Co9S8 Hollow Research Articles

Hollow Co9S8-carbon fiber hierarchical heterojunction with Schottky contacts for tunable microwave absorption

Heterogeneous interface engineering of hollow hierarchical structures with Schottky contacts is an attractive approach for designing light weight and efficient microwave absorption (MA) materials. Herein, hollow Co9S8-carbon fiber (CF) composites were prepared by solvothermal, electrostatic spinning, and pyrolysis methods. CF was used as the main chain and hollow Co9S8 derived from metal-organic frameworks (MOFs) was homogeneously embedded in it, which overcame the difficulties of the traditional template method and effectively avoided the particle agglomeration problem. The interface polarization relaxation process is improved by the construction of Co9S8-CF heterojunction with Schottky contacts, which effectively modulates the dielectric loss. The internal hollow macroporous cavity and CF with lightweight properties enhance the reflection attenuation of the internal cavity. In addition, the electromagnetic characteristics can be flexibly adjusted to achieve the tunable MA performance by varying the reaction parameters. As a result, the Co9S8-CF-3–700 exhibits optimum MA performance, with a reflection loss (RL) of −60.83 dB at 10.85 GHz and a thickness of 2.76 mm. The effective absorption bandwidth (EAB) extends to 5.6 GHz at a thickness of 2.19 mm. This research provides a promising approach to creating light weight and efficient MA materials with potential applications in radar and communication systems.

Cobalt‐based zeolitic imidazole framework derived hollow Co3S4 nanopolyhedrons for supercapacitors

Transition metal sulfides with designed nanostructures are expected to provide superior electrochemical performance when used as electrode materials for pseudocapacitors compared to their oxide counterparts. In this paper, hollow Co3S4 dodecahedra were successfully prepared using cobalt‐based zeolite imidazolium skeleton (ZIF‐67) as the precursor and thioacetamide (TAA) as the sulfur source combined with a facile one‐step vulcanization process. The hollow cavity structure not only shortens the carrier transport distance but also provides a higher specific surface area and abundant active sites, which promotes an efficient mass transfer process. In addition, the one‐step synthesis of hollow Co3S4 has greater advantages than the one‐step synthesis in terms of cost control and process simplification. The specific capacitance of the produced hollow Co3S4 nanopolyhedra was 668 F/g at 1 A/g and remained at 353 F/g at 10 A/g when used as a pseudocapacitor electrode, demonstrating its superior multiplication capability. In addition, the capacitance retention is 86.4% after 5000 cycles at 4 A/g, indicating its long cycle stability. Notably, employing commercial activated carbon as negative electrode and the as‐prepared hollow Co3S4 polyhedrons as positive electrode, the assembled asymmetry supercapacitor device delivers a high energy density of 20.7 Wh/kg at a power density of 716 kW/kg. The capacitance value of the device remains up to 81.4% after 2000 charging/discharging cycles. The simple synthesis process opens new opportunities to develop advanced hollow nanostructures exhibiting potential for various applications.

Photoelectron Migration Boosted by Hollow Double-Shell Dyads Based on Covalent Organic Frameworks for Highly Efficient Photocatalytic Hydrogen Generation.

Photocatalytic hydrogen production based on noble metal-free systems is a promising technology for the conversion of solar energy into green hydrogen, it is pivotal and challenging to tailor-make photocatalysts for achieving high photocatalytic efficiency. Herein, we reported a hollow double-shell dyad through uniformly coating covalent organic frameworks (COFs) on the surface of hollow Co9S8. The double shell architecture enhances the scattering and refraction efficiency of incident light, shortens the transmission distance of the photogenerated charge carriers, and exposes more active sites for photocatalytic conversion. The hydrogen evolution rate is as high as 23.15 mmol g-1 h-1, which is significantly enhanced when compared with that of their physical mixture (0.30 mmol g-1 h-1) and Pt-based counterpart (11.84 mmol g-1 h-1). This work provides a rational approach to the construction of noble-metal-free photocatalytic systems based on COFs to enhance hydrogen evolution performance.

