Triphasic Ni2P-Ni12P5-Ru with Amorphous Interface Engineering Promoted by Co Nano-Surface for Efficient Water Splitting

This research designs a triphasic Ni2P-Ni12P5-Ru heterostructure with amorphous interface engineering strongly coupled by a cobalt nano-surface (Co@NimPn-Ru) to form a hierarchical 3D interconnected architecture. The Co@NimPn-Ru material promotes unique reactivities toward hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media. The material delivers an overpotential of 30 mV for HER at 10 mA cm-2 and 320 mV for OER at 50 mA cm-2 in freshwater. The electrolyzer cell derived from Co@NimPn-Ru(+,-) requires a small cell voltage of only 1.43 V in alkaline freshwater or 1.44 V in natural seawater to produce 10 mA cm-2 at a working temperature of 80 °C, along with high performance retention after 76 h. The solar energy-powered electrolyzer system also shows a prospective solar-to-hydrogen conversion efficiency and sufficient durability, confirming its good potential for economic and sustainable hydrogen production. The results are ascribed to the synergistic effects by an exclusive combination of multi-phasic crystalline Ni2P, Ni12P5, and Ru clusters in presence of amorphous phosphate interface attached onto cobalt nano-surface, thereby producing rich exposed active sites with optimized free energy and multi open channels for rapid charge transfer and ion diffusion to promote the reaction kinetics.

Metal-Organic Framework-Based Materials for Advanced Sodium Storage: Development and Anticipation

As a pioneering battery technology, even though sodium-ion batteries (SIBs) are safe, non-flammable, and capable of exhibiting better temperature endurance performance than lithium-ion batteries (LIBs), because of lower energy density and larger ionic size, they are not amicable for large-scale applications. Generally, the electrochemical storage performance of a secondary battery can be improved by monitoring the composition and morphology of electrode materials. Because more is the intricacy of a nanostructured composite electrode material, more electrochemical storage applications would be expected. Despite the conventional methods suitable for practical production, the synthesis of metal-organic frameworks (MOFs) would offer enormous opportunities for next-generation battery applications by delicately systematizing the structure and composition at the molecular level to store sodium ions with larger sizes compared with lithium ions. Here, the review comprehensively discusses the progress of nanostructured MOFs and their derivatives applied as negative and positive electrode materials for effective sodium storage in SIBs. The commercialization goal has prompted the development of MOFs and their derivatives as electrode materials, before which the synthesis and mechanism for MOF-based SIB electrodes with improved sodium storage performance are systematically discussed. Finally, the existing challenges, possible perspectives, and future opportunities will be anticipated.

Precise design and in situ synthesis of hollow Co9S8@CoNi-LDH heterostructure for high-performance supercapacitors

Layered double hydroxides (LDHs) and metal sulfides (MSs) have been widely used as promising electrode materials for supercapacitors, and the rational architectural design of MS/LDH heterogeneous structures is critical to optimize large energy storage. Herein, a precisely designed hollow Co9S8 nanotubes@CoNi-LDH nanosheet heterostructure on Ni foam, facilely prepared by an ingenious in situ strategy in this Co9S8 nanoarray was first used as the self-sacrificing template and metal source to in situ synthesize Co-ZIF-67 polyhedron to form the Co9S8@ZIF-67 heterostructure, and then Co9S8@ZIF-67 was in situ etched successfully using Ni2+ ions to form the final Co9S8@CoNi-LDH/NF core-shell nanoarray. This in situ synthetic strategy to fabricate the heterostructure is conducive to boosting the structural stability, modifying the electric structure and regulating the interfacial charge transfer. Due to the synergistic effect and tight heterogeneous interface, Co9S8@CoNi-LDH/NF displayed an outstanding capacitance of 9.65 F cm-2 at a current density of 2 mA cm-2 and excellent capacitance retention rate of 91.7% after 5000 cycles. In addition, the ASC device assembled with AC has an extremely high energy density of 1.0 mW h cm-2 at 2 mA cm-2 and maintains 96.9% capacitance retention after 5000 cycles. This work provides a skillful strategy for the precise design and in situ synthesis of MS/LDH heterostructures with fascinating features for electrochemical energy storage applications.

