Hierarchical Hollow Research Articles

Fabrication of ternary NiCoMoOx with yolk-shell hollow structure as a positive electrode material for high-performance electrochemical capacitor applications.

Although the fabrication of hollow nanostructures from single and binary transition metal oxides has been accomplished effectively, there still exists a significant challenge in creating advanced hollow morphologies comprising mixed transition metal oxides such as ternary and quaternary compositions. In this context, we have adopted an alternative approach by employing a straightforward self-templating method to synthesize ternary metal molybdate nanomaterials. These materials possess the chemical composition of NiCoMoOx and exhibit a unique nanoporous yolk-shell hollow structure. Commencing with mixed metal-glycerate solid spheres, we have successfully guided the formation of this chemical composition and distinctive yolk-shell hollow sphere architecture through meticulous thermal treatment control. The consistency of our results is confirmed through SEM images. Thanks to their robust structural integrity, advanced internal morphology, and increased surface area, these hierarchical hollow spheres demonstrate remarkable electrochemical performance when utilized as advanced electrode materials for supercapacitors. When serving as electrode materials in supercapacitors, these nanoporous NiCoMoOx yolk-shell hollow spheres deliver a specific capacitance of 1125 F g-1 at a current density of 0.5 A g-1, maintaining an impressive cycling stability of 91.48% even after 5000 cycles. In a hybrid device configuration wherein activated carbon (AC) functions as the negative electrode and NiCoMoOx yolk-shell hollow spheres serve as the positive electrode, exceptional performance is observed. This configuration achieves a substantial specific energy density of 44.67 W h kg-1, alongside a maximum power density of 8000 W kg-1, and exceptional cycling stability of 93.03% even after 5000 cycles.

Preparation of hierarchical hollow structured Ni/C microspheres with strong and broadband microwave absorption properties in Ku band

As microwave absorbers, hierarchical hollow structured magnetic metal/carbon composites exhibit good microwave absorption properties in the Ku band (12–18 GHz), while their effective absorption bandwidths still cannot cover the whole Ku band. In this paper, we prepared hierarchical hollow structured Ni/C microspheres by a two-step strategy of hydrothermal synthesis and vacuum heat treatment. The effects of different vacuum heat treatment temperatures on the microwave absorption properties of the Ni/C microspheres were investigated. The Ni/C-700 sample exhibited broader microwave absorption bandwidth than homologous composites. The minimum reflection loss (RL) of −48.74 dB was obtained at 1.60 GHz with a matching thickness of 2.7 mm. As the matching thickness decreased to 2.5 mm, the effective absorption band (RL < −10 dB) reached 7.35 GHz (10.65–18 GHz), which covered the entire Ku band. The excellent microwave absorption properties could be attributed to the optimization of high-frequency impedance matching by the synergy of dual polarization relaxation and exchange resonance. These results suggested that such Ni/C microspheres can be used for microwave absorption at the Ku band.

Amorphous nanosheets constructed nickel cobalt hydroxysulfide hollow spheres as cathode materials for hybrid supercapacitors

Tailoring architecture and multi-composition of electrode materials via a facile and cost-effective strategy are highly favorable to optimize physiochemical properties for developing energy storage devices. Herein, hierarchical nickel cobalt hydroxysulfide hollow spheres decorated with amorphous nanosheets and dual-ligands (denoted as NiCo-DHS) are synthesized through hydrolysis of self-templating metal alkoxides, followed by room-temperature anionic exchange process. The resultant dual-ligands hydroxysulfide possesses weak metallicity, reduced band gap and enhanced conductivity owing to the electronic regulation of the formed M−OH/S bonds. Additionally, the nanosheet-constructed amorphous structure contributes to accelerating ions diffusion and enlarging specific surface area, further exposing more active sites to enrich redox reactions. Benefiting from the compositional and structural superiorities, the optimized NiCo-DHS-12 electrode presents desirable electrochemical performance, including high specific capacity of 973.6 C g−1 (1 A g−1) and stable durability over 8000 cycles with a small capacity loss of 7.4 % at 10 A g−1. Moreover, the hybrid device assembled with NiCo-DHS-12 and porous activated carbon delivers an energy density of 65.91 Wh kg−1 at a power density of 0.89 kW kg−1 and considerable cycling stability. These encouraging results demonstrate a simple and reliable approach in constructing high-performance electrode materials for advanced supercapacitors in potential.

