Ruthenium Oxide Research Articles

Preparation of cyclohexanol from lignin-based phenolic concoction using controlled hydrogen delivery tool over in-situ Ru catalyst

This work investigated hydrodeoxygenation-hydrogenation of lignin-based methoxyphenols (obtained through hydrothermal liquefaction (HTL) of lignin) to cyclohexanol in high yields over in situ generated Ru(0)@Mg(OH)2 catalyst in aqueous medium. The active catalyst Ru(0)@Mg(OH)2 is generated in situ from hydrous ruthenium oxide (HRO)/Mg(OH)2 under reaction conditions, as confirmed by various physiochemical techniques. Continuous and controlled addition of H2 at constant temperature facilitated in improving the selectivity of cyclohexanol compared to the conventional batch mode (pre-set pressure) process. Complete conversion of methoxyphenols with 93–99% selectivity for cyclohexanol was achieved at 10 mL/min H2 flow under comparatively milder reaction conditions. The adopted procedure and the in situ catalyst reported in this work is also effective for lignin-derived phenolic concoction.

Biocompatibility of hydroxyethyl cellulose/glycine/RuO2 composite scaffolds for neural-like cells

Fabrication of scaffolds for nerve regeneration is one of the most challenging topics in regenerative medicine at the moment, which is also interlinked with the development of biocompatible substrates for cells growth. This work is targeted towards the development of green biomaterial composite scaffolds for nerve cell culture applications. Hybrid scaffolds of hydroxyethyl cellulose/glycine (HEC/Gly) composite doped with different concentrations of green ruthenium oxide (RuO2) were synthesized and characterized via a combination of different techniques. X-rays diffraction (XRD) and differential scanning calorimetry (DSC) analyses showed a crystalline nature for all the samples with noticeable decrease in the peak intensity of the fabricated scaffolds as compared to that for pure glycine. Fourier transform infrared spectroscopy (FTIR) tests revealed an increase in the vibrational bands of the synthesized RuO2 containing scaffolds which are related to the functional groups of the natural plant extract (Aspalathuslinearis) used for RuO2 nanoparticles (NPs) synthesis. Scanning electron microscopy (SEM) results revealed a 3D porous structure of the scaffolds with variant features attributed to the concentration of RuO2 NPs in the scaffold. The compressive test results recorded an enhancement in mechanical properties of the fabricated scaffolds (up to 8.55 MPa), proportionally correlated to increasing the RuO2 NPs concentration in HEC/Gly composite scaffold. Our biocompatibility tests revealed that the composite scaffolds doped with 1 and 2 ml of RuO2 demonstrated the highest proliferation percentages (152.2 and 135.6%) compared to control. Finally, the SEM analyses confirmed the impressive cells attachments and differentiation onto the scaffold surfaces as evidenced by the presence of many neuron-like cells with apparent cell bodies and possessing few short neurite-like processes. The presence of RuO2 and glycine was due to their extraordinary biocompatibility due to their cytoprotective and regenerative effects. Therefore, we conclude that these scaffolds are promising for accommodation and growth of neural-like cells.

Ultra-Fine Ruthenium Oxide Quantum Dots/Reduced Graphene Oxide Composite as Electrodes for High-Performance Supercapacitors.

This study synthesized ultra-fine nanometer-scaled ruthenium oxide (RuO2) quantum dots (QDs) on reduced graphene oxide (rGO) surface by a facile and rapid microwave-assisted hydrothermal approach. Benefiting from the synergistic effect of RuO2 and rGO, RuO2/rGO nanocomposite electrodes showed ultra-high capacitive performance. The impact of different RuO2 loadings in RuO2/rGO nanocomposite on their electrochemical performance was investigated by various characterizations. The composite RG-2 with 38 wt.% RuO2 loadings exhibited a specific capacitance of 1120 F g−1 at 1 A g−1. In addition, it has an excellent capacity retention rate of 84 % from 1A g−1 to 10 A g−1, and excellent cycling stability of 89% retention after 10,000 cycles, indicating fast ion-involved redox reactions on the nanocomposite surfaces. These results illustrate that RuO2/rGO composites prepared by this facile process can be an ideal candidate electrode for high-performance supercapacitors.

