1307-99-9Relevant articles and documents
Mechanism and improvement strategy of CoSe capacity change during lithiation/delithiation
Wang, Qingtao,Hou, Minmin,Liu, Dongxu,Zhou, Xiaozhong,Lei, Ziqiang
, (2021)
Studying the reaction mechanism of materials in the process of lithiation/delithiation is important to understand and optimize the electrode materials. In this work, the petal-like CoSe is prepared by a simple hydrothermal method, and its lithium storage mechanism is studied. During the charge/discharge cycles, the capacity of the CoSe decreases first and then increases. In the initial stage, the volume of CoSe expands due to the intercalation of lithium ions, which results in the amorphousness of CoSe and reduces the specific capacity. The subsequent increase in capacity is due to the recrystallization of the material and the formation of a conductive SEI film. The petal-like CoSe displays a specific capacity of 450 mA h g?1 at the current density of 100 mA g?1 after 300 cycles. To improve the lithium storage performance, a CoSe/rGO composite is prepared. The addition of GO during the preparation of CoSe changes the morphology of CoSe from a larger petal shape to a smaller rod shape, which weakens the effect of volume change during lithium ion intercalation and shortens the lithium ion diffusion distance, so improves the reduction of specific capacity. At a current density of 100 mA g?1, the specific capacity of CoSe/rGO composite can be as high as 730 mA h g?1 after 200 cycles. Even under a large current density of 1000 mA g?1, the specific capacity of the CoSe/rGO composite can still reach 570 mA h g?1 after 1000 cycles.
Tunable K vacancies in K1? xCo2Se2 and their effects on structure and ferromagnetism
Guo, Zhongnan,Yan, Xiaoxiao,Zheng, Lirong,Han, Xue,Wu, Dan,Liu, Ning,Sun, Fan,Wang, Da,Yuan, Wenxia
, (2019)
Deeply understanding the role of intermediate metal A on structure and related properties of ThCr2Si2-type transition metal compounds ATM2X2 is of great importance for designing novel layered functional materials. However, inducing A vacancies usually trends to destroy the original structure in reported systems so far, which hampers the further research. Here we report the controllable K vacancies in K1? xCo2Se2 system (0 ≤ x ≤ 0.3), where both the ThCr2Si2-type structure and intact tetrahedral [CoSe] layers can be maintained with the varying occupancies of K. By inducing K vacancies in structure, tetragonality of the lattice for K1? xCo2Se2 increases with the shortened a and elongated c. The (CoSe4) tetrahedron is also compressed perpendicular to the c direction resulted from the K deficiency. X-ray absorption near-edge structure reveals that the valence state of Co is basically unaffected by K deficient with the absorption edge of Co K-edge unchanged. Concerning the physical properties, K vacancies increase the resistivity of metallic K1? xCo2Se2 due to the decreased charge transfer from K+ to [CoSe] layers. More importantly, the ferromagnetic interaction of K1? xCo2Se2 is unexpectedly weakened by raising K vacancies with the Curie temperature shifted from 80 to 52 K, despite the shortened Co-Co distance. First-principles calculation reveals that the spin polarization is weakened resulted from the K vacancies, mainly attributed to the reduced charge transfer from K+ to [CoSe] host. Our results clearly indicate the domination of transferred electrons from intermediate metal A on the magnetic interaction of ATM2X2, and also show the feasibility to regulate the structure and related properties of ATM2X2 by controlling the A content.