ZIF-8 derived hierarchical ZnO@ZnFe2O4 hollow polyhedrons anchored with CdS for efficient photocatalytic CO2 reduction

Converting CO2 into chemical energy by efficient photocatalysts is a promising strategy to meet the increasing energy demand and decrease greenhouse gases. In this work, hierarchical ZnO@ZnFe2O4 hollow polyhedrons decorated with CdS quantum dots were designed and prepared to improve photocatalytic CO2 reduction performance. The facile strategy for the synthesis of hierarchical ZnO@ZnFe2O4 hollow polyhedrons involves the synthesis of ZnO hollow polyhedrons derived from the thermal decomposition of 2-Methylimidazole zinc salt (ZIF-8) precursor and in situ generating Zn-Fe layer double hydroxide nanosheets on the surface of ZnO hollow polyhedrons and subsequent thermal treatment. More importantly, the in situ formation of ZnFe2O4 nanosheets can form strong interaction between ZnO hollow polyhedrons and ZnFe2O4 nanosheets. The hierarchical hollow polyhedral structure of the ZnO@ZnFe2O4 sample possesses more preferable active sites to promote CO2 adsorption and reduction process. The prepared hierarchical ZnO@ZnFe2O4 hollow polyhedron sample shows a significantly enhanced performance for photocatalytic CO2 reduction compared with single-component catalysts (ZnO, ZnFe2O4, and CdS) with a CO evolution rate of 95.84 μmol g−1h−1. The decoration of CdS quantum dots makes the ternary heterostructure hybrid form multichannel charge transfer path, which further accelerate charge separation and enhance electrons utilization, resulting in a significant improvement of photocatalytic activity. Noticeably, the CO evolution rate reaches 197.66 μmol g−1h−1, 3 and 2 times higher than that of the bare ZnO and binary ZnO@ZnFe2O4 hollow polyhedrons, respectively. This work gives a promising direction to prepare high-active photocatalysts for solar fuel production.

Regulating Morphological Features of Nickel Single‐Atom Catalysts for Selective and Enhanced Electroreduction of CO2

Single-atom catalysts (SACs) are of interest for chemical transformations of significant energy and environmental relevance because of the envisioned efficient use of active sites and the flexibility in tuning their coordination environment. Future advancement in this vein hinges upon the ability to further increase the number and accessibility of active sites in addition to fine-tuning their chemical environment. In this work, a Ni SAC is reported with a unique hierarchical hollow structure (Ni/HH) that allows increased accessibility of the active sites. The successful obtainment of such a uniquely structured catalystwasenabled by the judiciously chosen solvent mixtures for the preparation of the precursor whose hierarchical feature is maintained during the subsequent pyrolysis and etching of the pyrolysis product. Comparative catalytic and mechanistic studies with reference to three closely related but more compact Ni SACs established the superior performance of Ni/HH for selective electroreduction of CO2 to CO. Experimental analyses by in situ attenuated total reflection surface-enhanced infrared spectroscopy reveal that it is the facilitated formation of the *COOH intermediate in the rate-determining step that leads to the enhanced reaction kinetics and the overall catalytic performance.

Linking Enhanced Kinetics of Electrocatalytic Oxygen Reduction Reaction with Increased Utilization of Active Sites in a Hierarchical Single-Atom Catalyst.

