Hierarchical Hollow Structure Research Articles

Single-exposure femtosecond laser direct writing of Salvinia-inspired micropatterned functional surface

Bioinspired functional surfaces have attracted considerable attention within multiple scientific and industrial fields. In particular, the hollow hierarchical structure and chemical heterogeneity endow Salvinia leaves with superhydrophobicity and underwater air retention capability. However, replicating complex three-dimensional Salvinia-like patterns at the microscale currently relies on time-consuming additive manufacturing methods, preventing their wide adoption in industrial applications. Here, we report a high-throughput femtosecond laser direct writing strategy based on the quadrifurcate abruptly autofocusing beam for the single-exposure fabrication of Salvinia-like microstructures. Combined with chemical functionalization, both the hollow morphology and heterogeneous chemical properties of the natural counterpart were mimicked. The obtained bioinspired surfaces can repel and manipulate water droplets, and maintain superhydrophobicity even immersed underwater. The proposed single-exposure fabrication strategy is expected to contribute to the mass production of Salvinia-inspired surfaces, whose unique wetting properties promise great potential in chemical engineering, micro bioanalysis, and microfluidic devices.

Hierarchical Hollow TiO2@Bi2WO6 with Light-Driven Excited Bi(3-x)+ Sites for Efficient Photothermal Catalytic CO2 Reduction.

Converting CO2 into valuable chemicals via sustainable energy sources is indispensable for human development. Photothermal catalysis combines the high selectivity of photocatalysis and the high yield of thermal catalysis, which is promising for CO2 reduction. However, the present photothermal catalysts suffer from low activity due to their poor light absorption ability and fast recombination of photogenerated electrons and holes. Here, a TiO2@Bi2WO6 heterojunction photocatalyst featuring a hierarchical hollow structure was prepared by an in situ growth method. The visible light absorption and photothermal effect of the TiO2@Bi2WO6 photocatalyst is promoted by a hierarchical hollow structure, while the recombination phenomenon is significantly mitigated due to the construction of the heterojunction interface and the existence of excited Bi(3-x)+ sites. Such a catalyst exhibits excellent photothermal performance with a CO yield of 43.7 μmol h-1 g-1, which is 15 and 4.7 times higher than that of pure Bi2WO6 and that of physically mixed TiO2/Bi2WO6, respectively. An in situ study shows that the pathway for the transformation of CO2 into CO over our TiO2@Bi2WO6 proceeds via two important intermediates, including COO- and COOH-. Our work provides a new idea of excited states for the design and synthesis of highly efficient photothermal catalysts for CO2 conversion.

Hierarchical core-shell structured CoZn-MOFs derived materials anode with raspberry-like shape for high-performance lithium storage

Significant progress had been made in various fields with transition metal oxide electrode materials, particularly in battery materials where structural control played a crucial role in enhancing their electrochemical properties. Therefore, this study aimed to investigate the potential of a raspberry-like hierarchical core-shell structure derived from Co–Zn MOF as anode materials by varying concentration of reaction solution in hydrothermal method. The hierarchical raspberry-like hollow shell structure was beneficial to expose more active sites and reduced the diffusion distance of Li+ to the internal electroactive sites, improving the overall electrical conductivity of the electrode by full contact with carbon. Carbon nanotubes were incorporated into more suitable core-shell structure. They were uniformly coated the hollow sphere and filled inside of that to form a carbon skeleton. Specifically, the carbon nanotubes inside of the hollow sphere supported the shell not to collapse. This mitigated volume expansion during the cycling process, maintains structure stability, and allowed for rearrangement to occur during cycling to achieve a high specific capacity. Furthermore, the carbon nanotubes inside and outside of the hollow sphere created a high-density interface that enhanced interfacial polarisation and accelerated the rate of Li+ passage during cycling. These effects had resulted in an improvement in the material's performance. It is noteworthy that the specific capacity attains 1050 mAh g-1 when exposed to a current density of 0.2 A g-1. Notably, even after conducting 500 cycles at a current density of 0.5 A g-1, the specific capacity remains stable at 652 mAh g-1.

