Full-Temperature All-Solid-State Ti3C2Tx/Aramid Fiber Supercapacitor with Optimal Balance of Capacitive Performance and Flexibility

Full-temperature all-solid-state flexible symmetrical fiber supercapacitors (FSCs) are assembled by using montmorillonite flake/polyvinyl alcohol organic hydrogel (F-MMT/PVA OHGE) as the electrolyte and separator and Ti₃C₂T_x/ANF-5% (T/A-5) fiber as the electrode, in which T/A-5 fiber is prepared by using delaminated Ti₃C₂T_x nanosheets as assembled units and 5% of aramid nanofiber (ANF) as the functional additive using a wet spinning method in a coagulated bath with 0.5 m FeCl₂ solution. The T/A-5 hybrid fiber exhibits a specific capacity of 807 F cm⁻³ in 3 m H₂SO₄ electrolyte, a superior mechanical strength of 104 MPa, and a high conductivity of 1025 S cm⁻¹. The assembled F-MMT/PVA OHGE T/A-5 FSC not only shows a specific capacitance of 295 F cm⁻³ and a capacitance retention of 91% at a current density of 5 A cm⁻³ after 10 000 charging/discharging cycles, but also a maximum volumetric energy density of 26.2 mWh cm⁻³. Meanwhile, the assembled device displays good flexibility and excellent capacitance in a wide temperature range of −40 to 80 °C, the electrochemical performance of the FSC is maintained under varying degrees of bending. This study provides an effective strategy for designing and assembling of full-temperature all-solid-state symmetrical flexible FSCs with the optimal balance of capacitive performance and flexibility.     

Ultrahigh-Areal Capacitance Flexible Supercapacitors Based on Laser Assisted Construction of Hierarchical Aligned Carbon Nanotubes

Electrochemical energy storage is a key technology for a clean and sustainable energy supply. In this respect, supercapacitors (SC) have recently received considerable attention due to their excellent performance, including high-power density and long-cycle life. However, the poor binding strength between the active materials and substrate, the low active material loading, and small specific capacitance hinder the overall performance improvement of the device. In this study, an ultrahigh-areal capacitance flexible SC based on the Al micro grid-based hierarchical vertically aligned carbon nanotubes (VACNTs) is studied. Interestingly, the Al micro grid-based VACNTs exhibit ultrahigh loading (13 mg cm⁻²), and the as-fabricated VACNTs electrode display outstanding electrochemical performance, including an impressive areal capacitance of 1,300 mF cm⁻² at the current density of 13 mA cm⁻² and excellent stability with a retention ratio of 90% after 20,000 cycles at the current density of 130 mA cm⁻². Furthermore, the hierarchical VACNT electrodes show excellent mechanical flexibility when assembled into quasi-solid-state SC using Na₂SO₄-PVA gel as the electrolyte. The capacitance of this device is hardly changed bending different angles, even 180°. This study demonstrates the tremendous potential of Al micro grid-based hierarchical VACNTs as electrodes for high-performance flexible and wearable energy storage devices.     

Hierarchical Crystalline/Amorphous Heterostructure MoNi/NiMoOx for Electrochemical Hydrogen Evolution with Industry-Level Activity and Stability

The design of cheap, efficient, and durable electrocatalysts for high-throughput H₂ production is critical to give impetus to hydrogen production from fundamental to practical industrial applications. Here, a hierarchical heterostructure hydrogen evolution reaction (HER) electrocatalyst (MoNi/NiMoO_x) with 0D MoNi nanoalloys nanoparticles embedded on well-assembled 1D porous NiMoO_x microrods in situ grown on 3D nickel foam (NF) is successfully constructed. The synergetic effect of different building units in the unique hierarchical structure endows the MoNi/NiMoO_x composites with the highly active heterogeneous interface with low water dissociation energy (ΔG_diss = −1.2 eV) and optimized hydrogen adsorption ability (ΔG_H* = −0.01 eV), fast electron/mass transport, and strong catalyst-support binding force. As a result, optimal MoNi/NiMoO_x exhibits an ampere-level current density of 1.9 A cm⁻² at an ultralow overpotential of 139 mV in 1.0 м KOH and 289 mV in 1.0 м PBS solution, respectively. Particularly, scaled-up MoNi/NiMoO_x electrodes in a 10 × 10 cm² membrane electrode assembly (MEA) electrolyzer reach a high H₂ production rate of 12.12 L h⁻¹ (12.12 times than that of commercial NF) and exhibit ultralong stability of 1600 h, verifying its huge potential for industrial hydrogen production.     