Photoelectron Migration Boosted by Hollow Double‐Shell Dyads Based on Covalent Organic Frameworks for Highly Efficient Photocatalytic Hydrogen Generation

AbstractPhotocatalytic hydrogen production based on noble metal‐free systems is a promising technology for the conversion of solar energy into green hydrogen, it is pivotal and challenging to tailor‐make photocatalysts for achieving high photocatalytic efficiency. Herein, we reported a hollow double‐shell dyad through uniformly coating covalent organic frameworks (COFs) on the surface of hollow Co9S8. The double shell architecture enhances the scattering and refraction efficiency of incident light, shortens the transmission distance of the photogenerated charge carriers, and exposes more active sites for photocatalytic conversion. The hydrogen evolution rate is as high as 23.15 mmol g−1 h−1, which is significantly enhanced when compared with that of their physical mixture (0.30 mmol g−1 h−1) and Pt‐based counterpart (11.84 mmol g−1 h−1). This work provides a rational approach to the construction of noble‐metal‐free photocatalytic systems based on COFs to enhance hydrogen evolution performance.

Constructing Co[sbnd]N[sbnd]C coordination in Co9S8 embedded N,S-codoped carbon nanotube as an advanced electrode for supercapacitor and Na-ion battery

Yolk-shell-structured transition metal sulfides (TMSs)/carbon nanocomposites are highly desirable in advanced energy storage system, such as sodium-ion batteries (SIBs) and supercapacitors (SCs). Nevertheless, practical applications are still prevented by the loose attachment of TMSs with carbon caused by conversion stress, the aggregation of TMSs nanoparticles and the sluggish ion transport caused by high crystallinity of carbon. Here, the disperse hollow Co9S8 nanoparticles encapsulated into N,S-codoped carbon nanotubes (CNTs) with poor crystallinity through CoNC bond was synthesized (CS-NSCNT) to overcome the above obstacles. The designed CS-NSCNT can provide the short diffusion path and prevent the huge volume expansion of conversion reaction. Moreover, the established CoNC bond endows the strong interaction and regulates the electronic structure thus promote the stability and rate performance effectively. The CS-NSCNT SCs’s electrode delivers a high specific capacitance of 1150 F g−1 at 1 A g−1, with a high cycling life stability and rate performance. For SIBs, the CS-NSCNT cathode demonstrates an initial reversible capacity of 475 mAh g−1 at 0.1 A g−1 and an excellent rate performance with a capacity retention of 53 % at 10 A g−1. This work may satisfy the long-stability, high-capacitance/capacity, high-power/energy density application requirements of future applications.

High-capacity and amorphous MoS3 decorated hollow Co9S8 nano-spheres composites for boosted sodium ion storage

Herein, the high-capacity and amorphous MoS3 has been employed to decorate the hollow Co9S8 nano-spheres to fabricate the Co9S8/MoS3 composites by a three-step synthesis. The chain-like and amorphous MoS3 can provide a high capacity of 894 mAh g−1 and generate abundant active sites to boost the sodium storage properties of Co9S8 based electrode. The heterogeneous interface between Co9S8 and MoS3 is conducive to the promotion of charge transfer and Na+ diffusion kinetics. Thus, the Co9S8/MoS3 as the novel anode materials exerts more outstanding sodium storage properties than pure Co9S8. At a given current density of 0.5 A g−1, the Co9S8/MoS3 delivers a desired reversible capacity of 621 mAh g−1 for 90 cycles. Even at 2 A g−1, the Co9S8/MoS3 exhibits a stable cyclic performance, the charge specific capacity is about 518 mAh g−1 for 500 cycles. At a high rate of 5 A g−1, a high capacity of 486 mAh g−1 can be achieved, which is obviously higher than that of pure Co9S8. The remarkable sodium storage properties of Co9S8/MoS3 are mainly resulted from the cooperate effects of amorphous MoS3 and hollow Co9S8 nano-spheres, which demonstrate the promising application of Co9S8/MoS3 in future sodium storage devices.