Designed Synthesis and Electrochemical Performance Regulation of the Hierarchical Hollow Structure Cu2S/Cu7S4/NC Anode for Hybrid Supercapacitors.

Copper-based compounds have attracted increasing attention as electrode materials for rechargeable devices, but their poor conductivity and insufficient stability inhibit their further development. Herein, an effective method has been proposed to improve the electrochemical properties of the copper-based electrodes by coating carbon materials and generating unique micro/nanostructures. The prepared Cu2S/Cu7S4/NC with hierarchical hollow structure possesses excellent electrochemical performance, attributing to the composition and structure optimization. The superior charge storage performance has been assessed by theoretical and experimental research. Specifically, the Cu2S/Cu7S4/NC exhibits remarkably higher electrical conductivity and lower adsorption-free energy for O* and OH* than those of Cu2O. Moreover, the Cu2S/Cu7S4/NC delivers a high specific capacitance of 1261.3 F·g-1 at the current density of 1 A·g-1 and also has great rate performance at higher current densities, which are much better than those of the Cu2O nanocubes. In addition, the assembled hybrid supercapacitor using Cu2S/Cu7S4/NC as the anode exhibits great energy density, power density, and cycling stability. This study has proposed a novel and feasible method for the synthesis of high-performance copper-based electrodes and their electrochemical performance regulation, which is of great significance for the advancement of high-quality electrode materials and rechargeable devices.

Polymer Binder-Free aqueous spinning of biomimetic CNT based hierarchical hollow fiber for structural and energy storage application

Assembly of functional nanomaterials into structural–functional integrated materials, such as structural-energy storage materials, are highly desirable for lightweight, high-performance wearable electronics, automobiles, and aviation/aerospace vehicles, yet extremely challenging due to the paradox between functional properties and the maintenance of mechanical properties. Herein, inspired by wheat-straw structures, we reported a polymer binder-free aqueous spinning strategy to manufacture biomimetic hollow carbon nanotube-based fibers (H-CNTF), where two-dimensional graphene oxide (GO) nanosheets are employed as an alternative to polymer binder for assisting the formation of hollow structures by rapid interaction with cations in coagulation, forming strong interaction with CNTs and tunning rheological property of spinning dope. The hierarchical hollow structure consisting of micron-scale hollow tubular space and porous walls endows H-CNTF with large surface area and abundant loading sites for guest materials, and the good CNT orientation and the absence of polymer binder enable H-CNTF excellent electrical and mechanical properties. As a proof of concept, the resulting H-CNTF supercapacitor electrodes exhibit high electrochemical energy storage performance with a specific capacity of 163 F/cm3 and high tensile strength of 0.35 N/tex. In addition, the polymer composite based on H-CNTF is about 100 % stronger than that based on solid fiber owing to the more uniform composite structure. The combination of outstanding electrochemical and mechanical properties makes this hollow fiber a promising material for future structural and energy storage applications.

Hierarchical architecture of ZIF-8@ZIF-67-Derived N-doped carbon nanotube hollow polyhedron supported on 2D Ti3C2Tx nanosheets targeting enhanced lithium-ion capacitors

The matching of long cycle life, high power density, and high energy density has been an inevitable requirement for the development of efficient anode materials for lithium-ion capacitors (LICs). Here, we introduce an N-doped carbon nanotube hollow polyhedron structure (Co3O4-CNT-800) with high specific surface area and active sites, which is anchored with two-dimensional (2D) Ti3C2Tx nanosheets with metallic conductivity and abundant surface functional groups by electrostatic adsorption to form a hierarchical multilevel hollow semi-covered framework structure. Benefiting from the synergistic effect between Co3O4-CNT-800 and Ti3C2Tx, the composites exhibit superior energy storage efficiency and long cycling stability. The Co3O4-CNT-800/Ti3C2Tx electrodes exhibit a high specific capacity of 817C/g at a current density of 0.5 A/g under the three-electrode system, and the capacity retention rate is 91 % after 5000 cycles at a current density of 2 A/g. Additionally, we assembled Co3O4-CNT-800/Ti3C2Tx as the anode and Activated carbon (AC) cathode to form LIC devices, which showed an electrochemical test result of 90.01 % capacitance retention after 8000 cycles at 2 A/g, and the maximum power density of the LIC was 3000 W/kg and the maximum energy density was 121 Wh/kg. This work pioneered the combination of N-doped carbon nanotube hollow polyhedron structure with two-dimensional Ti3C2Tx, which provides an effective strategy for preparing LIC negative electrode materials with high specific capacitance and long cycling stability.

