

Electrocatalysis is the most promising strategy to generate clean energy H₂, and the development of catalysts with excellent hydrogen evolution reaction (HER) performance at high current density that can resist strong alkaline and acidic electrolyte environment is of great significance for practical industrial application. Therefore, a P doped MoS₂@Ni₃S₂ nanorods array (named P-NiMoS) was successfully synthesized through successive sulfuration and phosphorization. P-NiMoS presents a core/shell structure with a heterojunction between MoS₂ (shell) and Ni₃S₂ (core). Furthermore, the doping of P modulates the electronic structure of the P-NiMoS; the electrons transfer from the t_2g orbital of Ni element to the e_g empty orbital of Mo element through the Ni−S−Mo bond at the Ni₃S₂ and MoS₂ heterojunction, facilitating the hydrogen evolution reaction. As a result, P-NiMoS exhibits excellent HER activity; the overpotential is 290 mV at high current density of 250 mA cm⁻² in alkaline electrolyte, which is close to Pt/C (282 mV@250 mA cm⁻²), and P-NiMoS can stably evolve hydrogen for 48 h.     

Hybrid porous Ni(OH)2-MnO2 nanosheets/plasma-grafted MWCNTs for boosted supercapacitor performance

The utilization of nickel hydroxide and manganese dioxide solely as high-performance supercapacitive materials is hindered by their low capacitance retention and electrical conductivity. As Ni(OH)₂ and MnO₂ give a synergistic effect, porous Ni(OH)₂-MnO₂ nanosheets with a thickness of 9 nm are successfully grown on carbon fiber (CF) via a single-step hydrothermal co-deposition method. Multi-walled carbon nanotubes (CNT) are grafted with maleic anhydride (MA) through plasma-grafted process, followed by thiol-ene reaction to synthesize CNT-MA−S (CMS) to increase their aqueous dispersion behavior. The electrochemical properties of Ni(OH)₂-MnO₂ are further enhanced by dip-coating CMS on nanosheets. The composition and morphology of CMS and Ni(OH)₂-MnO₂ nanosheets are characterized using scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), electron spectroscopy for chemical analysis (ESCA), transmission electron microscopy (TEM), thermogravimetric analyses (TGA), nuclear magnetic resonance (NMR), and Raman spectroscopy. The electrochemical characteristics of fabricated electrodes are analyzed using cyclic voltammetry and chronopotentiometry methods. CF−Ni(OH)₂-MnO₂/CMS electrode is successfully synthesized without using any binder, exhibited ultrahigh specific capacitance (2049 F g⁻¹ at a current density of 1 A g⁻¹), and excellent capacitance retention (>80 %) at 2 A g⁻¹ charge/discharge rate after 5000 cycles.     

Amidation-Dominated Re-Assembly Strategy for Single-Atom Design/Nano-Engineering: Constructing Ni/S/C Nanotubes with Fast and Stable K-Storage

An amidation-dominated re-assembly strategy is developed to prepare uniform single atom Ni/S/C nanotubes. In this re-assembly process, a single-atom design and nano-structured engineering are realized simultaneously. Both the NiO₅ single-atom active centers and nanotube framework endow the Ni/S/C ternary composite with accelerated reaction kinetics for potassium-ion storage. Theoretical calculations and electrochemical studies prove that the atomically dispersed Ni could enhance the convention kinetics and decrease the decomposition energy barrier of the chemically-absorbed small-molecule sulfur in Ni/S/C nanotubes, thus lowering the electrode reaction overpotential and resistance remarkably. The mechanically stable nanotube framework could well accommodate the volume variation during potassiation/depotassiation process. As a result, a high K-storage capacity of 608 mAh g⁻¹ at 100 mA g⁻¹ and stable cycling capacity of 330.6 mAh g⁻¹ at 1000 mA g⁻¹ after 500 cycles are achieved.     

One-pot hydrothermal synthesis of porous anatase TiO2 nanotube formed bundles for lithium ion battery anodes

Anatase phase of TiO₂ nanomaterial has been deemed a potential anode material for lithium ion battery (LIB) applications because of its remarkable electrochemical properties. However, TiO₂ anodes always suffer from intrinsic poor electrical conductivity and slow ion kinetics, which would restrict their practical usage. To address this issue, efficient control and design of the anatase crystal structure of TiO₂ material with desirable morphology is one of the critical approaches. In this work, a good lithium storage capability of 181 mA hr g⁻¹ at rate of 0.2C, high rate performance of 70 mA hr g⁻¹ at 20C, and excellent cyclability of 117 mA hr g⁻¹ with a capacity retention of 93% at 1C after 100 cycles and 84 mA hr g⁻¹ at 10C after 1,000 cycles are observed in an optimized porous anatase TiO₂ one-dimensional nanotube bundle nanomaterial fabricated through a simple hydrothermal process with post calcination treatment. These excellent electrochemical properties of the product can be ascribed to its anatase crystal phase, 1D nanostructure, and porous framework with a large surface area, which provide it with an efficient electrode/electrolyte contact area and a faster ion/electron diffusion pathway.     