Electrospinning Synthesis of Self-Standing Cobalt/Nanocarbon Hybrid Membrane for Long-Life Rechargeable Zinc–Air Batteries

Integrating high-efficiency oxygen electrocatalyst directly into air electrodes is vital for zinc–air batteries to achieve higher electrochemical performance. Herein, a self-standing membrane composed of hierarchical cobalt/nanocarbon nanofibers is fabricated by the electrospinning technique. This hybrid membrane can be directly employed as the bifunctional air electrode in zinc–air batteries and can achieve a high peak power density of 304 mW cm⁻² with a long service life of 1500 h at 5 mA cm⁻². Its assembled solid-state zinc–air battery also delivers a promising power density of 176 mW cm⁻² with decent flexibility. The impressive rechargeable battery performance would be attributed to the self-standing membrane architecture integrated by oxygen electrocatalysts with abundant cobalt–nitrogen–carbon active species in the hierarchical electrode. This study may provide effective electrospinning solutions in integrating efficient electrocatalyst and electrode for energy storage and conversion technologies.     

Fabrication of Hybrid Supercapacitor by MoCl5 Precursor-Assisted Carbonization with Ultrafast Laser for Improved Capacitance Performance

Hybrid supercapacitors use electric double-layer capacitance and Faradaic pseudocapacitance as energy storage mechanisms. This type of supercapacitor is becoming a prime candidate for next-generation energy storage devices, with advantages in terms of energy density, specific capacitance, and life cycle. However, reducing the electrode area and increasing the specific capacitance of hybrid supercapacitors remain challenging. In this study, a MoCl₅ Precursor-assisted Ultrafast Laser Carbonization (MPAULC) method to fabricate symmetric hybrid supercapacitors with improved capacitance and reduced size is proposed. The method uses an ultrafast laser to induce the formation of carbon/MoO₃ composite with the assistance of the MoCl5 precursor. This ultrafast laser carbonization method exhibited high processing precision. The role of the precursor in laser processing is studied using time-resolved imaging and temperature calculations. The specific area capacitance of the C/MoO₃ hybrid supercapacitor is 11.85 mF cm⁻², 9.2 times higher than that of the laser-induced carbon supercapacitor without precursor. The MPAULC method provides a reliable pathway for fabricating miniaturized hybrid supercapacitors with carbon/metal oxide composite electrodes on polymer substrates.     

Alternative-Ultrathin Assembling of Exfoliated Manganese Dioxide and Nitrogen-Doped Carbon Layers for High-Mass-Loading Supercapacitors with Outstanding Capacitance and Impressive Rate Capability

Manganese dioxide (MnO₂) materials have received much attention as promising pseudocapacitive materials owing to their high theoretical capacitance and natural abundance. Unfortunately, the charge storage performance of MnO₂ is usually limited to commercially available mass loading electrodes because of the significantly lower electron and ion migration kinetics in thick electrodes. Here, an alternatively assembled 2D layered material consisting of exfoliated MnO₂ nanosheets and nitrogen-doped carbon layers for ultrahigh-mass-loading supercapacitors without sacrificing energy storage performance is reported. Layered birnessite-type MnO₂ is efficiently exfoliated and intercalated by a carbon precursor of dopamine using a fluid dynamic-induced process, resulting in MnO₂/nitrogen-doped carbon (MnO₂/C) materials after self-polymerization and carbonization. The alternatively stacked and interlayer-expanded structure of MnO₂/C enables fast and efficient electron and ion transfer in a thick electrode. The resulting MnO₂/C electrode shows outstanding electrochemical performance at an ultrahigh mass loading of 19.7 mg cm⁻², high gravimetric and areal capacitances of 480.3 F g⁻¹ and 9.4 F cm⁻² at 0.5 mA cm⁻², and rapid charge/discharge capability of 70% capacitance retention at 40 mA cm⁻². Furthermore, asymmetric supercapacitor based on high-mass-loading MnO₂/C can deliver an extremely high energy of 64.2 Wh kg⁻¹ at a power density of 18.8 W kg⁻¹ in an aqueous electrolyte.     

