CoS2 Nanoparticles Research Articles

TCNQ-derived N/S dual-doped carbon cube electrocatalysts with built-in CoS2 nanoparticles for high-rate lithium-oxygen batteries

• CoS 2 @NS-C cubes were synthesized using TCNQ coordination polymer and CoI 2. • CoS 2 @NS-C cube is composed of N/S dual-doped carbon cube with embedded CoS 2 . • CoS 2 nanoparticles (D ≈ 5 nm) are uniformly distributed in N/S dual-doped carbon sheath. • CoS 2 @NS-C cubes provide high electronic conductivity and ORR/OER activity. • CoS 2 @NS-C cubes are achieved to high-rate performance and quick-charging capability. Nitrogen/Sulfur dual-doped carbon cubes with built-in CoS 2 nanoparticles (CoS 2 @NS-C cubes) as an electrocatalyst are developed to improve the high-rate and long-term performance of lithium-oxygen batteries. The CoS 2 @NS-C cubes were synthesized by coprecipitation between a cobalt salt and 7,7,8,8-tetracyanoquinodimethane (TCNQ) and subsequent thermal sulfidation. TCNQ acted as the coordination polymer for a cube shape and as the nitrogen source for nitrogen-dopants. The CoS 2 @NS-C cubes comprise uniformly distributed CoS 2 nanoparticles in a nitrogen/sulfur dual-doped carbon matrix, providing fast catalytic activity for oxygen reduction/evolution reactions. The CoS 2 @NS-C cubes exhibited a high-rate performance of 5000 mA g −1 as well as long-term performance of > 100 cycles with a current density of 2000 mA g −1 . These results confirmed the enhanced performance of the lithium-oxygen battery, with fast charging capability.

Construction of multifunctional and flame retardant separator towards stable lithium-sulfur batteries with high safety

Considering the unprecedented advantages such as superb theoretical capacity, high energy density and low cost, lithium-sulfur batteries (LSBs) have been under spotlight in past several years. Nevertheless, limited by its intrinsic drawbacks of highly insulating character, serious shuttle effect and lithium dendrites growth, there is still a long way from large-scale application of LSBs. Here, a [email protected] organic frameworks ([email protected]) composite-derived heteroatoms doped [email protected] CoS2 nanoparticles ([email protected]2) modified separator is designed to surmount these issues. Notably, the modified separator shows improved flame retardancy. By using this separator, the effective suppression on shuttle behavior as well as boost in polysulfides conversion kinetics are realized, which can be assigned to the integrative superiorities of conductive carbon fiber network, electrocatalytic activity, polar-polar interaction and Lewis acid-base interaction. The cell with modified separator shows an initial discharge capacity of 1140.7 mAh g−1. After running for 100 cycles, a high capacity of 631.6 mAh g−1 is retained. Notably, the inhibited growth of lithium dendrites is also obtained, indicating the promoted battery safety. Overall, this work may provide useful inspirations for the utilization of MOFs-derived hierarchical composite in implementing safer high-performance LSBs.

Promoting polysulfide redox kinetics by Co9S8 nanoparticle-embedded in N-doped carbon nanotube hollow polyhedron for lithium sulfur batteries

Lithium-sulfur (Li-S) battery is one of the most promising candidates for next-generation rechargeable batteries, while the volume expansion, severe shuttle effect, and sluggish reaction kinetics hinder its practical applications. Herein, a novel structure composed of Co9S8 nanoparticles embedded in a N-doped carbon nanotube hollow polyhedron (Co9S8@NCNHP) is designed to address these issues. Co9S8 nanoparticles can efficiently accelerate the kinetics of redox reaction and anchor the polysulfides, enhancing the electrochemical performance of cathodes. Furthermore, NCNHP can accommodate the huge volume expansion and block the diffusion of lithium polysulfides. Benefiting from this rational design, the Co9S8@NCNHP/S cathode exhibits a high initial discharge capacity of 1186 mAh·g−1 with a decay rate of 0.1% per cycle during 200 cycles at 0.2 C. An initial discharge capacity of 780 mAh·g−1 as well as a decay rate of 0.15% per cycle after 200 cycles can be obtained at a sulfur loading of 3.2 mg·cm−2. This strategy based on the combination of rational structure design and electrocatalysis could advance the cathode construction in Li-S batteries.

