Cobalt Selenide Research Articles

Carbon Nanotube Composites with Bimetallic Transition Metal Selenides as Efficient Electrocatalysts for Oxygen Evolution Reaction

Hydrogen fuel is a clean and versatile energy carrier that can be used for various applications, including transportation, power generation, and industrial processes. Electrocatalytic water splitting could be the most beneficial and facile approach for producing hydrogen. In this work, transition metal selenide composites with carbon nanotubes (CNTs) have been investigated for electrocatalytic water splitting. The synthesis process involved the facile one-step hydrothermal growth of transition metal nanoparticles over the CNTs and acted as an efficient electrode toward electrochemical water splitting. Scanning electron microscopy and XRD patterns reveal that nanoparticles were firmly anchored on the CNTs, resulting in the formation of composites. The electrochemical measurements reveal that CNT composite with nickel–cobalt selenides (NiCo-Se/CNTs@NF) display remarkable oxygen evolution reaction (OER) activity in basic media, which is an important part of hydrogen production. It demonstrates the lowest overpotential (η10mAcm−2) of 0.560 V vs. RHE, a reduced Tafel slope of 163 mV/dec, and lower charge transfer impedance for the OER process. The multi-metallic selenide composite with CNTs demonstrating unique nanostructure and synergistic effects offers a promising platform for enhancing electrocatalytic OER performance and opens up new avenues for efficient energy conversion and storage applications.

Size-controlled synthesis of La and chitosan doped cobalt selenide nanostructures for catalytic and antibacterial activity with molecular docking analysis

Co-precipitation method was adopted to synthesize ternary heterostructure catalysts La/CS-CoSe NSs (lanthanum/chitosan‑cobalt selenide nanostructures) without the use of a surfactant. During synthesis, a fixed amount (3 wt%) of CS was doped with 2 and 4 wt% La to control the growth, recombination rate and stability of CoSe NSs. The doped samples served to enhance the surface area, porosity and active sites for catalytic degradation of rhodamine B dye and antibacterial potential against Staphylococcus aureus (S. aureus). Additionally, the synthesized catalysts were examined for morphological, structural and optical characteristics to assess the influence of dopants to CoSe. XRD spectra verified the hexagonal and cubic structure of CoSe, whereas the porosity of the undoped sample (CoSe) increased from 45 to 60 % upon incorporation of dopants (La and Cs). Among the samples analyzed during this study, 4 % La/CS-CoSe exhibited significant bactericidal behavior as well as the highest catalytic reduction of rhodamine B dye in a neutral environment. Molecular docking analysis was employed to elucidate the underlying mechanism behind the bactericidal activity exhibited by CS-CoSe and La/CS-CoSe NSs against DHFRS. aureus and DNA gyraseS. aureus.

Porous Carbon Cloth@CoSe2 as Kinetics‐Enhanced and High‐Loading Integrated Sulfur Host for Lithium–Sulfur Batteries

AbstractCarbon cloth (CC) possesses great potential as a sulfur host because of its excellent conductivity, flexibility, and easily modified free‐standing structure. However, the previous works do not take full advantage of CC except for the role of support and current collector. The smooth surface, small specific surface area, and poor binding force between coating materials and CC matrix are unfavorable for loading coating materials. The slow redox kinetics and low sulfur loading of sulfur cathodes still seriously restrict the development of Lithium–Sulfur (Li–S) batteries. Herein, the porous carbon cloth loading cobalt selenide (PCC@CoSe2) is constructed as an integrated sulfur host through a pore‐creating and selenylation strategy. The pore‐creating engineering greatly optimizes the 3D pore structure of CC to raise the sulfur and catalyst loading and provides enough space to accommodate the volume change of sulfur species. In addition, CoSe2 particles as nano‐catalyst units embedded in PCC can effectively adsorb‐catalyze polysulfides and improve the reaction kinetics. The resulting integrated sulfur cathode has realized the high‐efficiency polysulfide catalytic conversion and fast lithium ion migration, significantly enhancing redox kinetics and sulfur loading.