Hollow Hierarchical Porous and Antihydrolytic Spherical Zeolitic Imidazolate Frameworks for Enzyme Encapsulation and Biocatalysis.

The creation of a new metal-organic framework (MOF) with a hollow hierarchical porous structure has gained significant attention in the realm of enzyme immobilization. The present work employed a novel, facile, and effective combinatorial technique to synthesize modified MOF (N-PVP/HZIF-8) with a hierarchically porous core-shell structure, allowing for the preservation of the structural integrity of the encapsulated enzyme molecules. Scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, confocal laser scanning microscopy, and other characterization tools were used to fully explore the changes of morphological structure and surface properties in different stages of the preparation of immobilization enzyme CRL-N-PVP/HZIF-8, thus showing the superiority of N-PVP/HZIF-8 as an enzyme immobilization platform and the logic of the immobilization process on the carrier. Additionally, the maximum enzyme loading was 216.3 mg mL-1, the relative activity of CRL-N-PVP/HZIF-8 increased by 15 times compared with the CRL@ZIF-8 immobilized in situ, and exhibited quite good thermal, chemical, and operational stability. With a maximal conversion of 88.8%, CRL-N-PVP/HZIF-8 demonstrated good catalytic performance in the biosynthesis of phytosterol esters as a proof of concept. It is anticipated that this work will offer fresh concepts from several perspectives for the creation of MOF-based immobilized enzymes for biotechnological uses.

Reinforcement of Electrocatalytic Oxygen Evolution Activity Enabled by Constructing Silver-Incorporated NiCo-PBA@NiFe-LDH Hierarchical Nanoboxes.

Complicated oxygen evolution reaction (OER) poses the bottleneck in improving the efficiency of hydrogen production through water electrolysis. Herein, an integrated strategy to modulate the electronic structure of NiFe layered double hydroxide (NiFe-LDH) is reported by constructing Ag-incorporated NiCo-PBA@NiFe-LDH heterojunction with a hierarchical hollow structure. This "double heterojunction" facilitates local charge polarization at the interface, thereby promoting electron transfer and reducing the adsorption energy of intermediates, ultimately enhancing the intrinsic activity of the catalyst. It is noteworthy that an exchange bias field is observed between NiCo-PBA and NiFe-LDH, which will be conducive to regulating the electron spin states of metals and facilitating the production of triplet oxygen. Additionally, the unique hierarchical nanoboxes provide a large specific surface area that ensures adequate exposure to adsorption sites and active sites. Profiting from the synergistic advantages, the overpotential is as low as 190mV at a current density of 10mAcm-2 , with a low Tafel slope of 21mVdec-1 . Moreover, density functional theory (DFT) calculation further substantiated that the incorporation of Ag in the heterojunction can effectively reduce the adsorption energy of reactant intermediates and enhance the conductivity.

Integrated PtxCoy-Hierarchical Carbon Matrix Electrocatalyst for Efficient Hydrogen Evolution Reaction.