Ionic liquid-assisted synthesis of tri-functional ruthenium oxide nanoplatelets for electrochemical energy applications

Ionic liquid-assisted synthesis of tri-functional ruthenium oxide nanoplatelets for electrochemical energy applications

Improved Nb–substituted La0.5Sr0.5CoO3 ceramics as new and low–cost functional materials for thick–film resistors

The use of ruthenium oxides as a functional material for commercial thick–film resistors is not conducive to further lowering manufacturing costs. In this study, we propose Nb–substituted La0.5Sr0.5CoO3 (La0.5Sr0.5Co1-yNbyO3, LSCNb, y = 0.02–0.08) ceramics as new and low–cost functional materials for thick–film resistors. The conductivity and temperature coefficient of resistance (TCR) of the LSCNb samples sintered at different temperatures displayed similar downward trends with increasing Nb5+ content. A relatively high conductivity of 1670 S/cm and a minimum absolute TCR of −168 ppm/°C were attained for the sample with y = 0.06 sintered at 1225 °C. Furthermore, zero TCR was achieved for samples within the doping range of 0.05 < y < 0.06. The variation in density of states, electron density, and bond population could explain the change in electrical properties in the experiment. Additionally, the LSCNb ceramics showed good frequency stability. Therefore, the improved Nb–substituted La0.5Sr0.5CoO3 ceramics can be promising candidates for low–cost functional materials of thick–film resistors.

Enhancement in the Charge-Transfer Kinetics of Pseudocapacitive Iridium-Doped Layered Manganese Oxide.

Birnessite manganese oxide is a promising candidate as an electrode material for aqueous supercapacitors owing to its pseudocapacitance associated with fast redox processes. While manganese oxides are semiconductive, the conductivity is much lower than that of typical materials used for capacitive electrodes such as activated carbon or ruthenium oxide. In an attempt to increase the electronic conductivity of birnessite, a new solid solution phase, Ky(Mn1-xIrx)O2, was synthesized, and the electrochemical charge storage capability of Ir-doped birnessite was studied in aqueous Li2SO4. Structural characterization revealed that the single-phase Ky(Mn1-xIrx)O2 could be synthesized up to x = 0.1. An increase in the pseudocapacitive charge was observed with the increase in Ir content. In addition to the increase in the pseudocapacitive charge, an unusual change in the peak potential was observed. The peak-to-peak difference for the Mn4+/Mn3+ redox decreased with increasing Ir content, indicating an increase in the reversibility of the pseudocapacitive process. The decrease in peak-to-peak difference was observed only by Ir substitution and was not observed for physical mixtures of K0.28MnO2 and IrO2, suggesting a strong electronic interaction between the host Mn ion and the substituting Ir ion.

Defect-enriched heterointerfaces N–MoO2–Mo2C supported Pd nanocomposite as a novel multifunctional electrocatalyst for oxygen reduction reaction and overall water splitting

Developing highly efficient, cost-saving, and durable multifunctional electrocatalysts for oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER) continues to be a significant challenge in the energy field. In this work, we decide to prepare an unusual multifunctional electrocatalyst, such as icosahedral palladium nanocrystals (PdNCs) encapsulating on N–MoO2–Mo2C half-hollow nanotube (HHNT) heterointerface, using an in-situ chemical reaction and following sonic probe irradiation method. All the experiments demonstrate that special defect-enriched heterointerfaces N–MoO2–Mo2C supported Pd nanocomposite can greatly improve the ORR activity (Eonset = 1.01 V and E1/2 = 0.90 V) with good stability, outstanding HER (η10 = 65 mV) and OER (η10 = 180 mV) performances than those of commercial precious electrocatalysts (Platinum on carbon [Pt/C] and ruthenium oxide [RuO2]). The overall water splitting electrolyzer fabricates by Pd/N–MoO2–Mo2C as both anode and cathode electrodes to achieve a current density of 10 Ma/cm2 at a cell voltage of 1.56 V, which surpasses the most recent reported electrocatalysts.

