Sulfide Phases Research Articles

The origin of olivine basalts from Medvezhya Mount (Avachinsky group of volcanoes, Kamchatka): The evidence of assimilation of sulfide-bearing cumulates

The role and conditions of liquid immiscibility and crystallization of sulfide phase during evolution of subduction related magmas remains to be a debated topic, which bears relevance to mechanisms of porphyry copper deposit formation and evolution of the continental crust. We studied rare volcanic rocks with inclusions of magmatic sulfides in olivine – the basalts of Medvezhya Mount in the Avachinsky group of volcanoes. The rocks belong to primitive (Mg# = 66 mol. %) middle-K island arc olivine basalts. Olivine with normal zoning predominate (~98%) among phenocrysts. The olivine compositions are typical for Kamchatka basalts, except for an unusual trend of increase of MnO content from 0.20 to 0.55 wt. % and decrease of Fe/Mn from 60 to 35 with change of olivine composition from Fo87.8 to Fo78.2. Olivines of this group contain numerous inclusions of minerals of the spinel group varying in composition from chromium spinel to magnesian magnetite. Olivine phenocrysts with sulfide inclusions are characterized by the absence or weak reverse zoning and reduced contents of Ca, Ni, Mn, Cr, and Al. The estimated crystallization temperatures for olivines of the prevailing type are 1036–1241°C, for sulfide-bearing olivines – 1010–1062°C. The data suggest that crystallization of the main olivine population occurred under relatively shallow conditions and was accompanied by strong oxidation of the magmas. On the contrary, the zoning and composition features of sulfide-bearing olivine suggest its xenogenic origin and probable crystallization at conditions of deep crust from low temperature water-rich and/or low-Ca magmas. The results obtained confirm the possibility of saturation of oxidized island-arc magmas with sulfide phase at lower crustal conditions, but show that this process is rare and not typical for low-pressure crystallization stage.

Ethylenediamine-assisted solvothermal synthesis of ZnS/ZnO photocatalytic heterojunction for high-efficiency hydrogen production.

Organic-inorganic hybrid materials have emerged as a class of novel materials over the last two decades, as they combine functional organic components and inorganic building blocks into unique materials through various chemical or physical interactions. In the present work, the importance of the use of ethylenediamine in sulfided materials applied to photocatalytic processes in the H2 production is demonstrated. The ZnS/ZnO heterojunction was prepared by the solvothermal synthesis in the presence and absence of ethylenediamine. The photocatalytic behavior showed that the addition of ethylenediamine increases the photocatalytic efficiency up to eight times compared to the photocatalyst without the organic agent. The materials were characterized by X-ray diffraction, scanning electron microscopy, infrared and UV-visible spectroscopies of solids, N2 adsorption-desorption isotherms, X-ray photoelectron spectroscopy, and photoelectrochemical characterization. The ethylenediamine plays a double role: to stabilize the cubic phase of zinc sulfide and to act as a promoter molecule of charge transfer on the surface of ZnS/ZnO/en heterojunction, slowing down the rate of recombination of the electron-hole pair, which is reflected in a decrease in the resistance to transfer of charge carriers, improving the H2 production rate until 1564µmolh-1g-1.

Bioleaching of zinc, copper and antimony from a tetrahedrite concentrate using acidophilic microorganisms

