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We introduce N-P pair into the carbon matrix to construct N,P-C electrocatalyst by a facile pyrolysis strategy. Benefiting from the moderate adsorption energy of *OH on the active sites (C adjacent to P atom in N-P), the achieved N,P-C-1000 displays outstanding alkaline ORR performance and high power density primary liquid and solid ZABs. [Display omitted] • N-P pair was introduced into the carbon matrix to construct N,P-C electrocatalyst by a facile pyrolysis strategy. • The catalyst exhibits superior ORR activity with a E 1/2 of 0.83 V, comparable to that of commercial 20 wt% Pt/C. • Its C-2p orbit has higher interaction strength with the intermediates, thus reducing the overall reaction energy barrier. • High power density primary liquid and solid ZABs are achieved using N,P-C-1000 as cathodic catalysts. Developing sustainable metal-free carbon-based electrocatalysts is essential for the deployment of metal-air batteries such as zinc-air batteries (ZABs), among which doping of heteroatoms has attracted tremendous interest over the past decade. However, the effect of the heteroatom covalent bonds in carbon matrix on catalysis was neglected in most studies. Here, an efficient metal-free oxygen reduction reaction (ORR) catalyst is demonstrated by the N-P bonds anchored carbon (termed N,P-C-1000). The N,P-C-1000 catalyst exhibits superior specific surface area of 1362 m2 g−1 and ORR activity with a half-wave potential of 0.83 V, close to that of 20 wt% Pt/C. Theoretical computations reveal that the p-band center for C-2p orbit in N,P-C-1000 has higher interaction strength with the intermediates, thus reducing the overall reaction energy barrier. The N,P-C-1000 assembled primary ZAB can attain a large peak power density of 121.9 mW cm−2 and a steady discharge platform of ∼1.20 V throughout 120 h. Besides, when served as the cathodic catalyst in a solid-state ZAB, the battery shows flexibility, conspicuous open circuit potential (1.423 V), and high peak power density (85.8 mW cm−2). Our findings offer a strategy to tune the intrinsic structure of carbon-based catalysts for improved electrocatalytic performance and shed light on future catalysts design for energy storage technologies beyond batteries. [ABSTRACT FROM AUTHOR]

Two-dimensional/three-dimensional hierarchical self-supporting potassium ammonium vanadate@MXene hybrid films exhibit excellent electrochemical performance. [Display omitted] Currently, aqueous zinc ion batteries (AZIBs) have grown to be a good choice for large-scale energy storage systems due to their high theoretical specific capacity, low redox potential, low cost, and non-toxicity of the aqueous electrolyte. However, it is still challenging to obtain high specific capacity and stability suitable cathodes. Herein, hierarchical self-supporting potassium ammonium vanadate@MXene (KNVO@MXene) hybrid films were prepared by vacuum filtration method. Due to the three-dimensional nanoflower structure of KNVO with dual ions intercalation, high conductivity of two-dimensional Ti 3 C 2 T x MXene, and the hierarchical self-supporting structure, the AZIB based on the KNVO@MXene hybrid film cathode possessed superior specific capacity (481 mAh/g at 0.3 A/g) and cycling stability (retaining 125 mAh/g after 1000 cycles at a high current density of 10 A/g). In addition, the storage mechanism was revealed by various ex-situ characterizations. Hence, a new viewpoint for the preparation of AZIB self-supporting cathode materials is presented. [ABSTRACT FROM AUTHOR]

The porous bismuthene/MXene heterostructure obtained using a simple self-assembly method exhibits high desalination capacity, fast desalination rate, and good cycling performance. [Display omitted] Capacitive deionization (CDI) is perceived as a promising technology for freshwater production owing to its environmentally friendly nature and low energy consumption. To date, the development of high-performance electrode materials represents the foremost challenge for CDI technology. In this work, the porous bismuthene/MXene (P-Bi-ene/MXene) heterostructure was synthesized using a simple interfacial self-assembly method with two-dimensional (2D) bismuthene and Ti 3 C 2 T x MXene. Within the P-Bi-ene/MXene heterostructure, the porous structure can increase the active site and facilitate ion transport. Simultaneously, MXene effectively enhances the conductivity of the heterostructure, resulting in accelerating electron transport. Due to these attributes, the P-Bi-ene/MXene heterostructure demonstrates high desalination capacity (90.0 mg/g), fast desalination rate, and good cycling performance. The simple self-assembly strategy between 2D/2D materials described herein may offer inspirations for the synthesis of innovative electrode materials with high performance. [ABSTRACT FROM AUTHOR]