Quantum Magnetic Properties and Metal‐to‐Insulator Transition in Chemically Doped Calcium Ruthenate Perovskite

Ruthenates provide a comprehensive platform to study a plethora of novel properties, such as quantum magnetism, superconductivity, and magnetic fluctuation mediated metal–insulator transition (MIT). Herein, an overview of quantum mechanical phenomenology in calcium ruthenium oxide with varying compositions is provided. While the stoichiometric composition of exhibits non‐fermi liquid (FL) behavior with quasi‐criticality, chemically doped compounds depict prominent signatures of quantum magnetic fluctuations at low temperature that in some cases are argued to mediate in metal–insulator transition. In the case of cobalt‐doped , an unusual continuum fluctuation is found to persist deep inside the glassy phase of the material. These observations reflect the richness of the ruthenate research platform in the study of quantum magnetic phenomena of fundamental importance.

Mixed Oxide Electrodes Based on Ruthenium and Copper: Electrochemical Properties as a Function of the Composition and Method of Manufacture

The development of mixed oxide electrodes is being intensively investigated to reduce the high cost associated with the use of noble metals and to obtain versatile and long-lasting devices. To evaluate their use for charge storage or anodic oxidation, in this paper, thin-film electrodes coated with ruthenium (RuOx) and copper oxide (CuOx) are fabricated by thermal decomposition of organic solutions containing the precursors by drop-casting on titanium (Ti) foils. The coating consisted of four layers of metal oxide. To investigate the effect of copper (Cu) on electrochemical performances, different approaches are adopted by varying the ratios of precursors’ concentration and including a RuOx interlayer. A comparison with samples obtained by only RuOx has been also performed. The electrodes are characterized using scanning electron microscopy (SEM), cyclic (CV) and linear sweep (LSV) voltammetry, electrochemical impedance spectroscopy (EIS), and corrosion tests. The addition of Cu enhances the capacitive response of the materials and promotes electron transfer reversibility. The coatings obtained by the highest Ru:Cu ratio (95:5) exhibit a more uniform surface distribution and increased corrosion resistance. The interlayer is beneficial to further reduce the corrosion susceptibility and to promote the oxygen evolution but detrimental in the charge storage power. The results suggest the possibility to enhance the electrochemical performance of expensive RuOx through a combination with a low amount of cheaper and more abundant CuOx.

Redirecting dynamic structural evolution of nickel-contained RuO2 catalyst during electrochemical oxygen evolution reaction

Electrochemical oxygen evolution reaction (OER) is a main efficiency bottleneck of water electrolysis. Commercial ruthenium oxide (RuO2) catalyst displays remarkable activities but poor stability for OER. The instability stems from lattice oxygen oxidation, resulting in the oxidation of Ru4+ to soluble Rux+ (x > 4) species. Herein, we redirect dynamic structural evolution of Ru-based catalysts through introducing oxidized nickel (Ni) components. By virtue of comprehensive structural characterizations, such as high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), X-ray photoelectron spectroscopy (XPS), operando Raman and so forth, it is demonstrated that when the atomic content of Ni exceeds that of ruthenium (Ru), the Ni components can efficiently inhibit the Ru4+ oxidation and structural collapse. Density functional theory (DFT) calculations suggest that the introduction of Ni component hinders the formation of oxygen vacancies, and makes lattice oxygen mediated mechanism turn to adsorbate evolution mechanism, which eventually improves the stability. The optimized nickel-contained RuO2 catalyst delivers an effective reactivity with an overpotential of less than 215 mV to attain 10 mA cm−2 and remarkable stability with only 5 mV increment after 5000 potential cycles. This work provides insights into the origin of dynamic structural evolution of transition-metal-modified RuO2 electrocatalysts.

Fabrication of poly(3-methylthiophene)/poly(ethylene oxide)/ruthenium oxide composite electrospun nanofibers for supercapacitor application

Fabrication of poly(3-methylthiophene)/poly(ethylene oxide)/ruthenium oxide composite electrospun nanofibers for supercapacitor application

Development and applications of Ru and Ce based iron oxides as photocatalysts

This paper describes cerium and ruthenium oxides as catalysts in photo-degradation of Congo Red. Results show an alteration in the chemical properties and crystal structure as Ru or Ce are incorporated into the system. Ruthenium materials, are a mixture of carbonous iron oxides, Ru2O and Ru0 clusters and cerium catalysts are a distorted spinel ferrite. Diffuse Reflectance Spectroscopy reveals direct bandgaps of 2.03 and 2.46 eV for Ru and Ce materials respectively. The photo-oxidation of Congo red followed first-order kinetics (k = 3.3 × 10−3 mol·min−1) in the presence of Ru catalysts whereas cerium materials performed poorly (k = 0.7 × 10−3 mol·min−1). A DFT structural optimization was attempted for ruthenium catalysts involving a mixture of Fe(CH3COO)2, Ru2O and Ru07 but for Ce materials, an inverse spinel with CeFe2O4 composition is presented.