Enhanced performances of NiCoSe2 electrode coated with Ag nanoparticles by magnetron sputtering for the applications of asymmetric supercapacitors

In this work, a binder-free energy-storage electrode material of Ag nanoparticles coated nickel cobalt selenide (NiCoSe2) on Ni foam (NF) was first proposed. Wherein, NiCoSe2 was synthesized by one-step hydrothermal method using ascorbic acid as reductant, and the coating of Ag nanoparticles on NiCoSe2 were performed by magnetron sputtering method. The specific surface area was greatly increased due to the deposited Ag nanoparticles, and in this way the impedance of the electrode decreased, and the electrochemical properties were enhanced. When the magnetron sputtering time is 10 s, Ag/NiCoSe2 electrode exhibits the most excellent performances. However, further increase of sputtering time may result in the over cover on NiCoSe2, with great deterioration in electrochemical behavior. Single NiCoSe2 electrode possesses an area capacitance of 1600.7 mF cm−2 at a current density of 2 mA cm−2, while Ag/NiCoSe2 electrode could reach up to 2280 mF cm−2. The asymmetric supercapacitor (ASC) assembled by Ag/NiCoSe2 and activated carbon (AC) electrodes shows a high energy density of 0.171 mWh cm−2 as well as a power density of 17.340 mW cm−2, and the cyclic stability remains at 90.1% after 4000 cycles, which is superior to 83.7% of the NiCoSe2 single electrode.

Structural and vacancy assisted engineering of cobalt selenide for ultrahigh energy density sodium ion pouch cell

Cobalt selenide (CoSe) exhibits potential as an anode material in sodium-ion batteries (SIBs), but challenges remain in achieving stable Na+ storage and high energy density full cells by controlling CoSe.

A grain-boundary-rich cobalt selenide hollow multi-shelled structure as a highly efficient electrocatalyst for lithium–sulfur batteries

A unique grain-boundary-rich cobalt selenide hollow multi-shelled structure (GB-CoSe HoMS) has been rationally designed and synthesized as a high-efficiency electrocatalyst to adsorb and convert the polysulfides for lithium–sulfur batteries.

Engineering hierarchical snowflake-like multi-metal selenide catalysts anchored on Ni foam for high-efficiency and stable overall water splitting.

The development of excellent bifunctional electrocatalysts is an effective way to promote the industrial application of electrolytic water. In this work, a free-standing W-doped cobalt selenide (W-CoSe300/NF) electrocatalyst with a snowflake-like structure supported on nickel foam was prepared by a hydrothermal-selenization strategy. Benefiting from the high specific surface area of the 3D snowflake-like structure and the regulation of tungsten doping on the electronic structure of the metal active center, W-CoSe300/NF shows remarkable electrocatalytic water decomposition performance. In 1.0 M KOH, the W-CoSe300/NF electrocatalyst achieved an efficient HER and OER at a current density of 50 mA cm-2 with overpotentials as low as 84 mV and 283 mV, respectively. More importantly, W-CoSe300/NF acts as both the anode and cathode of the electrolytic tank, requiring only a potential of 1.54 V to obtain 10 mA cm-2 and can operate continuously for more than 120 hours at this current density. This study proposes a new way for the design of high efficiency and affordable bifunctional electrocatalysts.

Se vacancy-driven nickel cobalt selenide electrode enhancing reaction kinetics for boosting supercapacitive performance

In this manuscript, we report the induction of vacancy engineering at the atomic level by NaBH4 heat treatment to obtain biomimetic sea urchin-like Va-NiCo2Sex with adjustable vacancy concentrations.