Due to the presence of the hierarchical freestanding structure, outstanding MXene conductive networks and abundant oxygen vacancy, the d-NVO@MXene hybrid film exhibits excellent electrochemical properties. [Display omitted] Aqueous zinc ion batteries (AZIBs) have gained extensive attention due to the numerous advantages of zinc, such as low redox potential, high abundance, low cost as well as high theoretical specific capacity. However, the development of AZIBs is still hampered due to the lack of suitable cathodes. In this work, the freestanding defective ammonium vanadate@MXene (d-NVO@MXene) hybrid film was synthesized by simple vacuum filtration strategy. Due to the presence of the hierarchical freestanding structure, outstanding MXene conductive networks and abundant oxygen vacancy (in the d-NVO nanoribbons), the d-NVO@MXene hybrid film can not only expose more active sites but also possess outstanding conductivity and kinetics of charge transfer/ion diffusion. When the d-NVO@MXene hybrid film was directly used as the cathode, it displayed a high specific capacity of 498 mAh/g at 0.5 A/g and superior cycling stability performance with near 100 % coulomb efficiency. Furthermore, the corresponding storage mechanism was elucidated by ex situ various characterizations. This work provides new ideas for the development of freestanding vanadium-based cathode materials for AZIBs. [ABSTRACT FROM AUTHOR]

Strong Interface Coupling Boosting Hierarchical Bismuth Embedded Carbon Hybrid for High-Performance Capacitive Deionization. [Display omitted] Capacitive deionization (CDI) is regarded as a promising desalination technology owing to its low cost and environmental friendliness. However, the lack of high-performance electrode materials remains a challenge in CDI. Herein, the hierarchical bismuth-embedded carbon (Bi@C) hybrid with strong interface coupling was prepared through facile solvothermal and annealing strategy. The hierarchical structure with strong interface coupling between the bismuth and carbon matrix afforded abundant active sites for chloridion (Cl−) capture, improved electrons/ions transfer and the stability of the Bi@C hybrid. As a result of these advantages, the Bi@C hybrid showed a high salt adsorption capacity (75.3 mg/g under 1.2 V), salt adsorption rate and good stability, making it a promising electrode material for CDI. Furthermore, the desalination mechanism of the Bi@C hybrid was elucidated through various characterizations. Therefore, this work provides valuable insights for the design of high-performance bismuth-based electrode materials for CDI. [ABSTRACT FROM AUTHOR]

Hierarchical Amorphous Vanadium Oxide and Carbon Nanotubes Microspheres with Strong Interface Interaction for Superior Performance Aqueous Zinc-ion Batteries. [Display omitted] Aqueous zinc-ion batteries have attracted more and more attention due to their safety, environmental benignity and high theoretical capacity. However, the lack of appropriate cathode materials with high capacity and long cycle life have become an obstacle to the development of aqueous zinc-ion batteries. Herein, the hierarchical amorphous vanadium oxide and carbon nanotubes (a-V 2 O 5 @CNTs) microspheres with strong interface interaction were successfully prepared by combing facile spray drying technique with annealing treatment. Benefiting from the a-V 2 O 5 amorphous characters, CNTs framework high conductivity and hierarchical microspheres with strong interface interaction, the a-V 2 O 5 @CNTs exhibited abundant active sites, fast reaction kinetics as well as eminent structure stability. As a promising electrode material, the a-V 2 O 5 @CNTs displayed high specific capacity (480 mAh g−1 at 0.5 A g−1), good rate capability and long-term stability under high current density (158 mAh g−1 at 30 A g−1 over 1000 cycles). Meanwhile, the corresponding mechanism was further illustrated through different characterizations. Furthermore, the as-assembled flexible pouch battery based on the a-V 2 O 5 @CNTs delivered outstanding flexibility and feasibility. Hence, this work provides a new idea for developing high performance cathode materials of aqueous zinc-ion batteries. [ABSTRACT FROM AUTHOR]