In this study, bacterial leaching of zinc, copper and antimony from tetrahedrite concentrate was investigated with mixed mesophilic and mixed moderately thermophilic microorganisms. The mineralogical studies showed that tetrahedrite ((Cu,Fe)12Sb4S13), ankerite (Ca(Fe,Mg)(CO3)2) and quartz (SiO2) are the main mineral phases. During bioleaching experiments, the effects of different chemicals and factors such as graphite, silver nitrate, L-cysteine, pyrite, and mechanical activation were studied for the first time. It was found that the removal of toxic antimony from tetrahedrite concentrate by alkaline Na2S-NaOH facilitates the growth of microorganisms and extraction rates of metals. The maximum extraction of zinc, copper and antimony was 99.7%, >99.9% and 92.8% with ORP, cell counts and Fe(III) concentration of 666 mV, 108 cells/ml and 9.58 g/l, respectively, using the moderately thermophilic culture with the tetrahedrite residue obtained after alkaline leaching (low-Sb). Under the same control leaching conditions with H2SO4, the maximum extraction of zinc, copper and antimony was 26.2%, 46.1% and 10.7% with low ORP and Fe(III) concentration of 464 mV and 5.18 g/l, respectively. The results showed that bacterial leaching of tetrahedrite concentrate significantly improves the extraction of metals compared to control test. As an important result, mechanical activation by planetary mill played a significant role during tetrahedrite bioleaching. Residual analysis proved the formation of antimony sulfide (Sb2S5) and jarosite (K3Fe9S6O42H18) phase as dissolution inhibitors and acanthite phase (Ag2S) as accelerator for dissolution kinetics.

Integrated hydrothermal-green approach to synthesize Fe, Ag doped copper sulfide nanopowders and investigations of their thermoelectric properties

Copper sulfide and Fe, Ag doped copper sulfide nanopowders were synthesized by integrated hydrothermal-green approach, using Urtica dioica leaf extract as a solvent. With Fe and Ag doping, covellite as the major phase was sustained but reduction in crystallite size and change in morphology was observed. Decrease in electrical conductivity from ∼186.24 Scm−1 for undoped copper sulfide to ∼34.97 Scm−1 and ∼23.26 Scm−1 on doping Fe and Ag, respectively, at 300 K, was witnessed due to formation of different phases of copper sulfide and incorporation/segregation of Ag/Fe into copper sulfide lattice. Conversely, Seebeck coefficient showed enhanced values on doping Fe and Ag. The maximum power factor of ∼22.22 μW/mK2 was found for undoped copper sulfide. Thus, the incorporation/segregation of Fe/Ag ions in copper sulfide lattice and grain boundaries was found to alter the thermoelectric performance of copper sulfide.

Precise phase adjustment and antibacterial property of copper sulfide particles in confined mesoporous silica nanoreactor

Bacteria-caused wound infection greatly threatens human health, thus developing an efficient and safe antibacterial agent without drug resistance is still a great challenge. Herein, a confined vulcanization strategy is proposed to construct copper sulfides-loaded dual-mesoporous silica nanospheres (CuxSy@DMSNs) with various crystal phases for reactive oxygen species (ROS)-mediated and photothermal antibacterial application. With the pore confinement of DMSNs, the crystal phases of copper sulfides including CuS, Cu9S5 and Cu1.96S can be easily controlled by changing the vulcanization temperature. The relationships between the crystal phases and photothermal properties as well as peroxidase-like activity of copper sulfides were systematically investigated. Results show that the obtained CuS@DMSNs exhibited higher photothermal ability with remarkable photothermal conversion efficiency of 36.86% in the second near-infrared region (NIR-II) and better peroxidase-like activity, compared to those of Cu9S5@DMSNs and Cu1.96S@DMSNs. As a result, the in vitro experiments showed the good antibacterial effect against both gram-negative E. coli and gram-positive S. aureus under 1064 nm laser irradiation and the presence of H2O2. Besides, the CCK-8 assay indicated that CuS@p-DMSNs have minimal cytotoxicity against normal human umbilical vein endothelial cells at the ranged concentrations. Therefore, the resultant CuS@p-DMSNs could act as a promising antibacterial agent for deep wound bacterial infection treatment.

