Laurite Research Articles

High-Pressure Synthesis of High-Entropy Metal Disulfides with Pyrite-Type Structure

We succeed in synthesizing equimolar-multi metal solid solutions of (Fe, Co, Ni, Cu)S2 and (Fe, Co, Ni, Cu, Ru)S2 by sintering at 900 °C under 2–4 GPa. These were stabilized by the high-entropy effect. Nevertheless, (Fe, Co, Ni, Cu, M)S2 (M = Zn, Mn, or Cd) was not obtained as single phase under the same synthetic conditions, mostly owing to the relatively large ionic radius of M2+. Single-crystal X-ray diffraction analysis shows that (Fe, Co, Ni, Cu)S2 crystallizes into a pyrite type with the space group \(Pa\bar{3}\) (#205) [a = 5.777(3) Å], randomly distributed at one site. The results of electrical resistivity and magnetic dc-susceptibility measurements indicate that both (Fe, Co, Ni, Cu)S2 and (Fe, Co, Ni, Cu, Ru)S2 are metals with ferrimagnetic ordering below Tc = 130 K. The band structure and the projected density of states (Fe, Co, Ni, Cu)S2, were obtained by density functional theory calculations in a high-entropy representative supercell, supporting the experimental results.

Synthesis of ruthenium sulfide nanoparticles decorated on reduced graphene oxide/multi-walled carbon nanotubes as a catalytic counter electrode for dye-sensitized solar cells exceeding 13 % efficiency

The luxury price, shortage, and instability of platinum (Pt) markedly hamper its commercialization in dye-sensitized solar cells (DSSCs). Consequently, developing an efficient alternative catalyst in lieu of noble Pt is imperative issue for the promotion of DSSCs. In this paper, a robust and electrochemically stable 3D nanocomposite comprised of amorphous ruthenium sulfide nanoparticles (RuS2 NPs), reduced graphene oxide (RGO), and functionalized multi-walled carbon nanotubes (MWCNTs) was prepared by the facile hydrothermal method and explored as a counter electrode (CE) in DSSCs. The RuS2 NPs uniformly decorated on the surfaces of the RGO/MWCNTs to form the RuS2/RGO/MWCNTs composite, which adequately inhibited aggregation of the RuS2 NPs to fully exploit its impressive electrochemical activity. Benefiting from the unexceptionable catalytic activity of RuS2 NPs in the RuS2/RGO/MWCNTs as well as superior electronic transmission channels provided by the conductive RGO/MWCNTs network, the designed DSSC with RuS2/RGO/MWCNTs exhibited a remarkable power conversion efficiency (PCE) of 13.24 % exceeding that of Pt CE (PCE: 9.53 %). Consequently, this research opens a new avenue to fabricate advanced cathode catalysts based on metallic sulfides and carbon-based materials with excellent performance for their potential application in next-generation energy storage and conversion devices such as DSSCs, water splitting, and other electrochemical applications.

In-situ formed Cu-doped RuS2 hollow polyhedrons integrated with simultaneously heterostructure engineering with metallic Ru for boosting hydrogen evolution in alkaline media

Promoting hydrogen evolution reaction (HER) in alkaline media is currently vital to practicing the sustainable development of hydrogen economy. As an emerging candidate, pyrite-structured ruthenium disulfide (RuS2) is a promising electrocatalyst for alkaline HER. Nevertheless, much less efforts have been devoted to RuS2, thus whose intrinsic properties still remain to be improved via promoting the water dissociation and hydrogen adsorption processes. Herein, we report the facile synthesis of Cu-doped RuS2 hollow polyhedrons coupled with metallic Ru from bimetallic MOF of RuCu-BTC to boost alkaline hydrogen evolution. In which, in-situ Cu doping integrated with simultaneous heterostructure engineering with metallic Ru are achieved for RuS2. Benefitting from modified electronic structure, heterogeneous interfaces and 3D hollow polyhedral morphology, the Cu-doped RuS2/Ru heterostructure exhibits admirable electrocatalytic activity with small overpotential of 169 mV at a high current density of 200 mA cm−2 in 1 M KOH, superior to that of commercial Pt/C. Density functional theory calculations indicate that the incorporation of Cu heteroatoms can not only decrease the energy barrier for water dissociation of RuS2 but also optimize its hydrogen adsorption. Simultaneously, the construction of heterointerfaces between RuS2 and metallic Ru demonstrates further improved conductivity, increased active sites and enhanced specific activity. This work discloses an innovative strategy for the simultaneous implementation of heteroatom doping and heterostructure engineering on RuS2 to collaboratively promote the HER electrocatalytic performance.