Heterostructured FeSe2-CoSe2 Nanorods Supported on Nitrogen and Sulfur co-doped Reduced Graphene Oxide as High‐Performance Electrocatalyst for Oxygen Evolution Reaction

With the aim of hydrogen production from electrochemical water splitting on a high scale, the core challenge is to develop an effective oxygen evolution reaction (OER) electrocatalyst with high activity as well as a low cost. Herein, we developed a heterostructure of Iron and cobalt selenide supported by a dual heteroatom (Nitrogen and Sulphur) doped reduced graphene oxide, synthesized by an easy solvothermal method. The as-synthesized CoSe2-based catalyst consists of urchin-like assembled nanorods resulting in the highly exposed reaction sites and shows excellent electrochemical performance with the much lowest overpotentials of 216 mV and 291 mV at a current density of 10 and 50 mA cm−2, respectively, Tafel slope of 53.4 mV dec−1 and long-term stability for 50 h in an alkaline environment. As a result, the improved OER activity of the as-synthesized electrocatalyst could be attributed to the highly accessible heterointerfaces served as abundant catalytic active sites as well as strong synergistic interaction and enhanced electrical conductivity that increased the movement of electron transfer. The achieved results manifest the superiority of the prepared electrocatalyst towards OER and it can be a remarkable electrocatalyst which is helpful for further development in the practical application of water splitting to decrease energy utilization at a high scale.

Water Splitting Reaction Mechanism on Transition Metal (Fe-Cu) Sulphide and Selenide Clusters-А DFT Study.

The tetracarbonyl complexes of transition metal chalcogenides M2X2(CO)4, where M = Fe, Co, Ni, Cu and X = S, Se, are examined by density functional theory (DFT). The M2X2 core is cyclic with either planar or non-planar geometry. As a sulfide, it is present in natural enzymes and has a selective redox capacity. The reduced forms of the selenide and sulfide complexes are relevant to the hydrogen evolution reaction (HER) and they provide different positions of hydride ligand binding: (i) at a chalcogenide site, (ii) at a particular cation site and (iii) in a midway position forming equal bonds to both cation sites. The full pathway of water decomposition to molecular hydrogen and oxygen is traced by transition state theory. The iron and cobalt complexes, cobalt selenide, in particular, provide lower energy barriers in HER as compared to the nickel and copper complexes. In the oxygen evolution reaction (OER), cobalt and iron selenide tetracarbonyls provide a low energy barrier via OOH* intermediate. All of the intermediate species possess favorable excitation transitions in the visible light spectrum, as evidenced by TD-DFT calculations and they allow photoactivation. In conclusion, cobalt and iron selenide tetracarbonyl complexes emerge as promising photocatalysts in water splitting.

Modulation of Phase Transition in Cobalt Selenide with Simultaneous Construction of Heterojunctions for Highly-Efficient Oxygen Electrocatalysis in Zinc-Air Battery.

Phase transformation of cobalt selenide (CoSe2 ) can effectively modulate its intrinsic electrocatalytic activity. However, enhancing electroconductivity and catalytic activity/stability of CoSe2 still remains challenging. Heterostructure engineering may be feasible to optimize interfacial properties to promote the kinetics of oxygen electrocatalysis on a CoSe2 -based catalyst. Herein, a heterostructure consisting of CoSe2 and cobalt nitride (CoN) embedded in a hollow carbon cage is designed via a simultaneous phase/interface engineering strategy. Notably, the phase transition of orthorhombic-CoSe2 to cubic-CoSe2 (c-CoSe2 ) accompanied by in situ CoN formation is realized to build the c-CoSe2 /CoN heterointerface, which exhibits excellent/highly stable activities for oxygen reduction/evolution reactions (ORR/OER). Notably, heterostructure can modulate the local coordination environment and increase Co-Se/N bond lengths. Theoretical calculations show that Co-site (c-CoSe2 ) with an electronic state near Fermi energy level is the main active site for ORR/OER.Energetical tailoring of the d-orbital electronic structure of the Co atom of c-CoSe2 in heterostructure by in situ CoN incorporation lowers thermodynamic barriers for ORR/OER. Attractively, a zinc-air battery with a c-CoSe2 -CoN cathode displays excellent cycling stability (250h) and charge/discharge voltage loss (0.953/0.96V). It highlights that heterointerface engineering provides an option for modulating the bifunctional activity of metal selenides with controlled phase transformation.

