Nickel Sulfide Phase Research Articles

Compositional alteration of low dimensional nickel sulfides under hydrogen evolution reaction conditions in alkaline media

Developing cost-effective electrodes for electrochemical water splitting with minimal kinetic losses remains a primary challenge in water electrolysis. Nickel-based dichalcogenides, particularly sulfides, have emerged as promising candidates for the hydrogen evolution reaction (HER). However, the stability of various nickel sulfide (NixSy) phases under cathodic potentials in alkaline electrolytes is subject to debate. In this study, we investigate the HER activity and durability of both 2-dimensional (2D) and 3-dimensional (3D) NixSy nanostructures with diverse chemical compositions. Through cross-correlation analysis of spectroscopic and electrochemical characterization data, we elucidate the transformation behavior of these materials under operating conditions. Our findings reveal that NiS2 tends to undergo conversion to nickel hydroxide (Ni(OH)2), while Ni-rich phases like Ni3S4 and NiS exhibit greater stability. Furthermore, we demonstrate that in 3D nanostructures, the initial formation of a protective hydroxide layer on the surface inhibits further sulfide transformation. This nickel sulfide/hydroxide composite shows an improved HER activity with lower onset potential (−0.25 V), Tafel slope (105 mV s−1), and charge transfer resistance (17.3 Ω).

Temperature-Sensitive Localized Surface Plasmon Resonance of α-NiS Nanoparticles.

The presented work shows a synthesis route to obtain nanoparticles of the hexagonal α-NiS phase and core–shell particles where the same material is grown onto previously prepared Au seeds. In the bulk, this nickel sulfide phase is known to exhibit a metal–insulator type phase transition (MIT) at 265 K which drastically alters its electrical conductivity. Since the produced nanoparticles show a localized surface plasmon resonance (LSPR) in the visible range of the electromagnetic spectrum, the development of their optical properties depending on the temperature is investigated. This is the first time an LSPR of colloidal nanoparticles is monitored regarding such a transition. The results of UV–vis absorbance measurements show that the LSPR of the particles can be strongly and reversibly tuned by varying the temperature. It can be switched off by cooling the nanoparticles and switched on again by reheating them above the transition temperature. Additional to the phase transition, the temperature-dependent magnetic susceptibility of α-NiS and Au-NiS nanoparticles suggests the presence of different amounts of uncompensated magnetic moments in these compounds that possibly affect the optical properties and may cause the observed quantitative differences in the LSPR response of these materials.

Synergistic Electrocatalytic Hydrogen Evolution in Ni/NiS Nanoparticles Wrapped in Multi-Heteroatom-Doped Reduced Graphene Oxide Nanosheets.

Hydrogen production is a key driver for sustainable and clean fuels used to generate electricity, which can be achieved through electrochemical splitting of water in alkaline solutions. However, the hydrogen evolution reaction (HER) is kinetically sluggish in alkaline media. Therefore, it has become imperative to develop inexpensive and highly efficient electrocatalysts that can replace the existing expensive and scarce noble-metal-based catalysts. Herein, we report on the rational design of nonprecious heterostructured electrocatalysts comprising a highly conductive face-centered cubic nickel metal, a nickel sulfide (NiS) phase, and a reduced graphene oxide (rGO) doped with phosphorous (P), sulfur (S), and nitrogen (N) in one ordered heteromaterial named Ni/NiS/P,N,S-rGO. The Ni/NiS/P,N,S-rGO electrode shows the best performance toward HER in 1.0 M KOH media among all materials tested with an overpotential of 155 mV at 10.0 mA cm-2 and a Tafel slope of 135 mV dec-1. The performance is comparable to the herein used Pt/C-20% benchmark catalyst examined under the same experimental conditions. The chronoamperometry and chronopotentiometry measurements have reflected the high durability of the Ni/NiS/P,N,S-rGO electrode for technological applications. At the same time, the current catalyst showed a high robustness and structure retention after long-term HER performance, which is reflected by SEM, XRD, and XPS measurements.

A novel (α-β)NiS/Ni3S4-rGO electrode material for supercapacitors

A novel electrode material of α-NiS, β-NiS and Ni3S4 particles co-decorated rGO is obtained by co-reduction of Ni2+ and GO with thiourea. The multiple nickel sulfide phases and rGO synergistically improve the electrochemical performance of the supercapacitor electrode, which shows high specific capacity of 609.4C g−1 at current density of 1 A g−1. The electrode can keep a good stability with coulombic efficiency of as high as 99.5% after 1000 cycles. The small solution and charge transfer resistances of 0.42 and 0.24 Ω indicate the positive synergistic effects of the multiple phases of NiS and graphene on the electrochemical performance.

