High-temperature Sulfurization Research Articles

Efficiency enhancement of Cu2ZnSnS4 solar cells via surface treatment engineering.

Pure-sulphide Cu2ZnSnS4 (CZTS) thin film solar cells were prepared by a low-cost, non-toxic and high-throughput method based on the thermal decomposition and reaction of sol–gel precursor solution, followed by a high temperature sulfurization process in sulphur atmosphere, which usually gave rise to the unexpected Cu-poor and Zn-rich phase after sulfurization. In order to remove the formation of detrimental secondary phases, e.g. ZnS, a novel method with hydrochloric acid solution treatment to the CZTS absorber layer surface was employed. By using this method, a competitive power conversion efficiency as high as 4.73% was obtained, which is a factor of 4.8 of that of the control CZTS solar cell without surface treatment. This presents a customized process for CZTS photovoltaic technologies that is more environmentally friendly and considerably less toxic than the widely used KCN etching approach.

Template-assisted sol–gel synthesis of porous MoS2/C nanocomposites as anode materials for lithium-ion batteries

Porous MoS2/C nanocomposites have been successfully via a sol–gel route with ammonium molybdatetetrahydrate ((NH4)6Mo7O24·4H2O) as molybdenum source, glucose as carbon source and tetramethyloxysilane (TMOS) as gelation accelerator, subsequently followed by high-temperature sulfuration and further NaOH etching to remove silica template derived from TMOS. The as-prepared MoS2/C nanocomposites were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FT-IR), and nitrogen adsorption–desorption, and the effect of molybdenum precursor mass on the synthesis of product was also investigated. The Mo and TMOS mass ratio obviously affects the gelation time, phase composition and morphology of the resultant product, and an appropriate Mo and TMOS mass ratio allows the formation of lamellar structure as well as perfect MoS2 phase. The as-prepared MoS2/C nanocomposite with Mo and TMOS mass ratio of 7:3 exhibits a BET surface area of 31 m2g−1 and a mesopore size of 20 nm, and demonstrates good electrochemical performances with 400 mA h g−1 specific reversible capacity after 60 cycles owing to the pore structure and synergistic effect between MoS2 and amorphous carbon.

Boosting efficiency and stability of a Cu2ZnSnS4 photocathode by alloying Ge and increasing sulfur pressure simultaneously

Cu2ZnSnS4 (CZTS) is a very promising absorber for solar driven photovoltaics and water splitting applications due to its high theoretical efficiency, low-cost and non-toxicity. Alloying Ge into CZTS is a potential method to improve the efficiency of CZTS-based devices. However, decomposition of Ge-CZTS during a high temperature sulfurization process usually leads to serious Ge element loss and secondary phases, which lower the performance of Ge-CZTS based devices. Moreover, inconsistent optimum Ge content over a wide range was reported in previous studies. To date, there is no reasonable explanation on this unusual phenomenon. In this study, for the first time, we found that an optimum Ge content sensitively depended on sulfur pressure. By increasing sulfur pressure and alloying Ge simultaneously, a high crystalline Ge-CZTS without Ge element loss and secondary phases was obtained, which remarkably increased a half-cell solar to hydrogen efficiency (HC-STH) of a CZTS photocathode 27 times. After further modification, the Ge-CZTS photocathode indicated a stable photocurrent density of 11.1mAcm−2 at 0 VRHE. To the best of our knowledge, it is the highest value among CZTS based photocathodes for solar water splitting. Moreover, the stability of a CZTS photocathode was also improved by increasing sulfur pressure and alloying Ge simultaneously due to higher crystalline of Ge-CZTS film.

Synthesis and properties of the molybdenum and tungsten disulfide thin films

In the paper results of thin film synthesis and primary characterization of molybdenum and tungsten disulfides are presented. The synthesis is performed by means of the high-temperature sulfurization of the metallic Mo and W films in the flow of argon. Chemical and phase compositions and morphology of thin films are reported. Optical transmission and Raman spectra are presented and discussed.