Electrodeposited Heterostructures of Cobalt Sulfide/Molybdenum Sulfide Trigger both Acidic and Alkaline HER

MoS2 has attracted significant attention as a non-platinum group electrocatalyst for the hydrogen evolution reaction (HER). There have been extensive efforts demonstrating that by doping MoS2 with various transition metals, such as Co, the HER activity of the catalyst is enhanced. In particular, this work has shown that various cobalt sulfide phases can act as a co-catalyst with MoS2. Here, we report on the electrodeposition of a c-CoSx/MoS2 heterostructure catalyst for the HER reaction in both acidic and alkaline conditions. Using Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and scanning electron microscopy, it is demonstrated that depending on the precursor concentrations, various morphologies, grain size, and c-CoSx phases can be achieved, all of which have an impact on the activity and stability of the c-CoSx/MoS2 catalysts. The most promising catalyst composition demonstrated excellent stability in both acidic and alkaline conditions with low overpotentials to reach 10 mA cm−2 of 112 mV and 60 mV and with Tafel slopes of 113 mV dec−1 and 81 mV dec−1, respectively. This report demonstrates that the c-CoSx/MoS2 heterostructure is one of the most catalytically active materials for HER, especially in alkaline conditions.

Thermal and electrical properties of nanocrystalline superionic NaxCu1.75S (x=0.1, 0.15, 0.2, 25) compounds

The paper presents the results of the studies of thermal properties of nanocrystalline superionic Na x Cu 1.75 S (x = 0.1, 0.15, 0.2, 25) compositions, and preliminary results of Na 0.1 Cu 1.75 S using as energy stored cathode material in Na-ion half-cell with NaPF 6 electrolyte and Na anode. The compositions contain a few copper sulfide phases: monoclinic chalcocite Cu 2 S, orthorhombic anilite Cu 1.75 S, triclinic roxbyite Cu 1.74÷1.82 S, also the compositions can contain monoclinic Na 2 Cu 4 S 3 , orthorhombic Na 2 S, cubic Cu 2 O as inclusion phases. The sizes of powder particles lie in the range from 10 to 113 nm. Differential scanning calorimetry revealed in Na 0.1 Cu 1.75 S the endothermic thermal effects with critical temperatures near 123 o C, 422 o C and 442 o C, caused by structural transitions in copper sulfide. Fourth endothermic peak at 323 o C presumably belongs to Na 2 S phase. The minimum for the Fermi level at about 420°C is found with using of the e.m.f. E of the electrochemical cell of the Cu/CuBr/Na 0.10 Cu 1.75 S/Pt, which corresponds to minimum for the carrier concentration. This conclusion correlates well with the observed conductivity minimum at about 410°C. Electrode material Na 0.10 Cu 1.75 S achieved a significant specific energy density 146.5 mAh/g in half-cell assembled from the cathode active material, electrolyte (NaPF 6 in 0.5 mol PC) and Na anode.

The Controllable Synthesis of High-Quality Two-Dimensional Iron Sulfide with Specific Phases.

2D Fe-chalcogenides have drawn significant attention due to their unique structural phases and distinct properties in exploring magnetism and superconductivity. However, it remains a significant challenge to synthesize 2D Fe-chalcogenides with specific phases in a controllable manner since Fe-chalcogenides have multiple phases. Herein, a molecular sieve-assisted strategy is reported for synthesizing ultrathin 2D iron sulfide on substrates via the chemical vapor deposition method. Using a molecular sieve and tuning growth temperatures to control the partial pressures of precursor concentrations, hexagonal FeS, tetragonal FeS, and non-stoichiometric Fe7 S8 nanoflakes can be precisely synthesized. The 2D h-FeS, t-FeS, and Fe7 S8 have high conductivities of 5.4 × 105 S m-1 , 5.8 × 105 S m-1 , and 1.9 × 106 S m-1 . 2D tetragonal FeS shows a superconducting transition at 4 K. The spin reorientation at ≈30 K on the non-stoichiometric Fe7 S8 nanoflakes with ferrimagnetism up to room temperature has also been observed. The controllable synthesis of various phases of 2D iron sulfide may provide a route for synthesizing other 2D compounds with various phases.

