Unique Yolk-shell Structure Research Articles

Design of a yolk-shell ternary metal sulfide with a tunable structure for high-performance electromagnetic wave absorption.

Herein, we report a strategy for preparing a novel ternary metal sulfide (TMS) with a yolk-shell structure based on a "penetration-solidification-annealing" method. A series of FeCoNiSxGy with tunable structure, different morphology and composition was synthesized by adjusting the degree of sulfuration. Due to the synergistical manipulation of rich interface, defects, vacancies and electrical conductivity, as well as the unique yolk-shell structure, the appropriate sulfuration strategy achieved excellent impedance-matching and strong dielectric loss. The as-synthesized FeCoNiSxGy sulfides were blended with paraffin wax (under a filler loading of 30 wt%), which had the minimum reflection loss of -49.44 dB (2.20 mm) and the effective absorption bandwidth of 4.76 GHz (1.6 mm). In conclusion, this work could aid the design and regulation of a new type of ternary metal sulfides with high-performance electromagnetic wave absorption.

A one-pot hydrothermal synthesis of morphologically controllable yolk-shell structured CoFe glycerate spheres for oxygen evolution reaction

CoFe-based catalysts are efficient electrocatalysts for the oxygen evolution reaction (OER) in alkaline media. Here, we present a simple one-pot hydrothermal method for synthesizing a series of CoFe glycerates with controllable surface morphologies and investigate their potential as highly efficient catalysts for the OER in alkaline media. These CoFe glycerates exhibit a unique yolk-shell microsphere structure assembled from ultrathin nanosheets. The adjustment of the surface nanosheet size is achieved by varying the CoFe ratio, ensuring a more efficient electrocatalytic system for the OER process. Due to the abundant active sites provided by the yolk-shell structure and interleaved ultrathin nanosheets, Co3Fe1 glycerate (Co3Fe1 gly) demonstrates a low overpotential (283 mV) and a small Tafel slope (44.61 mV dec−1) at 10 mA cm−2. Additionally, Co3Fe1 gly exhibits excellent durability in alkaline electrolytes. Moreover, a series of characterizations demonstrate that the active sites of Co3Fe1 gly are the high-valence Co species generated during the OER process. This study opens a promising avenue for utilizing efficient and low-cost electrocatalysts to enhance OER performance.

Antimony nanoparticles encapsulated in interconnected nitrogen-doped carbon nanospheres for high performances PIBs

Antimony (Sb) has attracted significant attention as an anode material for potassium-ion batteries (PIBs) due to its high theoretical capacity and suitable working voltage. However, the severe volume variations of Sb during potassiation/depotassiation process lead to sluggish kinetics and poor cyclic stability for PIBs. In this study, Sb nanoparticles are confined within interconnected N-doped carbon nanospheres (Sb@NC) through an effective carbothermal reduction process. The potassium storage performances and mechanism are elucidated through electrochemical tests combined with ex-XRD analysis. When used as an anode for PIBs, the optimized Sb@NC-2 anode exhibits excellent cycle stability of 463.0 mAh g−1 at 200 mA g−1 over 100 cycles and superior rate capability of 113.4 mAh g−1 at a high current density of 2 A g−1. Besides, a full cell comprising an Sb@NC-2 anode and a PTCDA cathode is also tested to validate the practical feasibility of the anode. Furthermore, Density Functional Theory (DFT) calculations demonstrate that N-doped carbon can enhance the adsorption of K+ and improve the kinetics of electrochemical reactions. Therefore, the unique yolk-shell structure in this study effectively restricts volume expansion and aggregation of Sb particles while facilitating rapid electron/ion transfer. These findings provide a potential alternative anode material for advanced PIBs.