Hierarchical Rhree-dimensional CoNi LDH-Ni3S2 Supported on Ni Foam as a Stable and Efficient Electrocatalytic Material for Overall Water Splitting

Herein, a novel self-supporting three-dimensional nanostructured CoNi LDH-Ni₃S₂ catalyst was generated in a two-step process combining hydrothermal synthesis and high-temperature electrodeposition techniques. The CoNi LDH-Ni₃S₂/NF electrode exhibits superior electrocatalytic performance with low overpotentials of 193 and 382 mV in 1 M KOH to drive a high current density of 100 mA cm⁻² for HER and OER, respectively. Meanwhile, a small cell voltage of 1.51 V was obtained upon using CoNi LDH-Ni₃S₂/NF as a dual-functional catalyst. Additionally, CoNi LDH-Ni₃S₂/NF exhibits high stability with almost no change in HER and OER overpotentials and electrocatalytic total decomposition of water within 80,000 s.     

In Situ Growth of Hierarchical Ni-Mn-O Solid Solution on a Flexible and Porous Ni Electrode for High-Performance All-Solid-State Asymmetric Supercapacitors

To endow all-solid-state asymmetric supercapacitors with high energy density, cycling stability, and flexibility, we design a binder-free supercapacitor electrode by in situ growth of well-distributed broccoli-like Ni_0.75Mn_0.25O/C solid solution arrays on a flexible and three-dimensional Ni current collector (3D-Ni). The electrode consists of a bottom layer of compressed but still porous Ni foam with excellent flexibility and high electrical conductivity, an intermediate layer of interconnected Ni nanoparticles providing a large specific surface area for loading of active substances, and a top layer of vertically aligned mesoporous nanosheets of a Ni_0.75Mn_0.25O/C solid solution. The resultant 3D-Ni/Ni_0.75Mn_0.25O/C cathode exhibits a specific capacitance of 1657.6 mF cm⁻² at 1 mA cm⁻² and shows no degradation of the capacitance after 10 000 cycles at 3 mA cm⁻². The assembled 3D-Ni/Ni_0.75Mn_0.25O/C//activated carbon asymmetric supercapacitor has a high specific capacitance of 797.7 mF cm⁻² at 2 mA cm⁻² and an excellent cycling stability with 85.3 % of capacitance retention after 10 000 cycles at a current density of 3 mA cm⁻². The energy density and power density of the asymmetric supercapacitor are up to 6.6 mW h cm⁻³ and 40.8 mW cm⁻³, respectively, indicating a fairly promising future of the flexible 3D-Ni/Ni_0.75Mn_0.25O/C electrode for efficient energy storage applications.     

Ultrathin Mn Doped Ni-MOF Nanosheet Array for Highly Capacitive and Stable Asymmetric Supercapacitor

In this study, we demonstrate that an Mn-doped ultrathin Ni-MOF nanosheet array on nickel foam (Mn_0.1-Ni-MOF/NF) serves as a highly capacitive and stable supercapacitor positive electrode. The Mn_0.1-Ni-MOF/NF shows an areal capacity of 6.48 C cm⁻² (specific capacity C: 1178 C g⁻¹) at 2 mA cm⁻² in 6.0 m KOH, outperforming most reported MOF-based materials. More importantly, it possesses excellent cycle stability to maintain 80.6 % capacity after 5000 cycles. An asymmetric supercapacitor device utilizing Mn_0.1-Ni-MOF/NF as the positive electrode and activated carbon as the negative electrode attains a high energy density of 39.6 Wh kg⁻¹ at 143.8 Wkg⁻¹ power density with a capacitance retention of 83.6 % after 5000 cycles.     