Single-atom catalysts (SACs) are of tremendous current research due to maximized use of metal atoms and enhanced activity and selectivity for a great variety of chemical reactions. Hierarchically structured SACs have been explored to further increase the number and accessibility of active sites to realize the full potentials of SACs. However, though plausible-sounding, these supposed advantages of hierarchically structured SACs are largely untested. The assumed enhancing effects on the formation of intermediates on and the overall reaction kinetics remain largely unknown. Herein is reported a Fe-SAC with a hierarchical hollow structure (Fe/HH) that showed excellent activity in oxygen reduction reaction and proton exchange membrane fuel cell. Comparative experimental and computational studies with respect to Fe/SS-the counterpart of Fe/HH with a compact primary structure-reveal a significantly increased number of active sites and their utilization in Fe/HH as reflected by the facilitated formation of the rate-determining-step intermediate Fe-OOH*. This work thus establishes unambiguously the connection between the increased utilization of active sites and the enhanced kinetics of the electrocatalytic reduction of oxygen.

Porous NiS@Ni2P nanoframe as a multi-functional catalyst for enhanced oxygen evolution and urea oxidation reactions

During water electrolysis, multifunctional electrocatalysts with outstanding functionality and endurance must be thoughtfully constructed and designed. Below, we report a hollow NiS@Ni2P nanoframe heterostructure that works well as a substitute catalyst for the urea oxidation and general water splitting reactions. The hollow NiS@Ni2P nanoframe was synthesized by ion exchange, sulfurization and phosphating, which is favorable for achieving a heterostructure. The NiS@Ni2P catalyst exhibits excellent catalytic activity and strong long-term stability in 1.0 M KOH solutions for the hydrogen evolution reaction, which needs 121 mV to achieve 10 mA cm−2. And for the oxygen evolution reaction, the catalyst needs 311 mV to acquire 50 mA cm−2. These advantages come from the optimal electronic structural configuration, hierarchical hollow nanoframe structure, and large surface area. It could attain 10 mA cm−2 at 1.41 V when utilized as a urea oxidation reaction anode, which is lower than the oxygen evolution reaction. For total water splitting and urea oxidation process, NiS@Ni2P as a bifunctional catalyst holds tremendous promise due to its strong electrocatalytic activity, ease of manufacture, and low cost of raw ingredients.

Ni-Co-P hollow nanobricks enabled humidity sensor for respiratory analysis and human-machine interfacing

Metal phosphide has been widely exploited in the field of energy storage and catalysis instead of chemical sensors. In this work, Ni-Co-P hollow nanobricks (HNBs) was developed via template synthesis method followed by etching and phosphating treatments. The hierarchical morphology and composition of the Ni-Co-P HNBs were respectively characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), nitrogen sorption analysis and transmission electron microscopy (TEM). High sensitivity (~ 3.6 kΩ / % RH), low hysteresis (~ 3% RH) and good repeatability were achieved in a wide moisture range from 0% RH to 97.5% RH. By adjusting the ratio of Ni and Co, humidity sensing performance can be efficiently modulated. The optimal humidity sensing properties were attained at a ratio of Ni and Co of 1:5. Finally, the as-prepared sensor demonstrates great capability in respiratory analysis and noncontact human-machine interfacing. This work opens up a new paradigm for developing high-performance wearable sensing devices. • Metal phosphides Ni-Co-P are employed to fabricate humidity sensor. • The hierarchical hollow nanobricks endows a large surface area and abundant adsorption sites to interact with water molecules. • The optimal humidity sensing properties are attained at a ratio of Ni and Co of 1:5. • The sensor enables non-contact monitoring of breath and limb motions.