Boosting degradation of C4mim cation by metal alkoxide-derived Co4S3-activated Oxone: Yolk-Shell-Engineered enhancement and DFT-assisted toxic evaluation

The low bio-degradability of room-temperature ionic liquids (RTILs) makes RTILs a new class of persistent contaminants. It is urgent to develop useful technology to eliminate RTILs to prevent their presence in the environment. Sulfate-radical advanced oxidation processes (SR-AOPs) are particularly suitable for degrading such low-biodegradability pollutants. This study introduces a novel SR-AOP aimed at eliminating the representative RTIL, 1-butyl-3-methylimidazolium chloride (C4M), using an enhanced catalyst to activate Oxone. Traditionally, cobalt (Co) has been used for Oxone activation, but homogeneous catalysis with Co ions poses recovery challenges and secondary pollution risks. Recent studies suggest that cobalt sulfides (CSs) are more promising due to their superior redox properties, which are critical for effective Oxone activation. In this work, we developed a catalyst composed of cobalt sulfide (CS) with a unique yolk-shell (YS) structure, termed YSCS, to maximize catalytic activity. YSCS was easily fabricated from Co-Glycerate (CoG) precursors through a self-destruction/reconstruction process during sulfidization, resulting in a YS structure covered by self-assembled Co4S3 nanoplates. This morphology provides a highly mesoporous structure, enhanced electrochemical properties, and expanded active sites. Consequently, YSCS demonstrated significantly higher catalytic activity for Oxone activation compared to its precursor CoG and the benchmark Co3O4, with a reaction rate constant (k) of 0.108 min-1, surpassing those of Co3O4 NP + Oxone (0.007 min-1) and CoG + Oxone (0.023 min-1). Additionally, YSCS + Oxone exhibited a lower activation energy (Ea) of 17.8 kJ/mol for C4M degradation. The degradation pathway of C4M by YSCS + Oxone was thoroughly investigated using Fukui indices and analyzing the degradation by-products. Toxicity assessments showed that YSCS + Oxone significantly reduces the acute toxicity and bioconcentration factor of C4M, as well as potential mutagenicity and developmental toxicity risks. These findings confirm that YSCS is a highly effective catalyst for Oxone activation and RTIL degradation in water.

Highly-porous CuFe2O4@ZnFe2O4 yolk-shell heterostructure for photocatalytic reduction of nitrobenzene

Developing novel photocatalytic materials and underlying the charge separation mechanisms are keys for achieving excellent performances. However, currently reported photocatalysts suffer low charge separation efficiency and low stability during irradiation. In this work, highly-porous CuFe2O4@ZnFe2O4 yolk-shell heterostructure was prepared by a facile hydrothermal method. The characterization of transmission electron microscopy (TEM) indicates that the as prepared composite consists a core particle located within a well-defined shell with a clear gap between the two, forming a unique yolk-shell structure. The optimal sulfur-doped CuFe2O4@ZnFe2O4 yolk-shell heterostructure presents a photocurrent of 35.42 μA·cm−2, which is five times higher than undoped sample of 7.06 μA·cm−2. Photoelectrochemical method are used to analyze the behavior of photoinduced charges to reveal the structure-property relationship. The built-in electric field of heterojunctions effectively improves the separation of photoinduced charges, and the surface sulfur ions have an enrichment effect on photoinduced electrons. The yolk-shell heterostructure exhibits superior activity for photocatalytic reduction of nitrobenzene showing a selectivity of 99% and yield of 60.6%.

Yolk-Shell Construction of Na3V2(PO4)2F3 with Copper Substitution Microsphere as High-Rate and Long-Cycling Cathode Materials for Sodium-Ion Batteries.

Na3V2(PO4)2F3 (NVPF) is emerging as a promising cathode material for high-voltage sodium-ion batteries. Whereas, the inferior intrinsic electrical conductivity leading to poor rate performance and cycling stability. To address this issue, a strategy of synthesizing unique yolk-shell structured NVPF with copper substitution via spray drying method is proposed. Besides, the synergistic modulation of both crystalline structure and interfacial properties results in significantly enhanced intrinsic and interfacial conductivity of NVPF. The optimized yolk-shell structured cathode materials can possess a high capacity of 117.4 mAh g-1 at 0.1 C, and remains a high-capacity retention of 91.3% after 5000 cycles. A detailed investigation of kinetic properties combined with in situ XRD technology and DFT calculations, has been implemented, particularly with regard toelectron conduction and sodium ion diffusion. Consequently, the yolk-shell structured composition of Na3V1.94Cu0.06(PO4)2F3 with nitrogen-modified carbon coating layer shows the lowest polarization potential because of the effectively enhanced electronic conductivity and Na+ diffusion process in the bulk phase. The robust electrochemical performance suggests that developing the unique yolk-shell structure with the collaboration of interface and bulk crystal properties is a favorable strategy to design cathode material with a high performance for sodium-ion batteries.

