Cobalt Pyrite Research Articles

Architecture and active motif engineering of N–CoS2@C yolk–shell nanoreactor for boosted tetracycline removal via peroxymonosulfate activation: Performance, mechanism and destruction pathways

Rational construction of yolk-shell architecture with regulated binding configuration is crucially important but challengeable for antibiotic degradation via peroxymonosulfate (PMS) activation. In this study, we report the utilization of yolk-shell hollow architecture consisted of nitrogen-doped cobalt pyrite integrated carbon spheres (N–CoS2@C) as PMS activator to boost tetracycline hydrochloride (TCH) degradation. The creation of yolk-shell hollow structure and nitrogen-regulated active site engineering of CoS2 endow the resulted N–CoS2@C nanoreactor with high activity for PMS activating toward TCH degradation. Intriguingly, the N–CoS2@C nanoreactor exhibits an optimal degradation performance with a rate constant of 0.194 min−1 toward TCH via PMS activation. The 1O2 and SO4•− species are demonstrated as the dominant active substances for TCH degradation through quenching experiments and electron spin resonance characterization. The possible degradation mechanism, intermediates and degradation pathways for TCH removal over the N–CoS2@C/PMS nanoreactor are unveiled. Graphitic N, sp2−hybrid carbon, oxygenated group (C–OH) and Co species are verified as the possible catalytic sites of N–CoS2@C for PMS activation toward TCH removal. This study offers a unique strategy to engineer sulfides as highly efficient and promising PMS activators for antibiotic degradation.

SnO2 coupled cobalt pyrite for Hg0 removal from simulated flue gas

SnO2 doped cobalt pyrite (CoS2/SnO2) adsorbent is facilely prepared using a molten salt method and used to capture Hg0 capture in simulated flue gas. Bare CoS2 and SnO2 display relatively lower Hg0 adsorption ability. SnO2 addition can evidently enhance the Hg0 capture ability of CoS2 likely owing to the synergetic effect between CoS2 and SnO2. NO and SO2 can negatively affect Hg0 capture processes due to competitive adsorption or side reaction. Co2+, S22-, Sn4+ ions serve as the major adsorption sites for elemental mercury capture over CoS2/SnO2. Chemisorbed oxygen may be participated in the mercury removale process.

Nitrogen-Doped Cobalt Pyrite Yolk-Shell Hollow Spheres for Long-Life Rechargeable Zn-Air Batteries.

Limited by the sluggish four‐electron transfer process, designing high‐performance nonprecious electrocatalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is urgently desired for efficient rechargeable Zn–air batteries (ZABs). Herein, the successful synthesis of porous nitrogen‐doped cobalt pyrite yolk–shell nanospheres (N‐CoS2 YSSs) is reported. Benefiting from the abundant porosity of the porous yolk–shell structure and unique electronic properties by nitrogen doping, the as‐prepared N‐CoS2 YSSs possess more exposed active surface, thus giving rise to superior activity for reversible oxygen electrocatalysis and outstanding cycling stability (more than 165 h at 10 mA cm−2) in ZABs, exceeding the commercial Pt/C and RuO2 hybrid catalysts. Moreover, the assembled ZABs, delivering a specific capacity of 640 mAh gZn −1, can be used for practical devices. This work provides a novel tactic to engineer sulfides as high efficiency and promising bifunctional oxygen electrocatalysts for advanced metal–air batteries.

Carbon-Based Metallic Cobalt Pyrite Nanotubes as Stable Electrode Materials for Electrochemical Hydrogen Evolution

Transition metal dichalcogenides (TMDs) have attracted tremendous research attention because of their potential performance in the electrochemical hydrogen evolution reaction. Also, the three-dimensional (3D) hollow structure can provide additional excellent electrochemical activities. Here, we report for the first time that a carbon-based metallic cobalt pyrite (C@CoS2) hollow tubelike structure (nanotubes) can be achieved by a sulfuration process. This process adopts a simple one-step chemical vapor diffusion-controlled strategy, and the growth of nanotubes can be adjusted by simply changing the gas reaction condition. The obtained C@CoS2 nanotubes have an outstanding electrocatalytic performance. The results show the overpotential (220 mV) and Tafel slope (55.04 mV dec–1) of C@CoS2 nanotubes are much lower than those of C@CoS2 nanorods (slightly higher than the Pt electrode) when the cathode current density is 10 mA cm–2. Additionally, the current density of the C@CoS2 electrode does not decrease much at an overpotential of −250 mV (vs the reversible hydrogen electrode, RHE) after a 36 h test, demonstrating a good durability. The hollow structure of the nanotubes plays a key role in the hydrogen evolution reaction (HER), the polyporous carbon materials work for improving the conductivity, and exposed active sites increase the catalytic activity, which together enhance the whole HER activities. The facile strategy may provide an alternative to prepare other multifunctional TMD nanomaterials for water splitting or other electrochemical reactions.