Electrochemical sensor based on cobalt ruthenium sulfide nanoparticles embedded on boron nitrogen co-doped reduced graphene oxide for the determination of nitrite

The oxidation of ammonia to nitrate produces nitrite as an intermediate product. Nitrite is used in food to protect against microbial contamination, for salty taste, and, act as additives to improve the food quality. However, it is discharged into the environment is harmful to the ecosystem and human health, therefore quick, portable, and economical sensors are essential for the detection of nitrite in vegetables, fruits, processed meats, and pharmaceutical samples. In this work, we successfully developed the cobalt ruthenium sulfide (CRS) nanoparticles embedded on (BN-RGO) boron, nitrogen co-doped reduced graphene oxide nanocomposite by a facile hydrothermal assisted ultrasonication method, and the CRS/BN-RGO based sensor was used for the detection of nitrite, which is more selective, sensitive, and economical. The newly synthesized CRS/BN-RGO sensor material was characterized by various morphological and structural investigation studies. The BN-RGO nanosheets improved the electrical conductivity of the CRS nanoparticles, which was confirmed by EIS and CV studies. According to the electrochemical investigations, our proposed CRS/BN-RGO sensor exhibited good selectivity and sensitivity towards nitrite. Moreover, the nitrite was detected under the optimized experimental conditions, and the CRS/BN-RGO sensor exhibited the low detection limit (LOD) of 0.0159 µM, good sensitivity of 1.5309 μA μM−1 cm−2, and a wide linear range of 0.001–1290 µM. Furthermore, we examined the proposed CRS/BN-RGO sensor's practical performance towards nitrite in the real water samples, which exhibited good recovery results.

Oxygenic Enrichment in Hybrid Ruthenium Sulfide Nanoclusters for an Optimized Photothermal Effect.

Transition-metal dichalcogenide (TMD)-based nanomaterials have been extensively explored for the photonic therapy. To the best of our knowledge, near-infrared (NIR) light is a requirement for the photothermal therapy (PTT) to achieve the feature of deep-tissue penetration, whereas no obvious absorption peaks existing in the NIR region for existing TMD nanomaterials limit their therapeutic efficacy. As one category of TMD nanomaterials, ruthenium sulfide-based nanomaterials have been less exploited in biomedical applications including tumor therapy so far. Here, we develop a facile biomineralization-assisted bottom-up strategy to synthesize oxygenic hybrid ruthenium sulfide nanoclusters (RuSx NCs) by regulating the oxygen amounts and sulfur defects for the optimized PTT. By regulating the increasing initial molar ratios of Ru to S, RuSx NCs with small sizes were endowed with increasing oxygen contents and sulfur defects, leading to the photothermal conversion efficiency (PCE) increasing from 32.8 to 41.9%, which were higher than that of most small-sized inorganic photothermal nanoagents. In contrast to commercial indocyanine green, these RuSx NCs exhibited higher photostability under NIR laser irradiation. The high PCE and superior photostability allowed RuSx NCs to effectively and completely ablate cancer cells. Thus, the proposed defect engineering strategy endows RuSx NCs with an excellent photothermal effect for the PTT of tumors of living mice, which also proves the potential of further exploring the properties of RuSx NCs for future biomedical applications.

Well-dispersed pyrite-type RuS2 nanocrystals anchored on porous nitrogen and sulfur co-doped hollow carbon spheres for enhanced alkaline hydrogen evolution