Superhydrophobic hierarchical hollow carbon microspheres for microwave-absorbing and self-cleaning two-in-one applications

Advanced microwave absorbing materials with excellent microwave absorption properties and other fascinatingly additional functions continue to be highly sought after, while their fabrication still remains a huge challenge. Herein, through a facile and low-cost approach, we prepare a novel N-doped carbon microsphere with hierarchically micro-nano surface, multiporous shell, and hollow cavity to serve as a high-performance microwave absorbing material integrated with an exceptional superhydrophobicity. Specifically, the microwave absorption of the N-doped hollow carbon microspheres (N-HCMs) presents lightweight (a filler loading of 15 wt%), ultrastrong (a reflection loss of −61.2 dB), thin (a matching thickness of 1.45 mm), and very wide (an effective absorption bandwidth of 6.8 GHz) features. In particular, the absolute values of their specific reflection loss are far beyond the previously reported state-of-the-art carbon-based microwave absorbers with similar structures. Fascinatingly, the superhydrophobicity of N-HCMs is excellent and can tolerate the diversely harsh water-containing environments, which endows the microwave absorbing coatings with universally waterproof capacity as well as attractive self-cleaning function. We believe that this work can actively inspire the research of developing next-generation advanced microwave absorbing materials and pave the way for their multifunctional applications.

Unlocking the Potential of Vanadium Oxide for Ultrafast and Stable Zn2+ Storage Through Optimized Stress Distribution: From Engineering Simulation to Elaborate Structure Design.

Compared with lithium-ion batteries (LIBs), aqueous zinc batteries (AZIBs) have received extensive attention due to their safety and cost advantages in recent years. The cathode determines the electrochemical performance of AZIBs to a large extent. Vanadium-based materials exhibit excellent capacity when used as AZIB cathodes. However, unexpected structural stress is inevitably induced during cycling and high current densities, which can gradually lead to structural deterioration and capacity decay. In fact, the stress/strain distribution in nanomaterials is crucial for electrochemical performance. In this work, the optimized stress distribution of the hierarchical hollow structure is verified by the finite element simulation of COMSOL software firstly. Guided by this model, a simple solvothermal method to synthesize hierarchical hollow vanadium oxide nanospheres (VO-NSs), consisting of ≈10nm ultrathin nanosheets and ≈500nm hollow inner cavities, is employed. And a highly disordered structure is introduced to the VO-NSs by in situ electrochemical oxidation, which can also weaken the structural stress during Zn2+ insertion and extraction. Benefiting from this unique structure, VO-NSs exhibit high-rate and stable Zn2+ storage capability. The strategy of engineering-driven material design provides new insights into the development of AZIB cathodes.

Fabricating 1D/2D Co3O4/ZnIn2S4 core–shell heterostructures with boosted charge transfer for photocatalytic hydrogen production

Multidimensional hierarchical hollow Co3O4/ZnIn2S4 tubular core–shell heterostructures were prepared by growing ultrathin two-dimensional ZnIn2S4 nanosheets on one-dimensional hollow Co3O4 nanotubes by a simple solvothermal method. The design of this multidimensional hollow core–shell heterostructure not only avoids the self-assembly aggregation of ZnIn2S4 nanosheets but also broadens their light-absorption range and improves the utilization of visible light. The internal electric field formed by the p–n heterojunction in the photocatalyst can promote the separation and migration of photogenerated e− and h+ species, and therefore the recombination of photogenerated carriers can be effectively suppressed.

Hierarchical construction of hollow NiCo2S4 nanotube@NiCo2S4 nanosheet arrays on Ni foam as an efficient and durable electrocatalyst for hydrogen evolution reaction

Ternary transition metal chalcogenide (TTMC) with multicomponent, different phases and unique electronic structures have been studied in electrocatalytic hydrogen evolution reaction (HER). However, the strong interaction between adsorbed H (H∗) and sulfur leads to the unfavorable hydrogen desorption properties of considerable TTMC. Herein, we constructed the hierarchical hollow NiCo2S4 nanotube@NiCo2S4 nanosheet arrays on Ni foam substrate (NT-NiCo2S4@NS-NiCo2S4/NF) by ion-exchange method. Homogeneous anion diffusion facilitates the formation of regular ultrathin nanosheets on hollow NiCo2S4 nanotube arrays, which presents hierarchical architecture with more surface area and channels to active site exposure, electrolyte diffusion, and gas desorption for HER. As-synthesized optimal NT-NiCo2S4@NS-NiCo2S4/NF electrode demonstrates an excellent HER activity, especially an overpotential of 221 mV, a Tafel slope of 108 mV dec−1, and remarkable stability at current densities of 100 mA cm−2 in 1.0 M NaOH electrolyte.