CNTs and rGO synergistically enhance the cycling stability of yolk-shell silicon anodes for efficient lithium storage

Si-based anode materials have received a lot of attention from researchers due to their ultra-high theoretical specific capacity. However, poor conductivity and volume expansion during cycling have seriously hindered their further commercialization. To address the problems of Si-based materials, the multidimensional carbon materials constructed from Zeolitic imidazolate framework (ZIF) derived carbon and carbon nanotubes (CNTs) followed by the addition of reduced graphene oxide (rGO) are employed to encapsulate silicon nanoparticles (Si@C-ZIF@CNTs@rGO) to prepare a composite anode with a yolk-shell structure, which are prepared by mechanical stirring, electrostatic self-assembly and two-step calcination. The heat-treated ZIF materials not only form a unique yolk-shell structure that can effectively inhibit the volume expansion of silicon nanoparticles, but also derive rigid carbon shells and carbon nanotubes to improve the electrical conductivity of the anode materials, while rGO introduced by electrostatic self-assembly provides a large number of transport paths for electrons and ions. In a full battery test composed of LiFePO4 cathode, the composite cathode material loses only 2.4 % of its specific capacity after 100 cycles at 0.5 C current density. This work provides new ideas for multidimensional carbon structures to improve the lithium storage performance of silicon-based anodes.

Construction of Co3O4/SnO2 yolk-shell nanofibers for acetone gas detection

In this work, Co3O4/SnO2 heterojunctions were proposed and fabricated by single-nozzle electrospinning. Interestingly, novel yolk-shell nanofibers could be formed in a proper doped content of Co3O4. The gas sensing properties of sensors based on Co3O4/SnO2 yolk-shell nanofibers were evaluated, and a superior response of ∼216–100 ppm acetone at 350 °C was obtained. Additionally, Our sensors have an ultrafast response time of ∼0.62 s, demonstrating remarkable selectivity for acetone and excellent stability for both humidity and long-term use. These exceptional performances are attributed to the synergistic effect of nano-heterojunctions that enhance the effective interfacial area, as well as the unique yolk-shell structure of SnO2/Co3O4, which increases gas transport channels. Our results demonstrate that constructing Co3O4/SnO2 yolk-shell nanofibers is an effective strategy for achieving high-performance acetone gas detection.

Yolk-shell V2O3/nitrogen-doped carbon spheres as an ultra-long life anode for half/full sodium-ion batteries

With abundant resources and multiple electron transfer, V2O3 is a potential anode material for sodium ion batteries (SIBs). However, dramatic volume changes and slow reaction kinetics during the charge/discharge process still limit its application. Herein, porous yolk-shell V2O3/nitrogen-doped carbon (V2O3/NC) spheres are produced by a simple solvothermal method combined with subsequent carbonization. In this hierarchical structure, ultra-fine nanoparticles as primary building unit facilitate ion/electron transport; unique yolk-shell structure relieves the volume strain improving the structure integrity; nitrogen-doped carbon enhances electrochemical conductivity; moreover, rational mesoporous structure accelerates electrolyte penetration and high specific surface area supplies abundant reaction sites. Based on the above merits, yolk-shell V2O3/NC spheres exhibit satisfactory sodium ion storage performance (129.5 mAh g−1 at 5.0 A g−1 after 12,000 ultra-long cycles). What's more, an assembled V2O3/NC//Na3V2(PO4)3 full cell displays outstanding cycle performance (46 mAh g−1 after 300 cycles at 0.2 A g−1), demonstrating its potential value for practical applications.

