Layered Metal Sulfides Research Articles

Synthesis of Optimized CZTS Thin Films for Photovoltaic Absorber Layers by Sputtering from Sulfide Targets and Sulfurization

AbstractCu2ZnSnS4 (CZTS) is a promising alternative for Cu(In,Ga)Se2 (CIGS) absorber layers in thin film solar cells and is comprised of commodity elements which will enable scale-up of chalcopyrite panel production unhindered by elemental supplies and costs. Various CZTS synthesis methods, especially sulfurization of stacked metal or metal sulfide layers, are being studied and have led to cell efficiencies up to 6.7% [1]. Here we report our studies of CZTS thin film synthesis via room temperature sputtering from a single CZTS target and co-sputtering from Cu2S, ZnS and SnS2 binary targets, both followed by sulfurization between 500 C - 600 C using either elemental sulfur vapor or in-situ generated H2S. Sputtering from sulfur-containing targets is designed to increase the sulfur content in the precursor films to promote stoichiometry. We report on the effects of processing including deposition on soda-lime and borosilicate glasses and deposition of Na-containing layers on film morphology (AFM/SEM), composition (EDS), phase (XRD), grain size (XRD/EBSD), grain boundary structure (EBSD), optical (spectroscopic ellipsometry) and electrical properties. Processing conditions producing desirable Zn-rich/Cu-poor films are identified [1]. The formation of MoSe2 at Mo/CIGS interface is believed to promote Ohmic contacts, but in CZTS we associate excessive formation of frangible MoS2 with film delamination from Mo/borosilicate glass substrates. Strategies for preventing delamination including adhesion layers are investigated and discussed. P-N junctions are formed with CdS/ZnO using chemical bath deposition and sputtering, and I-V characteristics are reported. Schottky junctions are formed and C-V measurements are used to determine the doping in the CZTS absorber layers.[1] H. Katagiri, et al., MRS Symp. Proc. 1165 1165-M04-01 (2009).

Solar hydrogen production over novel metal sulfide photocatalysts of AGa2In3S8 (A = Cu or Ag) with layered structures

Layered metal sulfides of CuGa(2)In(3)S(8) with a 1.91-eV band gap and AgGa(2)In(3)S(8) with a 2.27-eV band gap gave 15% apparent quantum yields at 560 nm and 460 nm for H(2) evolution from aqueous solutions containing K(2)SO(3) and Na(2)S as electron donors with assistance of Rh cocatalysts, respectively, and Rh/CuGa(2)In(3)S(8) responded to 680 nm for the photocatalytic H(2) evolution.

ChemInform Abstract: Sequestration of Heavy Metals from Water with Layered Metal Sulfides.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Sequestration of Heavy Metals from Water with Layered Metal Sulfides

Extraordinarily effective heavy metal ion scavenger: We show here that the material K(2x)Mn(x)Sn(3-x)S(6) (x = 0.5-0.95) (KMS-1) overcomes the limitations of the known heavy metal ion sorbents, showing the capability to rapidly reduce the concentrations of Cd, Hg, and Pb ions well-below the legally acceptable levels for drinking water. KMS-1 is inexpensive, easily prepared in large quantities, and may play a role in addressing the global problem of water contamination with heavy metal ions. The paradigm of heavy metal ion absorption of KMS-1 is the ability to form very strong M-S bonds.

Highly Efficient and Rapid Cs+ Uptake by the Layered Metal Sulfide K2xMnxSn3−xS6 (KMS-1)