Interface Engineering of Biomass-Derived Carbon used as Ultrahigh-Energy-Density and Practical Mass-Loading Supercapacitor Electrodes

The development of flexible electrodes with high mass loading and efficient electron/ion transport is of great significance but still remains the challenge of innovating suitable electrode structures for high energy density application. Herein, for the first time, lignosulfonate-derived N/S-co-doped graphene-like carbon is in situ formed within an interface engineered cellulose textile through a sacrificial template method. Both experimental and theoretical calculations disclose that the formed pomegranate-like structure with continuous conductive pathways and porous characteristics allows sufficient ion/electron transport throughout the entire structures. As a result, the obtained flexible electrode delivers a remarkable integrated capacitance of 6534 mF cm⁻² (335.1 F g⁻¹) and a superior stability at an industrially applicable mass loading of 19.5 mg cm⁻². A pseudocapacitive cathode with ultrahigh capacitance of 7000 mF cm⁻² can also be obtained based on the same electrode structure engineering. The as-assembled asymmetric supercapacitor achieves a high areal capacitance of 3625 mF cm⁻², and a maximum energy density of 1.06 mWh cm⁻², outperforms most of other reported high-loading supercapacitors. This synthesis method and structural engineering strategy can provide materials design concepts and a wide range of applications in the fields of energy storage beyond supercapacitors.     

Layered Double Hydroxide with Interlayer Quantum Dots and Laminate Defects for High-Performance Supercapacitor

Owing to the flexible adjustability of laminates, layered double hydroxides (LDHs) can achieve enhanced conductivity and capacitance. However, the regulation of interlayer activity is a great challenge because of the unconquerable charge repulsion between laminates. Herein, a dual-activity design of LDHs is uniquely realized, including laminate defects and interlayer ZnS quantum dots (QDs). Via pre-embedding Zn2+ and controllable vulcanization, ZnS-QDs interpenetrate between CuCo-LDH layers, exposing abundant active sites and widening the layer spacing. Meanwhile, sulfur replaces part of the oxygen on the laminates to form rich oxygen vacancies (CuCo-LDH-S), which does not damage the layered spatial structure and ensures the fast ions/electron transport. Theoretical calculations indicate that the new active centers exhibit higher charge density as compared to CuCo-LDH. Moreover, the copper foam directly provides copper source to ensure that CuCo-LDH-S/ZnS-QDs present a 3D self-supporting structure with ultrastability. Hence, it delivers an ultrahigh capacitance of 7.82 F cm⁻² at 2 mA cm⁻² and 4.43 F cm⁻² at 20 mA cm⁻². The hybrid supercapacitors display an outstanding energy density of 299 µWh cm⁻² at power density of 1600 µW cm⁻², with outstanding capacitance retention of 102.3% and coulomb efficiency of 96.2% after 10 000 cycles.     