Long-term stability of lithium–sulfur batteries via synergistic integration of nitrogen-doped graphitic carbon-coated cobalt selenide nanocrystals within porous three-dimensional graphene-carbon nanotube microspheres

Three-dimensional porous microspheres consist of highly conductive reduced graphene oxide-carbon nanotube (rGO‒CNT) framework with well-embedded cobalt selenide (CoSe2) nanocrystals coated with N-doped graphitic carbon (NGC) were synthesized (referred as “P–CoSe2@NGC/rGO‒CNT” microspheres) and utilized as an electrocatalytic interlayer to enhance the performance of lithium-sulfur (Li–S) batteries. The incorporation of the NGC layer and rGO‒CNT framework not only enhances the electronic conductivity significantly but also offers numerous conductive pathways (primary and secondary) for efficient electron transport. Macropores (φ = 100 nm) formed by the decomposition of PS nanobeads (φ = 200 nm) guarantee effective electrolyte penetration and short diffusion pathways. Moreover, the CoSe2 nanocrystals offer a multitude of polar active sites that effectively anchor polysulfide intermediates, reducing the loss of active material. Benefiting from the nanostructure merits, Li–S cells featuring a P–CoSe2@NGC/rGO‒CNT-coated separator and a conventional sulfur electrode demonstrated outstanding rate capability (up to 2.0 C) and remarkable cycling stability (1000 cycles at 2.0 C). Even under more demanding cell conditions, such as high sulfur content (71 %), high sulfur loading (4.6 mg cm−2), and low E/S (5.6 μL mg−1) ratio, the cell exhibits impressive cycling stability with 420 cycles at 0.1 C, along with feasible rate performance up to 0.3 C.

Novel structured carbon nanotubes fiber based microelectrodes for efficient electrochemical water splitting and glucose sensing

An efficient electrocatalyst composed of nickel and cobalt selenide over unique structure carbon nanotubes (NiCo-Se@CNTs) fiber has been fabricated via a single-step hydrothermal method which showed efficient electrocatalytic performance towards electrochemical non-enzymatic glucose sensing and overall water splitting applications. The structural and elemental composition of a modified electrode (NiCo-Se@CNTs) was ascertained via transmission electron microscopy (TEM), X-rays diffraction (XRD) pattern, X-rays photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) along with energy dispersive X-ray spectroscopy (EDX) techniques. Modified fiber-based electrode was used for the electrochemical water splitting which showed a low overpotential value (η10 = 260 mV) with a corresponding Tafel slope of 138 mV dec−1. These values are far superior in contrast with pristine CNTs fiber, having 384 mV overpotential and 318 mV dec−1 of Tafel slope. In extension, while studying overall water splitting by engaging both modified CNTs fiber as anode and cathode, it exhibited excellent performance with an overpotential (η10) of 297 mV and corresponding Tafel slop of 159 mV dec−1. The fabricated electrode was further investigated for electrochemical glucose sensing which exhibited excellent performance towards the glucose detection with a linear dynamic range of up to 10 mM, a detection limit of 0.59 μM in an alkaline condition (pH=13) and high sensitivity of 813 mAmM−1cm−2. The outcomes demonstrated that fabricated fiber (NiCo-Se@CNTs) might be a promising material in future as a multifunctional electrocatalyst for flexible and wearable energy and sensing related applications.

Fully exposed (101) plane endowing CoSe anode with fast and stable potassium storage

Transition-metal selenides, especially cobalt selenides (CoSe), are widely regarded as a promising anode for potassium-ion batteries (KIBs) due to their high theoretical capacity and good electrical conductivity. However, CoSe easily suffers from a substantial volume change upon repeated cycling, leading to a fast capacity decay and poor cycling stability. Herein, a dual-carbon confined CoSe is successfully designed by using metal-organic frameworks as raw materials. Various characterizations disclose that the introduction of the extra carbon phase is conducive to the growth of (101) plane of CoSe, and based on this, rationally regulating carbonization temperature can further promote the exposure of (101) plane. Such fully exposed (101) plane not only provides sufficient active surface to uptake K-ions, but also favors the accommodation of electrode structure fluctuation, accounting for a high capacity and prolonged cycle lifespan. As a result, the optimized sample (denoted as 750 °CNC@CoSe/NC) delivers 392.5 mAh g−1 at 0.5 A g−1, accompanied by an excellent cycling stability over 400 cycles with 196.7 mAh g−1 at a high current density of 1 A g−1. This work is expected to offer effective guidance for constructing advanced CoSe anode toward KIBs.