Controllable construction of ZIF-derived Co9S8 hollow polyporous polyhedrons with Ru-doping for enhanced hydrogen evolution reaction.

Ru-doped Co9S8 hollow porous polyhedrons (Ru-Co9S8 HPPs) derived from zeolitic-imidazolate-frameworks were synthesized through hydrothermal coprecipitation and thermal decomposition methods. The results indicate that Ru-Co9S8-500 HPPs possess a strong Ru-Co synergistic effect, large electrochemical surface area, and sufficient active sites, endowing them with excellent hydrogen evolution reaction performance.

Design and construction of hollow metal sulfide/selenide core-shell heterostructure arrays for hybrid supercapacitor.

Transition metal sulfides and selenides are common electrode materials in supercapacitors. However, the slow redox kinetics and structural collapse during charge-discharge cycles of single-component materials have impeded their electrochemical performance. In this study, hollow Co9S8 nanotubes were synthesized through a rational morphology design approach. Subsequently, NiSe2 or Co0.85Se was electrodeposited onto the Co9S8 nanotubes, yielding two core-shell heterostructure arrays, namely, NiSe2@Co9S8 and Co0.85Se@Co9S8. By fully leveraging the advantages and synergistic effects of these dual-phase heterostructures, the NiSe2@Co9S8 and Co0.85Se@Co9S8 configurations demonstrated outstanding areal capacitances of 12.54 F cm-2 and 9.61 F cm-2, respectively, at 2 mA cm-2. When integrated with activated carbon in hybrid supercapacitors, the NiSe2@Co9S8//AC and Co0.85Se@Co9S8//AC devices exhibited excellent energy storage performance, with energy densities of 0.959 mW h at 1.681 mW and 0.745 mW h at 1.569 mW, respectively. Additionally, these hybrid supercapacitors demonstrated remarkable cycling stability, with capacitance retention of 87.5% and 89.5% after 5000 cycles for NiSe2@Co9S8//AC and Co0.85Se@Co9S8//AC, respectively. This study provides a novel approach to the synthesis of multiphase core-shell heterostructures based on metal sulfides and selenides, opening new avenues for future research.

Construction of hierarchical carbon fiber Aerogel@Hollow Co9S8 polyhedron for high-performance electromagnetic wave absorption at low-frequency

The development of low-frequency electromagnetic wave absorption materials faces considerable obstacles due to intense coupling of wave impedance and electromagnetic dissipation capacity. Herein, a novel hierarchical structure composed of 3D interconnected carbon fibers aerogel loaded with hollow cobalt (Co)-sulfide polyhedrons (CFA@HCS) is designed. Typical 3D interconnected carbon fibers derived from bamboo cellulose fiber aerogel serve as a skeleton to support the Co9S8 with a hollow structure. The electromagnetic parameters of the composite are effectively modified by combining the carbon-based skeleton with the hollow Co9S8. The coupling interaction of the electromagnetic characteristics at low frequency can be significantly improved. Accordingly, the minimum reflection loss (RLmin) of CFA@HCS with 15 wt% filler loading reaches −53.6 dB at 3.36 GHz and its effective absorption bandwidth can cover almost all the S and C bands (3.04–8 GHz). In addition, the minimum reduction of the radar cross section (RCS) reaches –22.6 dB m2 when the incidence theta is −60°. This work demonstrates that low-frequency EMW absorption could be improved by constructing hierarchical composites of carbon fiber/transition metal sulfide.