Molybdenum oxide decorated Ru catalyst for enhancement of lignin oil hydrodeoxygenation to hydrocarbons

Herein, the catalysts of ruthenium and molybdenum oxide nanoparticles supported on activated carbon (AC) were synthesized by precursor stepwise impregnation and employed for the hydrodeoxygenation (HDO) of lignin oil. The XRD, TEM, XPS and NH3-TPD-MS result of RuMoOx/AC catalysts confirm that the method of loading molybdenum precursor before ruthenium precursor is advantageous for the MoOx and Ru nanoparticles high dispersion and the reduction of MoOx species enhance the amount of acidity of catalyst. Meanwhile, the reduction temperature of RuMoOx/AC-1-T catalysts could effectively regulate the MoOx species that determine the activity and product distribution of HDO. The conversion of aromatic monomers/dimers were up to 96% with high selectivity of hydrocarbon over RuMoOx/AC-1-350 catalyst at 160 °C and 30 bar H2. Which is attributed to the MoO3 and Ru species possess the excellent activity of benzene ring deep hydrogenation, ether bond breaking and acid dehydration. The RuMoOx/AC-1-350 catalyst effectively converted lignin oil (from the depolymerization of cornstalk hydrolysis residue) into hydrocarbons (56.9 wt%) and cyclohexanol/ethers (18.7 wt%) under 280 °C and 3 bar H2. The durability of the RuMoOx/AC-1-350 catalyst for HDO of lignin oil was also investigated and showed that the RuMoOx/AC-1-350 catalyst had good stability, regenerability and repeatability.

Gamma Alumina Supported Zinc Oxide Promoted with Ruthenium Oxide (Ruo2-Zno/Al2o3) and Palladium Oxide Nanoparticles (Pdo-Zno/Al2o3): Efficient Electrocatalysts for Hydrazine Oxidation Reaction (Hzor)

Gamma Alumina Supported Zinc Oxide Promoted with Ruthenium Oxide (Ruo2-Zno/Al2o3) and Palladium Oxide Nanoparticles (Pdo-Zno/Al2o3): Efficient Electrocatalysts for Hydrazine Oxidation Reaction (Hzor)

Computational study of bulk and surface properties on ruthenium oxide (RuO2)

Metal oxides are widely used in lithium-air batteries to improve the formation of stable discharge products and improve lifespan and electrochemical performance. Despite the intense studies on metal oxides catalysts, ruthenium oxide attracted the most attention since it doesn’t only catalyse the redox processes but reduces the over-potential and stabilizes the Li cyclability. Hence, in this work we discuss the bulk and low Miler index surfaces of RuO2 using the first principle density functional theory calculations. It was found that the lattice parameters are in good agreement with the reported results, with less than 1.4% difference. Furthermore, RuO2 was also found to be mechanically stable with all positive independent elastic constants (Cij) obeying the mechanical stability criteria and a positive tetragonal shear modulus (C’&gt; 0). The bulk to shear ratio indicates that the structure is ductile. The density of states shows a slight pseudo gap for RuO2 at the Fermi energy, which suggests that the structure is stable. Finally, low Miller index surfaces (i.e. (110), (010), (001), (111), and (101)) were modelled using METADISE code, and the most stable facet was in agreement with the reported literature.