Rational design of a cobalt sulfide/bismuth sulfide S-scheme heterojunction for efficient photocatalytic hydrogen evolution

Following a simple one-pot hydrothermal method, a Co9S8/Bi2S3 composite was successfully synthesized using peanut-like BiVO4 as a precursor. After hydrothermal sulfuration, BiVO4 was transformed into Bi2S3 while maintaining its original peanut-like structure. Meanwhile, Co9S8 nanoparticles were successfully coated onto the peanut-shaped surface of Bi2S3, forming an S-scheme heterojunction by in situ hydrothermal method. For the growth system of Co9S8, the special three-dimensional (3D) structure of Bi2S3 provides a good growth site for zero-dimensional (0D) Co9S8 nanoparticles, avoiding their aggregation and exposing, more reaction area of Co9S8. Moreover, the S-scheme heterojunction retains a more effective redox potential for this system and promotes the recombination of nonessential electron-hole pairs. The 0D/3D spatial structure and the construction of the S-scheme heterojunction provide a more efficient and convenient path for the transfer of photogenic charge, which greatly promotes the effective separation and diversion of the electrons. Besides, the cladding structure of the composite and the S-scheme heterojunction formed between Bi2S3 and Co9S8 complement each other for jointly improving the hydrogen production performance of Co9S8/Bi2S3.

Cobalt sulphide/graphene aerogel nanocomposite with enhanced anode performance for lithium energy storage

Cobalt sulphide/graphene aerogel nanocomposite (CGA) is successfully fabricated via a one-pot hydrothermal approach aided with ethylenediamine. CoS nanoparticles constructed by nanoplates are uniformly anchored and well distributed on the loose graphene aerogel framework. Owing to a synergistic effect combining nanosized CoS with graphene aerogel advantages, CGA as an anode material for lithium energy storage exhibits high reversible capacity, superior long-cycle property and excellent high-rate capability. Prominently, CGA maintains a high capacity approaching ~1100 mAh g−1 after 200 cycles at 100 mA g−1. Even at 1 A g−1, CGA still delivers a capacity of 460 mAh g−1. This approach can be readily applicable to prepare other graphene aerogel-based nanocomposites as anode materials.

Cobalt sulfide catalysts for single-walled carbon nanotube synthesis

Catalysts play a critical role in carbon nanotube (CNT) synthesis. The challenge in precisely controlling CNT structures for various applications creates a long-standing goal to develop new and efficient CNT synthesis catalysts. Although sulfur-containing compounds are often used as promoters in CNT synthesis, metal sulfides have not been directly used as catalysts in CNT synthesis. Here, we study a series of cobalt sulfide catalysts supported on porous silica (CoS/SiO2) for CNT synthesis. Catalysts were first reduced in H2 at different temperatures and then exposed to ethanol at 900 °C to grow CNTs. We found the reduction temperature in H2 and the Co mass loading can strongly influence their catalytic performance. After the CoS/SiO2 catalyst with 1 wt% Co was reduced in H2 at 700 °C, it yields single-walled CNTs (SWCNTs) with a relatively narrow diameter distribution from 0.8 to 1.1 nm. We found that Co9S8 in the catalyst was partially reduced to metallic Co. The coexistence of Co9S8 and metallic Co nanoparticles can stabilize metallic Co nanoparticles and limit their fast aggregation. The Co mass loading in CoS/SiO2 catalysts can be further increased to 5 wt% while retaining catalysts' selectivity towards SWCNTs. When the Co mass loading increases to 7 or 10 wt%, aggregated large Co metal particles result in mainly multi-walled CNTs and graphite. Overall, our results show that CoS/SiO2 catalysts are a potential catalyst candidate for CNT synthesis.