Core-shell heterostructure by coupling layered ReS2 with Co9S8 nanocubes for boosted oxygen evolution reaction

The controllable morphology and composition of catalysts are crucial to improving the electrocatalytic activity of oxygen evolution reaction (OER). Herein, we construct a bimetallic heterostructure by sulfidation and hydrothermal methods, and the layered ReS2 is vertically aligned on Prussian blue-derived hollow Co9S8 nanocubes (Co9S8@ReS2). The core-shell structure of Co9S8@ReS2 can effectively prevent the restacking of layered ReS2, expose the abundant surface area and improve the utilization of electrocatalytic sites, resulting in fast electrolyte diffusion and charge transfer during OER. Due to the synergistic effect of the core-shell morphology and the formed bimetallic heterostructure, Co9S8@ReS2 exhibits excellent catalytic OER performance. At 10 mA/cm2, only 288 mV of overpotential is required with the Tafel slope of 73.3 mV/dec for Co9S8@ReS2, which are both lower than that of Co9S8 and ReS2. Meanwhile, Co9S8@ReS2 exhibits high catalytic stability and low charge transfer resistance and the boosted active sites are confirmed by density functional theory. This work provides a rational design of the OER catalysts by constructing the bimetallic heterostructure.

Hollow Co3S4 Nanocubes Interconnected with Carbon Nanotubes as Nanoreactors to Accelerate Polysulfide Conversion for High-Performance Lithium–Sulfur Batteries

Lithium–sulfur batteries (LSBs) with a high energy density of 2600 Wh kg–1 have drawn intensive attention based on the double electron reaction of sulfur. Nevertheless, blocked by the shuttle effect of lithium polysulfides and sluggish sulfur conversion kinetics, LSBs display a small specific capacity and a rapid capacity loss. Herein, we describe a conductive framework and electrocatalyst where numerous carbon nanotubes run through the hollow Co3S4 nanocubes as the sulfur host. The hollow structure can buffer the volume change during the discharge/charge process, while the CNTs link cubes together to facilitate electron transport. The Co3S4 catalyst can not only effectively accelerate the conversion from liquid LiPSs into solid Li2S1/2 but also promote the conversion of Li2S2 into Li2S. Based on the DFT theoretical calculation, the Li–S bond of Li2S2 became longer after interaction with Co3S4, indicating that it is easier to break into Li2S. Thus, the Co3S4/CNTs composite cathode shows a higher initial specific capacity (1252 mAh g–1) than the CNT cathode (928 mAh g–1) at 0.1C. In addition, it also shows a specific capacity of 440 mAh g–1 after 800 cycles with a decay rate of 0.08% per cycle at 1.0C. This work provides a new perspective for improving the sluggish transformation kinetics, which is conducive to the enhancement of sulfur utilization.

S‐Scheme Co9S8@Cd0.8Zn0.2S‐DETA Hierarchical Nanocages Bearing Organic CO2 Activators for Photocatalytic Syngas Production

AbstractDelicate modulations of CO2 activation and charge carrier separation/migration are challenging, yet imperative to augment CO2 photoreduction efficiency. Herein, by supporting diethylenetriamine (DETA)‐functionalized Cd0.8Zn0.2S nanowires on the exterior surface of hollow Co9S8 polyhedrons, hierarchical Co9S8@Cd0.8Zn0.2S‐DETA nanocages are fabricated as an S‐scheme photocatalyst for reducing CO2 and protons to produce syngas (CO and H2). The amine groups strengthen adsorption and activation of CO2, while the “nanowire‐on‐nanocage” hierarchical hollow heterostructure with an S‐scheme interface boosts separation and transfer of photoinduced charges. Employing Co(bpy)32+ as a cocatalyst, the optimal photocatalyst effectively produces CO and H2 in rates of 70.6 and 18.6 µmol h−1 (i.e., 4673 and 1240 µmol g−1 h−1), respectively, affording an apparent quantum efficiency of 9.45% at 420 nm, which is the highest value under comparable conditions. Ultraviolet photoelectron spectroscopy, Kelvin probe, and electron spin resonance confirm the S‐schematic charge‐transfer process in the photocatalyst. The key COOH* species responsible for CO2‐to‐CO reduction is detected by in‐situ diffuse reflectance infrared Fourier transform spectroscopy and endorsed by density functional theory calculations, and thus a possible CO2 reduction mechanism is proposed.