Investigation of mineral commodity residues based on alkalinity, solubility and other physicochemical aspects aiming the management of amazonian acidic soils

The large amounts of mineral residues generated by the bauxite-alumina industries in the Amazon — with a production scale in the same order of magnitude as their source commodities — have been seen as new sources of raw materials (secondary mines) and/or an inseparable part of a sustainable production system, i.e., a source for the generation of co-products within a circular economy system. In the present study, two alkaline residues from this mining-metallurgical industry were assessed for their potential to amend productive acidic Amazonian soils, namely, (1) insoluble solid residue from the Bayer process (bauxite residue, BR) and (2) ash from energy production from coal (coal combustion residues, CCRs: fly ash, FA, and bottom ash, BA). A physicochemical investigation was performed to evaluate the possible benefits that these residues can offer to the soil‒plant system. The alkalinity of the residues was adjusted “to a value of pH 8–10” by leaching with H3PO4 using a central composite experimental design. The chemical analyses indicated high levels (total and soluble) of essential elements such as Ca and S in the CCRs. All residues showed a high cation exchange capacity (CEC). Regarding the water holding capacity (WHC), FA showed a higher value than the other residues (68.6%). After pH adjustment, available P increased significantly for all residues, and the Ca and S contents remained high for the CCRs, while in BR, there was a decrease in available Na, and aluminum (Al3+) was not available because the potential acidity (H + Al) < 0.6. Finally, complementary analyses showed that with respect to mineralogy, BR is composed mainly of iron oxyhydroxides and aluminosilicate phases, while carbonate, sulfide and silicate phases dominate the CCRs. The neutralizing character, the presence of nutrients in the CCRs and the unavailability of Al3+ in BR are positive physicochemical characteristics for the management of Amazonian acid soils; the use of this residues would add to the circular economy and sustainability of the Amazon.

Environmentally assisted cracking of a single crystal nickel-based superalloy

ABSTRACT Single crystal material, of CMSX-4® alloy composition, was cast and secondary orientation was controlled at the machining stage, to produce c-ring cross-section tubes with known crystallographic orientations. The c-ring tubes were coated with NaCl before being subject to loading up to 700MPa and heated for durations of up to 2 hrs at 550°C in flowing environments containing air and SO2. No cracking was observed in short term tests that were run in the absence of either NaCl, or SO2, indicating a symbiotic interaction is required to initiate cracking. Experiments confirm the presence of oxygen, chlorine and sulphur at the crack tips, formed along {001} crystallographic planes, however, they were distributed discretely, with several oxide and sulphide phases observed. In this work, we image, analyse and identify the phases formed during the cracking and corrosion of CMSX-4® superalloy and hypothesise on the complex chemical interactions that take place during crack initiation.

Unveiling the Role of In Situ Sulfidation and H2O Excess on H2S Decomposition to Carbon-Free H2 over Cobalt/Ceria Catalysts

The emerging energy and environmental concerns nowadays are highlighting the need to turn to clean fuels, such as hydrogen. In this regard, hydrogen sulfide (H2S), an abundant chemical compound found in several natural sources and industrial streams, can be considered a potential carbon-free H2 source through its decomposition. In the present work, the H2S decomposition performance of Co3O4/CeO2 mixed oxide catalysts toward hydrogen production is investigated under excess H2O conditions (1 v/v% H2S, 90 v/v% H2O, Ar as diluent), simulating the concentrated H2S-H2O inflow by the Black Sea deep waters. The effect of key operational parameters such as feed composition, temperature (550–850 °C), and cobalt loading (0–100 wt.%) on the catalytic performance of Co3O4/CeO2 catalysts was systematically explored. In order to gain insight into potential structure-performance relationships, various characterization studies involving BET, XRD, SEM/EDX, and sulfur elemental analysis were performed over the fresh and spent samples. The experimental results showed that the 30 wt.% Co/CeO2 catalyst demonstrated the optimum catalytic performance over the entire temperature range with a H2 production rate of ca. 2.1 μmol H2∙g−1·s−1 at 850 °C and a stable behavior after 10 h on stream, ascribed mainly to the in-situ formation of highly active and stable cobalt sulfided phases.