Electrospinning synthesis of porous carbon nanofiber supported CoSe2 nanoparticles towards enhanced sodium ion storage

CoSe2-based anode materials are highly attractive for sodium-ion batteries (SIBs) due to their high theoretical specific capacity, but the weak rate capability and rapid capacity fading hinder their practical application. Herein, porous carbon nanofiber supported CoSe2 nanoparticles (denoted as CS@PCNFs) are designed and fabricated through electrospinning and subsequent heat treatment with PAN (polyacrylonitrile) as the carbon source and PMMA (polymethyl methacrylate) as the pore-forming agent to design the porous architecture of the carbon nanofibers and control the amount of CoSe2 grains anchored on the fiber surface. Benefiting from the desired structural features including the large specific surface area, appropriate pore volume and robust structure stability, when examined as anode materials for SIBs, the as-prepared CS@PCNFs demonstrated excellent sodium-ion storage performances. Experimental results show that the CS@PCNFs with an optimized PAN/PMMA mass ratio of 6:4 can deliver a high reversible capacity of 413.6 mA h g−1 at 0.2 A g−1 after 150 cycles and an excellent rate capability of 401.5 mA h g−1 at 2.0 A g−1.

In Situ Growth of CoSe2 Coated in Porous Carbon Layers as Anode for Efficient Sodium‐Ion Batteries

A novel composite material of CoSe2/N‐doped carbon box (CoSe2/NC) is successfully synthesized using zeolitic imidazolate frameworks‐67 as the sacrificial templates through a simple two‐step calcine process. The CoSe2 nanoparticles are encapsulated in N‐doped carbon layers, which can seriously avoid agglomeration. When used CoSe2/NC as anode materials for sodium‐ion batteries (SIBs), it exhibits an excellent high reversible specific capacity and a superior cycling stability of 390.2 mA h g−1 at 5 A g−1 over 4000 cycles. The excellent performance of CoSe2/NC can be attributed to cooperation of CoSe2 nanoparticles and N‐doped carbon layers. Carbon layers coated on the surface of CoSe2 nanoparticles not only improve a well conductivity to facilitate the charge transfer, but also buffer the structure to expand during the Na+ insertion/extraction process. Furthermore, this novel porous structure provides more active sites and increases contact areas between the materials and the electrolyte, thus increasing the specific capacity and cycle stability. This work provides a possibility of anode materials for SIBs with excellent electrochemistry performance.

Improving the performance of lithium ion capacitor by stabilizing anode working potential using CoSe2 nanoparticles embedded nitrogen-doped hard carbon microspheres

Lithium-ion capacitors (LIC) have problems such as the imbalance of electrochemical kinetics between the battery-type anode and the capacitive cathode, and the large change in the working potential of the hard carbon anode during charge and discharge, which limit the improvement of electrochemical performance for LIC. To solve these problems, CoSe2 nanoparticles embedded nitrogen-doped hard carbon microspheres (NCS-CoSe2) are synthesized and used as the anode material of LIC. Electrochemical tests show that NCS-CoSe2 has a reversible specific capacity of as high as 500 mAh g−1 at a current density of 1 A g−1, which can effectively stabilize the working potential of the anode. At a high working voltage window of 2.2–4.5 V, the potential change of the NCS-CoSe2 anode is as low as 0.35 V, significantly smaller than that of the pure hard carbon (0.87 V). Regarding the electrode kinetics, the NCS-CoSe2 anode is matched with the active carbon cathode well. When the power density rises sharply from 335 W kg−1 to 6700 W kg−1, the energy density of NCS-CoSe2//AC LIC can attain 82 Wh kg−1 (56.9% of initial energy density).

One-step vapor-pressured induced synthesis of spherical-like Co9S8/N, S-codoped carbon nanocomposites with superior rate capability as lithium-ion-battery anode