Sphere-like Ni3S4/NiS2/MoOx composite modified glassy carbon electrode for the electrocatalytic determination of d-penicillamine

This article describes the synthesis of Ni3S4/NiS2/MoOx composite as an electrode material for the electrocatalytic sensor for d-penicillamine (D-PA). The detection of D-PA is important in biodiagnostics and therapeutic dosage control. The present study compared the performance of Ni3S4/NiS2/GC and Ni3S4/NiS2/MoOx/GC electrodes for the electrocatalytic detection of D-PA. The nickel sulfide phases containing MoOx demonstrated two-fold higher catalytic current response than the controlled one (Ni3S4/NiS2/GC). The excellent performance of the Ni3S4/NiS2/MoOx/GC electrode is confirmed by electrochemical parameters, such as electrochemical charge transfer resistance (133 Ω), diffusion coefficient (3.569 × 10−6 cm2 s−1), and catalytic rate constant (7.415 × 105 M−1 s−1). The Ni3S4/NiS2/MoOx/GC electrode exhibited wide concentration detection of D-PA from 5 to 796 μM with high sensitivity (0.08 μA μM−1), low limit of detection (0.26 μM), and good interference tolerance ability. The proposed electrode was also successfully utilized towards D-PA detection in human urine samples, wherein good recovery ranges (105.6 and 103.5%) were obtained.

Изучение фазового состава продуктов электрохимического окисления сульфидных гранул системы Cu1.96S–Ni3S2–Cu–Ni

The crystallization rate of copper and nickel sulfides influences on the phase formation processes. The high crystallization rate (about 103 degrees/s), achieved through granulation of the sulfide copper-nickel melt, leads to the stabilization of non-stoichiometric phases, the formation of ultrafine structures, which are grains and partial dissolution of the metal component in the sulfide. The structure of the granules is formed by nickel sulfide (Cu1.96S) phases in the form of dendritic inclusions of 2-20 µm in size in the nickel sulfide phase (Ni3S2). According to the phase diagram of the state of Cu – Ni – S, a solid solution of Cu – Ni may be present in the composition of eutectic compounds with copper and nickel sulphides. The electrochemical oxidation of copper and nickel sulfides in a solution of sulfuric acid occurs through a series of successive phase transformations described in the work, during which the conversion of sulfides occurs in intermediate oxidation states oxidizing to the elemental state: Cu1.96S → Cu1.8S → Cu1.75S → CuS → S; Ni3S2 → NiS → S. The non-stoichiometric composition of compounds suggests the presence of excessive or deficient sulfur and metal contents in the crystal lattice, which can affect the mechanism and sequence of phase transformations during the electrochemical oxidation of sulfide granules. Dissolution occurs not only on the surface of the granules, but also along the grain boundaries. The leached areas form capillaries inside the granules, through which electrolyte enters the electrochemical reactions. Porous sulfur sulfide sludge forms on the surface of the granules. The phase composition of the sludge was studied. The main phase components of poorly soluble products are nickel granules Ni3+хS2–Cu2-хS.

Solution combustion synthesis of nickel sulfide composite powders

Nickel sulfide powders were synthesized through solution combustion method using a suitable combination of thiourea fuel as reducing/sulfidizing agent with glycine fuel as auxiliary reductant agent. Effects of fuel contents on the combustion behavior, phase evolution, microstructure and optical properties were investigated by infrared spectroscopy, thermal analysis, X-ray diffractometry, electron microscopy and diffuse reflectance spectrometry techniques. Single phase NiS2 powders were formed using thiourea fuel at higher content, while a mixture of nickel sulfide phases was appeared in the presence of glycine fuel. The amount of different sulfide phases was considerably dependent on the thiourea content. Particle size of the as-combusted powders increased with the increase of thiourea; while the existence of glycine fuel together with thiourea led to the bulky microstructure. Maximum photodegradation (~ 56%) of methylene blue was achieved by as-combusted powders at a thiourea fuel to the oxidant molar ratio of 1, as a consequence of their high ability of light absorption.