Schottky heterojunction‐assisted photocatalytic hydrogen evolution by ZnIn2S4/Co3S4 hollow leaves derived from Co‐ZIF‐L

The hetero‐photocatalysts in hollow structure may provide more dispersive reactive sites, the easily accessible open channel for substrates and the intensive visible light harvest ability, which have shown evidently promoting photocatalytic efficiency. Herein, a novel photocatalyst ZIS/Co3S4HLs in hierarchical hollow heterostructure has been constructed by epitaxially growing 2D ZnIn2S4 (ZIS) nanosheets on Co‐ZIF‐L‐derived Co3S4 hollow leaves (Co3S4HLs). The formation of the Schottky junction has promoted the photogenerated charges transfer, which is well proven by the electrochemical analyses and the DFT calculation. It is suggested that both constructed hierarchical hollow heterostructure and the Schottky junction with well‐matched band potentials are responsible for the remarkable H2 evolution rates under the visible light irradiation, which are much higher than most of the reported results by other ZIS‐based composite photocatalysts. The good cyclic photocatalytic activity and structural stability of these hierarchical hollow leaves provide new insight into designing a high‐efficient heterostructure being used in solar energy conversion.

Hierarchical FeS&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;@FeS&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;@N,S-C hollow nanocubes for lithium storage

<p indent="0mm">With the increasingly prominent problems of energy shortage and environmental pollution, the requirement for high-efficiency energy storage devices is becoming more urgent. Lithium-ion batteries (LIBs) are commonly used in portable electronic devices, such as laptops, mobile phones. However, their limited performances cannot meet the demands of ultrahigh energy density and safety in the fields of new energy vehicles and energy storage systems. The development and application of novel anode materials can increase the capacity of LIBs. Transition metal sulfides (TMSs) with ultrahigh theoretical capacity and chemical stability present bright application prospects. Among them, iron sulfide (FeS_{<italic>x</italic>}) is regarded as one of the most promising anode materials due to its abundant reserves and environmental friendliness. However, the shortcomings of large volume expansion during cycling severely hinder the application of FeS_{<italic>x</italic>}<italic> </italic>and other TMSs. Designing TMS anode materials with special structures and combining them with carbon-based materials can effectively improve their electrochemical performance. Constructing nanosized TMSs with a hierarchical hollow structural property is a common strategy to increase their cycling stability. The abundant free volume inside the hollow structure can serve as a buffer space for TMSs with severe volume expansion, greatly reducing the structural fracture phenomenon. The internal free volume is also conducive to the electrolytic penetration into the composites. In addition, the dense nanosheets on the surface enable the active materials to fully contact the electrolyte, and subsequently, more reaction sites are generated for the electrochemical reactions. Combining amorphous carbon with TMSs can increase the dispersity of composites and reduce the presence of agglomerated structures. The amorphous carbon layer can serve as a stable interface for electrochemical reactions, which is beneficial for maintaining high coulombic efficiency and structure retention during cycling. The disordered structures and defects inside the amorphous carbon layer can accelerate the transport of the electrolyte and Li⁺ ions. Moreover, the amorphous carbon layers can also provide a structural support network and electronic conduction paths for TMSs, thereby improving the electrochemical performance of composites. Polydopamine (PDA) demonstrates special “viscosity,” which can coat almost any material’s surface under a weak alkaline condition. After carbonization, PDA is carbonized into an amorphous carbon layer with nitrogen doping, and the increased carbon interlayer spacing and defects can serve as additional active sites for lithium storage. In this study, the hierarchical FeS₂@FeS₂@N,S-C hollow nanocubes are successfully synthesized by a series of solvothermal, PDA <italic>in-situ</italic> polymerization, and high-temperature vulcanization processes. The inner hierarchical hollow FeS₂ is encapsulated in the heteroatom-doped carbon layer and in LIBs; the fabricated composites with a special structural property demonstrate improved electrode reaction kinetics. The results show that the discharge capacities of FeS₂@FeS₂@N,S-C are 505.6, 472.2, and 360 mAh/g at 0.2, 0.5, and <sc>2 A/g,</sc> respectively. Moreover, the reversible capacity of 492.1 mAh/g is maintained after 500 cycles at <sc>1 A/g,</sc> and the structure remains intact after cycling. The excellent electrochemical performance of FeS₂@FeS₂@N,S-C can be attributed to the heteroatom-doped carbon layer coating the hierarchical hollow structure and the synergistic effect of multiple components.