As high theoretical capacity and excellent electrical conductivity, Co9S8 as a promising electrode material in lithium-ion batteries (LIBs) has attracted wide attention. In the present work, a simple vaporpressured induced route is developed for fabricating spherical-like Co9S8/N, S-codoped carbon nanocomposites (Co9S8/NSC), in which Co9S8 nanoparticles with an average size of 100 nm are encapsulated into N, S-codoped carbon matrix, by pyrolysis of mixture of cobalt isooctanoate dissolved into dimethylformamide and thiourea in a sealed vessel for the first time. As anode for LIBs, the Co9S8/NSC shows an excellent reversible capacity, a superior rate performance, and a long cycling stability. For example, a high capacity of 975.3 mA h g-1 can be achieved after 100 cycles at 0.1 A g-1. When cycled at 1 A g-1, it also maintains a high specific capacity of 791.5 mA h g-1 after 1000 cycles. Besides, it also shows a superior rate performance (329.8 mAh g-1 at 20 A g-1). Such superior performances may arise from its structural advantages that the smaller Co9S8 nanoparticles encapsulated into N, S-codoped carbon could enhance active sites, electrical conductivity, and structural stability.

Directly embedded Ni3S2/Co9S8@S-doped carbon nanofiber networks as a free-standing anode for lithium-ion batteries

A facile electrospinning strategy to simultaneously and in situ generate Co9S8 and Ni3S2 nanoparticles within S-doped carbon nanofiber matrix as free-standing anode materials for LIBs.

HPO42- enhanced catalytic activity of N, S, B, and O-codoped carbon nanosphere-armored Co9S8 nanoparticles for organic pollutants degradation via peroxymonosulfate activation: critical roles of superoxide radical, singlet oxygen and electron transfer.

In this study, we report a facile synthesis of a novel N, S, B, and O-codoped carbon nanosphere-armored Co9S8 nanoparticle composite (Co9S8@NSBOC) and its superior activation performance toward peroxymonosulfate (PMS) for methylene blue (MB) and ofloxacin degradation. The effects of various experimental parameters and the general applicability of the catalyst were investigated. Particularly, Co9S8@NSBOC exhibited high catalytic activity in a wide pH range of 3-12 and HPO42- exhibited a synergic catalytic effect with Co9S8@NSBOC in the degradation system. Radical quenching tests, EPR measurements and electrochemical analysis demonstrated that the degradation mechanism of pollutants in the Co9S8@NSBOC/PMS system included both radical and non-radical pathways, in which ˙O2-, 1O2 and electron transfer played dominant roles. Co2+, S2-, carbon defects, C[double bond, length as m-dash]O/C-O-C, pyridinic-N, graphitic-N, BC2O and C-S-C species on Co9S8@NSBOC, all contributed to PMS activation. The degradation pathways of MB and ofloxacin were proposed based on HPLC-MS/MS analysis of their degradation intermediates. This work not only presents a facile and practical synthetic method of cobalt sulfide-coupled multi-heteroatom-doped carbocatalysts, but also provides useful insights into their active sites and activation mechanisms toward PMS activation.

Co9S8@carbon nanofiber as the high-performance anode for potassium-ion storage.

Thanks to their intrinsic merits of low cost and natural abundance, potassium-ion batteries have drawn intense interest and are regarded as a possible replacement for lithium-ion batteries. The larger radius of potassium, however, provides slow mobility, which normally leads to sluggish diffusion of host materials and eventual expansion of volume, typically resulting in electrode failure. To address these issues, we design and synthesize an effective micro-structure with Co9S8 nanoparticles segregated in carbon fiber utilizing a concise electrospinning process. The anode delivers a high K+ storage capacity of 721 mA h g−1 at 0.1 A g−1 and a remarkable rate performance of 360 mA h g−1 at a high current density of 3 A g−1. A small charge-transfer resistance and a high pseudocapacitive contribution that benefit fast potassium ion migration are indicated by quantitative analysis. The outstanding electrochemical performance can be attributed to the distinct architecture design facilitating high active electrode–electrolyte area and fast kinetics as well as controlled volume expansion.

Yolk-shell structured CoSe2/C nanospheres as multifunctional anode materials for both full/half sodium-ion and full/half potassium-ion batteries.