Effect of thermal spray coating cermets on superalloy to combat hot corrosion

AbstractBurning coal emits contaminant gases that come into contact with turbine parts and speed up hot corrosion. To overcome the corrosion effect, it is necessary to opt for thermal spray coatings that offer resistance to hot corrosion. In the current study, hot corrosion investigations were done on both uncoated and high‐velocity oxygen fuel spray‐coated Superco‐650 alloys at 700°C for 50 cycles, in Na2SO4 + 60% V2O5 salt environment. At the end of each cycle, the weight gains or loss was recorded. We used powder X‐ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy (EDS) to examine the hot corrosion impact. Our finding demonstrated that the uncoated Superco‐605 alloy was subjected to extensive spallation in the form of oxide scale remgoval due to the formation of an unprotected Fe2O3 oxide phase. Contrarily the coated Superco‐605 alloy gained less weight, and the oxide scales remained undamaged. The nickel, chromium oxides, and their sulfide phases were revealed by the EDS examination of the oxide scale over the coated sample, which is presumed to offer resistance to high‐temperature corrosion effects.

Stabilizing far-from-equilibrium (Mo,Ti)S2 thin films by metal sulfurization at reduced temperature

We report the synthesis of large-area, high-Ti-content, Mo1−xTixS2 alloy thin films in the 2H phase at temperature as low as 500 °C using a scalable two-step method of metal film deposition, followed by sulfurization in H2S. Film processing at higher temperature accelerates Ti segregation, film coarsening, and the formation of TiS2 in the 1T phase. Crystal growth at higher temperature results in the formation of multiple binary sulfide phases, in agreement with the equilibrium phase diagram. Making highly metastable, smooth, and uniform single-phase alloy films, therefore, hinges on developing low-temperature processing. Our results are relevant to the development of technologies based on designer transition metal dichalcogenide alloys, including in photonic integrated circuits and gas sensing.

Evolution of Nonmetallic Inclusions in Ti‐Bearing Al‐Killed Steel during Heat Treatment at 1200 °C

To understand the evolution behaviors of the inclusions in Ti‐bearing Al‐killed steel, steel samples taken from a 20CrMnTi casting billet are heated at 1200 °C for different times, and the changes in composition, size, and numbers of the inclusions are investigated. Some modeling experiments are also designed to reveal the interaction between solid steel and inclusions using premelted slags. It is found that oxysulfide, sulfide, and nitride inclusions are detected in the casting billet before heating. During heating, small changes are observed in the types of inclusions, while the size of these inclusions increases with time. The Mn and S in steel transfer to the sulfide phase of these inclusions and further generate a (Ca, Mn)S solution. The Ti in steel replaces some of the Al element in the oxide part of the inclusions, resulting in the increase of TiOx content and the drop of Al2O3 content in the inclusions. When the TiOx content is sufficient, a thin layer of TiN is predicated at the edges of the oxide part. The reaction between the TiOx in inclusions and the N in steel plays a role in this evolution.

Palladium, platinum, selenium and tellurium enrichment in the Jiguanzui-Taohuazui Cu-Au Deposit, Edong Ore District: Distribution and comparison with Cu-Mo deposits