Redox Poly-Counterion Doped Conducting Polymers for Pseudocapacitive Energy Storage

Conducting polymers (CPs) have been widely studied for electrochemical energy storage. However, the dopants in CPs are often electrochemically inactive, introducing “dead-weight” to the materials. Moreover, commercial-level electrode materials with high mass loadings (e.g., >10 mg cm⁻²) often encounter the problems of inferior electrical and ionic conductivity. Here, a redox-active poly-counterion doping concept is proposed to improve the electrochemical performance of CPs with ultra-high mass loadings. As a study prototype, heptamolybdate anion (Mo₇O₂₄⁶⁻) doped polypyrrole (PPy) is synthesized by electro-polymerization. A 2 mm thick PPy electrode with mass loading of ≈192 mg cm⁻² reaches a record-high areal capacitance of ≈47 F cm⁻², competitive gravimetric capacitance of 235 F g⁻¹, and volumetric capacitance of 235 F cm⁻³. With poly-counterion doping, the dopants also undergo redox reactions during charge/discharge processes, providing additional capacitance to the electrode. The interaction between polymer chains and the poly-counterions enhances the electrical conductivity of CPs. Besides, the poly-counterions with large steric hindrance could act as structural pillars and endow CPs with open structures for facile ion transport. The concept proposed in this work enriches the electrochemistry of CPs and promotes their practical applications.     

VOx@MoO3 Nanorod Composite for High‐Performance Supercapacitors

Vanadium oxide is a promising pseudocapacitive electrode, but their capacitance, especially at high current densities, requires improvement for practical applications. Herein, a VO_x@MoO₃ composite electrode is constructed through a facile electrochemical method. Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy demonstrate a modification on the chemical environment and electronic structure of VO_x upon the effective interaction with the thin layer of MoO₃. A careful investigation of the electrochemical impedance spectroscopy data reveals much enhanced power capability of the composite electrode. More charge storage sites will also be created at/near the heterogeneous interface. Due to those synergistic effects, the VO_x@MoO₃ electrode shows excellent electrochemical performance. It provides a high capacitance of 1980 mF cm⁻² at 2 mA cm⁻². Even at the high current density of 100 mA cm⁻², it still achieves 1166 mF cm⁻² capacitance, which doubles the sum of single electrodes. The MoO₃ layer also helps to prevent VO_x structure deformation, and 94% capacitance retention over 10 000 cycles is obtained for the composite electrode. This work demonstrates an effective strategy to induce interactions between heterogeneous components and enhance the electrochemical performance, which can also be applied to other pseudocapacitive electrode candidates.     

Development of Fluorine-Free Tantalum Carbide MXene Hybrid Structure as a Biocompatible Material for Supercapacitor Electrodes

The application of nontoxic 2D transition-metal carbides (MXenes) has recently gained ground in bioelectronics. In group-4 transition metals, tantalum possesses enhanced biological and physical properties compared to other MXene counterparts. However, the application of tantalum carbide for bioelectrodes has not yet been explored. Here, fluorine-free exfoliation and functionalization of tantalum carbide MAX-phase to synthesize a novel Ta₄C₃T_x MXene-tantalum oxide (TTO) hybrid structure through an innovative, facile, and inexpensive protocol is demonstrated. Additionally, the application of TTO composite as an efficient biocompatible material for supercapacitor electrodes is reported. The TTO electrode displays long-term stability over 10 000 cycles with capacitance retention of over 90% and volumetric capacitance of 447 F cm⁻³ (194 F g⁻¹) at 1 mV s⁻¹. Furthermore, TTO shows excellent biocompatibility with human-induced pluripotent stem cells-derived cardiomyocytes, neural progenitor cells, fibroblasts, and mesenchymal stem cells. More importantly, the electrochemical data show that TTO outperforms most of the previously reported biomaterials-based supercapacitors in terms of gravimetric/volumetric energy and power densities. Therefore, TTO hybrid structure may open a gateway as a bioelectrode material with high energy-storage performance for size-sensitive applications.     