Pt-based catalysts are regarded as state-of-the-art electrocatalysts for producing clean hydrogen energy; however, their wide application is restricted by their low abundance, high cost, and poor stability. Herein, we report an integrated PtxCoy-hierarchical carbon matrix electrocatalyst (Pt/Co@NCNTs, Pt3Co@NCNTs, PtCo@NCNTs, and PtCo3@NCNTs) that is developed using a thermally driven Co migration strategy forming alloy nanoparticles to achieve efficient hydrogen evolution reaction (HER). Benefiting from its electronic regulation effect and unique hierarchical hollow structure, the Pt3Co@NCNTs catalyst loaded with 11.5 wt % Pt exhibits superior catalytic performance and durability for HER compared with commercial 20 wt % Pt/C. Under both alkaline and acidic conditions, Pt3Co@NCNTs exhibits excellent HER activity with overpotentials of 21 and 45 mV at 10 mA cm-2, respectively. Density functional theory (DFT) results further verify that the interaction between Pt and Co in Pt3Co@NCNTs can modulate electronic rearrangement, optimize the d-band center, and accelerate water dissociation and *H desorption, thereby enhancing HER activity.

Charged-Particle-Irradiated Tin Oxyhydroxide Nanoparticle Anodes for Lithium-Ion Batteries

Metal oxyhydroxides have been promising ceramic materials in miscellaneous electrochemical fields due to their multiple redox states, interlayer conductivity, and structural stability as well as electrocatalytic activity. When applied to anode active materials for secondary batteries, particularly lithium-ion batteries, metal oxyhydroxides have a much larger theoretical capacity than that of commercial graphite by conversion and/or alloying reactions with lithium ions rather than intercalation. However, the inevitable volume variation of metal oxyhydroxides during battery operation impinges other primary components in anode materials such as binders and conducting agents, leading to pulverizing the anode materials. Moreover, metal oxyhydroxides are not electrically conductive so much that electrochemical reactions cannot be facilitated efficiently during cycling. Accordingly, many efforts, for example, nanostructuring, constructing hierarchical configurations or hollow structures, and hybridization with carbonaceous materials, have been attempted to overcome the limitations of metal oxyhydroxide anode active materials. In addition, crystal defects in anode materials are greatly helpful to promote electrochemical activity by tuning electronic and chemical properties. Hydrogen annealing, plasma treatment, and chemical reduction method are common approaches to inducing a large number of defects in materials, but they are generally employed at high temperatures or under controlled-pressure circumstances. Therefore, we deploy charged particle irradiation to generate numerous defects in the metal oxyhydroxide anode materials. Incident charged particles interact with a lot of atoms in the anode materials, causing atomic displacement. As a result of the displacement, diverse kinds of defects are produced, which change the electronic and chemical structures of the anode materials. Charged particle irradiation introduces a high density of defects and selective defect types for short time at room temperature. Amorphization is also induced by charged particle irradiation, which is beneficial to improve the electrochemical performance of metal oxyhydroxide anode materials. Herein, we first synthesize tin oxyhydroxide nanoparticles (SnOOH NPs), one of the potential anode active materials using simple nanostructuring, via an electrochemical route, anodization. Anodization is a very fast and concise process to obtain nanostructured metal oxides as well as NPs. Electrodes with SnOOH NPs are irradiated with various charged particles including electrons, protons, helium ions, nitrogen ions, and argon ions, and the irradiation effects are investigated. SnOOH NP anodes irradiated with each type of charged particle show different electrochemical performances from each other, but all of the irradiated SnOOH NP anodes exhibit enhanced discharge capacity or cycle life compared with a pristine SnOOH NP anode. Plausible mechanisms of the irradiation effects depending on charged particles are also proposed. Charged particle irradiation can be utilized for not only metal oxyhydroxides but any kind of ceramic materials in diverse applications including lithium-ion batteries. Figure 1

Nanodiamond@hollow carbon sphere architectures for synergistically enhanced electromagnetic absorption and thermal insulation

Carbon materials stood out for electromagnetic absorption due to the lightweight, high-stability and well designability. At present, the research bottleneck lied in achieving broadband absorption and versatility. Novel nanodiamond@hollow carbon sphere architectures were designed in this work, involved with all‑carbon hollow structures and the multiple heterophase interfaces. Bifunctional improvement was realized through the all‑carbon architectures design. Superior electromagnetic wave absorption performance was obtained at an extremely low loading ratio of 5 wt% of the nanodiamond@hollow carbon sphere architectures. With a thickness of 2.15 mm, the optimal reflection loss peak could be −47.1 dB, and the specific absorbing value achieved 438 dBmm−1. Meanwhile, the nanodiamond@hollow carbon sphere architectures exhibited significantly improved thermal insulation characteristics. The simultaneously enhanced electromagnetic absorption and thermal insulation performances were proved to be benefited from the multiple CN hybridizations and the novel all‑carbon hollow hierarchical structures with controllable interfaces. This work serves as a referencing significance for the development of lightweight multi-functional electromagnetic absorbing materials.