Synthesis of Porous Ni-Doped CoSe2/C Nanospheres towards High-Rate and Long-Term Sodium-Ion Half/Full Batteries

Carbon-layer-coated porous Ni-doped CoSe₂ (Ni-CoSe₂/C) nanospheres have been fabricated by a facile hydrothermal method followed by a new selenization strategy. The porous structure of Ni-CoSe₂/C is formed by the aggregation of many small particles (20–40 nm), which are not tightly packed together, but are interspersed with gaps. Moreover, the surfaces of these small particles are covered with a thin carbon layer. Ni-CoSe₂/C delivers superior rate performance (314.0 mA h g⁻¹ at 20 A g⁻¹), ultra-long cycle life (316.1 mA h g⁻¹ at 10 A g⁻¹ after 8000 cycles), and excellent full-cell performance (208.3 mA h g⁻¹ at 0.5 A g⁻¹ after 70 cycles) when used as an anode material for half/full sodium-ion batteries. The Na storage mechanism and kinetics have been confirmed by ex situ X-ray diffraction analysis, assessment of capacitance performance, and a galvanostatic intermittent titration technique (GITT). GITT shows that Na⁺ diffusion in the electrode material is a dynamic change process, which is associated with a phase transition during charge and discharge. The excellent electrochemical performance suggests that the porous Ni-CoSe₂/C nanospheres have great potential to serve as an electrode material for sodium-ion batteries.     

Structural Design and Synthesis of an SnO2@C@Co-NC Composite as a High-Performance Anode Material for Lithium-Ion Batteries

To overcome the drawbacks of the structural instability and poor conductivity of SnO₂-based anode materials, a hollow core–shell-structured SnO₂@C@Co-NC (NC=N-doped carbon) composite was designed and synthesized by employing the heteroatom-doping and multiconfinement strategies. This composite material showed a much-reduced resistance to charge transfer and excellent cycling performance compared to the bare SnO₂ nanoparticles and SnO₂@C composites. The doped heteroatoms and heterostructure boost the charge transfer, and the porous structure shortens the Li-ion diffusion pathway. Also, the volume expansion of SnO₂ NPs is accommodated by the hollow space and restricted by the multishell heteroatom-doped carbon framework. As a result, this structured anode material delivered a high initial capacity of 1559.1 mA h g⁻¹ at 50 mA g⁻¹ and an initial charge capacity of 627.2 mA h g⁻¹ at 500 mA g⁻¹. Moreover, the discharge capacity could be maintained at 410.8 mA h g⁻¹ after 500 cycles with an attenuation rate of only 0.069 % per cycle. This multiconfined SnO₂@C@Co-NC structure with superior energy density and durable lifespan is highly promising for the next-generation lithium-ion batteries.     

Rational Construction of 2D Fe3O4@Carbon Core–Shell Nanosheets as Advanced Anode Materials for High-Performance Lithium-Ion Half/Full Cells

Transition metal oxides have vastly limited practical application as electrode materials for lithium-ion batteries (LIBs) due to their rapid capacity decay. Here, a versatile strategy to mitigate the volume expansion and low conductivity of Fe₃O₄ by coating a thin carbon layer on the surface of Fe₃O₄ nanosheets (NSs) was employed. Owing to the 2D core–shell structure, the Fe₃O₄@C NSs exhibit significantly improved rate performance and cycle capability compared with bare Fe₃O₄ NSs. After 200 cycles, the discharge capacity at 0.5 A g⁻¹ was 963 mA h g⁻¹ (93 % retained). Moreover, the reaction mechanism of lithium storage was studied in detail by ex situ XRD and HRTEM. When coupled with a commercial LiFePO₄ cathode, the resulting full cell retains a capacity of 133 mA h g⁻¹ after 100 cycles at 0.1 A g⁻¹, which demonstrates its superior energy storage performance. This work provides guidance for constructing 2D metal oxide/carbon composites with high performance and low cost for the field of energy storage.     

Hierarchical Hollow-Nanocube Ni−Co Skeleton@MoO3/MoS2 Hybrids for Improved-Performance Lithium-Ion Batteries

