Synthesis of nanostructured powders and thin films of iron sulfide from molecular precursors

Impact of FeS on the TiO2 Layer As Support System in QDSCs

We report on the passivation of titanium oxide with FeS from three molecular precursors with tin sulfide (SnS) photon absorbers that were fabricated and assembled to increase the performance of quantum dot sensitized solar cells (QDSSCs). FeS was loaded on the TiO2 surfaces, and then, SnS photosensitizer was deposited to form a ternary modified device. The morphology, structural structure, size distribution, chemical composition, and conversion efficiency were explored by FE-SEM, XRD, TEM, UV-vis, EDS, EIS, and J-V analysis. The CV, LSV, and stability state were also investigated for migration and separation of photogenerated charge carriers in the as-prepared cells labeled F-S-1, F-S-2, and F-S-3. The FE-SEM image of the F-S-2 cell is composed of FeS interconnected with SnS and FeS, which provided paths for electron movement compared with the F-S-1 and F-S-3 devices. The semicircle for the F/S-1 and F/S-3 solar device diameters illustrates that the high-medium frequency regain is greater than that of the F/S-2 device, implying that both cells have charge-transfer impedances and lower contact. Apparently, the F/S-2 device shows superior catalytic activity, which can be linked to the hybridization of TiO2/FeS/SnS due to the synergistic effect. The F/S-2/S-2l has a maximum efficiency η of 6.73% in comparison to F/S-1 and F/S-3, which have the same conversion efficiency of 3.82%. The results of the F/S-2 device follow a similar trend to the chronoamperometry analysis, CV, and LSV results from this study.

Yolk-shell FeS@N-doped carbon nanosphere as superior anode materials for sodium-ion batteries

Iron sulfides have shown great potential as anode materials for sodium-ion batteries (SIBs) because of their high sodium storage capacity and low cost. Nevertheless, iron sulfides generally exhibit unsatisfied electrochemical performance induced by sluggish electron/ion transfer and severe pulverization upon the sodiation/desodiation process. Herein, we constructed a yolk-shell FeS@NC nanosphere with an N-doped carbon shell and FeS particle core via a simple hydrothermal method, followed by in-situ polymerization and vulcanization. The FeS particles intimately coupled with N-doped carbon can accelerate the electron transfer, avoid severe volume expansion, and maintain structural stability upon repeated sodiation/desodiation process. Furthermore, the small particle size of FeS can shorten ion-diffusion distance and facilitate ion transportation. Therefore, the FeS@NC nanosphere shows excellent cycling performance and superior rate capability that it can deliver a high capacity of 520.1 mAh g-1 over 800 cycles at 2.0 A g-1 and a remarkable capacity of 625.9 mAh g-1 at 10.0 A g-1.

Unlocking the Potential of Iron Sulfides for Sodium-Ion Batteries by Ultrafine Pulverization

Iron sulfides have attracted tremendous research interest for the anode of sodium-ion batteries due to their high capacity and abundant resource. However, the intrinsic pulverization and aggregation of iron sulfide electrodes induced by the conversion reaction during cycling are considered destructive and undesirable, which often impedes their capacity, rate capability, and long-term cycling stability. Herein, an interesting pulverization phenomenon of ultrathin carbon-coated Fe1- xS nanoplates (Fe1- xS@C) is observed during the first discharge process of sodium-ion batteries, which leads to the formation of Fe1- xS nanoparticles with quantum size (≈5 nm) tightly embedded in the carbon matrix. Surprisingly, no discernible aggregation phenomenon can be detected in subsequent cycles. In/ex situ experiments and theoretical calculations demonstrate that ultrafine pulverization can confer several advantages, including sustaining reversible conversion reactions, reducing the adsorption energies, and diffusion energy barriers of sodium atoms, and preventing the aggregation of Fe1- xS particles by strengthening the adsorption between pulverized Fe1- xS nanoparticles and carbon. As a result, benefiting from the unique ultrafine pulverization, the Fe1- xS@C anode simultaneously exhibits high reversible capacity (610 mAh g-1 at 0.5 A g-1), superior rate capability (427.9 mAh g-1 at 20 A g-1), and ultralong cycling stability (377.9 mAh g-1 after 2500 cycles at 20 A g-1).