Transition metal selenides (TMSs) are suitable for SIBs and PIBs owing to their satisfactory theoretical capacity and superior electrical conductivity. However, the large radius of Na+/K+ easily leads to sluggish kinetics and poor conductivity, which hinder the development of SIBs and PIBs. Structure design is an effective method to solve these obstacles. In this study, Co2+ ions combined with glycerol molecules to form self-assembled nanospheres at first, and then they were in situ converted into CoSe2 nanoparticles embedded in a carbon matrix during the selenization process. This structure has three-dimensional ion diffusion channels that can effectively hamper the aggregation of metal compound nanoparticles. Meanwhile, the CoSe2/C of the yolk-shell structure and a large number of pores help alleviate volume expansion and facilitate electrolyte wettability. These structural advantages of CoSe2/C endow it with remarkable electrochemical performances for full/half SIBs and full/half PIBs. The obtained CoSe2/C exhibits superior stability and excellent performance (312.1 mA h g-1 at 4 A g-1 after 1600 cycles) for SIBs. When it is used as an anode material for PIBs, 369.2 mA h g-1 can be retained after 200 cycles at 50 mA g-1 and 248.1 mA h g-1 can be retained after 200 cycles at 500 mA g-1; in addition, CoSe2/C also shows superior rate capacity (186.4 mA h g-1 at 1000 mA g-1). A series of ex situ XRD measurements were adapted to explore the possible conversion mechanism of CoSe2/C as the anode for PIBs. It is worth noting that the full-cell of CoSe2/C//Na3V2(PO4)3@rGO for SIBs and the full-cell of CoSe2/C//PTCDA-450 for PIBs were successfully assembled. The relationship between the structure and performance of CoSe2/C was investigated through density functional theory (DFT).

Heterostructure enhanced sodium storage performance for SnS2 in hierarchical SnS2/Co3S4 nanosheet array composite

Herein, a uniformly distributed SnS2/Co3S4 heterostructure nanosheet array was grown on carbon cloth (CC) fibers by a solvothermal method and an oil bath method. The protective layer of Co3S4 nanoparticles can enhance the sodium storage performance.

Designed preparation of CoS/Co/MoC nanoparticles incorporated in N and S dual-doped porous carbon nanofibers for high-performance Zn-air batteries

The development of low-cost and highly efficient bifunctional electrocatalysts toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is of critical importance for clean energy devices such as fuel cells and metal-air batteries. Herein, a sophisticated nanostructure composed of CoS, Co and MoC nanoparticles incorporated in N and S dual-doped porous carbon nanofibers (CoS/Co/MoC-N, S-PCNFs) as a high-efficiency bifunctional electrocatalyst is designed and synthesized via an efficient multi-step strategy. The as-prepared CoS/Co/MoC-N, S-PCNFs exhibit a positive half-wave potential (E1/2) of 0.871 V for ORR and a low overpotential of 289 mV at 10 mA/cm2 for OER, outperforming the non-noble metal-based catalysts reported. Furthermore, the assembled Zn-air battery based on CoS/Co/MoC-N, S-PCNFs delivers an excellent power density (169.1 mW/cm2), a large specific capacity (819.3 mAh/g) and robust durability, demonstrating the great potential of the as-developed bifunctional electrocatalyst in practical applications. This work is expected to inspire the design of advanced bifunctional nonprecious metal-based electrocatalysts for energy storage.

Enhanced photocatalytic degradation of glyphosate over 2D CoS/BiOBr heterojunctions under visible light irradiation

Two-dimensional (2D) heterojunction photocatalysts can shorten the carrier transfer pathway. In this study, CoS nanoparticles were deposited on the surface of 2D BiOBr nanosheets to fabricate novel ultrathin and intimate-contact 2D heterojunction photocatalysts by a two-step solvothermal route. Under visible-light (λ > 400 nm) irradiation, the apparent reaction rate constant of glyphosate degradation over 10%CoS/BiOBr reaches 0.0074 min–1 (74.7% glyphosate was degraded within 3 h), which is about 5.3 times that of pure BiOBr (0.0014 min–1). The extraordinary photocatalytic performance is attributed to the strong visible-light absorption, the effective charge separation and low charge transfer resistance. The possible photocatalytic reaction process and mechanism over CoS/BiOBr heterojunctions are proposed. Moreover, the 10%CoS/BiOBr sample shows good reusability and stability. This work could provide a new insight for the design and development of 2D heterojunction photocatalysts.