Mo-/Co-N-C Hybrid Nanosheets Oriented on Hierarchical Nanoporous Cu as Versatile Electrocatalysts for Efficient Water Splitting

Designing robust and cost-effective electrocatalysts based on Earth-abundant elements is crucial for large-scale hydrogen production through electrochemical water splitting. Here, nitrogen-doped carbon engrafted Mo₂N/CoN hybrid nanosheets that are seamlessly oriented on hierarchical nanoporous Cu scaffold (Mo-/Co-N-C/Cu), as highly efficient electrocatalysts for alkaline hydrogen evolution reaction are reported. The constituent heterostructured Mo₂N/CoN nanosheets work as bifunctional electroactive sites for both water dissociation and adsorption/desorption of hydrogen intermediates while the nitrogen-doped carbon bridges electron transfers between electroactive sites and interconnective Cu current collectors by making use of Mo-/Co-N-C bonds and intimate C/Cu contacts at interfaces. As a consequence of unique architecture having electroactive sites to be sufficiently accessible, self-supported nanoporous Mo-/Co-N-C/Cu hybrid electrodes exhibit outstanding electrocatalysis in 1 m KOH, with a negligible onset overpotential and a low Tafel slope of 47 mV dec⁻¹. They only take overpotential of as low as 230 mV to reach current density of 1000 mA cm⁻². When coupled with their electro-oxidized derivatives that mediate efficiently the oxygen evolution reaction, the alkaline water electrolyzer can achieve ≈100 mA cm⁻² at 1.622 V in 1 m KOH electrolyte, ≈0.343 V lower than the device constructed with commercially available Pt/C and Ir/C nanocatalysts immobilized on nanoporous Cu electrodes.     

Nature-Inspired Interconnected Macro/Meso/Micro-Porous MXene Electrode

The geometric multiplication development of MXene has promoted it to become a star material in numerous applications including, but not limited to, energy storage. It is found that pore structure modulation engineering can improve the inherent properties of MXene, in turn significantly enhancing its electrochemical performance. However, most of the current works have focused on exploring the structure-effective relationships of the single-scale pore structure regulation of MXene. Inspired by Murray's law from nature where a highly graded structure of the organisms is discovered and used to achieve effective diffusion and maximize mass transfer, a hierarchically interconnected porous MXene electrode across micro-meso-macroporous is constructed. This MXene-based electrode provides large amounts of active sites while greatly shortening the ion diffusion channel. Finally, the zinc ion microcapacitor based on this MXene electrode exhibits an ultrahigh area-specific capacitance up to 410 mF cm⁻² and an energy density up to 103 µWh cm⁻² at a power density of 2100 µW cm⁻². The areal energy density outperforms the currently reported zinc ion microcapacitors. This study supports an effective strategy for electrode materials (including but not limited to MXene) to achieve ultra-short ion diffusion channels and maximum transport efficiency for next-generation high-performance energy storage.     

Flexible Carbon Dots-Intercalated MXene Film Electrode with Outstanding Volumetric Performance for Supercapacitors

2D MXenes have emerged as promising supercapacitor electrode materials due to their metallic conductivity, pseudo-capacitive mechanism, and high density. However, layer-restacking is a bottleneck that restrains their ionic kinetics and active site exposure. Herein, a carbon dots-intercalated strategy is proposed to fabricate flexible MXene film electrodes with both large ion-accessible active surfaces and high density through gelation of calcium alginate (CA) within the MXene nanosheets followed by carbonization. The formation of CA hydrogel within the MXene nanosheets accompanied by evaporative drying endow the MXene/CA film with high density. In the carbonization process, the CA-derived carbon dots can intercalate into the MXene nanosheets, increasing the interlayer spacing and promoting the electrolytic diffusion inside the MXene film. Consequently, the carbon dots-intercalated MXene films exhibit high volumetric capacitance (1244.6 F cm⁻³ at 1 A g⁻¹), superior rate capability (662.5 F cm⁻³ at 1000 A g⁻¹), and excellent cycling stability (93.5% capacitance retention after 30 000 cycles) in 3 m H₂SO₄. Additionally, an all-solid-state symmetric supercapacitor based on the carbon dots-intercalated MXene film achieves a high volumetric energy density of 27.2 Wh L⁻¹. This study provides a simple yet efficient strategy to construct high-volumetric performance MXene film electrodes for advanced supercapacitors.     