Enhanced High-Rate Capability and Long Cycle Stability of FeS@NCG Nanofibers for Sodium-Ion Battery Anodes

The development of advanced hierarchical anode materials has recently become essential to achieving high-performance sodium-ion batteries. Herein, we developed a facile and cost-effective scheme for synthesizing graphene-wrapped, nitrogen-rich carbon-coated iron sulfide nanofibers (FeS@NCG) as an anode for SIBs. The designed FeS@NCG can provide a significant reversible capacity of 748.5 mAh g^-1 at 0.3 A g^-1 for 50 cycles and approximately 3.9-fold higher electrochemical performance than its oxide analog (Fe₂O₃@NCG, 192.7 mAh g^-1 at 0.3 A g^-1 for 50 cycles). The sulfur- and nitrogen-rich multilayer package structure facilitates efficient suppression of the porous FeS volume expansion during the sodiation process, enabling a long cycle life. The intimate contact between graphene and porous carbon-coated FeS nanofibers offers strong structural barriers associated with charge-transfer pathways during sodium insertion/extraction. It also reduces the dissolution of polysulfides, enabling efficient sodium storage with superior stable kinetics. Furthermore, outstanding capacity retention of 535 mAh g^-1 at 5 A g^-1 is achieved over 1010 cycles. The FeS@NCG also exhibited a specific capacity of 640 mAh g^-1 with a Coulombic efficiency of above 99.8% at 5 A g^-1 at 80 °C, indicating its development prospects in high-performance SIB applications.

Planar Blatter radicals through Bu3SnH- and TMS3SiH-assisted cyclization of aryl iodides: azaphilic radical addition

Radical chain cyclization of aryl iodides provides an efficient synthesis of planar Blatter radicals, and, for the first time, access to functionalized sulphur-containing analogues.

Carbon-Free Crystal-like Fe1-xS as an Anode for Potassium-Ion Batteries

Potassium-ion batteries (PIBs) as a new electrochemical energy storage system have been considered as a desirable candidate in the post-lithium-ion battery era. Nevertheless, the study on this realm is in its infancy; it is urgent to develop electrode materials with high electrochemical performance and low cost. Iron sulfides as anode materials have aroused wide attention by virtue of their merits of high theoretical capacities, environmental benignity, and cost competitiveness. Herein, we constructed carbon-free crystal-like Fe_1-xS and demonstrated its feasibility as a PIB anode. The unique structural feature endows the prepared Fe_1-xS with plentiful active sites for electrochemical reactions and short transmission pathways for ions/electrons. The Fe_1-xS electrode retained capacities of 420.8 mAh g^-1 after 100 cycles at 0.1 A g^-1 and 212.9 mAh g^-1 after 250 cycles at 1.0 A g^-1. Even at a high rate of 5.0 A g^-1, an average capacity of 167.6 mAh g^-1 was achieved. In addition, a potassium-ion full cell is assembled by employing Fe_1-xS as an anode and potassium Prussian blue as a cathode; it delivered a discharge capacity of 127.6 mAh g^-1 at 100 mA g^-1 after 50 cycles.