Extraction of Cobalt and Iron from Refractory Co-Bearing Sulfur Concentrate

In this study, oxidizing roasting, segregation roasting, and magnetic separation are used to extract cobalt and iron from refractory Co-bearing sulfur concentrate. The Co-bearing sulfur concentrate containing 0.68% Co, 33.26% Fe, and 36.58% S was obtained from V-Ti magnetite in the Panxi area of China by flotation. Cobalt pyrite and linneite were the Co-bearing minerals, and the gangue minerals were mica, chlorite, feldspar, and calcite in Co-bearing sulfur concentrate. The results show that cobalt is transformed from Co-pyrite and linneite to a Co2FeO4-dominated new cobalt mineral phase, and iron is transformed from pyrite to Fe2O3 and an Fe3O4-dominated new iron mineral phase after oxidizing roasting. Cobalt changed from CoFe2O4 to a new cobalt mineral phase dominated by [Co] Fe solid solution, and iron changed from Fe2O3 to a new iron mineral phase dominated by metal Fe and Fe3O4 after segregation roasting. Cobalt concentrate with a cobalt grade of 15.15%, iron content of 71.22%, and cobalt recovery of 90.81% as well as iron concentrate with iron grade of 60.06%, cobalt content of 0.11%, and iron recovery of 76.23% are obtained. The main minerals in the cobalt concentrate are Fe, [Co]Fe, Fe3O4, and SiO2, and the main minerals in the iron concentrate are Fe3O4, FeO, Ca2Si2O4, and Ca2Al2O4.

Electrocatalytic Production of H2O2 by Selective Oxygen Reduction Using Earth-Abundant Cobalt Pyrite (CoS2)

Decentralized on-site production of hydrogen peroxide (H2O2) relies on efficient, robust, and inexpensive electrocatalysts for the selective two-electron (2e–) oxygen reduction reaction (ORR). Here...

Accelerated Hydrogen Evolution Reaction in CoS2 by Transition-Metal Doping

Cobalt pyrite (CoS2) is one of the promising candidate catalysts for electrocatalytic hydrogen evolution because of its efficient catalytic activity sites and inherent metallicity. Herein, we report the greatly improved electrocatalytic activity of CoS2 resulting from Mn doping. First, we give the theoretical prediction that Mn is the most excellent dopant to activate the electrocatalytic activity of CoS2 with the smallest Gibbs free energy (|ΔGH*|) while remaining metallic. Second, to provide experimental evidence, Mn-doped CoS2 nanowires are prepared by a hydrothermal and postsulfuration method. The optimized sample shows a low overpotential of 43 mV at 10 mA/cm2, a Tafel slope of only 34 mV/dec, and long-time stability for the hydrogen evolution reaction. This work reveals a new way to stimulate the electrocatalytic activity of other pristine candidate catalysts.

Activating and Optimizing Activity of CoS2 for Hydrogen Evolution Reaction through the Synergic Effect of N Dopants and S Vacancies

Here, N-doped cobalt pyrite (CoS2) electrocatalytic material is developed via utilizing the synergic effect of N dopants and S vacancies. The catalyst displays high activity and stability for hydrogen evolution reaction. Density functional theory calculations and electrochemical characterizations reveal that the electrochemical activity of the CoS2 catalyst is directly associated with the content of N dopants and S vacancies, where proper combinations of N dopants and S vacancies yield a minimized overpotential close to that of commercial Pt. What’s more, optimized performance has been achieved by carefully manipulating the amounts of N dopants and S vacancies in N-doped CoS2 catalyst, which exhibits a Tafel slope as small as 48 mV/dec, an ultralow overpotential of 57 mV at 10 mA/cm2, and satisfying stability. This work highlights a feasible strategy to explore efficient electrocatalysts via nonmetal element doping and defect engineering.