An Ultrafast,High-Loading,and Durable Poly(p-aminoazobenzene)/Reduced Graphene Oxide Composite Electrode for Supercapacitors

Although challenging, the fabricated supercapacitor electrodes with excellent rate capability, long cycling stability, and high mass-loading are crucial for practical applications. Herein, a novel 3D porous poly(p-aminoazobenzene)/reduced graphene oxide hydrogel is designed and prepared as an ultrafast, high-loading, and durable pseudocapacitive electrode through a facile two-step self-assembly approach. Owing to abundant stable redox-active sites, fast electrolyte diffusion, and efficient charge conduction, the PRH electrode (5 mg cm⁻²) shows a high specific capacitance (701 F g⁻¹ at 2 A g⁻¹) and ultrafast rate (97% capacitance retention at 100 A g⁻¹). Furthermore, even with a mass-loading of 10 mg cm⁻², the electrode still exhibits comparable high performance and excellent long-term cycling life (only 6.7% capacitance loss after 10 000 cycles). This work demonstrates novel polyaniline analog composites for constructing novel electrodes, promising to open an avenue toward practical applications.     

Three-Dimensional Printed Mechanically Compliant Supercapacitor with Exceptional Areal Capacitance from a Self-Healable Ink

Known for its capability to architect tailored structures for the scaling of active materials in energy storage devices that cater for future electronics having stringent requirements on areal performance, 3D printing is receiving serious attention. However, lingering challenges originating from the notorious interfacial issue and weak component interaction restrain current devices from making a breakthrough in deliverable capacity and structural flexibility. In this work, the printed electrode delivers a record-breaking electrical double layer (EDL) areal capacitance of 27.1 F cm⁻² under an extremely large loading density of 134 mg cm⁻². This translates to a deliverable record-high EDL energy density of 1.26 mWh cm⁻² for device performance, which even rivals the highest value reported from highly loaded pseudocapacitors. The bespoke devices are enabled by a strategically formulated 3D printable ink that initiates efficient autonomous room-temperature self-healing and strong interplay between constituting ink components. These contribute to interlayer coalescing for eliminated interlayer resistance for a solid electrochemical performance and printed electrodes of great mechanical compliance. By tapping into the huge potential of 3D printing, this work lays a solid foundation on which flexible devices with customized geometry, functionality, and outstanding performance for a broad range of applications can be readily realized.     

High Performance Core/Shell Ni/Ni(OH)2 Electrospun Nanofiber Anodes for Decoupled Water Splitting

Decoupled water splitting is a promising new path for renewable hydrogen production, offering many potential advantages such as stable operation under partial-load conditions, high-pressure hydrogen production, overall system robustness, and higher safety levels. Here, the performance of electrospun core/shell nickel/nickel hydroxide anodes is demonstrated in an electrochemical-thermally activated chemical decoupled water splitting process. The high surface area of the hierarchical porous electrode structure improves the utilization efficiency, charge capacity, and current density of the redox anode while maintaining high process efficiency. The anodes reach average current densities as high as 113 mA cm⁻² at a working potential of 1.48 V_RHE and 64 mA cm⁻² at 1.43 V_RHE, with a Faradaic efficiency of nearly 100% and no H₂/O₂ intermixing in a membrane-free cell.     

Multicomponent Hierarchical Cu‐Doped NiCo‐LDH/CuO Double Arrays for Ultralong‐Life Hybrid Fiber Supercapacitor