Cobalt selenide nanoparticles composited with carbon nanotube and reduced graphene oxide for high-performance lithium/sodium storage

Composites of cobalt selenide nanoparticles, carbon nanotubes and reduced graphene oxide (CoSe/CNTs/rGO) are successfully prepared by the hydrothermal method followed by ball milling. The CoSe nanoparticles are dispersed into the carbon matrix formed by rGO and CNTs. The composite can be used as the electrode material for lithium and solidum ion storage. As the anode material for lithium ion battery (LIB), the optimum composite exhibits the reversible specific capacity of 848 mAh g−1, 745 mAh g−1 and 406 mAh g−1 at 0.2 A g−1, 1 A g−1, and 2 A g−1, respectively. When used as the anode material for sodium ion battery (SIB), the optimum composite exhibits the reversible specific capacity of 448 mAh g−1, 379 mAh g−1 and 279 mAh g−1 at 0.5 A g−1, 1 A g−1, and 2 A g−1, respectively. Appropriate amounts of CNTs and rGO generate highly dispersed CoSe nanoparticles in the carbon matrix, which yield abundant electrochemically active sites, reduced charge transfer resistance, and accelerated ion diffusion. Evidences for conversion mechanism of charge storage is given in both LIB and SIB, and the contribution of capacitive-controlled process to the charge storage is higher in LIB than SIB.

Intermediates Regulation via Electron-Deficient Cu Sites for Selective Nitrate-to-Ammonia Electroreduction.

Ammonia (NH3 ), known as one of the fundamental raw materials for manufacturing commodities such as chemical fertilizers, dyes, ammunitions, pharmaceuticals, and textiles, exhibits a high hydrogen storage capacity of ≈17.75%. Electrochemical nitrate reduction (NO3 RR) to valuable ammonia at ambient conditions is a promising strategy to facilitate the artificial nitrogen cycle. Herein, copper-doped cobalt selenide nanosheets with selenium vacancies are reported as a robust and highly efficient electrocatalyst for the reduction of nitrate to ammonia, exhibiting a maximum Faradaic efficiency of ≈93.5% and an ammonia yield rate of 2360µg h-1 cm-2 at -0.60V versus reversible hydrogen electrode. The in situ spectroscopical and theoretical study demonstrates that the incorporation of Cu dopants and Se vacancies into cobalt selenide efficiently enhances the electron transfer from Cu to Co atoms via the bridging Se atoms, forming the electron-deficient structure at Cu sites to accelerate NO3 - dissociation and stabilize the *NO2 intermediates, eventually achieving selective catalysis in the entire NO3 RR process to produce ammonia efficiently.

Impact of temperature difference on the features of spray deposited yttrium doped cobalt selenide (YCoSe) thin films for photovoltaic application

In this investigation, spray deposited yttrium doped cobalt selenide (YCoSe) thin materials were synthesized in soda lime glass and the impact of substrate temperature (140 oC, 160 oC, 180 oC and 200 oC) on their elemental composition, surface morphology, structural, electrical and optical properties were investigated using scanning electron microscopy-SEM X-ray diffraction –XRD, four-point probe and UV-VIS spectrophotometer respectively. The EDX plots of the deposited undoped and Y-doped cobalt selenide revealed the major elements: cobalt, selenium and yttrium. This confirms the deposition of CoSe and Y-doped CoSe thin materials. The morphology of undoped CoSe thin materials was very rough containing randomly oriented non-uniform thin particles while addition of Y dopant (0.1 mol%) at substrate temperature of 140 oC gave a homogenous distribution of compact rectangular-like nanograins. The XRD result shows that the films are cubic polycrystalline in nature and the film grown at substrate temperature of 180 oC was seen to give the most excellent crystalline quality and a preferential orientation along (111) direction. From electrical results it was observed that increase in substrate temperature increased the film thickness with decreased resistivity and increased conductivity. The optical properties were found to vary with substrate temperature despite the fact that the variation was not totally linear, as the film deposited at substrate temperature of 160 oC deviated from the linearity in all the optical properties. The energy band gap of the deposited samples ranges from 1.25 eV–1.75 eV. The materials produced could be used in the production of photovoltaic devices.