Construction of Cu7 S4 @CuCo2 O4 Yolk-Shell Microspheres Composite and Elucidation of Its Enhanced Photocatalytic Activity, Mechanism, and Pathway for Carbamazepine Degradation.

Water pollution caused by the massive use of medicines has caused significant environmental problems. This work first reports the synthesis and characterization of the Cu7 S4 /CuCo2 O4 (CS/CCO) yolk-shell microspheres via hydrothermal and annealing methods, and then investigates their photocatalytic performance in removing organic water pollutants. The 10-CS/CCO composite with yolk-shell microspheres exhibits the highest photodegradation rate of carbamazepine (CBZ), reaching 96.3% within 2h. The 10-CS/CCO also demonstrates more than two times higher photodegradation rates than the pure (Cu7 S4 ) CS and (CuCo2 O4 ) CCO. This outstanding photocatalytic performance can be attributed to the unique yolk-shell structure and the Z-scheme charge transfer pathway, reducing multiple reflections of the acting light. These factors enhance the light absorption efficiency and efficiently transfer photoexcited charge carriers. In-depth, photocatalytic degradation pathways of CBZ are systematically evaluated via the identification of degradation intermediates with Fukui index calculation. The insights gained from this work can serve as a guideline for developing low-cost and efficient Z-scheme photocatalyst composites with the yolk-shell structure.

Revealing the synergistic mechanism of the generation, migration and nearby utilization of reactive oxygen species in FeOCl-MOF yolk-shell reactors

Fenton-like reactions is attractive for environmental pollutant control, but there is an urgent need to improve the utilisation of hydroxyl radicals (·OH) in practical applications. Here, for the first time, FeOCl is encapsulated within a Metal Organic Framework (MOF) (Materials of Institut Lavoisier-101 (MIL-101(Fe))) as a yolk-shell reactor (FeOCl-MOF) by in situ growth. The interaction between FeOCl and the MOF not only increases the electron density of FeOCl, but also shifts down the d-band centre. The increase of electron density could promote the efficient conversion of H2O2 to ·OH catalysed by FeOCl. And the shift of the d-band centre to the lower energy level facilitates the desorption of ·OH. Experimental and theoretical calculations showed that the high catalytic performance was attributed to the unique yolk-shell structure that concentrates the catalytic and adsorption sites in a confinement space, as well as the improved electron density and d-band centre for efficient generation, rapid desorption and utilized nearby of ·OH. Which is utilized nearby by the organic pollutants adsorbed by the surface MOF, thus greatly improving the effective conversion of H2O2 and the ·OH utilisation (from 25.5% (Fe2+/H2O2) to 77.1% (FeOCl-MOF/H2O2)). In addition, a catalytic reactor was constructed to achieve continuous efficient treatment of organic pollutants. This work provides a Fenton-like microreactor for efficient generation, rapid desorption, and nearby utilization of ·OH to improve future technologies for deep water purification in complex environments.

Coordination polymer-derived hierarchically structured MnO/NC composites as anode materials for high-performance lithium-ion batteries

Coordination polymer-derived metal oxides/carbon composites have advantages of uniform carbon coating, strong bonding ability with active materials, and in-situ introduction of heteroatom-doped carbon, which make them suitable for lithium-ion battery anode materials, and they have been extensively studied. However, it is still a challenging task to design and synthesize metal oxide/heteroatom-doped carbon composites with special morphology. In this work, flower-like Mn-based coordination polymers constructed by nanosheets, which were designed and synthesized by adjusting the coordination mode of ligands. The hierarchical structured MnO/NC composites were successfully synthesized by calcination in a reducing atmosphere. The composite exhibits a unique yolk-shell structure, the yolk-shell structure is composed of micro-flowers assembled from nitrogen-doped carbon nanosheets uniformly loaded with MnO nanoparticles as the outer shell and MnO/NC nanoparticle aggregates as the inner core. It exhibits high specific capacity (1108.9 mAh g-1 after 300 cycles at 0.5 A g-1), and excellent long cycle stability (768 mAh g-1 after 1000 cycles at 1 A g-1). The outstanding Li-storage performance is owing to the synergistic effect of unique yolk-shell structure and continuous nitrogen-doped carbon coating, which makes the spread of electrolyte and the transport of Li+ faster, alleviates the volume change of the electrode material during cycling, and increases the pseudo-capacitance behavior.