The details of the ion-exchange properties of the layered sulfide material K(2x)Mn(x)Sn(3-x)S(6) (x = 0.5-0.95) (KMS-1) with Cs(+) and Rb(+) cations are reported. X-ray photoelectron spectroscopy (XPS), elemental analyses, and powder and single-crystal diffraction studies revealed that the Cs(+) and Rb(+) ion exchange of KMS-1 is complete (quantitative replacement of K(+) ions) and topotactic. These data also revealed that the Cs(+) exchange is accompanied with a rare topotactic oxidation of Mn(2+) to Mn(3+) caused by atmospheric oxygen, while the Rb(+) ion exchange only slightly alters the oxidation state of the layer manganese atoms. The absorption of Cs(+) by KMS-1 follows the Langmuir model with a high exchange capacity of 226(4) mg/g (pH approximately 7) and distribution coefficients as high as 2 x 10(4) mL/g. KMS-1 displays significant cesium uptake both under strongly acidic (pH 0.7-2.6) or basic conditions (pH 10-12). The kinetics of Cs(+) capture by KMS-1 is fast (>90% removal of approximately 1 ppm of Cs(+) within only 5 min). KMS-1 was also found capable to efficiently absorb Cs(+) from complex solutions containing various competitive cations in large excess. KMS-1 (containing Mn(3+) ions) can be regenerated and reused for Cs(+) exchange with an exchange capacity very similar to that of the pristine KMS-1. The results indicate that layered metal sulfides with ion-exchange properties may be considered as highly selective and cost-effective sorbents for remediation of water contaminated with the radioactive (137)Cs isotope. The selectivity over other alkali ions for Cs originates not from a size effect but from the more favorable Cs...S soft Lewis acid/Lewis base interactions.

H2xMnxSn3‐xS6 (x = 0.11–0.25): A Novel Reusable Sorbent for Highly Specific Mercury Capture Under Extreme pH Conditions

AbstractThe H2xMnxSn3‐xS6 (x = 0.11–0.25) is a new solid acid with a layered hydrogen metal sulfide (LHMS). It derives from K2xMnxSn3–xS6 (x = 0.5–0.95) (KMS‐1) upon treating it with highly acidic solutions. We demonstrate that LHMS‐1 has enormous affinity for the very soft metal ions such as Hg2+ and Ag+ which occurs via a rapid ion exchange process. The tremendous affinity of LHMS‐1 for Hg2+ is reflected in very high distribution coefficient KdHg values (>106 mL g−1). The large affinity and selectivity of LHMS‐1 for Hg2+ persists in a very wide pH range (from less than zero to nine) and even in the presence of highly concentrated HCl and HNO3 acids. LHMS‐1 is significantly more selective for Hg2+ and Ag+ than for the less soft cations Pb2+ and Cd2+. The Hg2+ ions are immobilized in octahedral sites between the sulfide layers of the materials via Hg–S bonds as suggested by pair distribution function (PDF) analysis. LHMS‐1 could decrease trace concentrations of Hg2+ (e.g. <100 ppb) to well below the acceptable limits for the drinking water in less than two min. Hg‐laden LHMS‐1 shows a remarkable hydrothermal stability and resistance in 6 M HCl solutions. LHMS‐1 could be regenerated by treating Hg‐loaded samples with 12 M HCl and re‐used without loss of its initial exchange capacity.

Twisted Nanostructures of 2H-MoS2 Slabs

AbstractIn the last decades, HRTEM approach has been quite fruitful to study structural characteristics of layered transition metal sulfide (LTMS) catalytic materials since providing direct local information about the structural organization of this quite important class of catalysts at the nanoscale level. However, up to now, HRTEM observations of some common localized structural organization like honeycomb-like structures have remained unexplained. In the present study, a structural model corresponding to stacked 2H-MoS2 slabs twisted along their basal direction is proposed to explain honeycomb like-structures observed by HRTEM. This model is based on a comparison between experimental and simulated images of 2H-MoS2 catalysts promoted with cobalt. The resulting Density of States (DOS) of the twisted structure was then calculated.

A straightforward wet-chemical route to the nanocomposites of general layered clays and metal sulfides

The nanocomposites of general layered clays and metal sulfides could be produced from reactions of the layered clay aqueous suspensions and water-soluble metal–thiourea complexes. The clay could be saponite, montmorillonite, hectorite and laponite, while the metal sulfide could be cobalt sulfide, nickel sulfide, zinc sulfide, cadmium sulfide, and lead sulfide. In the nanocomposites, the clay could be incorporated with the metal sulfide pillars and metal sulfide nanoparticles.