The Jiguanzui-Taohuazui Cu-Au deposit is located in the Edong ore district, Middle–Lower Yangtze River metallogenic belt, eastern China. The deposit is palladium, platinum, selenium and tellurium enriched; however, the distribution of these metals is unclear. Three mineral assemblages of ore in the deposit have been identified, namely: a magnetite-bornite-chalcopyrite-(hematite) assemblage (Mt-Bn-Cp-Hm), a chalcopyrite-pyrite assemblage (Cp-Py), and a pyrite-chalcopyrite-(sphalerite) assemblage (Py-Cp-Sph). Forty-eight bulk ore assay results show high concentrations of up to 66.9 ppb for Pd, 5.9 ppb for Pt, 150 ppm for Se and 249 ppm for Te. The high temperature Mt-Bn-Cp-Hm assemblage (530–380 °C) is enriched in Pt and Pd, whereas the Py-Cp-Sph assemblage in the marble-replacement ore (300–220 °C) hosts the major Se and Te mineralization. Palladium, Pt, and Se are mostly hosted in sulfide minerals, whereas Te is hosted in tellurides and Bi-Te-S sulfosalt minerals. Building on previous experimental and thermodynamic calculations, we propose the major controls on the Pd and Pt distribution in the deposit are temperature and salinity, whereas the Se and Te mineralization is promoted by the precipitation of major sulfide phases such as pyrite, chalcopyrite and sphalerite.A comparison of the ores from the Jiguanzui-Taohuazui Cu-Au and Tongshankou Cu-Mo deposits in the Edong ore district shows that the Cu-Au deposit has higher PGE and Te, but similar Se concentrations. This scenario is consistent with the average grades and bulk ore contents of these elements from global (oxidized) porphyry (±skarn) Cu deposits. This suggests that the saturation of magmatic sulfides in the magma chamber as a result of higher proportion of crustal S-rich and/or reduced material contamination can be detrimental for PGE and Te enrichment processes, and thus, Cu-Au porphyry (±skarn) deposits have more potential for higher Pd and Te concentrations than the Cu-Mo deposits.

Investigation and Determination of Electrochemical Reaction Kinetics in Lithium-Sulfur Batteries with Electrolyte LiTFSI in DOL/DME

A major challenge in the simulation of Li-S batteries is that the electrochemical reaction parameters supplied from the fitting of 0-d or 1-d models depend on the cathode and separator microstructure, so these parameters cannot be used in the design and optimization of material microstructure. The present investigation fits the electrochemical reaction kinetics employing a continuum model taking into account the pore size distribution and tortuosity of cathode and separator in the transport of sulfur molecules and ion species (Li+ ion, electrolyte and sulfide anions) in solvated or desolvated form depending on pore size. Hence, the specified reaction kinetics parameters are independent from the material microstructure. The Li-S redox reaction model includes six redox reactions in the cathode and the lithium redox reaction at the anode. Reactions are assumed to take place in the electrolyte solution rather than in the solid phase of sulfur or lithium sulfide precipitates, where dissolution/precipitation kinetics is modeled especially for the low solubility compounds: sulfur, Li2S and Li2S2. The fitting exercise is conducted based on experimental data of a cyclic voltammetry cycle accompanied by in operando UV–vis spectroscopy. The investigated battery has electrolyte LiTFSI in DOL/DME and no electrocatalysts in any part of the cell.

Energy-efficient ultrafast microwave crystalline phase evolution for designing highly efficient oxygen evolution catalysts

Lowering the production cost while maintaining the superb activity of catalysts for sluggish oxygen evolution reaction (OER) is the utmost challenge towards the success of electrolytic hydrogen-based green economy. Here, we report a fast (seconds scale) and very low energy-consuming recrystallization strategy for the universal development of nickel–iron-based sulfide, selenide and phosphide nanostructures with the state-or-the-art OER activity. Amorphous irregular bulk morphology of the iron nitrate treated nickel foam rapidly recrystallizes into the uniform nanostructures of sulfide, selenide and phosphide phases by microwave ultrafast thermal treatment upon graphene substrate. As-developed nanosheets of iron-doped Ni3S2/NiS in-plane heterostructure shows exceptionally high OER activity, with an overpotential of only 187 mV at 10 mA cm−2. It also requires only 289 mV to achieve a very high current density of 500 mA cm−2, which is well below the well-recognized target value (<300 mV) for commercial use. Comprehensive analysis reveals that NiS phase of Ni3S2/NiS selectively transforms into an amorphous (oxy)hydroxide phase under OER condition along with the in-situ yield of iron-doped Ni3S2/NiOOH heterostructure with a high activity. This efficient recrystallization protocol into high performance catalytic nanostructures is not only interesting for generating diverse crystalline phases, but also highly important for the low-cost practical utilization.