Copper dopants improved the hydrogen evolution activity of earth-abundant cobalt pyrite catalysts by activating the electrocatalytically inert sulfur sites

Cobalt pyrite (CoS2) is considered to be a promising catalyst for the hydrogen evolution reaction (HER) due to its intrinsic metallicity and high catalytic activity.

Metallic CoS2 nanowire electrodes for high cycling performance supercapacitors

We report metallic cobalt pyrite (CoS2) nanowires (NWs) prepared directly on current collecting electrodes, e.g., carbon cloth or graphite disc, for high-performance supercapacitors. These CoS2 NWs have a variety of advantages for supercapacitor applications. Because the metallic CoS2 NWs are synthesized directly on the current collector, the good electrical connection enables efficient charge transfer between the active CoS2 materials and the current collector. In addition, the open spaces between the sea urchin structure NWs lead to a large accessible surface area and afford rapid mass transport. Moreover, the robust CoS2 NW structure results in high stability of the active materials during long-term operation. Electrochemical characterization reveals that the CoS2 NWs enable large specific capacitance (828.2 F g−1 at a scan rate of 0.01 V s−1) and excellent long term cycling stability (0–2.5% capacity loss after 4250 cycles at 5 A g−1) for pseudocapacitors. This example of metallic CoS2 NWs for supercapacitor applications expands the opportunities for transition metal sulfide-based nanostructures in emerging energy storage applications.

Photoelectrochemical Solar Energy Conversion and Electrocatalysis Using Earth-Abundant Nanomaterials

The scale of renewable energy challenge not only calls for highly efficient technologies but also abundant, inexpensive, and robust materials. Nanomaterials can help to mitigate the poor properties of earth-abundant semiconductors and catalysts to enhance solar energy conversion. We have controlled the nanostructures and polymorphs of layered MS2 (M = Mo, W) materials and other earth-abundant metal chalcogenides, such as metallic cobalt pyrite (CoS2), to significantly enhance their catalytic activity in hydrogen evolution reaction (HER). We further establish ternary pyrite-type cobalt phosphosulfide (CoPS) as a high-performance earth-abundant HER catalyst that achieves geometrical catalytic current density of 10 mA/cm2 at overpotentials as low as 48 mV with outstanding long-term operation stability. These earth-abundant catalysts and semiconductors have been integrated to enable efficient solar energy conversion. Integrated photocathodes of the novel earth-abundant catalysts on n +-p-p + silicon micropyramids achieved high photocurrents up to 35 mA/cm2 and onset photovoltages as high as 450 mV vs RHE, and 5-6% solar-to-hydrogen conversion efficiency.

Selective Oxygen Reduction to Hydrogen Peroxide Using Earth-Abundant Metal Pyrites As High-Performance Electrocatalysts

It is important to develop alternative catalysts made of inexpensive and earth-abundant elements with high catalytic activity and stability to replace the noble metal catalysts in various environmental1 and renewable energy applications.2 Here we report earth-abundant metal pyrites MS2 (M as Fe, Ni, and Co) as high performance electrocatalysts3,4 for oxygen reduction reaction (ORR) that is selective for generating hydrogen peroxide. In neutral solution of 0.1 M sodium perchlorate and acidic solution of 0.1 M perchloric acid, all three MS2 show high ORR catalytic activity with excellent Tafel slopes. Based on Koutecky-Levich (K-L) analysis, all MS2 and noble metal show similar potential-dependent selectivity of the two-electron peroxide pathway in neutral condition, and CoS2 is the best among metal pyrites in terms of the positive potential for 50% H2O2selectivity. The stability of metal pyrites is quite good in under ORR operation in both neutral and acidic solutions. These inexpensive metal pyrites are excellent ORR catalysts for selective peroxide generation and could find promising applications in environmental and renewable energy technologies. 1. X.-W. Liu; W.-W. Li; H.-Q. Yu; “Cathodic catalysts in bioelectrochemical systems for energy recovery from wastewater” Chem. Soc. Rev., 2014, 43, 7718-7745. 2. Matthew S. F.; Song Jin; “Earth-abundant inorganic electrocatalysts and their nanostructures for energy conversion applications” Energy Environ. Sci., 2014, 7, 3519-3542. 3. Matthew S. F.; Mark A. L.; Qi Ding; Nicolas S. K.; Song Jin; “Earth-Abundant Metal Pyrites (FeS2, CoS2, NiS2, and Their Alloys) for Highly Efficient Hydrogen Evolution and Polysulfide Reduction” J. Phys. Chem. C, 2014, 118 (37), 21347-21356. 4. Matthew S. F.; Rafal D.; Mark A. L.; Nicholas S. K.; Qi Ding; Song Jin; “High-Performance Electrocatalysis Using Metallic Cobalt Pyrite (CoS2) Micro- and Nanostructures” J. Am. Chem. Soc., 2014, 136 (28), 10053-100061. Figure 1