Integration of hierarchical magnesium silicate with polypyrrole-coated hollow Fe3O4 hybrids as a synergistic adsorbent toward efficient water treatment

Here we demonstrate the rational design and synthesis of hierarchical Fe3O4@PPy/Mgsilicate composites for applications in water treatments. Through a facile step-by-step strategy, ultrathin Mgsilicate nanosheets (NSs) are grown on polypyrrole (PPy) coated Fe3O4 NPs to achieve the hollow structured Fe3O4@PPy/Mgsilicate composites. This smart design can effectively shorten the mass transfer of molecules, increase the specific surface area, and provide more active sites for adsorption of organic pollutants. Owing to its large specific surface area, hierarchical hollow structures, and the synergistic adsorption effect between the PPy interlayer and magnesium silicate outlayer, the resulting composites exhibited excellent adsorption on Congo Red (CR) with high adsorption capacity of 540.5 mg·g-1. The separation of the composites after sorption can be easily performed with an external magnet because of the multiple Fe3O4 cores. These results indicate that the Fe3O4@PPy/Mgsilicate composites can be employed as a highly promising adsorbent in water treatment.

Interface and morphology engineering of Ru-FeCoP hollow nanocages as alkaline electrocatalyst for overall water splitting

Interface and Morphology engineering strategies of electrocatalysts are of great importance to promote water splitting performance, although still facing many challenges. In this work, we present a facile method for preparing Ru-anchored hollow FeCoP nanocages electrocatalyst with ultrathin sheets. The hollow structure composed of ultrathin nanosheets and rich heterogeneous interfaces benefit the as-synthesized catalyst to exhibit small overpotentials of 310 mV and 94 mV at the current density of 10 mA·cm−2 for oxygen evolution reaction and hydrogen evolution reaction, respectively. When Ru-FeCoP nanocages were employed as the bifunctional catalyst for overall water splitting, the potential of 1.65 V was obtained to reach the current density of 10 mA·cm−2. The experimental results confirmed that the formation of hierarchical hollow structure facilitated the exposure of active sites and enhanced the electrocatalytic activity. Meanwhile, XPS and DFT data also reveal that the presence of heterogeneous interfaces changed the electronic structure, optimized the absorption of the intermediates, significantly reduced the energy barrier of water dissociation and promoted the release of H2. This work offers an effective route for rational design of low-loading noble metal-anchored metal phosphide with the hierarchical hollow structure and rich interfaces towards overall water splitting.

Artificial thylakoid membrane assisted NiMn2O4@PoPDA hierarchical hollow nanospheres for photo-enzyme integrated catalysis

The selective functionalization of CO2 is of profound significance concerning the global energy and environmental crisis. Herein, we cleverly designed and constructed a photoenzymatic system with a hierarchical hollow structure photo-enzyme integrated catalyst (nickel manganate -poly(o-phenylenediamine), NiMn2O4@PoPDA) by coating NiMn2O4 with artificial thylakoid membrane (PoPDA) to mimic the characteristics of natural thylakoid membranes and combined formate dehydrogenase (FDH) to upgrade CO2 to formic acid. The PoPDA membrane enhances the absorption of light energy and the efficiency of electron transfer, and improves the stability of the enzyme to avoid its deactivation. Most importantly, the favorable electronic coupling and band structure between NiMn2O4 and PoPDA separate holes and electrons to afford a MV•+ regeneration rate of 213.59 ± 4.91 mmol h−1 g−1 and a formic acid yield of 206 µmol. This work creates an efficient strategy using PoPDA as protector for enzyme stabilization to fabricate photobiocatalysts that realize highly efficient photoenzymatic catalysis.