Lattice confined Ru single sites in hollow Co9S8 polyhedron triggering Co-S-Ru catalytic centers for rechargeable Zn-air battery

Lattice confined Ru single sites in hollow Co9S8 polyhedron triggering Co-S-Ru catalytic centers for rechargeable Zn-air battery

Metal–organic framework-derived hollow Co9S8 nanotube arrays coupled with porous FeCo–P nanosheets as an efficient electrode material for hybrid supercapacitors

Hollow Co9S8 nanotubes@FeCo–P nanosheet arrays are synthesized on nickel foam for hybrid supercapacitors.

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.

Hollow Co9S8 cores encapsulated in hierarchical MXene@Bi2O3 multiple shells for constructing binder-free electrodes of foldable supercapacitors

Rational structure design and regulation are of paramount importance for obtaining electrode materials with desirable electrochemical performance. Here, a novel binder-free electrode with the hollow Co9S8 core@multi-shell structure (CS-x@MXene@Bi2O3) derived from metal-organic frameworks (MOFs) precursor is well designed by the electrospinning, sulfuration, carbonization, and hydrothermal processes. In this architecture, the concentration of Co9S8 (CS-x) is optimized for an ideal flexible substrate, which alleviates the dimensional variation for long cycle life. The unique cores and the MXene flakes engineered by Bi2O3 multiple shells can be responsible for the superior characteristics, including a fast electronic pathway, large specific surface area, enhanced electrical conductivity, and improved electrochemical performance. As expected, the obtained CS-2@MXene@Bi2O3 binder-free electrode exhibits a high discharge capacitance of 646.1 F g–1 (1 A g–1). Two binder-free electrodes can be assembled into a solid-state supercapacitor with desirable energy and power density, and long-term cyclic stability is demonstrated through 5000 cycles. Given these advantages, the CS-2@MXene@Bi2O3 is selected as the electrode in a foldable supercapacitor. More importantly, the specific capacitance is reserved after various deformations. Therefore, it is expected that binder-free electrode materials with the unique core@shell structure design could be applied in wearable and portable energy conversion devices.

Promoting “Strong Adsorption” and “Fast Conversion” of Polysulfides in Li‐S batteries Based on Conductive Sulfides Host with Hollow Prism Structure and Surface Defects

AbstractThe chemical binding between metal compounds and polysulfides provides a good solution to inhibit shuttle effect in Li‐S batteries. However, the Sabatier principle predicts that overly strong adsorption will commonly hinder the conversion of polysulfides, so building the synergetic effect mechanism between “strong adsorption” and “fast conversion” for polysulfides is a significant strategy. To realize this goal, in this study, the defect‐enriched Co9S8 hollow prisms (DHCPs) as both S host and catalyst material for Li‐S batteries are designed. Based on in situ UV–vis spectroscopy results, it is found that DHCPs can profitably promote the generation of radicals during the discharge process. In the case of the relatively high conversion barrier of “liquid–liquid” reaction, the generated radicals are responsible for the fast conversion reaction via a unique reaction pathway. When the sulfur loading is 4.63 mg cm−2, the cell with DHCP/S cathode delivers a high areal capacity of 4.75 mAh cm−2 at 0.1 C and keeps a high capacity of 2.99 mAh cm−2 after 100 cycles at 0.5 C. This study provides a positive attempt to achieve “strong adsorption” and “fast conversion” of polysulfides simultaneously, which will convincingly boost the development and practical process of Li‐S batteries.

Multifunctional Mesoporous Hollow Cobalt Sulfide Nanoreactors for Synergistic Chemodynamic/Photodynamic/Photothermal Therapy with Enhanced Efficacy.