Nucleation and growth mechanisms of Al2O3 atomic layerdeposition on synthetic polycrystalline MoS2.

Two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs) are of great interest for applications in nano-electronic devices. Their incorporation requires the deposition of nm-thin and continuous high-k dielectric layers on the 2D TMDs. Atomic layer deposition (ALD) of high-k dielectric layers is well established on Si surfaces: the importance of a high nucleation density for rapid layer closure is well known and the nucleation mechanisms have been thoroughly investigated. In contrast, the nucleation of ALD on 2D TMD surfaces is less well understood and a quantitative analysis of the deposition process is lacking. Therefore, in this work, we investigate the growth of Al2O3 (using Al(CH3)3/H2O ALD) on MoS2 whereby we attempt to provide a complete insight into the use of several complementary characterization techniques, including X-ray photo-electron spectroscopy, elastic recoil detection analysis, scanning electron microscopy, and time-of-flight secondary ion mass spectrometry. To reveal the inherent reactivity of MoS2, we exclude the impact of surface contamination from a transfer process by direct Al2O3 deposition on synthetic MoS2 layers obtained by a high temperature sulfurization process. It is shown that Al2O3 ALD on the MoS2 surface is strongly inhibited at temperatures between 125°C and 300°C, with no growth occurring on MoS2 crystal basal planes and selective nucleation only at line defects or grain boundaries at MoS2 top surface. During further deposition, the as-formed Al2O3 nano-ribbons grow in both vertical and lateral directions. Eventually, a continuous Al2O3 film is obtained by lateral growth over the MoS2 crystal basal plane, with the point of layer closure determined by the grain size at the MoS2 top surface and the lateral growth rate. The created Al2O3/MoS2 interface consists mainly of van der Waals interactions. The nucleation is improved by contributions of reversible adsorption on the MoS2 basal planes by using low deposition temperature in combination with short purge times. While this results in a more two-dimensional growth, additional H and C impurities are incorporated in the Al2O3 layers. To conclude, our growth study reveals that the inherent reactivity of the MoS2 basal plane for ALD is extremely low, and this confirms the need for functionalization methods of the TMD surface to enable ALD nucleation.

Corrosion Behaviour of Equipment in High Temperatures and Corrosion Resistant Alloys

Among the high temperature damages, this paper was discussed on the cases in which the materials were damaged mainly by the effect of environmental factors. That is, high temperature oxidation, steam oxidation, molten salt corrosion, high temperature particle erosion and corrosion, high temperature sulfurization, carburizing, metal dusting, nitriding, high temperature chloride corrosion and so on were introduced using my research data. Finally, anticipation to future research of high temperature corrosion was maintained.

Effect of Na on sulfurization growth of SnS thin films and solar cells using NaF/Sn-S precursor

The role of NaF treatment in the production of SnS thin films and solar cells was investigated. The grain size of SnS films containing Na was large (about 500nm) compared to that of SnS films prepared by conventional sulfurization (typically 250nm). The carrier concentration of SnS increased from 5×1016 to 2×1017cm−3 by Na diffusion into the SnS film, and Na acted as an acceptor. Moreover, the NaF layer exhibited a capping effect during high-temperature sulfurization at 500°C and suppressed the re-evaporation of SnS. The short-current density tended to increase from 1.1 to 8.8mA/cm2 with increasing thickness of the deposited NaF layer from 0 to 200nm, because of the larger grain size and carrier concentration of SnS.

Liquid CO2-based coating for dense CuInxGa1−xS2 film fabrication

A liquid CO2 (l-CO2)–based coating technique is used for the pore-filling of a porous copper indium gallium sulfide (CuInxGa1−xS2, CIGS) film synthesized by a solution-based method. In the l-CO2–based coating, copper and indium precursors dissolved in l-CO2 are deposited on the porous copper indium gallium oxide film, followed by low-temperature sulfurization. After the high-temperature sulfurization of the deposited film with the l-CO2–based coating, a highly dense CIGS film with almost complete pore-filling is obtained. The use of an indium rich solution in l-CO2 leads to the formation of near stoichiometric ratio of Cu:(In+Ga) that improves the pore filling behavior.