Phase transformation controlled Co1−xS-CoS2 heterostructures embedded in S-doped carbon nanofibers for superior Sodium-Ion storage

Cobalt-based sulfides are considered as a promising anode material for sodium-ion batteries (SIBs) due to its various chemical formulations and high theoretical capacity. However, slow kinetics and structural instability lead to unsatisfactory electrochemical performance. Herein, ultrafine particles with Co1−xS-CoS2 heterostructures precisely controlled by phase transformation has been integrated with the encapsulation with S-doped carbon nanofiber through the one-stone-two-birds strategy. Due to the abundant heterointerfaces, unique yolk-shell structure and increased carbon interlayer spacing in Co1−xS-CoS2/carbon nanofibers (Co1−xS-CoS2/CNF), the reaction kinetics and the diffusion rate of Na+ have been significantly improved. As expected, the as-prepared Co1−xS-CoS2/CNF anode exhibits extraordinary rate performance (495.3 mAh/g at 10 A/g) and cycling stability (380.1 mAh/g at 5 A/g after 5,000 cycles), outperforming most reported TMS materials. A sodium-ion full cell with a Co1−xS-CoS2/CNF anode and Na3V2(PO4)3 cathode also show excellent electrochemical performance. The electrochemical reaction mechanism of Co1−xS-CoS2/CNF is revealed by ex-situ XRD and ex-situ HRTEM. Hence, it is hoped that our work can provide constructive ideas for the design of electronic or morphological structures for building high-performance energy storage materials.

Rational construction of yolk-shell structured Co3Fe7/FeO@carbon composite and optimization of its microwave absorption

The construction of yolk-shell composites with dielectric/magnetic multiple loss mechanisms has become a promising strategy to obtain high-efficiency microwave absorbing materials. An ideal microwave absorber should possess dielectric and magnetic loss abilities, thereby leading to the attenuation and absorption of incident electromagnetic radiation. Herein, the yolk-shell structured CoFe2O4@carbon (YS-CoFe2O4@C) and Co3Fe7/FeO@carbon (YS-Co3Fe7/FeO@C) composites were designed and synthesized through a series of processes, which include in-situ coating, heat-treating, etching and subsequent carbonization reduction reaction. The composite materials with specific structure, composition, and electromagnetic parameters could be effectively obtained by controlling the reaction conditions. The combination of alloy with high magnetic loss and carbon with advanced dielectric loss as well as the unique yolk-shell structure endow YS-Co3Fe7/FeO@C improved impendence matching and large attenuation constant. The YS-Co3Fe7/FeO@C composites show optimized microwave absorption behaviors, the minimum reflection loss is up to −57.6 dB at 12.30 GHz with the of 2.5 mm and the corresponding effective absorption bandwidth is 5.27 GHz (10.10–15.37 GHz). Moreover, the widest effective bandwidth could reach 7.0 GHz (11–18 GHz) with the thickness of 2.3 m. This design provides a novel concept for tuning microwave absorption efficiency of magnetic/dielectric composites to prepare high-performance microwave absorbers.