The hydrogen evolution reaction (HER) activity in alkaline condition is generally suppressed due to sluggish water dissociation–related Volmer process. Consequently, developing new highly-active and cost-efficient electrocatalysts for the alkaline hydrogen production is greatly desirable for achieving sustainable water splitting in industrial plants. Pyrite-type RuS2 is a potential excellent electrocatalyst for alkaline HER but the related research is still in its infancy. Herein, well-dispersed crystalline RuS2 nanoparticles (c-RuS2 NPs) with ultrasmall particle size anchored on porous nitrogen and sulfur co-doped hollow carbon spheres (NSC) are synthesized for alkaline HER electrocatalysis. The conductive and porous hollow carbon spheres with nitrogen and sulfur doping is used as the effective support to provide abundant anchoring sites and modify the electronic structure of RuS2, beneficial to increasing the active sites and improving the intrinsic activity. Furthermore, the crystallinity modulation of ruthenium sulfide also has a significant impact on HER activity. In 1.0 M KOH solution, the proposed c-RuS2 NPs/NSC catalyst exhibits admirable activity for HER electrocatalysis with a low overpotential of 11 mV at a current density of 10 mA cm−2 and a small Tafel slope of 35.4 mV dec−1. With low Ru loading, superior hydrogen evolution in alkaline media is achieved for c-RuS2 NPs/NSC compared to the commercial Pt/C and the reported ruthenium-sulfide-based electrocatalysts.

Photocatalytic production of H2 is a multi-criteria optimization problem: Case study of RuS2/TiO2

Many parameters influence the photocatalytic production of H2. Identifying and quantifying them is necessary for correct comparison of photocatalysts and right understanding of involved mechanism.In this work, we studied the photocatalytic dehydrogenation of isopropanol with titania-supported ruthenium disulfide. We studied the influence of seven parameters on the photocatalytic activity: the temperature, the composition of the reactive mixture, the mass of the photocatalyst, the flux and the energy of the incident photons, the co-catalyst loading and the nature of the support. Their influence was studied, not only on the rate of hydrogen production (or photon yield) but also on the apparent activation energy and on the pre-exponential factor, deduced from an Arrhenius law.The photon yield as a function of the co-catalyst loading show an optimum of activity.A 6.9 % photon yield was obtained at 0.84 wt% and Ephotons=3.65 eV.The rate-determining step for the photocatalytic dehydrogenation of the isopropanol with RuS2/TiO2 is, at optimal conditions, the electron transfer from TiO2 to RuS2. The latter is not favored because of the band diagrams of RuS2 and TiO2. The electron transfer can be optimized working with incident photons having a higher energy, thanks to a hot carrier effect observed in RuS2/TiO2.

Crystallization of pyrrhotite from Fe-Ni-Cu-S-(Rh, Ru) melt

We have studied the composition and structure of the products of initial crystallization stage of melt with the following composition (in mol. %): Fe 31.90, Cu 16.03, Ni 1.70, S 50.31, and by 0.03 Ru and Rh. Directional solidification of the sample was carried out in the region of primary crystallization of pyrrhotite solid solution (Poss) in the Fe-Cu-Ni-S system. Results of optical microscopy and SEM-EDS showed that the distribution of the main components and Rh in the sample agrees with the theory of directed crystallization. Refractory ruthenium sulfide RuS2 (structure type FeS2, pyrite), formed in the sulfide melt, plays the part of mechanical dopant. On cooling of the crystallized sample, Poss partly decomposes to form nonstoichiometric isocubanite Cu1.1Fe2S3 (Icb*). On further cooling, Icb* decomposes into stoichiometric isocubanite CuFe2S3 (Icb) and Cu3Fe4S7 phase. These phase reactions do not influence the distribution of Rh and Ru in the sample volume. Crystallographic parameters, features of modulation and spatial orientation of pyrrhotite and cubanite phases of sulfide matrix were determined.

Structural and Chemical Transformations of Ruthenium, Cobalt, and Iron Clathrochelates Used as Electrocatalysts for a Hydrogen Evolution Reaction in a Water Electrolyzer

The structural evolution of three electrocatalytic systems for hydrogen evolution reaction using iron, cobalt, and ruthenium(II) clathrochelate complexes as catalysts in a water electrolyzer is studied by X-ray absorption near-edge structure (XANES)/extended X-ray absorption fine structure (EXAFS) spectroscopy. The complexes are shown to display essentially different robustness under water electrolysis conditions in pilot-scale hydrogen generators. The iron and cobalt(II) clathrochelates preserve their cage, macrobicyclic structure, and the encapsulated metal(II) ion is reduced to metal(I) cation; whereas in the case of ruthenium(II) clathrochelate, the cage complex undergoes partial decomposition to form sulfur-containing products of decomposition of the encapsulating macrobicyclic hexasulfide ligand, which results in the accumulation of the ruthenium disulfide RuS2 in used clathrochelate-containing cathode material. Taking into account our experimental data on the chemical transformation of clathrochelate electrocatalysts under the conditions of 2Н+/Н2 reaction, we discuss the possibilities for boosting the efficiency of electrocatalytic systems based on this class of coordination compounds.