Hollow Co9S8 spheres-derived polyhedrons uniformly anchored on N, S-doped graphene for efficient oxygen electrocatalysts

Exploring highly efficient and low-cost bifunctional electrocatalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is significant for the development of renewable energy. Here, Co9S8 nanospheres with hollow structure anchored on N and S dual-doped graphene oxide (Co9S8-NSGO) are synthesized by solvothermal strategy. After pyrolyzed, advanced bifunctional electrocatalysts with feature of sea-island architecture of Co9S8 polyhedrons evenly dispersed on N and S co-doped graphene sheets (Co9S8-NSG) are obtained, in which Co9S8 polyhedrons stem from the derivative of Co9S8 nanospheres. Ascribed to large surface area, sea-island structure of uniform dispersion of Co9S8 nanoparticles on graphene, synergistic effect between Co9S8 and graphene and more active sites based N and S doping, the as-prepared Co9S8-NSG catalyst exhibits excellent OER performance with a small overpotential (240 mV at 10 mA cm−2) and satisfactory ORR performance with half-wave potential (0.79 V). Notably, a zinc-air battery using Co9S8-NSG as air cathode shows high peak power density (120 mW cm−2) and outstanding cycling stability (120 h at 10 mA cm−2).

Solvothermal preparation of nano cobalt sulfide from tris (cyclohexylpiperazinedithiocarbamato)cobalt(III) and characterization, single crystal X-ray crystal structure of the precursor

Solvothermal formation of CoS nano particles is reported with a cobalt(III) dithiocarbamate as a single source precursor. Morphology and composition of the nano product have been characterized by PXRD and EDX analysis. Four unsymmetrically substituted tris cobalt(III) compounds, [Co(chmdtc)3] (1), [Co(chedtc)3] (2), [Co(achdtc)3] (3), and [Co(chpdtc)3] (4) (where chmdtc = cyclohexylmethylcarbodithioate, chedtc = cyclohexylethylcarbodithioate, achdtc = allylcyclohexylcarbodithioate and chpdtc = cyclohexylpiperazinecarbodithioate) were synthesized and characterized. Compounds (1)– (4) show bands at 634, 642, 635, and 643 nm respectively, due to d-d transitions. One electron quasi reversible reductions due to Co(III)/Co(II) redox process are observed in CV. In the 13C NMR spectra of the complexes, the thioureide (N13CS2) carbons resonate between 203.8 and 205.7 ppm. The observed deshielding of the –CH2 protons in 1H NMR of the compounds is attributed to the shift of electron density on the sulfur (or the metal) through the thioureide π system. TGA supported the proposed formulas of the compounds. Single crystal X-ray structure of [Co(chpdtc)3] (4) shows that the cobalt is in a distorted octahedral environment. Bond Valence Sum (BVS) calculations confirmed the formal oxidation state of cobalt as +3.

P-doped CoSe2 nanoparticles embedded in 3D honeycomb-like carbon network for long cycle-life Na-ion batteries

We report for the first time a Na-ion battery anode material composed of P-doped CoSe2 nanoparticles (P-CoSe2) with the size of 5–20 nm that are uniformly embed in a 3D porous honeycomb-like carbon network. High rate capability and cycling stability are achieved simultaneously. The honeycomb-like carbon network is rationally designed to support high electrical conductivity, rapid Na-ion diffusion as well as the accommodation of the volume expansion from the active P-CoSe2 nanoparticles. In particular, heteroatom P-doping within CoSe2 introduces stronger P-Co bonds and additional P-Se bonds that significantly improve the structure stability of P-CoSe2 for highly stable sodiation/desodiation over long-term cycling. P-doping also improves the electrical conductivity of the CoSe2 nanoparticles, leading to highly elevated electrochemical kinetics to deliver high specific capacities at high current densities. Benefiting from the unique nanostructure and atomic-level P-doping, the P-CoSe2(2:1)/C anode delivers an excellent cycle stability with a specific capacity of 206.9 mA h g−1 achieved at 2000 mA g−1 after 1000 cycles. In addition, this material can be synthesized using a facile pyrolysis and selenization/phosphorization approach. This study provides new opportunities of heteroatom doping as an effective method to improve the cycling stability of Na-ion anode materials.