Localized Surface Plasmon Resonances of Various Nickel Sulfide Nanostructures and Au–Ni3S2 Core–Shell Nanoparticles

In this work, we investigate the occurrence of localized surface plasmon resonances (LSPRs) in different nickel sulfide nanostructures. Therefore, spherical and anisotropic nickel sulfide nanoparticles (NPs) are synthesized and analyzed regarding their optical properties by UV/vis/NIR and transient absorption spectroscopy. Furthermore, new pathways for the synthesis of spherical Ni3S2 nanodots with an extremely narrow size distribution, as well as Au–Ni3S2 core–shell NPs with controllable shell thickness, are presented. Our results show that NPs of different metallic nickel sulfide phases like Ni3S2 and Ni3S4 exhibit LSPR bands in the visible regime of the electromagnetic spectrum, which possibly makes them a comparably cheaper alternative to NPs consisting of noble metals like Au and Ag. In case of the presented plasmonic core–shell particles, the resonance frequency of the plasmon can be tuned between those of pure gold and pure Ni3S2 NPs by varying the Ni3S2 shell thickness.

Trimetallic NiMoW sulfide catalysts by the thermal decomposition of thiosalt blends for the hydrodesulfurization of dibenzothiophene

A series of unsupported trimetallic NiMoW sulfide catalysts were synthesized by ex situ decomposition from mechanically prepared blends of [Ni(en)3]MoS4, a novel precursor, and (NH4)2WS4. N2 adsorption–desorption shows that the NiMoW catalysts are mesoporous materials with characteristic Type IV isotherms, having surface areas of 14.4–52.4 m2/g. Elemental analysis by X-ray energy dispersive spectroscopy (EDS) working in STEM mode finds high carbon/metal ratios (2.3 ≤ C/Mo ≤ 14.2 and 2.2 ≤ C/W ≤ 17.6). The XRD diffractograms of the NiMoW catalysts point to highly dispersed structures, given the absence of the (002) peak, as well as the broad and weakly intense (101) and (110) peaks; the nickel sulfide phase is barely detected. High dispersion is also evidenced by TEM microscopy showing unstacked atomic layers. The catalyst labeled NiMoW-0.20, exhibits the highest catalytic activity (k = 47.7 × 10−7 mol/g s). The NiMoW catalysts follow a zeroth order rate law. Increasing catalyst atomic ratio (more nickel sulfide phase) favors the desulfurization route.

In‐Situ Thermal Battery Discharge using NiS2 as a Cathode Material

AbstractNiS2 is a cathode material found in primary batteries which operate at high temperature. Herein we report the in situ battery discharge study of a thermal battery cell which uses NiS2 as a cathode, using simultaneous collection of powder neutron diffraction data and electrochemical data. Five different regions were observed upon battery discharge and the evolution of nickel sulfide phases has been studied. Four different nickel‐containing phases are observed during discharge (NiS2, NiS, Ni3S2 and Ni). A new discharge mechanism has been proposed which does not include Ni7S6. Multiphase quantitative Rietveld refinement has allowed the percentages of the phases to be monitored during discharge. High intensity synchrotron powder X‐ray diffraction has been used to study the resulting phases present in the cathode after battery discharge.

In situ Growth of Phase‐Controlled Nickel Sulfide Nanostructures on Reduced Graphene Oxide Nanosheets : A Improved Cost‐effective Catalyst for 4‐Nitrophenol Reduction

AbstractReduced graphene oxide (rGO)‐functionalized nickel sulfide nanoparticles were synthesized using a temperature‐controlled injection method. Syntheses were carried out in single (oleylamine) and mixed (oleylamine, oleic acid, and octadecene) solvents. Phase‐controlled NiS, NiS2, or Ni3S4 nanocrystals were decorated on rGO sheets through the single‐step temperature‐controlled injection processes. Problems with the synthesis of rGO/nickel sulfide yielding mixed phases were overcome by adjusting the solvent mixture and source concentrations. X‐ray diffraction and transmission electron microscopy were used to study the crystal structures and phases of nickel sulfide on the rGO sheets. The catalytic performances of rGO/nickel sulfide structures containing different nickel sulfide phases were analyzed by measuring the degradation rate of 4‐nitrophenol. Catalytic activity of as synthesized rGO/NiS, rGO/NiS2 and rGO/Ni3S4 were higher activity than pure NiS, among them rGO/NiS was showed better activity than those of rGO/NiS2 and rGO/Ni3S4.