d-NHVO nanoribbons with abundant oxygen vacancies have excellent electrochemical performance. [Display omitted] Vanadium-based oxides have gained widespread attention as promising cathode materials for aqueous zinc-ion batteries (AZIBs) due to their abundant valences, high theoretical capacity and low cost. However, the intrinsic sluggish kinetics and unsatisfactory conductivity have severely hampered their further development. Herein, a facile and effective defect engineering strategy was developed at room temperature to prepare the defective (NH 4) 2 V 10 O 25 ·8H 2 O (d-NHVO) nanoribbon with plenty of oxygen vacancies. Owing to the introduction of oxygen vacancies, the d-NHVO nanoribbon possessed more active sites, excellent electronic conductivity and fast ion diffusion kinetics. Benefiting from these advantages, the d-NHVO nanoribbon as an aqueous zinc-ion battery cathode material exhibited superior specific capacity (512 mAh g−1 at 0.3 A g−1), excellent rate capability and long-term cycle performance. Simultaneously, the storage mechanism of the d-NHVO nanoribbon was clarified via comprehensive characterizations. Furthermore, the pouch battery based on the d-NHVO nanoribbon was fabricated and presented eminent flexibility and feasibility. This work provides a novel thought for simple and efficient development of high- performance vanadium-based oxides cathode materials for AZIBs. [ABSTRACT FROM AUTHOR]

Few-layered Ti 3 C 2 T x MXene with abundant −O terminations and low oxidation degree is synthesized through a green etching method at near-ambient temperature. [Display omitted] MXene has drawn considerable attention in energy storage due to particular physicochemical properties. At present, among most near-ambient temperature preparation methods, water is usually served as the main solvent. However, MXene is usually subjected to fast structural degradation on account of water molecules attacking in aqueous solution. Herein, we report a novel water-free etching strategy for synthesizing few-layered Ti 3 C 2 T x MXenes in deep eutectic solvents at near-ambient temperature. Benefitting from the absence of water and macromolecular structure of deep eutectic solvents, the as-synthesized few-layered Ti 3 C 2 T x (DES-Ti 3 C 2 T x) MXene presents abundant −O terminations and low oxidation degree. As a consequence, the DES-Ti 3 C 2 T x MXene displays excellent specific capacitance of 320 F/g at 2 mV/s. Impressively, the DES-Ti 3 C 2 T x MXene exhibits splendid long-term stability that 97% specific capacitance retention can be acquired over 50 000 cycles at high current density of 50 A/g. Therefore, this study offers a new thought for preparing high performance MXene-based materials by water-free etching method. [ABSTRACT FROM AUTHOR]

[Display omitted] Aqueous zinc-ions batteries with low cost, reliable safety, high theoretical specific capacity and eco-friendliness have captured conspicuous attention in large-scale energy storage. However, the developed cathodes often suffer from low electrical conductivity and sluggish Zn2+ diffusion kinetics, which severely hampers the development of aqueous zinc-ions batteries. Herein, we successfully prepare Mg/PANI/V 2 O 5 •nH 2 O (MPVO) nanosheets through conducting polymers (polyaniline) and metal ions (Mg2+) co-intercalated strategy and systematically explore its electrochemical performance as cathode materials for aqueous zinc-ion batteries. Benefitting from the synergistic effect of polyaniline and Mg2+ co-intercalated, the MPVO exhibits larger interlayer spacing and higher electrical conductivity than the single guest intercalation, which significantly enhances the electrochemical kinetics. As a consequence, the MPVO cathodes deliver superior specific capacity, rate capability and long-term cycling performance. Moreover, multiple characterizations and theoretical calculations are executed to expound the relevant mechanism. Therefore, this work provides a novel thought for the design of high-performance cathode materials for aqueous ZIBs. [ABSTRACT FROM AUTHOR]