MIL-68 (In)-derived In2O3@TiO2 S-scheme heterojunction with hierarchical hollow structure for selective photoconversion of CO2 to hydrocarbon fuels

The hierarchical hollow structured photocatalysts of TiO2 nanosheet arrays-decorated In2O3 hexagonal nanotubes (core–shell structural In2O3@TiO2) were successfully fabricated by the in-situ hydrothermal method. Hierarchical hollow structure of In2O3@TiO2 photocatalysts with large specific surface area can improve the light harvesting efficiency and the adsorption capability for CO2 and H2O reactants. The internal electric field in In2O3@TiO2 photocatalysts provides the strong driving force for S-scheme electron transfer from conduction band of TiO2 to valence band of In2O3. The In2O3@TiO2 catalysts exhibited super performance for selectively photocatalytic CO2 conversion with H2O into hydrocarbon fuel (CH4) without sacrificial agent. Among the catalysts, In2O3@TiO2-10 catalyst has the largest yield (11.1 μmol g−1h−1) and selectivity (88.1 %) of CH4 product. Based on results of the characterizations, the mechanism of selective CO2 photoreduction is proposed: the surface enrichment of photogenerated electron induced by the S-scheme In2O3-TiO2 heterojunction is key-step for selective CO2 photoreduction into CH4. This work provides new ideas for the design and construction of high-efficient S-scheme photocatalysts.

Hierarchical Hollow CoWO4-Co(OH)2 Heterostructured Nanoboxes Enabling Efficient Water Oxidation Electrocatalysis.

Rational design and construction of well-defined hollow heterostructured nanomaterials assembled by ultrathin nanosheets overtakes crucial role in developing high-efficiency oxygen evolution reaction (OER) electrocatalysts. Herein, a reliable metal-organic framework-mediated and cation-exchange strategy to tune the geometric structure and multicomponent heterostructures has been proposed for the fabrication of hollow CoWO4-Co(OH)2 hierarchical nanoboxes assembled by rich ultrathin nanosheets. Benefiting from the hierarchical hollow nanostructure, the CoWO4-Co(OH)2 nanoboxes offer plenty of metal active centers available for reaction intermediates. Moreover, the well-defined nanointerfaces between CoWO4 and Co(OH)2 can function as the bridge for boosting the efficient electron transfer from CoWO4 to Co(OH)2. As a consequence, the optimized CoWO4-Co(OH)2 nanoboxes can exhibit outstanding electrocatalytic performance toward OER by delivering 10 mA cm-2 with a low overpotential of 280 mV and a small Tafel slope of 70.6 mV dec-1 as well as outstanding electrochemical stability. More importantly, this CoWO4-Co(OH)2 heterostructured nanocatalyst can couple with Pt/C to drive overall water splitting to achieve 10 mA cm-2 with a voltage of 1.57 V.

Molybdenum Oxynitride Atomic Nanoclusters Bonded in Nanosheets of N-Doped Carbon Hierarchical Microspheres for Efficient Sodium Storage

HighlightsMoO2.0N0.5 atomic nanoclusters bonded on nanosheets of N/C hierarchical hollow microsphere are synthesized via a facile self- templating strategy.Introduction of MoO2.0N0.5 atomic nanoclusters benefits the enhancement of electrochemical kinetic.Composite of MoO2.0N0.5/NC shows excellent electrochemical performance as an anode material for sodium-ion batteries.