Evaluating DNA Derived and Hydrothermally Aided Cobalt Selenide Catalysts for Electrocatalytic Water Oxidation
Karthick, Kannimuthu,Jagadeesan, Sathya Narayanan,Kumar, Piyush,Patchaiammal, Swathi,Kundu, Subrata
, p. 6877 - 6884 (2019)
Electrocatalysts with engaging oxygen evolution reaction (OER) activity with lesser overpotentials are highly desired to have increased cell efficiency. In this work, cobalt selenide catalysts were prepared utilizing both wet-chemical route (CoSe and CoSe-DNA) and hydrothermal route (Co0.85Se-hyd). In wet-chemical route, cobalt selenide is prepared with DNA (CoSe-DNA) and without DNA (CoSe). The morphological results in the wet-chemical route had given a clear picture that, with the assistance of DNA, cobalt selenide had formed as nanochains with particle size below 5 nm, while it agglomerated in the absence of DNA. The morphology was nano networks in the hydrothermally assisted synthesis. These catalysts were analyzed for OER activity in 1 M KOH. The overpotentials required at a current density of 10 mA cm-2 were 352, 382, and 383 mV for Co0.85Se-hyd, CoSe, and CoSe-DNA catalysts, respectively. The Tafel slope value was lowest for Co0.85Se-hyd (65 mV/dec) compared to CoSe-DNA (71 mV/dec) and CoSe (80 mV/dec). The chronoamperometry test was studied for 24 h at a potential of 394 mV for Co0.85Se-hyd and was found to be stable with a smaller decrease in activity. From the OER study, it is clear that Co0.85Se was found to be superior to others. This kind of related study can be useful to design the catalyst with increased efficiency by varying the method of preparation.
In situ growth of Co0.85Se and Ni0.85Se on conductive substrates as high-performance counter electrodes for dye-sensitized solar cells
Gong, Feng,Wang, Hong,Xu, Xin,Zhou, Gang,Wang, Zhong-Sheng
, p. 10953 - 10958 (2012)
We present herein a facile one-step low-temperature hydrothermal approach for in situ growth of metal selenides (Co0.85Se and Ni 0.85Se) on conductive glass substrates. The as-prepared metal selenides on conductive substrates can be used directly as transparent counter electrodes for dye-sensitized solar cells (DSSCs) without any post-treatments. It is found that graphene-like Co0.85Se exhibits higher electrocatalytic activity than Pt for the reduction of triiodide. As a consequence, the DSSC with Co0.85Se generates higher short-circuit photocurrent and power conversion efficiency (9.40%) than that with Pt.
Solid-solution hexagonal Ni0.5Co0.5Se nanoflakes toward boosted oxygen evolution reaction
Zhu, Lei,Liao, Yanxin,Jia, Yubao,Zhang, Xin,Ma, Ruguang,Wang, Kuikui
, p. 13113 - 13116 (2020)
The oxygen evolution reaction (OER) with sluggish kinetics is a bottleneck for the large-scale application of water electrolysis. Herein, solid-solution hexagonal Ni0.5Co0.5Se nanoflakes are designed and successfully synthesized via a facile hydrothermal method with a much lower overpotential of 216 mV at 10 mA cm-2 and a Tafel slope of 37.08 mV dec-1. This journal is
La2Co2Se2O3: A quasi-two-dimensional mott insulator with unusual cobalt spin state and possible orbital ordering
Wang, Cao,Tan, Ming-Qiu,Feng, Chun-Mu,Ma, Zhi-Feng,Jiang, Shuai,Xu, Zhu-An,Cao, Guang-Han,Matsubayashi, Kazuyuki,Uwatoko, Yoshiya
, p. 7069 - 7073 (2010)
The new oxyselenide La2Co2Se2O 3, containing Co2O square-planar layers, has been successfully synthesized using solid-state reactions under vacuum. The compound crystallizes in space group I4/mmm with lattice parameters a = 4.0697(8) A and c = 18.419(4) A. Magnetic susceptibility measurements indicate an antiferromagnetic transition at ～ 220 K. The magnetic entropy associated with the transition is close to R ln 2, suggesting an unusual low-spin state for the Co2+ ions. The as-prepared sample shows insulating behavior with room-temperature resistivity of ～107 ω cm, which decreases by 4 orders of magnitude under a pressure of 7 GPa. Band structure calculations using the LSDA+U approach reproduce the insulating ground state with low spin for Co and suggest strong orbital polarization for the valence electrons near the Fermi level. It is also revealed that the spin and orbital degrees of freedom in the antiferromagnetic checkerboard spin-lattice are mutually coupled.