A perylenediimide modified SiO2@TiO2 yolk-shell light-responsive nanozyme: Improved peroxidase-like activity for H2O2 and sarcosine sensing

Although light-responsive nanozyme have been widely used in colorimetric sensing, some limitations such as poor catalytic activity, low detection efficiency, and unclear structure-activity relationships remain unresolved. Herein, we prepared an excellent light-responsive peroxidase (POD) mimic, perylenediimide (PDI-OH) modified SiO2 @TiO2 yolk-shell spheres (SiO2 @TiO2/PDI-OH), based on DFT-assisted design. The experiment and DFT calculation revealed that the enhanced POD-like activity was mainly attributed to a suitable built-in electric field among adjacent PDI-OH molecules on the surface of the SiO2 @TiO2 and the unique yolk-shell structure with more reaction sites of SiO2 @TiO2. Consequently, the highly selective and ultrasensitive detection of H2O2 is achieved with a detection limit (LOD) of 7.6 × 10−8M. Further, the selective detection of sarcosine with LOD of 1.2 × 10−7 M was also achieved by introducing sarcosine oxidase (SOx). This colorimetric assay is successfully applied to selectively detect H2O2 and sarcosine levels in real samples. Controlled response time, anti-interference, and the robustness of the developed colorimetric sensor are the key advantages. And the present work firstly clarifies the effect of PDIs substituents on the POD-like activity of light-responsive nanozymes and provided new guidelines to develop high-performance nanozymes for hazardous substances detection.

Tailored dodecahedral polyoxometalates nanoframes with in situ encapsulated Co, N, C for oxygen evolution reaction

Hollow nanoframes with three-dimensional open architecture have diverse applications but their acquirement is still a big challenge. Herein, a crystal morphological evolution mechanism is proposed for the synthesis of dodecahedral [Co(CN)6]3-@POMs (polyoxometalates) frame-like nanostructure. Through an inside-out etching process, K3PW12O40 (POMs) dodecahedron are transformed to dodecahedral POMs nanoframes with encapsulation of [Co(CN)6]3- inside the nanochannels, which can be transformed to Co, N, C co-doped POMs nanoframes (CNCP) by a further N2-pyrolysis process. The hybrid nanoframes possess unique yolk-shell structure with multi-heteroatoms doping, showing great advantages for oxygen evolution reaction (OER). As an OER catalyst, it exhibits excellent electrochemical catalytic activities with a low overpotential of 241 mV at 10 mA cm−2, a small Tafel slope of 75.8 mV dec-1 and a long-term electrochemical stability. Our work not only provides novel dodecahedral Keggin-type polyoxometalates yolk-shell structure and nanoframes, but also provides a facile strategy to in situ encapsulate active components inside porous substrates, and thus will open a new perspective for the further utilization of POMs nanomaterials as potential catalysts for energy storage and conversion.

Orchestrated Yolk-Shell Nanohybrids Regulate Macrophage Polarization and Dendritic Cell Maturation for Oncotherapy with Augmented Antitumor Immunity.

The protumoral and immunosuppressive tumor microenvironments greatly limit the antitumor immune responses of nanoparticles for cancer immunotherapy. Here, the intrinsic immunomodulatory effects of orchestrated nanoparticles and their ability to simultaneously trigger tumor antigen release, thereby reversing immunosuppression and achieving potent antitumor immunity and augmented cancer therapy, are explored. By optimizing both the composition and morphology, a facile strategy is proposed to construct yolk-shell nanohybrids (Fe3 O4 @C/MnO2 -PGEA, FCMP). The intrinsic immunomodulatory effects of FCMP are utilized to reprogram macrophages to M1 phenotype and induce the maturation of dendritic cells. In addition, the chemical, magnetic, and optical properties of FCMP contribute to amplified immunogenic cell death induced by multiaugmented chemodynamic therapy (CDT) and synergistic tumor treatment. Taking advantage of the unique yolk-shell structure, accurate T1 -T2 dual-mode magnetic resonance imaging can be realized and CDT can be maximized through sufficient exposure of both the Fe3 O4 core and MnO2 shell. Potent antitumor effects are found to substantially inhibit the growth of both primary and distant tumors. Furthermore, the strategy can be extended to the synthesis of other yolk-shell nanohybrids with tailored properties. This work establishes a novel strategy for the fabrication of multifunctional nanoplatforms with yolk-shell structure for effective cancer therapy with immunomodulation-enhanced antitumor immunity.