Sodium titanium phosphate nanocube decorated on tablet-like carbon for robust sodium storage performance at low temperature

Sodium-ion batteries, featuring resource abundance and similar working mechanisms to lithium-ion batteries, have gained extensive interest in both scientific exploration and industrial applications. However, the extremely sluggish reaction kinetics of charge carrier (Na+) at subzero temperatures significantly reduces their specific capacities and cycling life. Herein, this study presents a novel hybrid structure with sodium titanium phosphate (NaTi2(PO4)3, NTP) nanocube in-situ decorated on tablet-like carbon (NTP/C), which manifests superior sodium storage performances at low temperatures. At even -25 °C, a stable cycling with a specific capacity of 94.3 mAh/g can still be maintained after 200 cycles at 0.5 A/g, delivering a high capacity retention of 91.5 % compared with that at room temperature, along with an excellent rate capability. Generally, the superionic conductor structure, flat voltage plateaus, as well as the conductive carbonaceous framework can efficiently facilitate the charge transfer, accelerate the diffusion of Na+, and decrease the electrochemical polarization. Moreover, further investigations on diffusion kinetics, solid electrolyte interface layer, and the interaction between NTP and carbonaceous skeleton reveal its high Na+ diffusion coefficient, robust solid electrolyte interface, and strong electronic interaction, thus contributing to the superior capacity retentions at subzero temperatures.

Nitrogen-Doped Hollow Carbon Spheres Based on Schiff Base Reaction as an Anode Material for High-Performance Lithium and Sodium Ion Batteries

Nitrogen-doped carbon has great potential in lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs), considering N-doping can not only improve the surface wettability of carbon materials, but also accelerate charge transfer by generating additional defects. However, designing carbon materials with a high nitrogen content and uniform distribution using conventional doping methods remains a challenge. In this study, a hollow carbon sphere with an ultrahigh nitrogen content of 9.58 wt % was successfully fabricated by rationally designing Schiff base chemistry (PTA-NHCS-700). Stable hierarchical pore structures, moderate defects, and large specific surface areas were formed during the carbonization process. Excellent electrochemical performance was observed in LIBs (204.2 mAh g^-1 after 7000 cycles at 5 A g^-1 ) and SIBs (154.2 mAh g^-1 after 10000 cycles at 5 A g^-1 ). This study not only promotes the development of efficient carbon anode materials for LIBs and SIBs, but also provides a novel idea for the doping of heteroatoms with special chemical structures.

Improved electrode kinetics of a modified Na3V2(PO4)3 cathode through Zr substitution and nitrogen-doped carbon coating towards robust electrochemical performance at low temperature

The substitution of V with Zr in a NASICON structure and an NC coating endow 0.1Zr-NVP/NC with excellent electrochemical performance at low temperature.

Rational design of walnut-like ZnO/Co3O4 porous nanospheres with substantially enhanced lithium storage performance

Rational fabrication and smart design of multi-component anode materials to achieve desirable reversible capacities and exceptional cyclability are significant for lithium-ion batteries (LIBs). Herein, walnut-like ZnO/Co₃O₄ porous nanospheres were prepared by a facile solvothermal method, which were then applied as a mechanically stable anode material for LIBs. The rationally designed hybridized electrode brings favorable structural features, particularly ZnO/Co₃O₄ porous nanospheres with abundant vacant space and enhanced surface area, enhancing lithium/electron transport and relieving volumetric stresses during the cycling process. Moreover, several in situ hybridized anode materials with electrochemical cooperation further overcome the challenge of capacity decay and conductivity deficiency. The as-obtained ZnO/Co₃O₄ delivered a much better lithium storage performance compared with ZnO, Co₃O₄, and their physical mix. We believe that the novel design criteria will bring opportunities in exploration and promote the practical application of transition metal oxides.

Boosting the lithium storage performance by synergistically coupling ultrafine heazlewoodite nanoparticle with N, S co-doped carbon

Transition metal sulfides, as an important class of inorganics, have been shown to be potential high-performance electrode candidates for lithium-ion batteries (LIBs) in account of their high activity towards lithium storage, rich types and diverse structures. Despite these advantages, structure degradation related with volume variations upon electrochemical cycling restricts their further development. In this present study, a unique hybrid structure with ultrafine heazlewoodite nanoparticles (less than 10 nm) in-situ confined in nitrogen and sulfur dual-doped carbon (Ni₃S₂@NSC) was constructed though a facile pyrolysis process, using a novel Ni-based metal chelates as the precursor. Specifically, enhanced structure stability, shortened Li⁺ migration distance and improved reaction dynamics can be obtained simultaneously in the designed structure, thereby allowing to realize high lithium storage performance. Consequently, a remarkable reversible capacity of 955.9 mAh g^-1 (0.1 A g^-1 after 100 cycles) and a superior long-term cycling stability up to 1200 cycles (863.7 mAh g^-1 at 1.0 A g^-1) are obtained. Importantly, the fundamental understanding on the improved lithium storage of Ni₃S₂@NSC based on the synergistic coupling reveals that the combination between Ni₃S₂ and NSC at the hetero-interface through the doped sulfur atoms contributes to the integrity of electrode and improved kinetics.