Improving the performance of anode materials for lithium-ion batteries (LIBs) is a hotly debated topic. Herein, hollow Ni−Co skeleton@MoS₂/MoO₃ nanocubes (NCM-NCs), with an average size of about 193 nm, have been synthesized through a facile hydrothermal reaction. Specifically, MoO₃/MoS₂ composites are grown on Ni−Co skeletons derived from nickel–cobalt Prussian blue analogue nanocubes (Ni−Co PBAs). The Ni−Co PBAs were synthesized through a precipitation method and utilized as self-templates that provided a larger specific surface area for the adhesion of MoO₃/MoS₂ composites. According to Raman spectroscopy results, as-obtained defect-rich MoS₂ is confirmed to be a metallic 1T-phase MoS₂. Furthermore, the average particle size of Ni−Co PBAs (≈43 nm) is only about one-tenth of the previously reported particle size (≈400 nm). If assessed as anodes of LIBs, the hollow NCM-NC hybrids deliver an excellent rate performance and superior cycling performance (with an initial discharge capacity of 1526.3 mAh g⁻¹ and up to 1720.6 mAh g⁻¹ after 317 cycles under a current density of 0.2 A g⁻¹). Meanwhile, ultralong cycling life is retained, even at high current densities (776.6 mAh g⁻¹ at 2 A g⁻¹ after 700 cycles and 584.8 mAh g⁻¹ at 5 A g⁻¹ after 800 cycles). Moreover, at a rate of 1 A g⁻¹, the average specific capacity is maintained at 661 mAh g⁻¹. Thus, the hierarchical hollow NCM-NC hybrids with excellent electrochemical performance are a promising anode material for LIBs.     

Facile Preparation of CuCo2S4/Cu7.2S4 Nanocomposites as High-Performance Cathode Materials for Rechargeable Magnesium Batteries**

Rechargeable magnesium batteries (RMBs) have been considered a promising energy-storage device due to their high energy density and high safety, but they still suffer from a lack of high-rate performance and cycle performance of the cathode. Nanosized CuCo₂S₄/Cu_7.2S₄ composites have been synthesized for the first time by a facile solvothermal method. Herein, the magnesium ion storage behavior when applied in the cathode for RMBs is discussed. Electrochemical results demonstrated that the CuCo₂S₄/Cu_7.2S₄ composites exhibit a high initial discharge capacity of 256 mAh g⁻¹ at 10 mA g⁻¹ and 123 mAh g⁻¹ at 300 mA g⁻¹ at room temperature and an outstanding long-term cyclic stability over 300 cycles at 300 mA g⁻¹. Furthermore, the electrochemical storage mechanism demonstrated that the storage process of magnesium ion in the CuCo₂S₄/Cu_7.2S₄ cathode is mainly driven by strong pseudocapacitive effects.     

Two-Dimensional SnSe2/CNTs Hybrid Nanostructures as Anode Materials for High-Performance Lithium-Ion Batteries

Tin diselenide (SnSe₂), as an anode material, has outstanding potential for use in advanced lithium-ion batteries. However, like other tin-based anodes, SnSe₂ suffers from poor cycle life and low rate capability due to large volume expansion during the repeated Li⁺ insertion/de-insertion process. This work reports an effective and easy strategy to combine SnSe₂ and carbon nanotubes (CNTs) to form a SnSe₂/CNTs hybrid nanostructure. The synthesized SnSe₂ has a regular hexagonal shape with a typical 2D nanostructure and the carbon nanotubes combine well with the SnSe₂ nanosheets. The hybrid nanostructure can significantly reduce the serious damage to electrodes that occurs during electrochemical cycling processes. Remarkably, the SnSe₂/CNTs electrode exhibits a high reversible specific capacity of 457.6 mA h g⁻¹ at 0.1 C and 210.3 mA h g⁻¹ after 100 cycles. At a cycling rate of 0.5 C, the SnSe₂/CNTs electrode can still achieve a high value of 176.5 mA h g⁻¹, whereas a value of 45.8 mA h g⁻¹ is achieved for the pure SnSe₂ electrode. The enhanced electrochemical performance of the SnSe₂/CNTs electrode demonstrates its great potential for use in lithium-ion batteries. Thus, this work reports a facile approach to the synthesis of SnSe₂/CNTs as a promising anode material for lithium-ion batteries.     

Hierarchical Carbon Nanowire/Ni@MnO2 Nanocomposites for High-Performance Asymmetric Supercapacitors

A 3D hierarchical carbon cloth/nitrogen-doped carbon nanowires/Ni@MnO₂ (CC/N-CNWs/Ni@MnO₂) nanocomposite electrode was rationally designed and prepared by electrodeposition. The N-CNWs derived from polypyrrole (PPy) nanowires on the carbon cloth have an open framework structure, which greatly increases the contact area between the electrode and electrolyte and provides short diffusion paths. The incorporation of the Ni layer between the N-CNWs and MnO₂ is beneficial for significantly enhancing the electrical conductivity and boosting fast charge transfer as well as improving the charge-collection capacity. Thus, the as-prepared 3D hierarchical CC/N-CNWs/Ni@MnO₂ electrode exhibits a higher specific capacitance of 571.4 F g⁻¹ compared with those of CC/N-CNWs@MnO₂ (311 F g⁻¹), CC/Ni@MnO₂ (196.6 F g⁻¹), and CC@MnO₂ (186.1 F g⁻¹) at 1 A g⁻¹ and remarkable rate capability (367.5 F g⁻¹ at 10 A g⁻¹). Moreover, asymmetric supercapacitors constructed with CC/N-CNWs/Ni@MnO₂ as cathode material and activated carbon as anode material deliver an impressive energy density of 36.4 W h kg⁻¹ at a power density of 900 W kg⁻¹ and a good cycling life (72.8 % capacitance retention after 3500 cycles). This study paves a low-cost and simple way to design a hierarchical nanocomposite electrode with large surface area and superior electrical conductivity, which has wide application prospects in high-performance supercapacitors.     