Iron and nitrogen anchored hierarchical hollow porous carbon microtubes for an electrocatalytic oxygen evolution reaction

The development of active nonprecious-metal and heteroatom-doped materials is critical for the oxygen evolution reaction (OER). Herein, asphaltene-derived carbon-coated Fe- and N-doped hierarchical hollow porous carbon microtubes were prepared through feasible freeze-drying and carbonization/activation strategies. Cotton with a fibrous morphology acted as a soft template and carbon precursor, while asphaltene with easy graphitization properties was utilized to stabilize the structure of microtubes and accelerate the charge conductivity. Meanwhile, Fe- and N-doping changed the electronic structure of carbon and increased the number of active sites. In particular, the optimum sample displayed excellent OER activity with a lower overpotential of 261.4 mV at 10 mA/cm2 and Tafel slope of 94.60 mV/dec under alkaline conditions. Moreover, the catalyst demonstrated excellent long-term durability with a 10% attenuation rate after continuous operation for 50 h by the chronoamperometry method at a constant potential of 1.5 V. This work provides a strategy for the effective resource utilization of biomass and asphaltene to prepare highly efficient OER electrocatalysts.

The Fig-Like hierarchical Double-Shelled hollow TiN particles as sulfur host for Lithium-Sulfur batteries

Lithium-sulfur battery(LSB)’s commercial manufacturing has been mainly retarded by the “shuttle effect” and low electrical conductivity of polysulfides (LiPSs). Designing a cathode with hollow and hierarchically porous structures was expected to solve the above problems. Herein, a kind of TiN particles with the hierarchical hollow double-shelled structures was synthesized and applied to cathodes of LSB. The Fig-like hollow TiO2 particles (FHTiO2s) were firstly synthesized by the hard-template method. Subsequently, the Fig-like hierarchical hollow double-shelled TiN particles (FHTiNs) were synthesized by the template-free sequential transformation and separation approach (STSA). It was verified that the heating temperature and time were key parameters. Special Fig-like double-shell hollow structures could greatly increase the loading of S, and the excellent initial capacity of FHTiNs cathodes was up to 1159 mAh/g. On the one hand, the Fig-like framework in internal cavity and double-shell structures could promote the ultrahigh specific surface area, and the adsorption to LiPSs was improved by increasing active sites; On the other hand, the shuttle effect of LiPSs was weakened by the fig-like framework and double-shell structures, which slowed down the massive dissolution of sulfur in the electrolyte. As a result, the pleasant rate performance of FHTiNs cathodes was up to 400 mAh/g at 5C. This novel structures and synthesis method provided a new strategy for the designing of LSB cathodes.

Metal-cation-directed self-assembly of hierarchical MoS2 nanotubes as high-performance anode for Na-ion batteries

Engineering MoS2 microstructure plays an important role in boosting its Na-ion storage performance. Herein, we demonstrate a metal-cation-directed self-assembly of hierarchical hollow MoS2 nanotubes, where MoO3 nanorods have been applied as Mo sources and self-sacrificing template. Meanwhile, the metal cations can cause the generation of abundant metallic phase (1T) MoS2, greatly expediting the electrons transfer. Moreover, a high ions conductivity is also obtained with rapid reaction kinetics in view of its hierarchical hollow nanostructure. Exemplified for Co-ion, the Co-MoS2 nanotubes deliver a high sodium storage capacity of 510 mAh g−1 at 0.2 A g−1 and 415 mAh g−1 at 10 A g−1 within 0.4–3 V. The nanotube is well-maintained with no obvious capacity decay after 5000 cycles at 2 A g−1. This finding provides a viable pathway to construct hollow MoS2 nanostructures with high content of 1T phase and can also potentially be suitable for other transition metal sulfides.