General synthesis of yolk-shelled FexQy@Carbon (Q = S, Se, P) film for high performance anode of sodium-ion batteries

Sodium-ion batteries (SIBs) have attracted widespread attention because of the economic benefit of low-cost and abundance of sodium resources. Iron-based electrodes (sulfide, selenide and phosphide) that operate through conversion mechanism have shown huge potential for excellent sodium-ion storage. However, the problems related with serious volume expansion and lack of general synthesis methods of iron-based materials shorten the cycle life and hindered their application in SIBs. Herein, a general synthetic strategy of electrospinning process was developed to achieve the yolk-shelled FexQy@C (Q = S, Se and P) film for binder-free anode of high-performance SIBs. Such method has more precursor materials to choose from and is highly scalable. More importantly, the designed electrodes have a unique yolk-shell structure and a three-dimensional conductive network. When applied as a binder-free anode of SIBs, all three samples exhibit outstanding sodium storage performance (FeS2@C-40: remaining 280 mAh g−1 after 400 cycles at 1 A g−1, Fe7Se8@C-40: remaining 186.5 mAh g−1 after 200 cycles at 0.1 A g−1 and FeP4@C-40: remaining 205 mAh g−1 after 1000 cycles at 0.5 A g−1). Therefore, the scalability and universality of this general synthetic strategy can open up a new direction for the exploration of high-energy density and flexible electrode materials.

Metal-organic frameworks derived RuP2 with yolk-shell structure and efficient performance for hydrogen evolution reaction in both acidic and alkaline media

Hydrogen generation from electrical water splitting has become a greatly increasing requirement for energy systems, however, highly effective and durable electrocatalysts towards universal-pH hydrogen evolution reaction (HER) remain a big challenge. Herein, we design and synthesize ruthenium di-phosphide (RuP2) confined in carbon layers (RuP2-C) with a unique yolk-shell structure (RuP2-C@RuP2-C) from MOF. As expected, it not only exceeds the HER activity of Pt catalysts, with very tiny overpotentials at 10 mA cm−2 (9 and 17 mV in 1.0 M KOH and 0.5 M H2SO4, individually), but also has high stability. Besides, it also exhibits a low overpotential (40 mV) close to Pt catalysts and high stability in 1.0 M PBS, indicating that RuP2-C@RuP2-C (RPC@RPC) owns outstanding HER performance at all pH values. Density functional theory (DFT) calculation results further unravel that the P-site on the surface of RPC@RPC possesses low hydrogen adsorption energy, beneficial for boosting the HER activity.

MgCo layered double hydroxide-based yolk shell polyhedrons as multifunctional sulfur mediator for lithium–sulfur batteries

The development of efficient sulfur host materials to address the shuttle effect issues of lithium polysulfides (LiPSs) is crucial in the lithium–sulfur (Li–S) batteries but still challenging. In the present study, a novel yolk shell structured MgCo-LDH/ZIF-67 composite is designed as Li–S battery cathode. In this composite, the shell layer is MgCo layered double hydroxide constructed by partially etching ZIF-67 nanoparticle by Mg2+, and the core is the unreacted ZIF-67 particle. The unique yolk shell structure not only provides abundant pores for sulfur accommodation, but also facilitates the electrolyte penetration and ion transport. The ZIF-67 core exhibits strong polar adsorption to LiPSs through the Lewis acid-base interactions, and the micropores/mesoporous can further trap LiPSs. Meanwhile, the MgCo-LDH shell exposes enough sulfur-philic sites for enhancing chemisorption and catalyzes LiPSs conversion. As a result, when MgCo-LDH/ZIF-67 is used as sulfur host in the cathode, the cell achieves a high discharge capacity of 1121 mAh g−1 at 0.2 C, and an areal capacity of 5.0 mAh cm−2 under high sulfur loading of 5.8 mg cm−2. The S/MgCo-LDH/ZIF-67 electrode holds a promising potential for the development of Li–S batteries.