Tribological behavior of Ni-based self-lubricating claddings containing sulfide of nickel, copper, or bismuth at temperatures up to 600 °C

Self-lubricating coatings extend the efficient dry-operational life of cutting and forming tools. In the current work, millimeter-thick NiCrBSi coatings with 10 wt% metal sulfide i.e. Ni3S2, CuS, or Bi2S3 were fabricated on a stainless steel substrate by laser cladding (in-situ alloying). Thermodynamic modelling utilizing the calculation of phase diagrams method (CALPHAD) was performed to predict the phase evolution during laser melting. Electron microscopy methods combined with X-ray diffraction and Raman spectroscopy were used to elucidate the developed microstructure. The coatings were further subjected to reciprocating dry sliding wear against a martensitic steel ball counterbody using a ball-on-plate configuration at 0.1 m/s and 50 N (Hertz contact pressure 1.7 GPa). The tests were conducted at room temperature (20), 400, and 600 °C. The results demonstrate a self-lubricating behavior of the sulfide coatings resulting in friction reduction by ⁓60 % at room temperature and ⁓40 % at 400 °C sliding, particularly for Bi2S3-added cladding, due to the prevalent existence of lubricious phases of chromium sulfide (CrxSy) along with others (NiBi, Bi) and leading to ‘self-healing’ phenomena. The results are reported in comparison to the unmodified NiCrBSi alloy.

Growth-control of hexagonal CdS-decorated ZnO nanorod arrays with low-temperature preheating treatment for improved properties and efficient photoelectrochemical applications.

The limitations of oxide semiconductor-based solar cells in achieving high energy conversion efficiencies have prompted incessant research efforts towards the creation of efficient heterostructures. Despite its toxicity, no other semiconducting material can fully replace CdS as a versatile visible light-absorbing sensitizer. Herein, we explore the aptness of preheating treatment in the successive ionic layer adsorption and reaction (SILAR) deposition technique and improve the understanding of the principle and the effects of a controlled growth environment on thus-formed CdS thin films. Single hexagonal phases of nanostructured cadmium sulfide (CdS)-sensitized zinc oxide nanorods arrays (ZnO NRs) have been developed without the support of any complexing agent. The influences of film thickness, cationic solution pH and post-thermal treatment temperature on the characteristics of binary photoelectrodes have been investigated experimentally. Interestingly, the preheating-assisted deposition of CdS, which is rarely applied for the SILAR technique, resulted in improved photoelectrochemical performance similar to the post-annealing effect. The X-ray diffraction pattern revealed that optimized ZnO/CdS thin films were polycrystalline with high crystallinity. Examination of the morphology of the fabricated films via field emission scanning electron microscopy showed that film thickness and medium pH altered the growth mechanism of nanoparticles, thereby changing their particle sizes, which had a significant influence on the film's optical behavior. The effectiveness of CdS as a photosensitizer and the band edge alignment for ZnO/CdS heterostructures were evaluated using ultra-violet visible spectroscopy. Facile electron transfer in the binary system as evidenced in electrochemical impedance spectroscopy Nyquist plots, therefore, promotes higher photoelectrochemical efficiencies from 0.40% to 4.30% under visible light illumination as compared with the pristine ZnO NRs photoanode.

Crystal phase of nickel sulfide dictates hydrogen evolution activity of various semiconducting photocatalysts

Nickel sulfides with different phase structures are prepared, exhibiting highly efficient and phase-dependent performance in promoting hydrogen evolution activity of various semiconducting photocatalysts.