Facile synthesis of CoSe nanoparticles encapsulated in N-doped carbon nanotubes-grafted N-doped carbon nanosheets for water splitting
Feng, Fan,Huang, Xiaokang,Jiang, Pengbo,Lan, Kai,Li, Rong,Li, Shuwen,Wang, Kaizhi,Yang, Honglei,Yang, Ming,Yang, Yuanyuan
, (2020)
Rationally designing a high-efficiency, inexpensive and stable electrocatalyst is important in the renewable energy field. Herein, a one-step strategy is adopted to synthesize 3D hybrid of CoSe nanoparticles encapsulated nitrogen-doped carbon nanotubes graft onto nitrogen-doped carbon nanosheets (denoted as CoSe?NCNT/NCN) with excellent hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activity in acidic and alkaline solutions, respectively. Benefiting from the unique morphology, the large surface area and good conductivity, the hybrid exhibits excellent electrocatalytic HER activity in 0.5 M H2SO4 solution, which is a low overpotential of 197 mV at a current density of 10 mA cm?2 with a Tafel slope of 43 mV dec?1. Meanwhile, it presents a low overpotential of 301 mV at a current density of 10 mA cm?2 with a Tafel slope of 75 mV dec?1 in 1 M KOH solution for OER. The good electrocatalytic property is comparable to most of the previously reported Co-based electrocatalysts and the synthetic method is low toxic and simple, which may be expanded to other transition metal dichalcogenides. The strategy provides a possibility for preparation for effective nonprecious high performance HER and/or OER electrocatalysts.
NMR study of the diluted magnetic semiconductor alloys Cd1-xMnxSe, Cd1-xCoxSe, and Cd1-xFexSe
Ladizhansky,Faraggi,Lyahovitskaya,Vega
, p. 6712 - 6718 (1997)
Diluted magnetic semiconductors Cd1-xMnxSe for x=0.01, Cd1-xFexSe for x=0.01 and 0.02, and Cd1-xCOxSe for x = 0.006, 0.009, and 0.01 were studied in the temperature range of 180-400 K by 113Cd magic-angle-spinning NMR spectroscopy. The NMR spectra of Cd1-xFexSe and Cd1-xCoxSe contain a set of resonance lines that are shifted away from the line of the undoped CdSe compound by the transferred hyperfine (THF) interaction between the cadmium nuclei and the paramagnetic ions. The temperature dependence of the THF shifts follows the Curie-Weiss law, and the spin-lattice relaxation times of the shifted lines are significantly shorter than that of the CdSe line. The 113Cd lines show anisotropies that are smaller than the values evaluated from the dipolar interaction between the paramagnetic ions (M) and their nearest-neighboring cations (M-Se-Cd). The detected anisotropies are therefore composed of dipolar and hyperfine contributions from next-nearest-neighboring (NNN) cadmium nuclei (M-Se-Cd-Se-Cd). The spin-lattice relaxation times of the spectral lines are determined by the electron-nuclear dipolar interaction with NNN cations. The number of observed lines corresponds to the number of nonequivalent NNN cations around each paramagnetic ion. Using the values of the relaxation times and the amplitudes of the lines, it is possible to correlate each line to a well-defined NNN conformation. The NMR spectra of Cd1-xMnxSe did not show any fine structure similar to that observed in the Co and Fe alloys.
Cobalt selenide nanostructures: Hydrothermal synthesis, considering the magnetic property and effect of the different synthesis conditions
Sobhani, Azam,Salavati-Niasari, Masoud
, p. 1089 - 1094 (2016)
Cobalt selenide (CoSe) nanostructures are produced via hydrothermal route from the reaction of cobalt salt and SeCl4 as precursors, in the presence of surfactant (CTAB, PVA, SDS) and reductant (N2H4.H2O). It is found that the temperature reaction, type of cobalt salt and surfactant play important roles in controlling the composition, structure, morphology and particle size of products. The experimental techniques of XRD, SEM, TEM, EDX and VSM are used to characterize the products and study their magnetic properties.
Hydrothermal synthesis of CoSe nanostructures without using surfactant
Sobhani, Azam,Salavati-Niasari, Masoud
, p. 334 - 338 (2016)
CoSe nanostructures are synthesized by hydrothermal route in the presence of reductant, without using surfactant. In this work, we use from SeCl4 as a new selenium source. By varying the type of metal salt and reductant, reaction time and temperature, the method permits us to synthesize products with different morphologies. SEM and TEM images show the morphology and size of the as-synthesized samples. Chemical composition of the samples is characterized by XRD and EDS. Magnetization measurement shows paramagnetic behavior for CoSe nanostructures.