Temperature and Pressure Effects on the Catalytic Performance of Metalloporphyrins during Hydrogenation of Naphthalene

AbstractTemperature and pressure effects on the catalytic performance of metalloporphyrins (MPs) for naphthalene hydrogenation were studied. Naphthalene hydrogenation over MPs and sulfur (S), or S alone was examined at varying temperatures and pressures. MPs showed catalytic activity for naphthalene hydrogenation by aid of S. The catalytic activity was promoted by increasing pressure and temperature. The promotion for nickel porphyrinseemed stronger than that for vanadyl porphyrin. Excessive temperature hindered catalytic performance due to coke formation. To reveal role of temperature and pressure in catalytic performance of MPs, the demetalation was traced by ultraviolet‐visible(UV/Vis) spectroscopy, and catalytic species were characterized by Raman and high‐resolution transmission electron microscopy (HRTEM). High catalytic activity was correlated with high conversion of MPs. The catalytic species were mixtures of different nickel sulfide phases. High pressure and temperature facilitatedformation of crystalline metal sulfides. This work can provide guidance for activating inherent MPs in heavy oil more effectively during hydroconversion.

Syntheses, characterization, and antimicrobial properties of nickel(II) dithiocarbamate complexes containing NiS4 and NiS2PN moieties

Three Ni(II) dithiocarbamate complexes, [Ni(buphdtc)2] (1), [Ni(buphdtc)(PPh3)(NCS)] (2) and [Ni(buphdtc)(PPh3)(NC)] (3) (where bu = butyl and ph = phenyl), were synthesized and characterized by elemental analysis, UVvis, and FTIR spectroscopies. Complexes 1 and 2 were further characterized by single-crystal X-ray structural analysis. The single-crystal X-ray structural analysis indicates a slightly distorted square planar geometry. In 2 and 3, the influences of the auxiliary ligands (PPh3, NCS, and NC) on their steric and electronic properties were observed. Thermal studies of the complexes showed decomposition starting at 250–300 °C, leading to formation of nickel sulfide phases around 400 °C. The complexes were screened against some bacteria strains, Staphylococcus aureus, Streptococcus pneumoniae, Bacillus subtilis, Escherichia coli, Klebsiella oxytoca and Pseudomonas aeruginosa, and two fungi species, Aspergillus niger and Fusarium oxysporum. The complexes showed moderate-to-strong antimicrobial potentials, with [Ni(buphdtc)2] (1) displaying the best antimicrobial activity. Fluconazole and streptomycin were used as reference drugs for antifungal and antibacterial assays, respectively.

Structural characterization and preliminary decomposition study of four unsymmetrically substituted nickel dithiocarbamate complexes

Single-crystal X-ray structures of four nickel dithiocarbamate complexes, the homoleptic mixed-organic bis-dithiocarbamates Ni[S2CN(isopropyl)(benzyl)]2, Ni[S2CN(ethyl)(n-butyl)]2, and Ni[S2CN(phenyl)(benzyl)]2, as well as the heteroleptic mixed-ligand complex NiCl[P(phenyl)3][(S2CN(phenyl)(benzyl)], were determined. A slightly distorted square-planar nickel coordination environment was observed for all four complexes. The organic residues adopt conformations to minimize steric interactions. Steric effects also may determine puckering, if any, about the nickel and nitrogen atoms, both of which are planar or nearly so. A trans-influence affects the Ni-S bond distances. Nitrogens interact with the CS2 carbons with a bond order near two; the other substituents on nitrogen display transoid conformations. There are no strong intermolecular interactions, consistent with prior observations of the volatility of nickel dithiocarbamate complexes. A preliminary thermolysis study of the homoleptic species results in production of 1 : 1 nickel sulfide phases, indicating the potential utility of these species as “single-source” precursors.

Low temperature solventless syntheses of nanocrystalline nickel sulfides with different sulfur sources

This work describes a novel synthesis for the production of very pure nanocrystalline hexagonal nickel sulfide phase (h-NiS) by the solventless route in air at temperatures of only 190°C. Only the cubic NiS2 nickel sulfide phase is obtained when the sulfur source reacting with the nickel acetate powder (NiAc) is switched from thiourea (TU) to elemental sulfur (SN). When using both TU and SN sulfur sources, phase mixture of h-NiS, NiS2 and Ni3S4 with less aggregated particles was obtained. Relative concentrations of the phases were quantified by the Rietveld refinement of the XRD powder patterns. The thermal evolution of stoichiometric reagents mixture was observed by TG-FTIR and DSC curves.