Understanding the Key Factors of Enhancing Phase and Compositional Controllability for 6% Efficient Pure-Sulfide Cu2ZnSnS4 Solar Cells Prepared from Quaternary Wurtzite Nanocrystals

Pure-sulfide Cu2ZnSnS4 thin film solar cells were fabricated employing a facile and low-cost preparation procedure by depositing wurtzite CZTS nanocrystals, followed by high temperature sulfurization. The exploration of previously reported devices with >4.8% efficiency has demonstrated the potential application of wurtzite nanocrystals in optoelectronic devices. Moreover, TEM-EDS characterization revealed the presence of compositional fluctuations within the fine-grained sublayer that may limit the performance of the final devices. To reduce the fine-grained sublayer and further improve the crystalline quality of the active large-grained layer of our solar cells, the Na doping method and the sulfurization process were both systematically studied in this work. The crystal phase, morphology, elemental composition, and photovoltaic performance were characterized. These results indicate that, for the wurtzite material system, (1) tuning the Na amount is necessary, yet insufficient to ensure the good performan...

Study on Properties of SnS Thin Films Fabricated by High Temperature Sulfurization

Study on Properties of SnS Thin Films Fabricated by High Temperature Sulfurization

Chalcogenide perovskites – an emerging class of ionic semiconductors

We report the synthesis and characterization of a novel class of ionic semiconductor materials – inorganic chalcogenide perovskites. Several different compounds including BaZrS3, CaZrS3, SrTiS3 and SrZrS3 were synthesized by high temperature sulfurization of their oxide counterparts. Their crystal structures were identified by XRD and composition by EDX. UV–vis and photoluminescence measurements confirmed that they are direct gap semiconductors with band gap values consistent with theoretical predictions. By adopting an anion alloying approach, we demonstrate widely tunable band gap from 1.73eV to 2.87eV. These strongly ionic semiconductors provide a new avenue for engineering the semiconducting properties for applications such as energy harvesting, solid state lighting and sensing.

A Review on the Properties of Iron Aluminide Intermetallics

Iron aluminides have been among the most studied intermetallics since the 1930s, when their excellent oxidation resistance was first noticed. Their low cost of production, low density, high strength-to-weight ratios, good wear resistance, ease of fabrication and resistance to high temperature oxidation and sulfurization make them very attractive as a substitute for routine stainless steel in industrial applications. Furthermore, iron aluminides allow for the conservation of less accessible and expensive elements such as nickel and molybdenum. These advantages have led to the consideration of many applications, such as brake disks for windmills and trucks, filtration systems in refineries and fossil power plants, transfer rolls for hot-rolled steel strips, and ethylene crackers and air deflectors for burning high-sulfur coal. A wide application for iron aluminides in industry strictly depends on the fundamental understanding of the influence of (i) alloy composition; (ii) microstructure; and (iii) number (type) of defects on the thermo-mechanical properties. Additionally, environmental degradation of the alloys, consisting of hydrogen embrittlement, anodic or cathodic dissolution, localized corrosion and oxidation resistance, in different environments should be well known. Recently, some progress in the development of new micro- and nano-mechanical testing methods in addition to the fabrication techniques of micro- and nano-scaled samples has enabled scientists to resolve more clearly the effects of alloying elements, environmental items and crystal structure on the deformation behavior of alloys. In this paper, we will review the extensive work which has been done during the last decades to address each of the points mentioned above.

Low-Temperature Solution-Processed Kesterite Solar Cell Based on in Situ Deposition of Ultrathin Absorber Layer.

