Papers by Keyword: FeS₂

Abstract: The electrochemical properties of carbon-coated FeS₂ were investigated as a positive electrode material for lithium secondary batteries. The carbon-coated FeS₂ powders were synthesized by ball-milling using polyaniline as the carbon source. The particles in the carbon-coated FeS₂ samples were smaller than those in the pristine FeS₂ samples. The electrochemical performance, including capacity, of these batteries was improved by carbon-coating by ball-milling. However, the initial coulombic efficiency decreased because of the reduction of the oxidized products on FeS₂ surface. The reduction in particle size provides a larger contact area for the electrolyte. Larger quantities of oxidation products were formed by the reduction of FeS₂ in the presence of air and water after carbon-coating. Therefore, the poor initial coulombic efficiencies of carbon-coated FeS₂ electrodes were caused by the reduction of the oxidized products on the FeS₂ surface.

Abstract: Pyrite (FeS₂) is an important semiconductor material which shows various excellent optical and electrical properties and extensive applied prospect as a new-type, photoelectrical functional materials. In this study, a low cost and efficient simple hydrothermal two-step synthetic method was given to obtain FeS₂ microspheres with 2-3 μm in diameter. The obtained products were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet and visible spectrophotometer (UV-Vis). XRD showed that the synthetic sample consisted of two crystal structures of FeS₂, pyrite and marcasite. SEM observation indicated that FeS₂ microspheres were well crystallized and had good uniformity. UV-Vis spectrum had a strong optical absorption in the region of 200-400 nm wave length. The reaction temperature had an impact on the size of FeS₂ microspheres. A possible mechanism for the size of the FeS₂ microspheres generated at high temperature is smaller than that at low temperature is discussed.

Abstract: Iron sulfide-AC adsorbents were prepared and their mercury removal capabilities were evaluated in the simulated coal combustion flue gases. The FeS₂ has much higher mercury removal rate than AC although it has much lower BET surface area than AC. FeS₂ also shows higher mercury removal rate than FeS, which is probably due to its higher free sulfur content on the FeS₂. The mercury removal capability of AC modified FeS₂ decreases with increasing of AC content. Temperature programmed desorption/decomposition process (TPDD) shows FeS and FeS₂ have more desorption peak than AC and the main peaks of FeS and FeS₂ are at around 240°C. The desorption peaks of AC modified FeS₂ are shifted to the higher temperature compared with that of FeS₂ and more mercury compositions are desorbed by AC modified FeS₂.

Abstract: Structure stability and electronic properties of Cu-doped FeS2 were studied using the first principle calculations based on plane wave pseudo-potential theory. The calculated results revealed that the band-gap Eg of Cu-doped FeS₂ was 0.47 eV. The valence band of the density of state (DOS) was mostly due to the Cu 3d and S p orbitals. The bottom part of conduction band was mostly due to the Fe 3d orbitals. The calculated covalent character of the Fe–S bonds gave large delocalization of the spin resulting in smaller values. The Cu, Fe and S had the spin compensated leading to configuration s0.47 p0.61d9.78, Fe s0.27p0.58d7.03, S s1.83p4.23, respectively. The tetrahedral environment of the Fe and Cu and the relatively weak field of the S2− ligand were consistent to the Fe3+ and Cu+.

Abstract: The FeS₂ was synthesized using S powder, FeCl₂4H₂O and PVP as main raw materials by solvothermal method. The FeS₂ product was characterized by XRD, SEM, DRS and TG-DTA. The results show that FeS₂ is the cube structure, particle size about 90 nm, band gap energy Eg=1.9 eV. Consequently, FeS₂ nanoparticles show high visible-light photocatalytic activity for decomposition of methylene blue, which degradation rate of 10mg/L methylene blue solution can reach to 95% for 90 min under visible-light irradiation.

Abstract: The effect of lithium salts such as LiPF6, LiBF4, LiCF3SO3 and LiN(CF3SO2)2 (LiTFSI) in tetra(ethylene glycol) dimethyl ether (TEGDME) electrolyte on the ionic conductivity, interfacial resistance and discharge properties of Li/pyrite cell at room temperature was studied. The electrolytes had good ionic conductivity at room temperature in the range 0.61 to 1.86 × 10-3 S/
. The discharge capacities of Li/pyrite cells with 1M LiPF6 and LiBF4 in TEGDME were lower compared to those of the other two non-HF containing salts. The best cycle performance was exhibited by LiTFSI in TEGDME electrolyte, with a discharge capacity of 438 mAhg-1 after 20 cycles, which is ~49% of FeS2 theoretical capacity (894 mAhg-1). The good performance of LiTFSI-TEGDME electrolyte resulted mainly from its low interfacial resistance in Li/FeS2 cells, which showed a decreasing trend with cycling.

Abstract: Iron, sulfur and transition metal powders were used as the starting materials to prepare iron disulfide (FeS2) cathode material at room temperature by high energy mechanical alloying. Modified FeS2 were also prepared by incorporation of transition metals like Co and Ni. Li/FeS2 cells with the prepared iron disulfides as cathodes were studied for discharge properties at room temperature using the 0.5M LiTFSI in tetra(ethylene glycol) dimethyl ether (TEGDME). The first discharge capacities of Li/composite FeS2 cell with 5 wt.% Co and 3 wt.% Ni were 571 and 844 mAh/g, respectively, compared to 389 mAh/g for the cell without any additive. The enhanced properties resulted from the better electronic conductivity of the material containing the metallic additive. The initial capacity and cyclic performance were improved when nickel and cobalt were added to prepare the modified iron disulfide.

Abstract: Iron disulfide (FeS2) is attractive as a positive electrode material in lithium batteries because of its low material cost, environmental non-toxicity, and high specific energy density. Furthermore, natural pyrite is a secondary product of the mining extraction of coal. For these reasons, natural and synthetic pyrites have been proposed as active cathode materials in secondary lithium batteries. We investigated the effect of various solvents on the electrochemical properties of lithium-FeS2 batteries. The specific discharge capacity of Li/FeS2 cells varied from 500 to 780mAh/g based on FeS2.

Abstract: Iron disulfide (FeS2) is attractive as a positive electrode material in lithium batteries because of its low material cost, environmental non-toxicity, and high specific energy density. Furthermore, natural pyrite is a secondary product of the mining extraction of coal. For such reasons, natural and synthetic pyrites have been proposed as active cathode materials in primary lithium batteries. We investigated the effect of temperature and current density on the electrochemical properties of lithium-FeS2 batteries. The specific discharge capacity of Li/FeS2 cells varied from 700 to 900mAh/g based on FeS2.