Synthesis and Crystal Structure of Ae2LiInGe2 (Ae = Ca, Sr): New Zintl Phases with a Layered Silicate-like Network

Two new Zintl phases Ae(2)LiInGe(2) (Ae = Ca 1; Sr 2) were obtained from stoichiometric reactions of the pure elements in sealed Nb tubing at 1000-1050 degrees C. The isomorphous polar intermetallic phases crystallize in the orthorhombic space group Pnma, with cell constants of a = 7.2512(7), b = 4.4380(5), and c = 16.902(1) A for compound 1, and a = 7.5033(8), b = 4.6194(5), and c = 17.473(2) A for compound 2. The crystal structure can be derived from the vertex-sharing of InGe(4/2) tetrahedral units that form "corrugated" sheets normal to the crystallographic c-axis. Calcium and lithium atoms act as "spacers" that effectively separate the anionic [InGe(2)](5-) layers. The layered anionic substructure is similar to those exhibited by layered metal oxides, sulfides, and silicates. The connectivity of the tetrahedral building unit, [InGe(4/2)](5-), is analogous and isoelectronic to the silicate [SiO(4/2)] unit.

Microporous layered tin sulfide, SnS-1: molecular sieve or intercalant?

The results of a detailed study of the structure, thermal/pressure stability, ion-exchange, amine intercalation and adsorption property relations, of microporous layered tin(iv) sulfides A2Sn3S7 , denoted SnS-1, where A=tetramethylammonium (TMA), quinuclidinium (QUIN), or tert-butylammonium (TBA), are reported and comparisons are made to zeolites and layered metal sulfides. The thermal stability of the materials indicates potential for the removal of void filling organic template without affecting the integrity of the lattice. The sensitivity of the materials to applied pressure is found to depend on the nature of the occluded template. Aqueous ion-exchange and gas-phase exchange by amines are observed in SnS-1 templated with the tertiary ammonium cation. This allows for an intercalation-like process similar to the layered chalcogenides. Adsorption isotherms for SnS-1 show it to exclude gaseous species of kinetic diameter >3.4 A, thus acting as a molecular sieve like zeolites and showing potential for catalysis, separation and chemical sensing applications.

The influence of biocides on the microbiologically influenced corrosion of mild steel and brass

The role of sulfate-reducing bacteria in the anaerobic corrosion of mild steel and brass was studied. Culture-media containing sulfide of biogenic and of chemical origin was used to see the effect of metal-sulfide layers developed in different ways. Biocides with different efficiency were used to inhibit metabolic activity of bacteria. Polarization resistances and open circuit potentials were recorded followed by potentiostatic polarization measurements on the metal samples to get information on corrosion rates and the mechanism of corrosion processes. An atomic force microscope was used to image the topography of sulfide layers.

Molecular Approach to Mesoporous Metal Sulfides

AbstractWe have synthesized metal-sulfide/surfactant nanocomposite materials by cooperative assembly of molecular precursors in an aqueous medium. The template-mediated synthetic approach is applicable to metal sulfides that exhibit aqueous thiometallate chemistry. The products are lamellar and have bilayers or interdigitated layers of surfactant molecules sandwiched between metal sulfide layers. The layers of anionic metal sulfide molecules are not completely condensed in the nanocomposites, which results in a negative charge on the metal sulfide layers. The materials are stable at room temperature in water, methanol, 1 M HCl, 30 wt% NH3, and 1 M NaOH. The materials do not dissolve at 80 °C in water and are stable to at least 180 0C in air. The nanocomposites exhibit ion exchange of smaller surfactants, alkali-metal ions, and divalent metal ions.

Hydration, Schichtsolvatbildung und Kationenaustauschreaktionen nichtstöchiometrischer ternärer Sulfide des Titans / Hydration, Layer Solvate Formation and Cation Exchange of Nonstoichiometric Ternary Sulfides of Titanium

Nonstoichiometric ternary phases (MI)x[TiS2] with MI = Li, Na, K were prepared by reaction of TiS2 in salt melts of the corresponding alkali halides under H2S/CS2 atmosphere. The compounds form hexagonal crystal plates with negatively charged [TiS2]x--layers of the CdJ2-type and alkali cations located between the metal sulfide sheets. They react with water to form hydrates, whose layer distances depend on the radius of the alkali cation and on the ambient water vapour pressure. A variety of layer solvate complexes is obtained by partial or total replacement of the water with polar molecules, which are able to solvate the metal sulfide layers and the interlayer cations. The latter may be exchanged with mono- and divalent inorganic and organic cations. Similar reactions were observed with a number of ternary layer chalcogenides (MI)x⁻ [(MII)yXz] with MI = Li, Na. K, Rb, Cs; MII = Zr, Hf, V. Nb, Ta, Cr, Ni, Pd, Pt and X = S, Se.