MoSe2 hollow nanospheres with expanded selenide interlayers for high-performance aqueous zinc-ion batteries

Transition metal dichalcogenides (TMDs) as materials for aqueous zinc-ion batteries (ZIBs) have received a lot of interest because of their large theoretical capacity and unique layered structure. However, the sluggish kinetics and inferior cyclic stability limit the usefulness of ZIBs. In the present investigation, the interlayer spacing enlarged MoSe2 hollow nanospheres comprised of nanosheets with ultrathin shells have been successfully synthesized through a combined strategy of template assistance and anion-exchange reaction. The hierarchical ultrathin nanosheets and hollow structure effectively suppress the agglomeration of pure nanosheets and ameliorate volume fluctuations induced by ion migration during (dis)charging/charging. The interlayer expansion provides good channels for the transport of Zn2+ ions and speeds up the insertion/extraction of Zn2+. In addition, in-situ carbon modification can significantly improve electronic conductivity. Therefore, the electrode prepared from MoSe2 hollow nanospheres with enlarged interlayer spacing not only exhibits outstanding cycle stability (capacity retention of 94.5% after 1600 cycles) but also exhibits high-rate capability (266.1 mA h g−1 at 0.1 A g−1 and 203.6 mA h g−1 at 3 A g−1). This work could provide new insights into the design of cathode using TMDs of hollow structure for Zn2+ storage.

Cu and Cu-Fe Bi-Metal Nanoparticles Encapsulated in Hollow S-1 Zeolite for Reverse Water Gas Shift Reaction

The hollow hierarchical structure Cu@S and CuFe0.5@S catalysts were successfully synthesized through the “dissolution-recrystallization” (D-R) method for the reverse water gas shift reaction (RWGS). The encapsulated catalysts had a hierarchical porous structure and better dispersion of Cu particles than the Cu-S and CuFe0.5-S samples prepared via the conventional impregnation method. Furthermore, CuFe0.5-S and CuFe0.5@S catalysts showed higher CO2 conversion and 100% selectivity of CO at the entire temperature range investigated in this work compared to the monometallic catalysts Cu-S and Cu@S. Interestingly, the reaction activity of all the samples increased according to the sequence: CuFe0.5@S > CuFe0.5-S > Cu@S > Cu-S at 400–550 °C under atmospheric pressure. These results indicate that the higher dispersion of encapsulation structure and the enhanced surface basicity derived from the addition of Fe play crucial roles in enhancing the catalytic performance of Cu-based catalysts in the RWGS reaction.

Nitrogen-doped graphene quantum dots embedding CuCo-LDH hierarchical hollow structure for boosted charge storage capability in supercapacitor

The nanostructure optimization of layered double hydroxide (LDH) can effectively alleviate fragile agglomerated problems. Herein, nitrogen-doped graphene quantum dots (NGQDs) embedded in CuCo-LDH hierarchical hollow structure is synthesized by hydrothermal and impregnation methods. The electrochemical results show that the ordered multi-component structure could effectively inhibit the aggregation and layer stacking. At the same time, the hierarchical structure establishes new electron and ion transfer channels, greatly reducing the resistance of interlayer transport and accelerating the diffusion rate of electrolyte ions. Besides, NGQDs have both good electrical conductivity and abundant active sites, which can further improve the electron transmission rate and effectively strengthen the energy storage capacity of the material. Therefore, the large specific capacity of 1009 F g−1 can be displayed at 1 A g−1. The energy density of the assembled carbon cloth (CC)@CuCo-LDH/NGQDs//activated carbon (AC) device can reach 58.6 Wh kg−1 at 850 W kg−1. Above test results indicate that CC@CuCo-LDH/NGQDs//AC devices exhibit stable multi-component hierarchical structure and excellent electrical conductivity, which provides an effective strategy for enhancing the electrochemical characteristics of asymmetric supercapacitors.