Dithiocarbamate Complexes as Single Source Precursors to Nanoscale Binary, Ternary and Quaternary Metal Sulfides

Nanodimensional metal sulfides are a developing class of low-cost materials with potential applications in areas as wide-ranging as energy storage, electrocatalysis, and imaging. An attractive synthetic strategy, which allows careful control over stoichiometry, is the single source precursor (SSP) approach in which well-defined molecular species containing preformed metal-sulfur bonds are heated to decomposition, either in the vapor or solution phase, resulting in facile loss of organics and formation of nanodimensional metal sulfides. By careful control of the precursor, the decomposition environment and addition of surfactants, this approach affords a range of nanocrystalline materials from a library of precursors. Dithiocarbamates (DTCs) are monoanionic chelating ligands that have been known for over a century and find applications in agriculture, medicine, and materials science. They are easily prepared from nontoxic secondary and primary amines and form stable complexes with all elements. Since pioneering work in the late 1980s, the use of DTC complexes as SSPs to a wide range of binary, ternary, and multinary sulfides has been extensively documented. This review maps these developments, from the formation of thin films, often comprised of embedded nanocrystals, to quantum dots coated with organic ligands or shelled by other metal sulfides that show high photoluminescence quantum yields, and a range of other nanomaterials in which both the phase and morphology of the nanocrystals can be engineered, allowing fine-tuning of technologically important physical properties, thus opening up a myriad of potential applications.

Novel perspectives of laser ablation in liquids: the formation of a high-pressure orthorhombic FeS phase and absorption of FeS-derived colloids on a porous surface for solar-light photocatalytic wastewater cleaning

A pulsed Nd : YAG laser ablation of FeS in water and ethanol produces FeS-derived colloidal nanoparticles that absorb onto immersed porous ceramic substrates and create solar-light photocatalytic surfaces. The stability, size distribution and zeta potential of the nanoparticles were assessed by dynamic light scattering. Raman, UV-Vis and XP spectroscopy and electron microscopy reveal that the sol nanoparticles have their outmost layer composed of ferrous and ferric sulphates and those produced in water are made of high-pressure orthorhombic FeS, cubic magnetite Fe3O4 and tetragonal maghemite γ-Fe2O3, while those formed in ethanol contain hexagonal FeS and cubic magnetite Fe3O4. Both colloids absorb solar light and their adsorption to porous ceramic surfaces creates functionalized ceramic surfaces that induce methylene blue degradation by daylight. The laser induced process thus offers an easy and efficient way for the functionalization of porous surfaces by photocatalytic nanoparticles that avoids aggregation in the liquid phase. The formation of an orthorhombic high-pressure FeS phase stable under ambient conditions is the first example of high-pressure structures produced by laser ablation in liquid without the assistance of an electric field.

Accessing γ-Ga2S3 by solventless thermolysis of gallium xanthates: a low-temperature limit for crystalline products

Alkyl-xanthato gallium(iii) complexes of the form [Ga(S₂COR)₃], where R = Me (1), Et (2), ⁱPr (3), ⁿPr (4), ⁿBu (5), ^sBu (6) and ⁱBu (7), have been synthesized and fully characterised. The crystal structures for 1 and 3-7 have been solved and examined to elucidate if these structures are related to their decomposition. Thermogravimetric analysis was used to gain insight into the decomposition temperatures for each complex. Unlike previously explored metal xanthate complexes which break down at low temperatures (<250 °C), to form crystalline metal chalcogenides, powder X-ray diffraction measurements suggest that when R ≥ Et these complexes did not produce crystalline gallium sulfides until heated to 500 °C, where γ-Ga₂S₃ was the sole product formed. In the case of R = Me, Chugaev elimination did not occur and amorphous Ga_xS_y products were formed. We conclude therefore that the low-temperature synthesis route offered by the thermal decomposition of metal xanthate precursors, which has been reported for many metal sulfide systems prior to this, may not be appropriate in the case of gallium sulfides.

A molecular precursor route to quaternary chalcogenide CFTS (Cu2FeSnS4) powders as potential solar absorber materials

In the present work we report on the synthesis of a tetragonal phase of stannite Cu₂FeSnS₄ powder from Sn(ii) and Sn(iv) using a solvent free melt method using a mixture of Cu, Fe, Sn(ii)/Sn(iv) O-ethylxanthates.