Hierarchical accordion-like manganese oxide@carbon hybrid with strong interaction heterointerface exhibits outstanding electrochemical performance. [Display omitted] Aqueous zinc ion batteries have attracted extensive concern as a promising candidate for large-scale energy storage because of their high theoretical specific capacity, low cost and inherent safety. However, the lacking of applicable cathode materials with outstanding electrochemical performance have severely hindered the further development of aqueous zinc ion batteries. Herein, we report a hierarchical accordion-like manganese oxide@carbon (MnO@C) hybrid with strong interaction heterointerface and comprehensively inquire into its electrochemical performance as cathode materials for aqueous zinc ion batteries. The unique hierarchical accordion-like layered structure coupling with strong interaction heterointerface between small MnO and carbon matrix efficaciously improve the ion/electron transfer process and enhance structure stability of the MnO@C hybrid. Benefitting from these unique advantages, the MnO@C hybrid bestows excellent specific capacity of 456 mAh g−1 at 50 mA g−1. Impressively, the MnO@C hybrid presents distinguished long-term cycling stability with fairly low decay rates of only 0.0079 % per cycle even over 2000 cycles at 2000 mA g−1. Moreover, comprehensive characterizations are executed to elucidate the mechanism involved. Therefore, this work affords a new idea for developing outstanding performance manganese-based cathode materials for aqueous zinc ion batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] Capacitive deionization has attracted wide concern on account of its high energy efficiency, low manufacturing cost and environmental friendliness. Nevertheless, the development of capacitive deionization is still impeded because of the scarcity of suitable electrode materials with superior performance. Herein, we successfully prepared the two-dimensional (2D) titanium carbide (Ti 3 C 2 T x) MXene/ reduced graphene oxide (rGO) superlattice heterostructure by a facile electrostatic self-assembly strategy and systematically investigated its performance as capacitive deionized electrode materials. The unique 2D/2D superlattice heterostructure not only effectively alleviates the self-stacking problem of Ti 3 C 2 T x MXene nanosheets, but also endows the heterostructure with superior conductivity and fast ion diffusion rate. As a result, the MXene/rGO superlattice heterostructure exhibits an outstanding salt (Na+) adsorption capacity (48 mg g −1) at 1.2 V significantly superior to pristine Ti 3 C 2 T x MXene nanosheets, along with outstanding long-term cycling performance. Furthermore, the mechanism involved was elucidated through comprehensive characterizations. Therefore, this study offers a new pathway for designing high-performance electrode materials for capacitive deionization. [ABSTRACT FROM AUTHOR]

Amorphous V 2 O 5 @C hybrid formed by electrochemical oxidation strategy exhibits outstanding electrochemical performance. [Display omitted] Aqueous zinc-ion batteries receive more and more attentions on account of their low cost, high theoretical density and inherent safety. Nevertheless, the lack of suitable cathode materials with excellent performance still severely impedes the development of aqueous zinc-ion batteries. Herein, an in-situ electrochemical induction strategy is developed to prepare hollow nanotube-like amorphous vanadium oxide and carbon (a-V 2 O 5 @C) hybrid and its electrochemical performance is investigated comprehensively as cathode materials for aqueous zinc-ion batteries. Benefitting from the unique amorphous structure of V 2 O 5 and intimate contact between amorphous V 2 O 5 and carbon, the a-V 2 O 5 @C hybrid possess the abundant ion storage sites, isotropic ion diffusion routes and excellent conductivity. As a result, the a-V 2 O 5 @C hybrid cathode shows outstanding specific capacity of 448 mAh g−1 at 0.15 A g−1. Impressively, the a-V 2 O 5 @C hybrid cathode exhibits superior cycling stability, even when cycling at high current density of 10 A g−1, that the 96.5% specific capacity retention can be gained over 1500 cycles, corresponding to an average specific capacity loss of only 0.0023% per cycle. Furthermore, the mechanism involved is illustrated by systematical characterizations. Therefore, this work affords a new way for developing high-performance cathode materials for aqueous zinc-ion batteries. [ABSTRACT FROM AUTHOR]

MXene containing iodine terminations exhibits outstanding supercapacitor performance due to the redox reaction of iodine terminations. [Display omitted] MXene has attracted a wide spread attention as promising supercapacitor electrode materials owing to excellent electronic conductivity and reversible surface redox capability. In fact, the supercapacitor performance strongly relies on surface terminations of MXene. However, regulating the types of surface terminations for enhancing the electrochemical performance of MXene is still one of major challenge. Herein, we successfully prepared a MXene containing iodine terminations (I-Ti 3 C 2 MXene) by facile Lewis-acidic-melt etching method and comprehensively investigated its supercapacitor performance. Benefiting from the presence of iodine terminations, the I-Ti 3 C 2 MXene with pseudocapacitor property exhibits significantly higher specific capacitance than that of hydrofluoric acid etching MXene (HF-Ti 3 C 2 T x MXene). Impressively, the I-Ti 3 C 2 MXene shows extraordinary long-term cyclic performance, even when cycled at high current density of 50 A/g, that the specific capacitance retention of 91% can be obtained over 100,000 cycles, corresponding to an average specific capacitance loss of only 0.00009% per cycle. Furthermore, the mechanisms involved were clarfied by systematical characterizations. This work will provide new insights for enhancing the supercapacitor performance of MXene-based materials by surface chemistry modification. [ABSTRACT FROM AUTHOR]