Direct Chemical Vapor Deposition Synthesis of Phase-Pure Iron Pyrite (FeS2) Thin Films

Resurgent interest in iron pyrite (FeS2) as an earth-abundant, nontoxic semiconductor for solar applications has resulted in many attempts to grow phase-pure thin films via chemical vapor deposition (CVD). However, all thin films grown via CVD or sulfidation to date have contained marcasite phase or other iron sulfide impurities. Here, we report the use of metallic cobalt pyrite (cattierite, CoS2) thin films as an ideal substrate leading to the first direct growth of phase-pure iron pyrite thin films via atmospheric pressure CVD. This synthesis was achieved by reacting FeCl3 and ditert butyl disulfide (TBDS) at 400–450 °C. The products were confirmed as phase-pure iron pyrite using X-ray diffraction (XRD), Raman spectroscopy, and energy dispersive X-ray spectroscopy (EDS). In addition to phase-purity, the synthesis produced crystal domains >1 μm and a conformal coating 3–5 μm thick, which are attributed to the <2% lattice mismatch of the isostructural cattierite substrate. The surface was characterized by...

High-performance electrocatalysis using metallic cobalt pyrite (CoS₂) micro- and nanostructures.

The development of efficient and robust earth-abundant electrocatalysts for the hydrogen evolution reaction (HER) is an ongoing challenge. We report metallic cobalt pyrite (cobalt disulfide, CoS2) as one such high-activity candidate material and demonstrate that its specific morphology--film, microwire, or nanowire, made available through controlled synthesis--plays a crucial role in determining its overall catalytic efficacy. The increase in effective electrode surface area that accompanies CoS2 micro- and nanostructuring substantially boosts its HER catalytic performance, with CoS2 nanowire electrodes achieving geometric current densities of -10 mA cm(-2) at overpotentials as low as -145 mV vs the reversible hydrogen electrode. Moreover, micro- and nanostructuring of the CoS2 material has the synergistic effect of increasing its operational stability, cyclability, and maximum achievable rate of hydrogen generation by promoting the release of evolved gas bubbles from the electrode surface. The benefits of catalyst micro- and nanostructuring are further demonstrated by the increased electrocatalytic activity of CoS2 nanowire electrodes over planar film electrodes toward polysulfide and triiodide reduction, which suggests a straightforward way to improve the performance of quantum dot- and dye-sensitized solar cells, respectively. Extension of this micro- and nanostructuring strategy to other earth-abundant materials could similarly enable inexpensive electrocatalysts that lack the high intrinsic activity of the noble metals.

Earth-Abundant Cobalt Pyrite (CoS2) Thin Film on Glass as a Robust, High-Performance Counter Electrode for Quantum Dot-Sensitized Solar Cells.

We report a cobalt pyrite (cobalt disulfide, CoS2) thin film on glass as a robust, high-performance, low-cost, earth-abundant counter electrode for liquid-junction quantum dot-sensitized solar cells (QDSSCs) that employ the aqueous sulfide/polysulfide (S(2-)/Sn(2-)) redox electrolyte as the hole-transporting medium. The metallic CoS2 thin film electrode is prepared via thermal sulfidation of a cobalt film deposited on glass and has been characterized by powder X-ray diffraction and electron microscopy. Using the CoS2 counter electrode, CdS/CdSe-sensitized QDSSCs display improved short-circuit photocurrent density and fill factor, achieving solar light-to-electricity conversion efficiencies as high as 4.16%, with an average efficiency improvement of 54 (±14)% over equivalent devices assembled with a traditional platinum counter electrode. Electrochemical measurements verify that CoS2 shows high electrocatalytic activity toward polysulfide reduction, rationalizing the improved QDSSC performance. CoS2 is also less susceptible to poisoning by the sulfide/polysulfide electrolyte, a problem that plagues platinum electrodes in this application; furthermore, CoS2 exhibits excellent stability in sulfide/polysulfide electrolyte, resulting in highly reproducible performance.