The production of high-performance, solution-processed kesterite Cu2ZnSn(Sx,Se1-x)4 (CZTSSe) solar cells typically relies on high-temperature crystallization processes in chalcogen-containing atmosphere and often on the use of environmentally harmful solvents, which could hinder the widespread adoption of this technology. We report a method for processing selenium free Cu2ZnSnS4 (CZTS) solar cells based on a short annealing step at temperatures as low as 350 °C using a molecular based precursor, fully avoiding highly toxic solvents and high-temperature sulfurization. We show that a simple device structure consisting of ITO/CZTS/CdS/Al and comprising an extremely thin absorber layer (∼110 nm) achieves a current density of 8.6 mA/cm(2). Over the course of 400 days under ambient conditions encapsulated devices retain close to 100% of their original efficiency. Using impedance spectroscopy and photoinduced charge carrier extraction by linearly increasing voltage (photo-CELIV), we demonstrate that reduced charge carrier mobility is one limiting parameter of low-temperature CZTS photovoltaics. These results may inform less energy demanding strategies for the production of CZTS optoelectronic layers compatible with large-scale processing techniques.

Nanoporous MoS2 as an Electrode Material Exhibiting High Levels of Pseudocapacitive Charge Storage with Both Li and Na-Ions

MoS2 is an attractive high power density energy storage material because of its layered crystal structure consisting of large van der Waals gaps that allow for fast ion diffusion. However, much of the work on MoS2 as an energy storage material has been focused on the high capacity four-electron reaction which irreversibly converts MoS2 into molybdenum metal and lithium sulfide in the first cycle. Subsequent cycles undergo lithium-sulfur redox chemistry leading to poor electrochemical reversibility. In this study, we show that MoS2 can reversibly store alkali ions without the irreversible conversion of the parent material by limiting the electrochemical processes to a one-electron transfer. The MoS2 layered crystal structure is preserved for the one-electron reaction which leads to fast charge transfer kinetics and high electrochemical reversibility. We have prepared mesoporous MoS2 thin films through di-block copolymer templating of molecular molybdenum precursors followed by high temperature sulfurization. This synthesis method yields an ordered three-dimensional mesoporous structure that leads to interconnected nanosized 2H-MoS2 grains that are ideal for fast ion diffusion and good electrolyte accessibility. These mesoporous thin films of MoS2 are examined as pseudocapacitive energy storage devices with high specific capacitances for Li-ions and Na-ions. Pseudocapcitive charge storage is an ideal hybrid between a battery and a capacitor because high power is achieved without significant expense to energy density. This ideal combination is achieved for mesoporous MoS2 through intercalation pseudocapacitance which occurs when ions intercalate into the channels or layers of a redox-active material accompanied by a faradaic charge-transfer, usually with no crystallographic phase change. In this work, we have shown that mesoporous MoS2 effectively stores energy through intercalation pseudocapacitance. When Li-ions are utilized, the material can be charged and discharged in 20 seconds and maintains 81% of the capacity observed for a 2000 second discharge. When mesoporous MoS2 is cycled with the bulkier Na-ion, a 23 second charging time still maintained 69% of the capacity observed for a 2000 second discharge. Detailed electrochemical kinetic analyses was used to quantitatively decouple the diffusion controlled and capacitive controlled charge storage processes. This analysis revealed that Li-ion storage in this material is 91% capacitive and Na-ion storage is 59% capacitive. The ideal nanoscale architecture of mesoporous MoS2 designed for this study leads to ultra-long cycle lifetimes with both Li and Na-ions. We have shown that mesoporous MoS2 can achieve over 10,000 cycles when cycled in a Li-ion electrolyte. Utilizing synchrotron grazing incidence x-ray diffraction techniques we have correlated superior electrochemical kinetics and cycle longevity with an ordered porous structure and textured crystal structure. This study underscores the utility of designing precise nanoscale architectures which allow for the development of new extrinsic pseudocapacitive charge storage materials that behave significantly different from the bulk. Figure 1

Preparation of perfect chalcopyrite ordering CuInS2 thin films by high-temperature sulfurization of metal oxide nanoparticles

In this letter, a low-cost non-vacuum process is introduced to fabricate the pure crystalline chalcopyrite (CH) CuInS2 thin films. Since the Chalcopyrite (CH) and CuAu (CA) ordering phases have very close formation energy and structures and tend to coexist in CIS films, it is very difficult to get single-phase chalcopyrite CIS in normal way. Simply, in this study, the high-temperature sulfurization of copper indium oxide nanoparticles precursor layers has been taken out and the presence of the metastable CuAu (CA) ordering phase is successfully avoided in the chalcopyrite CIS thin films. In addition, films sulfurized at high temperature show pure chalcopyrite phase, good crystallization and reliable optical properties, which are suitable for preparation of high efficiency solar cells.