The unique tumor microenvironment (TME) characteristic of severe hypoxia, overexpressed intracellular glutathione (GSH), and elevated hydrogen peroxide (H2O2) concentration limit the anticancer effect by monotherapy. In this report, glucose oxidase (GOx)-encapsulated mesoporous hollow Co9S8 nanoreactors are constructed with the coverage of polyphenol diblock polymers containing poly(oligo(ethylene glycol) methacrylate) and dopamine moieties containing methacrylate polymeric block, which are termed as GOx@PCoS. After intravenous injection, tumor accumulation, and cellular uptake, GOx@PCoS deplete GSH by Co3+ ions. GOx inside the nanoreactors produce H2O2 via oxidation of glucose to enhance •OH-based chemodynamic therapy (CDT) through the Fenton-like reaction under the catalysis of Co2+. Moreover, Co3+ ions possess catalase activity to catalyze production of O2 from H2O2 to relieve tumor hypoxia. Upon 808 nm laser irradiation, GOx@PCoS exhibit photothermal and photodynamic effects with a high photothermal conversion efficiency (45.06%) and generation capacity of the toxic superoxide anion (•O2-) for photothermal therapy (PTT) and photodynamic therapy (PDT). The synergetic antitumor effects can be realized by GSH depletion, starvation, and combined CDT, PTT, and PDT with enhanced efficacy. Notably, GOx@PCoS can also be used as a magnetic resonance imaging (MRI) contrast agent to monitor the antitumor performance. Thus, GOx@PCoS show great potentials to effectively modulate TME and perform synergistic multimodal therapy.

Low temperature growth of CuS nanosheets on hollow Co9S8 nanotubes: Synthesis and analytical application

Transition metal sulfides have found wide applications as promising catalysts and electrocatalysts. Herein, hollow Co9S8 nanotubes were prepared through hydrothermal method, on which CuS nanosheets were grown at low temperature, and hollow Co9S8@CuS heterostructure nanocomposite was synthesized. The prepared hollow Co9S8 nanotubes possess high specific surface area and efficient charge transfer ability, offering an ideal substrate for the growth of CuS nanosheets. Furthermore, the hollow structure of the synthesized Co9S8@CuS can accelerate mass transfer and provide more reaction sites with the specific area of 36.79 m2/g, and the heterostructure between Co9S8 and CuS enhanced their synergistic effect on the conductivity and electrocatalytic activities. For analytical application, the synthesized Co9S8@CuS nanocomposite was applied for the determination of glucose and H2O2, with the charge transfer rate constants of 3.89 and 1.94 s−1, respectively. Under optimal conditions, the Co9S8@CuS-modified glassy carbon electrode exhibits wide linear ranges of 0.03–13 mM and 0.05–14 mM with detection limits of 5.64 μM and 6.06 μM for the oxidation of glucose and the reduction of H2O2, respectively. Additionally, real sample analyses demonstrate satisfying recoveries of 96.43 % and 101.65 % to glucose and H2O2, respectively, indicating its potential to quantitatively analyze the real samples.

Hollow Co9S8 nanoparticles with carbon shells for wide-band and efficient microwave absorption

Aiming to obtain advanced microwave absorbing materials with high absorption efficiency, broad absorption bandwidth and low density, herein, a novel nanocomposite with irregular hollow nanostructure of Co9S8@C was successfully prepared via a soft template and annealing method. Due to the shrinkage process of the Co9S8 nanospheres by annealing, Co9S8 cores and carbon shells were easily obtained. Because of the unique microstructure with irregular outer shells and heterogeneous interfaces, improved polarization loss, multiple reflection loss as well as the impedance matching capability was achieved. As a result, greatly enhanced microwave absorption performance with a reflection loss (RL) of − 51.3 dB at 4.12 GHz, and effective absorption bandwidth (RL<−10 dB) of 5.44 GHz at a thickness of only 1.35 mm was obtained, suggesting the unique Co9S8@C nanocomposite in this work to be an intriguing and promising microwave absorber.