Fiber supercapacitors have aroused great interest in the field of portable and wearable electronic devices. However, the restrained surface area of fibers and limited reaction kinetics of active materials are unfavorable for performance enhancement. Herein, an efficient multicomponent hierarchical structure is constructed by integrating the Cu‐doped cobalt copper carbonate hydroxide@nickel cobalt layered double hydroxide (CCCH@NiCo‐LDH) core–shell nanowire arrays (NWAs) on Cu fibers with highly conductive Au‐modified CuO nanosheets (CCCH@NiCo‐LDH NWAs@Au–CuO/Cu) via a novel in situ corrosion growth method. This multicomponent hierarchical structure contributes to a large accessible surface area, which results in sufficient permeation of the electrolyte. The Cu dopant could reduce the work function and facilitate fast charge transfer kinetics. Therefore, the effective ion diffusion and electron conduction will facilitate the electrochemical reaction kinetics of the electrode. Benefiting from this unique structure, the electrode delivers a high specific capacitance (1.97 F cm^?2/1237 F g^?1/193.3 mAh g^?1) and cycling stability (90.8% after 30 000 cycles), exhibiting superb performance compared with most oxide‐based fiber electrodes. Furthermore, the hybrid fiber supercapacitor of CCCH@NiCo‐LDH NWAs@Au–CuO/Cu//VN/carbon fibers is fabricated, providing a remarkable maximal energy density of 34.97 Wh kg^?1 and a power density of 13.86 kW kg^?1, exhibiting a great potential in high‐performance fiber‐shape energy‐related systems.     

Ultrahigh‐Strength Ultrahigh Molecular Weight Polyethylene (UHMWPE)‐Based Fiber Electrode for High Performance Flexible Supercapacitors

Flexible fiber‐based supercapacitor (FSC) with excellent electrochemical performance and high tensile strength and modulus is strongly desired for some special circumstances, such as load‐bearing, abrasion resistant, and anticutting fabrics. Here, a series of ultrahigh‐strength fiber electrodes are prepared for flexible FSCs based on ultrahigh molecular weight polyethylene fibers, on which the polydopamine, Ag, and poly (3,4‐ethylene dioxythiophene): poly(styrenesulfonate) are deposited in sequence. The modified fiber‐based electrode exhibits superhigh strength up to 3.72 GPa, which is the highest among fiber‐based electrodes reported to date. In addition, FSCs fabricated with the optimized fiber electrode shows a specific areal capacity as high as 563 mF cm^?2 at 0.17 mA cm^?2, which corresponds to a high areal energy density of ≈50.1 µWh cm^?2 at a power density of ≈124 µW cm^?2. The specific areal capacity only decrease 8% after 1000 times bending test, indicating the outstanding bending performance of this composite fiber electrode. Furthermore, several FSCs can be connected in series or in parallel to get higher working voltage or higher capacity respectively, which demonstrates its potential for broad applications in flexible devices.     

A Kinetic Control Strategy for One-Pot Synthesis of Efficient Bimetallic Metal-Organic Framework/Layered Double Hydroxide Heterojunction Oxygen Evolution Electrocatalysts

Heterojunction materials are promising candidates for oxygen evolution reaction (OER) electrocatalysts to break the linear scaling relationship and lower the reaction barrier. However, the application of heterojunction materials is always hindered by the complicated multistep synthetic procedures which bring cost, complexity, and reproducibility issues. Herein, a strategy of kinetic controlled synthesis is developed to achieve the one-pot formation of bimetallic metal-organic framework (MOF)/layered double hydroxide (LDH) heterojunction electrodes as highly efficient OER electrocatalysts. The heterojunction electrodes present hierarchical structures with highly porous NiFe-LDH nanosheet networks vertically grown on the surface of NiFe-MOF-74 microprisms, promoting fast mass transport and high exposure of active sites. The strong interactions at the MOF/LDH heterojunction interfaces contribute to the outstanding OER activity surpassing the state-of-art RuO₂ OER catalysts. The MOF/LDH heterojunction electrode exhibits an ultralow overpotential of only 159.7 mV to reach the current density of 10 mA cm⁻², and yields large current densities at small overpotential (100 mA cm⁻² at 230.2 mV and 1000 mA cm⁻² at 284.3 mV) with long-term durability. This study presents an innovative approach to construct heterojunction materials with simple one-step synthesis, offering a promising pathway for high-efficiency electrocatalyst development.