Ru (III) Catalysed Oxidative Degradation of Sodium Bisulphite Derivatives of Aromatic Aldehydes by Potassium Hexacyano Ferrate (III) in Aqueous Alkaline Medium

Introduction: The catalysed oxidation of the derivatives of aromatic aldehydes with inorganic moieties is still unstudied with an economically cheaper oxidant like potassium hexacyanoferrate (III). The catalyst like ruthenium (III) chloride is very much effective at very low concentrations for oxidation reactions. Aims: The study is carried out to observe and to get the results about the oxidative degradation of derivatives of organic and inorganic moieties. Methodology: Benzaldehyde sodium bisulphite (BSS) and substituted aromatic aldehyde sodium bi sulphite like p-chloro benzaldeyde sodium bisulphite, p-methyl benzaldehyde sodium bisulphite, etc. are dissolved in water, can be oxidized in good yield by potassium hexacyanoferrate (III) as PHF in aqueous alkaline medium in presence of ruthenium (III) chloride. Result: The process requires lesser time and probably an intermediate complex of ruthenium (III) chloride, substrate and oxidant give the products. Conclusion: Oxidative degradation of Benzaldehyde sodium bisulfite (BSS) and substituted aromatic aldehyde sodium bisulphite like p-chloro benzaldeyde sodium bisulphite, p-methyl benzaldehyde sodium bisulphite, etc. give moderate to good yield of corresponding aromatic acids in presence of potassium hexacyanoferrate (III) and ruthenium (III) chloride.

In-Situ Assembly of Titanium-Mesh-Supported Platinum–Ruthenium(Iv) Oxide for High-Efficiency Acidic Overall Water Splitting

In-Situ Assembly of Titanium-Mesh-Supported Platinum–Ruthenium(Iv) Oxide for High-Efficiency Acidic Overall Water Splitting

Improved Interface of Encapsulating Sm-Doped TiO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; Thin Films/RuO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; Schottky Diodes for a Junction Spectropy Measurement

The excitation process of rare-earth ions in oxide semiconductors for optical emission is thought to be related to defect levels within the band-gap of the host material. In order to improve understanding of the role defect levels play in the energy transfer process, junction spectroscopy techniques can be used to investigate the electrically active emission centres. It has been reported that TiO2 is sensitive to humidity at low temperatures, such as those employed when conducting junction spectroscopy measurements. However, there are not many discussions how to prevent this effect and to improve the quality of measurements. After optimization of samples such as fabrication of flat surface and encupsulant for preventing external effect, temperature dependent-capacitance measurements (C-T) were carried out to characterise shallow traps formed within TiO2 band-gap. TiO2 and Sm-doped TiO2 thin films were deposited on SrTiO3 (100) templates by laser ablaton and rectifying Ruthenium Oxide Schottky diodes deposited on the TiO2 surface by laser ablation. A Sm or Sm-related shallow trap was observed in the Arrhenius plot of TiO2:Sm. In this paper, we show the optimized sample fabrication/preparation process that stabilizes the junction spectroscopy measurements, even in the presence of humidity and we present initial results obtained on samples using these optimized processing techniques.

Schematic synthesis of cobalt-oxide (Co3O4) supported cobalt-sulfide (CoS) composite for oxygen evolution reaction

Development of electrocatalysts has received great attention for storage and energy conversion technologies. Different electrocatalysts for oxygen evolution reaction (OER) have been produced and investigated but their role is not sufficient to mark of Ruthenium oxide (RuO2). Therefore, it is global requirement to produce an efficient, lower cost and earth-abundant electrocatalyst for OER. Herein, cobalt oxide-cobalt sulfide (Co3O4-CoS2) composite have been synthesized via hydrothermal chemical method with active performance OER. The desired overpotential is 280 mV to achieve current density of 20 mA cm-2 of as prepared composite with Tafel slope value of 74 mV dec-1 . As prepared Co3O4-CoS2 composite has efficient stability of 30 hours for long term electrochemical performance.

Cobalt Single Atom Incorporated in Ruthenium Oxide Sphere: A Robust Bifunctional Electrocatalyst for HER and OER

AbstractThe development of highly active and stable bifunctional noble‐metal‐based electrocatalysts for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) is a crucial goal for clean and renewable energy, which still remains challenging. Herein, we report an efficient and stable catalyst comprising a Co single atom incorporated in an RuO2 sphere for HER and OER, in which the Co single atom in the RuO2 sphere was confirmed by XAS, AC‐STEM, and DFT. This tailoring strategy uses a Co single atom to modify the electronic structures of the surrounding Ru atoms and thereby remarkably elevates the electrocatalytic activities. The catalyst requires ultralow overpotentials, 45 mV for HER and 200 mV for OER, to deliver a current density of 10 mA cm−2. The theoretical calculations reveal that the energy barriers for HER and OER are lowered after incorporation of a cobalt single atom.