Well-defined hollow tube@sheets NiCo2S4 core-shell nanoarrays for ultrahigh capacitance supercapacitor

Reasonable design of electrodes with well-defined nanostructure is the central aspect in the practical application of high-performance supercapacitors. Herein, hollow tube@sheets NiCo₂S₄ core-shell nanoarrays are rationally constructed to the free-standing electrode by in situ growing ZIF-67 on Co-precursor nanorods array and sequentially performing anion-exchange (S^2-) and cation-exchange (Ni²⁺). The well-defined nanostructures can shorten the ion transport path in the charging-discharging process, increase the specific surface area and electrochemical active cites, which help in improving electrochemical performance. Therefore, the unique tube@sheets NiCo₂S₄ core-shell nanoarrays exhibit intriguing electrochemical performance and show excellent areal capacitance of 11.3 F cm^-2 (3227.94 F g^-1) at a current density of 2 mA cm^-2 (2 A g^-1). The assembled asymmetric supercapacitor device delivers a high energy density of 0.42 mW h cm^-2 at a power density of 2.1 mW cm^-2 and displays outstanding cyclic stability (90.2% retention after 5000 cycles). Consequently, the well-defined nanostructure engineering strategy is beneficial for designing active electrode materials for efficient energy storage devices.

Facile in-situ synthesis of heazlewoodite on nitrogen-doped reduced graphene oxide for enhanced sodium storage

Nickel sulfide based anode materials, featuring rich types, high specific capacities and favorable conversion kinetics, have been proved to be promisingly applied in high-performance sodium-ion batteries (SIBs). Unfortunately, the poor electronic/ionic conductivity, together with the structure change induced degraded capacity upon cycling, restricts their further development. In this work, heazlewoodite nanoparticles decorated on nitrogen doped reduced graphene oxide (Ni₃S₂/NrGO) were fabricated via a facile combined approach with freeze-drying and subsequent in-situ sulfidation. In the obtained hybrid structure, the synergistic effect between Ni₃S₂ and NrGO endows the composite with highly conductive pathways, thus accelerating the charge transfer. Benefitting from the buffering matrix offered by NrGO as well as the tight combination between Ni₃S₂ and NrGO, this novel Ni₃S₂/NrGO demonstrates satisfying sodium storage performance, with a stable reversible capacity of 299.2 mAh g^-1 up to 100 cycles (0.1 A g^-1) and a high initial Coulombic efficiency of 76.8%. Importantly, the rational structure design and synthesis method, as well as the insights on the improved electrochemical performance reported in this work, should be helpful for the development of new-type host materials with high performance for SIBs.

A novel strategy for the synthesis of hard carbon spheres encapsulated with graphene networks as a low-cost and large-scalable anode material for fast sodium storage with an ultralong cycle life

We designed a cost-effective and novel strategy for the construction of hard carbon spheres enveloped with graphene networks as a high performance anode material for sodium-ion batteries.

Enhanced Li-Storage of Ni3 S2 Nanowire Arrays with N-Doped Carbon Coating Synthesized by One-Step CVD Process and Investigated Via Ex Situ TEM

In this work, a facile strategy for the construction of single crystalline Ni₃ S₂ nanowires coated with N-doped carbon shell (NC) forming Ni₃ S₂ @NC core/shell arrays by one-step chemical vapor deposition process is reported. In addition to the good electronic conductivity from the NC shell, the nanowire structure also ensures the accommodation of large volume expansion during cycling, leading to pre-eminent high-rate capacities (470 mAh g^-1 at 0.05 A g^-1 and 385 mAh g^-1 at 2 A g^-1 ) and outstanding cycling stability with a capacity retention of 91% after 100 cycles at 1 A g^-1 . Furthermore, ex situ transmission electron microscopy combined with X-ray diffraction and Raman spectra are used to investigate the reaction mechanism of Ni₃ S₂ @NC during the charge/discharge process. The product after delithiation consists of Ni₃ S₂ and sulfur, suggesting that the capacity of the electrode comes from the conversion reaction of both Ni₃ S₂ and sulfur with Li₂ S.