ICOPE-15-C096 Cellular automata simulation for high temperature oxidation and sulfuration of water wall materials

ICOPE-15-C096 Cellular automata simulation for high temperature oxidation and sulfuration of water wall materials

Hazard & Operability Study and Determining Safety Integrity Level on Sulfur Furnace Unit: A Case Study in Fertilizer Industry

In the process production, it is possible that some risks may be happen and potentially causing hazard. Therefore, it will lead to a failure to achieve the production target. Hazard & Operating Study (HAZOPS) of sulphur furnace are done in this research. Here, the nodes used are sulphur furnace, waste heat boiler, and steam superheater. From the analysis, it obtained 11 instruments attached on those three nodes with the highest hazard potential reaches extreme level based on AS/NZS 4360:2004 standard, while in standard of the factory it reaches a high level. Both of them are in low temperature sulphur furnace and high temperature sulphur furnace deviation. At the Safety Integrity Level (SIL) determination, it obtained 1st level of SIL on installed SIS in node sulphur furnace with a total of PFD 0,021 and RRF 48,3. Meanwhile, SIL 1 in waste heat boiler has a total value of Probability Failure of Demand (PFD) 0.0184 and Risk Reduction Factor (RRF) of 54.32. While in the last node, steam superheater, the SIS is not installed.

Mesoporous Monoclinic CaIn2S4 with Surface Nanostructure: An Efficient Photocatalyst for Hydrogen Production under Visible Light

A novel ternary sulfide photocatalyst of monoclinic CaIn2S4 with excellent photocatalytic H2 evolution activity is synthesized via a high-temperature sulfurization approach. The precursor orthorhombic CaIn2O4 can be converted in situ to monoclinic CaIn2S4 by using H2S gas as the sulfurization reagent once the sulfurization temperature exceeds 773 K. The obtained yellow powders have a mesoporous structure and a chain-shape morphology with large surface area and high pore volume. SEM and TEM observations indicate that specific nanostep structures are formed on the surface of monoclinic CaIn2S4. Under visible light irradiation, monoclinic CaIn2S4 exhibits considerable performance for photocatalytic hydrogen production. A high H2 evolution rate of 30.2 μmol/h with good stability is achieved from Na2S/Na2SO3 aqueous solution with the deposition of 0.5 wt % Pt nanoparticles, 30 times higher than that of cubic CaIn2S4, which makes it a new promising candidate photocatalyst for hydrogen production. This work can provide an effective approach to the fabrication of other mesoporous sulfide photocatalysts with high performance.

Transport Coefficients of High Temperature SF6 in Local Thermodynamic Equilibrium Using a Phenomenological Approach

The transport coefficients of high temperature sulfur hexafluoride (SF6) plasmas in local thermodynamic equilibrium are calculated using collision integrals derived in a phenomenological approach which could be a valuable tool in the calculation of complete data sets for complex mixtures, including interactions hardly handled in the accurate multipotential methods. A systematic comparison with transport coefficients obtained using an old data set and experimental test is performed to check the reliability of the proposed approach in evaluating transport cross sections.

High-Temperature Sulfur Removal from Biomass-Derived Synthesis Gas over Bifunctional Molybdenum Catalysts

Removal protocol: Molybdenum-based catalysts are efficient for the removal of H2S and organic sulfur species from gasified biomass at high temperatures. Water, which is ubiquitous in biomass, impedes desulfurization. In situ X-ray absorption spectroscopy analysis shows that H2S is removed from the biomass-derived producer gas through the sulfidation of MoO3 to MoS2, whereas MoO2 is the active phase for the removal of thiophene.