Podiform Chromitites and PGE Mineralization in the Ulan-Sar’dag Ophiolite (East Sayan, Russia)

In this paper, we present the first detailed study on the chromitites and platinum-group element mineralization (PGM) of the Ulan-Sar’dag ophiolite (USO), located in the Central Asian Fold Belt (East Sayan). Three groups of chrome spinels, differing in their chemical features and physical–chemical parameters, under equilibrium conditions of the mantle mineral association, have been distinguished. The temperature and log oxygen fugacity values are, for the chrome spinels I, from 820 to 920 °C and from (−0.7) to (−1.5); for chrome spinels II, 891 to 1003 °C and (−1.1) to (−4.4); and for chrome spinels III, 738 to 846 °C and (−1.1) to (−4.4), respectively. Chrome spinels I were formed through the interaction of peridotites with mid-ocean ridge basalt (MORB)-type melts, and chrome spinels II were formed through the interaction of peridotites with boninite melts. Chrome spinels III were probably formed through the interaction of andesitic melts with rocks of an overlying mantle wedge. Chromitites demonstrate the fractionated form of the distribution of the platinum-group elements (PGE), which indicates a high degree of partial melting at 20–24% of the mantle source. Two assemblages of PGM have been distinguished: The primary PGE assemblage of Os-Ir-Ru alloys-I, (Os,Ru)S2, and IrAsS, and the secondary PGM assemblage of Os-Ir-Ru alloys-II, Os0, Ru0, RuS2, OsS2, IrAsS, RhNiAs with Ni, Fe, and Cu sulfides. The formation of the secondary phases of PGE occurred upon exposure to a reduced fluid, with a temperature range of 300–700 °C, log sulfur fugacity of (−20), and pressure of 0.5 kbar. We have proposed a scheme for the sequence of the formation and transformation of the PGMs at various stages of the evolution of the Ulan-Sar’dag ophiolite.

Amorphous RuS2 electrocatalyst with optimized active sites for hydrogen evolution

Transition metal chalcogenides have attracted much attention as high-performance electrocatalysts for hydrogen evolution reaction (HER). Here, we synthesized an efficient HER electrocatalyst of amorphous ruthenium sulfide (A-RuS2), exhibiting an overpotential of 141 mV at the current density of 10 mA cm−2 and a Tafel slope of 65.6 mV dec−1. Experiments demonstrate amorphous RuS2 has much better catalytic activity than that of its crystalline counterparts. Our study shows that amorphous RuS2 has increased intrinsic activity and active sites. This work provides a feasible strategy for the development of HER electrocatalysts in amorphous state.

Synergistic activity of binary metal sulphide WS2–RuS2nanospheres for the electrochemical detection of the antipsychotic drug promazine

Schematic presentation for the synthesis of tungsten disulfide–ruthenium disulfide (WS2–RuS2) nanospheres and application for the electrochemical determination of antipsychotic drug promazine.

A ruthenium(IV) disulfide based non-enzymatic sensor for selective and sensitive amperometric determination of dopamine.

An electrochemical dopamine (DA) sensor has been fabricated by modifying a glassy carbon electrode (GCE) with ruthenium disulfide (RuS2) nanoparticles (NPs). FESEM and TEM micrographs show the NPs to have an average size of ~45nm. XRD, Raman and EDS, in turn, confirm the successful formation of cubic phased RuS2 NPs. The modified GCE displays has attractive features of merit that include (a) an ultra-low detection limit (73.8nM), (b) fast response time (< 4s), (c) a low oxidation potential (0.25V vs. Ag|AgCl), (d) excellent reproducibility and stability, (e) an electrochemical sensitivity of 18.4μAμM-1cm-2 and 1.8μA.μM-1.cm-2 in the linear ranges from 0.1-10μM of DA (R2 = 0.97) and 10-80μM of DA (R2 = 0.99), respectively. The sensor exhibits excellent specificity over potential interferents like ascorbic acid, glucose and uric acid. The superior performance of the sensor is attributed to its high electrical conductivity, large electro-active surface, and large numbers of exposed catalytically active sites resulting from the presence of unreacted sulfur atoms. Graphical abstract A ruthenium disulfide modified electrochemical sensor material was obtained by single-step hydrothermal synthesis. Sensitive and highly selective detection of dopamine is demonstrated.