Stabilizing sulfur doped manganese oxide active sites with phosphorus doped hierarchical nested square carbon for efficient asymmetric supercapacitor

The introduction of heteroatom species into hollow carbon lattice networks (HCLN) and metallic oxides have been exploited as an effective approach to enhance the performance of the electrochemical electrodes. Herein, square hierarchical P-doped porous carbon/S-doped manganese oxide (S-Mn5O8@PPC) is designed via a solvothermal, chemical vapor deposition and wet chemical growth method from the solid-state gas-steaming operation of zinc of square acids, offering a unique nested hierarchical and stable integrated structure. As a result, the as-fabricated S-Mn5O8@PPC and PPC demonstrated impressive electrochemical capacitance of 1819.8F g−1 and 325.1F g−1 at 1 A g−1, respectively, which both superior than the Mn5O8@PPC and porous carbon (PC, 1604.0F g−1 and 193.2F g−1). Especially, the specific capacitance of the PPC is preferred to that of most non-metallic heteroatom-doped MOFs-derived carbons. More importantly, two supercapacitor (SC) electrodes - square hierarchical P-doped porous carbon (PPC) and S-doped manganese oxide coated PPC - are further self-assembled a hybrid SC device, which possesses a wide voltage of 0–1.6 V, outstanding electrochemical capacitance of 154.8F g−1, impressive energy storage performance and a reliable capacitive stability (87.24% after 5000 cycles), apart from the ideal energy density and power density (55.1 W h kg−1 at 800.0 W kg−1). Such excellent features originate from the large specific surface area of the porous hierarchical hollow structure, the doping of heterogeneous P and S, the dispersive loading of manganese oxide, and harmonious matching of positive and negative electrodes.

The Facile Synthesis of Hollow CuS Microspheres Assembled from Nanosheets for Li-Ion Storage and Photocatalytic Applications.

Herein, well-defined hollow CuS microspheres assembled from nanosheets were successfully synthesized through a facile solvothermal method. Hollow CuS microspheres have an average diameter of 1.5 μm; moreover, the primary CuS nanosheets have an ultrathin thickness of about 10 nm and are bound by {0001} polar facets. When used as anodes for lithium-ion batteries (LIBs), hollow CuS microspheres exhibit excellent electrochemical properties, including a large discharge capacity (610.1 mAh g-1 at 0.5 C), an excellent rate capability (207.6 and 143.4 mAh g-1 at 1 and 5 C), and a superior cyclic stability (196.3 mAh g-1 at 1 C after 500 cycles). When used as photocatalysts for Rhodamine B (RhB), hollow CuS microspheres can degrade more than 99% of the initial RhB within 21 min. These excellent Li-ion storage properties and photocatalytical performances are attributed to their unique hierarchical hollow structure.

A MOF-to-MOF conversion assisted formation of hierarchical hollow Zn–Co1–xS/C@C composite for efficient potassium-ion storage

Hollow structured composite can enhance the structural stability of metal sulfide anode by accommodating its volume variation, while the performance is still hindered by its poor electron/ion conductivity. Herein, we develop a hierarchical hollow structure to achieve superior electrochemical performance, from which a MOF-to-MOF conversion is utilized to generate hollow Zn–Co1-xS/C composite followed with additional carbon coating layer. For potassium storage, as-prepared hollow Zn–Co1-xS/C@C composite displays high capacities of 375 mA h g−1 after 100 cycles at 0.2 A g−1 and 201 mA h g−1 after 500 cycles at 1 A g−1. Moreover, it also manifests outstanding rate capability of 200 mA h g−1 at 10 A g−1, outperforming hollow Co1-xS@C and majority of the reported cobalt-based anodes. With illustration by kinetics analysis and theoretical calculation, both of Zn doping and internal carbon matrix are conductive to promote the charge transportation ability of Co1-xS, thus accounting for the good cycling behavior and excellent rate capacity of hierarchical hollow Zn–Co1-xS/C@C composite.