Facile Synthesis of Microsphere-like Co0.85Se Structures on Nickel Foam for a Highly Efficient Hydrogen Evolution Reaction.

Microsphere-shaped cobalt selenide (Co0.85Se) structures were efficiently synthesized via a two-step hydrothermal process. Initially, cobalt hydroxide fluoride (Co(OH)F) microcrystals were prepared using a hydrothermal method. Subsequently, Co0.85Se microsphere-like structures were obtained through selenization. Compared to Co(OH)F, the microsphere-like Co0.85Se structure exhibited outstanding catalytic activity for the hydrogen evolution reaction (HER) in a 1.0 M KOH solution. Electrocatalytic experiments demonstrated an exceptional HER performance by the Co0.85Se microspheres, characterized by a low overpotential of 148 mV and a Tafel slope of 55.7 mV dec-1. Furthermore, the Co0.85Se electrocatalyst displayed remarkable long-term stability, maintaining its activity for over 24 h. This remarkable performance is attributed to the excellent electrical conductivity of selenides and the highly electroactive sites present in the Co0.85Se structure compared to Co(OH)F, emphasizing its promise for advanced electrocatalytic applications.

Fe doping induced selenium vacancy on cobalt selenide for enhanced hydrogen peroxides production

Electrocatalytic two-electron oxygen reduction reaction (2e-ORR) pathway for hydrogen peroxides (H2O2) generation has emerges as an appealing alternative to conventional anthraquinone craft. In this work, Fe doped CoSe was synthesized via hydrothermal and subsequent high temperature (HT) annealing process. The doping of trace amount of Fe could tune the crystal growth direction and induce the generation of Se vacancy during annealing. During the Electrocatalytic measurement, the Faraday efficiency of 2e-ORR can reach 99.1%, 83.2% and 93.6% in 0.1 M KOH, 0.1 M Na2SO4, and 0.05 M H2SO4, respectively. Under the neutral condition, the production rate of H2O2 reached 18.37 mmol L−1 in 120 min. Moreover, Fe-CoSe-HT exhibits good stability and Fe2+ regeneration during flow-Fenton reaction. Hence, the dual role of selenium-vacancy-enriched Fe-CoSe-HT greatly enhanced selectivity of 2e-ORR and accelerated Fe reduction, resulting in promoted ∙OH radical generation and organic pollutants treatment.

Deep etching assisted hollow-carbon-skeleton structured porous Co0.85Se nanocubes anchored on MXene nanosheets for superior sodium storage toward ultrahigh initial Coulombic efficiency

Cobalt selenide (CoSex), as a significant member of transition-metal selenides (TMSe), has attracted great interest as anode materials of sodium ion batteries (SIBs), owing to the superior sodium storage capacity. However, the low initial Coulombic efficiency (ICE), inferior rate capability and terrible cycling stability still restrict its practical application. Thus, we develop a method of tannic acid (TA) deep-etching to build up hollow Co metal-organic frameworks (Co-MOF), then combined with MXene nanosheets through the electrostatic self-assembly and meanwhile tailored the solid electrolyte interface (SEI) simultaneously to address above existing problems of CoSex anode. The hollow-carbon-skeleton structured porous Co0.85Se nanocubes anchored on the MXene nanosheets (TA-Co0.85Se-MXene) greatly buffer the huge volume changes, reinforce the structure of the electrode and accelerate the Na+/electron-transport kinetics. Furthermore, an ideal SEI film has been formed by employing the chosen ether-based electrolytes. Owing to the fabricated structure and tailored SEI, the TA-Co0.85Se-MXene anode exhibits ultrahigh ICE of 91 %, superior rate capability of 389 mA h g−1 at 5 A g−1, and outstanding long-term cycling stability of 418 mA h g−1 at 1 A g−1 for 1000 cycles. This work proposes an effective strategy to design transition metal selenides anodes with ultrahigh ICE and superior sodium storage properties.