Pyrite-type ruthenium disulfide with tunable disorder and defects enables ultra-efficient overall water splitting

Synergistic disorder and defect engineering in ruthenium disulfide enables efficient water splitting with an ultralow cell voltage of 1.527 V.

A novel design and synthesis of ruthenium sulfide decorated activated graphite nanocomposite for the electrochemical determination of antipsychotic drug chlorpromazine

A novel electrochemical sensor based on ruthenium sulfide nanoparticles decorated activated graphite sheets (RuS2/AG) was designed and fabricated for the determination of antipsychotic drug chlorpromazine hydrochloride (CPZ). Activated graphite sheets (AG) were prepared by non-explosive, non-hazardous and simple chemical activation technique. Then, the AG sheets were used for the synthesis of RuS2/AG nanocomposite by single step hydrothermal synthesis method. The synthesized materials were characterized using field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), Raman spectrometer, X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The synergistic effect of the RuS2/AG nanocomposite was applied for the determination of CPZ by cyclic voltammetry (CV) and differential pulse voltammetric (DPV) techniques. Fascinatingly, the RuS2/AG nanocomposite exhibited the excellent electrocatalytic activity and detects the CPZ at very lowest oxidation potential about 0.60 V vs Ag/AgCl in pH-7 PB solution. Moreover, the lowest LOD 8 nM and wider linear ranges from 0.05 to 79.75 and 79.75–1249 μM was obtained towards the CPZ determination. Besides, the proposed sensor shows the good selectivity, satisfactory repeatability, reproducibility and stability. Furthermore, the real time application was evaluated in pharmaceutical tablets and human urine samples.

Platinum-group mineral assemblage of the Prizhimny Creek (Koryak Highland)

In the alluvial deposits of the Prizhlimny Creek (southern part of the Koryak Highland), grains of platinum-group minerals are found along with gold. We have established that the grains are native platinum (Pt, Fe) containing Cu (up to 5 wt.%), Os (up to 8 wt.%), and Rh (up to 2 wt.%). Inclusions in the platinum are native osmium (the content of Ir impurity reaches 12 wt.%, the average content being 0.2–4 wt.%), an unnamed intermetallic compound of composition PtRh, sulfides and arsenides of PGE (cooperite, laurite, malanite, cuproiridsite, cuprorhodsite, sperrylite, hollingworthite, unnamed compounds PdS, (Ir,Ru)S2, (Ir,Pt)S2, Cu, and Fe (bornite, chalcopyrite), chromite, and Cr-magnetite. Replacement of native-osmium crystals by compound IrO2 is described. It has been established that this compound formed during oxidation accompanied by the replacement of isoferroplatinum by native platinum. The data obtained agree with the results of study of platinum-group mineral assemblages from placers localized in weakly eroded Ural–Alaskan-type massifs whose apical parts formed under high oxygen activity conditions. Clinopyroxenites of the Prizhimny massif are considered to be the potential source of PGE.

A Simple Route to Ruthenium Sulfide Nanoparticles via Thermal Decomposition of Precursor Complexes

The research work presented here investigate the use of homonuclear tris-dithiocarbamato ruthenium(III) complexes as single-source molecular precursors to ruthenium sulfide nanoparticles. The dithiocarbamate ligands with their respective precursor complexes were characterized by UV-Vis, FTIR, 1H- and 13C-NMR, and in addition TGA was used for precursors. The absorption spectra confirmed the geometry of tris-chelate ruthenium complexes [Ru(S2CNR2)3] to be octahedral and were very stable both in solution and in the solid state. The optical and structural properties of the ruthenium sulfide nanoparticles were examined using FTIR, XRD, EDS, SEM, TEM, UV-Vis and photoluminescence (PL). FTIR studies revealed that Ru2S3 nanoparticles are capped through the interaction of the –NH2 group of hexadecylamine (HDA) adsorbed on the surfaces of nanoparticles with the prominent band observed around 3330 cm-1 due to v(N-H). The XRD confirmed the successful formation of ruthenium sulfide nanoparticles with a cubic crystal structure within the nano-scale range. The optical band gap(Eg) determined from Tauc plot was found in the range (3.44 to 4.18 eV) values.