Intensified electrochemical hydrogen storage capacity of multi-walled carbon nanotubes supported with Ni nanoparticles

The electrochemical hydrogen storage properties of Ni-supported multi-walled carbon nanotube (Ni/MWCNT) electrodes were investigated using charge/discharge (C&D) and cyclic voltammetry (CV) techniques. Nickel NPs were deposited on the MWCNT surface, which was first chemically oxidized by H₂SO₄ and HNO₃ (3:1, v/v). Hydrogen storage was carried out by using the Ni/MWCNT electrode as the working electrode in the electrochemical cell. A set of various current densities were applied to the cell to produce (C&D) cycles, and it became optimum corresponding to 1.5 mA current. According to the electrochemical test results, the highest electrochemical discharge capacity of 1625 mAh g^?1 was obtained for the electrode with ratio of 4:1 (MWCNTs to Ni) in the initial cycle, which corresponded to 6.07 wt% H₂. The storage capacity was increased and reached to 4909 mAh g^?1 (18.34 wt% H₂) after 20 cycles, and the electrode maintained the specific capacity as cycling continued. Thus, the Ni/MWCNT electrode displays an excellent cycle stability and a high capacity reversibility. CV measurements also showed that the electrochemical adsorption and desorption amount of hydrogen was increased by Ni loading onto the CNTs and indicated that the electrochemical hydrogen adsorption of the electrode has an activated period.     

Synergism of Interface and Electronic Effects: Bifunctional N-Doped Ni3S2/N-Doped MoS2 Hetero-Nanowires for Efficient Electrocatalytic Overall Water Splitting

The realization of water electrolysis on the basis of highly active, cost-effective electrocatalysts is significant yet challenging for achieving sustainable hydrogen production from water. Herein, N-doped Ni₃S₂/N-doped MoS₂ 1D hetero-nanowires supported by Ni foam (N-Ni₃S₂/N-MoS₂/NF) are readily synthesized through a chemical transformation strategy by using NiMoO₄ nanowire array growth on Ni foam (NiMoO₄/NF) as the starting material. With the in situ generation of Ni₃S₂/MoS₂ heterointerfaces within nanowires and the incorporation of N⁻ anions, an extraordinary hydrophilic nature with abundant, well-exposed active sites and optimal reaction dynamics for both oxidation and reduction of water are obtained. Attributed to these properties, as-converted N-Ni₃S₂/N-MoS₂/NF exhibits highly efficient electrocatalytic activities for both hydrogen and oxygen evolution reactions under alkaline conditions. The superior bifunctional properties of N-Ni₃S₂/N-MoS₂/NF enable it to effectively catalyze the overall water-splitting reaction.     

Biomimetic Straw-Like Bundle Cobalt-Doped Fe2O3 Electrodes towards Superior Lithium-Ion Storage

Biomimetic straw-like bundles of Co-doped Fe₂O₃ (SCF), with Co²⁺ incorporated into the lattice of α-Fe₂O₃, was fabricated through a cost-effective hydrothermal process and used as the anode material for lithium-ion batteries (LIBs). The SCF exhibited ultrahigh initial discharge specific capacity (1760.7 mA h⁻¹ g⁻¹ at 200 mA g⁻¹) and cycling stability (with the capacity retention of 1268.3 mA h⁻¹ g⁻¹ after 350 cycles at 200 mA g⁻¹). In addition, a superior rate capacity of 376.1 mA h⁻¹ g⁻¹ was obtained at a high current density of 4000 mA g⁻¹. The remarkable electrochemical lithium storage of SCF is attributed to the Co-doping, which increases the unit cell volume and affects the whole structure. It makes the Li⁺ insertion–extraction process more flexible. Meanwhile, the distinctive straw-like bundle structure can accelerate Li ion diffusion and alleviate the huge volume expansion upon cycling.