The Catalytic Performance of Metalloporphyrins during Hydrogenation of Anthracene

AbstractThe potential catalytic performance of metalloporphyrins (MPs) for the hydrogenation of anthracene was investigated. The hydrogenation of anthracene with MPs, sulfur, or a combination of both was investigated. The MPs showed a small amount of catalytic activity for the hydrogenation reaction. Sulfur markedly improved the catalytic activity of the MPs. To probe demetalation of the MPs and the formation of catalytic species, conversions of the MPs were evaluated by UV/Vis spectroscopy. The solids formed in situ with α‐Al2O3 as a carrier during the hydrogenation with nickel tetraphenylporphyrin and sulfur were characterized by Raman, X‐ray photoelectron (XPS), and energy‐dispersive X‐ray spectroscopy (EDS). In the presence of sulfur, high conversions of the MPs were obtained. Raman spectroscopy, XPS, and EDS analyses suggested that the catalytic species were mixtures of different nickel sulfide phases with NiS as the main component. Thus, with the aid of sulfur, the MPs could be readily demetalated and then sulfided to catalytic species, and thus it is possible to activate inherent MPs to improve the hydroconversion of heavy oil.

Density Functional Theory Study of Sulfur Poisoning on Nickel Anode in Solid Oxide Fuel Cells: Effects of Surface and Subsurface Sulfur Atoms

Impurities such as sulfur compounds cause performance degradation in solid oxide fuel cells (SOFCs). We have studied the sulfur poisoning mechanism on an SOFC nickel anode using density functional theory method, focusing on the effects of surface and subsurface sulfur atoms. The binding energy of surface sulfur atoms decreases with an increase in sulfur coverage on the nickel surface. Subsurface sulfur atoms become stable relative to surface sulfur atoms at high sulfur coverage. A subsurface sulfur phase also appears between sulfur adsorption phase and nickel sulfide phase in the calculated phase diagram for Ni–S systems. Influences of sulfur atoms on intermediate adsorbates during surface reactions are also investigated. Sulfur hinders the reaction by destabilizing the reaction intermediates on the nickel surface.

On the exothermic peak during annealing of electrodeposited nanocrystalline nickel

Nanocrystalline metals frequently exhibit poor thermal stability, and the exothermic peak in differential scanning calorimetry is usually attributed to grain growth. We show from experiments on electrodeposited nano-Ni with varying levels of S, and tests with microcrystalline Ni and S powders, that the exothermic peak is associated with the formation of a nickel sulfide phase and concurrent grain growth. Analysis suggests that segregation plays a more important role in limiting grain growth than second-phase particles in nano-Ni.

Influence of Au promoter on hydrodesulfurization activity of thiophene over sulfided Au–Ni/SiO2 bimetallic catalysts

Au–Ni/SiO2 bimetallic catalysts with high performance on hydrodesulfurization (HDS) were prepared through consecutive impregnation route. The activities of the catalysts with different metal loading were estimated by thiophene HDS. The activity is affected by nickel and gold loadings as well as the catalyst pretreatment. It is found the presence of Au can partly inhibit the formation of nickel sulfide phase and significantly increase the HDS activity of Ni/SiO2 catalyst. The sulfided catalysts show higher activity than reduced or oxidized catalysts. Synergetic effect between gold and nickel species is preferable for high activity with low metal loadings.

Characterization and thiophene hydrodesulfurization activity of amorphous-silica–alumina-supported NiW catalysts

The influence of the preparation method and sulfidation conditions on the structure and activity of ASA-supported NiW catalysts was investigated by a combination of 57Co Mössbauer emission spectroscopy (MES), transmission electron microscopy (TEM), X-ray absorption spectroscopy (XAS), and thiophene hydrodesulfurization (HDS) activity measurements. Ni is sulfided already at low temperatures. This nickel sulfide phase redisperses at higher temperatures over the edges of WS 2 particles to form “Ni W S”-type phases. The formation of such highly active phases is facilitated by the partial transformation of intermediate WO x S y phases to WS 2 (W L III edge XAS) at 673 K. In addition to this “Co Mo S” analogue nickel sulfide particles are present in dispersed form close to an oxysulfidic tungsten phase. It is found that the sulfidation of NiW/ASA closely resembles that of NiW/Al 2O 3. Trends in the HDS activity as a function of catalyst pretreatment were evaluated. A higher calcination temperature (from 673 to 823 K) decreases the HDS performance stemming from a lower W sulfidation degree and a more dominant presence of small oxysulfidic tungsten particles. Increasing the sulfidation pressure from atmospheric pressure to 15 bar leads to a strong increase of the HDS activity. Whereas sulfidation at 923 K results in a well-crystallized WS 2 phase (XAS), the concomitant loss in dispersion (TEM) is detrimental to its performance. Moreover, indications are found that more complete crystallization of the WS 2 phase results in a lower activity.