Graphene/Ruthenium Active Species Aerogel as Electrode for Supercapacitor Applications.

Ruthenium active species containing Ruthenium Sulphide (RuS2) is synthesized together with a self-assembled reduced graphene oxide (RGO) aerogel by a one-pot hydrothermal synthesis. Ruthenium Chloride and L-Cysteine are used as reactants. The hydrothermal synthesis of the innovative hybrid material occurs at 180 °C for 12 h, by using water as solvent. The structure and morphology of the hybrid material are fully characterized by Raman, XRD, XPS, FESEM and TEM. The XRD and diffraction pattern obtained by TEM display an amorphous nanostructure of RuS2 on RGO crystallized flakes. The specific capacitance measured in planar configuration in 1 M NaCl electrolyte at 5 mV s−1 is 238 F g−1. This supercapacitor electrode also exhibits perfect cyclic stability without loss of the specific capacitance after 15,000 cycles. In summary, the RGO/Ruthenium active species hybrid material demonstrates remarkable properties for use as active material for supercapacitor applications.

Synthesis, spectroscopic, structural and optical studies of Ru2S3 nanoparticles prepared from single-source molecular precursors

Homonuclear tris-dithiocarbamato ruthenium(III) complexes, [Ru(S2CNR2)3] were prepared and characterized by spectroscopic techniques and thermogravimetric analyses. The thermogravimetric analyses (TGA) of the ruthenium complexes showed that the complexes decompose to ruthenium(III) sulfide nanoparticles. The ruthenium(III) complexes were dispersed in oleic acid and thermolysed in hexadecylamine to prepared oleic acid/hexadecylamine capped Ru2S3 nanoparticles. FTIR revealed that Ru2S3 nanoparticles are capped through the interaction of the –NH2 group of hexadecylamine HDA adsorbed on the surfaces of nanoparticles and it also showed that oleic acid (OA) is acting as both coordinating stabilizing surfactant and capping agent. EDS spectra revealed that the prepared nanoparticles are mainly composed of Ru and S, confirming the formation of Ru2S3 nanoparticles. Powder XRD confirms that the nanoparticles are in cubic phase. The inner morphology of nanoparticles obtained from transmission electron microscopy (TEM) showed nanoparticles with narrow particle size distributions characterized by an average diameter of 8.45 nm with a standard deviation of 1.6 nm. The optical band gap (Eg) determined from Tauc plot are in the range 3.44–4.18 eV.

Long Blood Residence and Large Tumor Uptake of Ruthenium Sulfide Nanoclusters for Highly Efficient Cancer Photothermal Therapy

Transition metal sulfide (TMS) holds great potential in cancer photothermal therapy (PTT) because of the high absorbance in the near-infrared (NIR) region. The short blood circulation time and limited tumor accumulation of TMS-based photothermal agents, however, limit their applications. Herein, we design a novel TMS-based PTT agent, ruthenium sulfide-based nanoclusters (NCs), to overcome the current limitations. We firstly develop a simple method to prepare oleic acid coated ruthenium sulfide nanodots (OA-RuS1.7 NDs) and assemble them into water-soluble NCs via sequentially coating with denatured bovine serum albumin (dBSA) and poly(ethylene glycol) (PEG). The obtained PEG-dBSA-RuS1.7 NCs possess excellent photothermal conversion ability. More significantly, they exhibit enhanced blood circulation time and tumor-targeting efficiency in vivo compared with other TMS-based PTT nanoagents, which may be attributed to their appropriate hydrodynamic diameter (~70 nm) and an ideal charge (~0 mV). These characteristics help the PEG-dBSA-RuS1.7 NCs to escape the removal by the reticuloendothelial system (RES) and kidney. All these advantages enable the PEG-dBSA-RuS1.7 NCs to selectively concentrate in tumor sites and effectively ablate the cancer cells upon NIR irradiation.