Synergistic Interaction between Ruthenium Catalysts and Grafted Niobium on SBA-15 for 2,5-Furandicarboxylic Acid Production Using 5-Hydroxymethylfurfural

This study entailed the synthesis of Ru nanocatalyst decorated on Nb-grafted SBA-15. A Nb-grafted SBA-15 support with varying Nb contents was utilized as a support for the Ru nanoparticles. The effect of Nb grafting on the immobilized Ru nanoparticle catalyst was systematically investigated, and its catalytic performance in the synthesis of furandicarboxylic acid using 5-hydroxymethylfurfural under base-free reaction conditions was evaluated. The results indicate the increased productivity of the Ru@Nb-grafted SBA-15 catalyst with a yield exceeding 95%, representing a significant advancement in catalysis. This study also affords insights into the complex relationship between the catalytic activity and selectivity and its unique surface attributes. Moreover, acidic sites were created, and the electron density within the active sites was modulated by monomeric Nb oxide species on the SBA-15. Additionally, the role of high-electron-density Ru atoms in facilitating the efficient adsorption and activation of the reactant, resulting in enhanced catalytic efficacy, was highlighted.

Highly Efficient Ru-Based Catalysts for Lactic Acid Conversion to Alanine

The primary objective of this research was to develop efficient solid catalysts that can directly convert the lactic acid (LA) obtained from lignocellulosic biomass into alanine (AL) through a reductive amination process. To achieve this, various catalysts based on ruthenium were synthesized using different carriers such as multi-walled carbon nanotubes (MWCNTs), beta-zeolite, and magnetic nanoparticles (MNPs). Among these catalysts, Ru/MNP demonstrated a remarkable yield of 74.0% for alanine at a temperature of 200 °C. This yield was found to be superior not only to the Ru/CNT (55.7%) and Ru/BEA (6.6%) catalysts but also to most of the previously reported catalysts. The characterization of the catalysts and their catalytic results revealed that metallic ruthenium nanoparticles, which were highly dispersed on the external surface of the magnetic carrier, significantly enhanced the catalyst's ability for dehydrogenation. Additionally, the -NH2 basic sites on the catalyst further facilitated the formation of alanine by promoting the adsorption of acidic reactants. Furthermore, the catalyst could be easily separated using an external magnetic field and exhibited the potential for multiple reuses without any significant loss in its catalytic performance. These practical advantages further enhance its appeal for applications in the reductive amination of lactic acid to alanine.

Catalytic Hydrogenation of CO2 to Formate Using Ruthenium Nanoparticles Immobilized on Supported Ionic Liquid Phases

Ruthenium nanoparticles (NPs) immobilized on imidazolium-based supported ionic liquid phases (Ru@SILP) act as effective heterogeneous catalysts for the hydrogenation of carbon dioxide (CO₂ ) to formate in a mixture of water and triethylamine (NEt₃ ). The structure of the imidazolium-based molecular modifiers is varied systematically regarding side chain functionality (neutral, basic, and acidic) and anion to assess the influence of the IL-type environment on the NPs synthesis and catalytic properties. The resulting Ru@SILP materials contain well-dispersed Ru NPs with diameters in the range 0.8-2.9 nm that are found 2 to 10 times more active for CO₂ hydrogenation than a reference Ru@SiO₂ catalyst under identical conditions. Introduction of sulfonic acid groups in the IL modifiers results in a greatly increased turnover number (TON) and turnover frequency (TOF) at reduced metal loadings. As a result, excellent productivity with TONs up to 16 100 at an initial TOF of 1430 h^-1 can be achieved with the Ru@SILP(SO₃ H-OAc) catalyst. H/D exchange and other control experiments suggest an accelerated desorption of the formate species from the Ru NPs promoted by the presence of ammonium sulfonate species on Ru@SILP(SO₃ H-X) materials, resulting in enhanced catalyst activity and productivity.

Nanoscaled and Atomic Ruthenium Electrocatalysts Confined Inside Super-Hydrophilic Carbon Nanofibers for Efficient Hydrogen Evolution Reaction

A series of Ru-based catalysts have been developed for the hydrogen evolution reaction (HER) by the facile impregnation of copious and eco-friendly bacterial cellulose (BC) with Ru(bpy)₃ Cl₂ (bpy = 2,2'-bipyridine) followed by pyrolysis. After the oxidation and molecular recomposition processes that occur within the BC precursors during pyrolysis, sub-2 nm Ru nanoparticles (NPs) and atomic Ru species confined within surface-oxidized N-doped carbon nanofibers (CNFs) can be observed in the derived catalysts. The surface oxidation of CNFs leads the derived catalysts with super hydrophilicity and water-absorbing capacity, and also provides dimensional confinement for the nanoscaled and atomic Ru species. With these added structural advantages and the component synergy, the derived catalysts show superior HER activities, for which the overpotentials are as low as 19.6 mV (1 m KOH) and 55.0 mV (0.5 m H₂ SO₄ ) for the most active case at the current density of 10 mA cm^-2 . Moreover, superior HER activity can be also achieved for the catalysts derived with a wide range of Ru loadings. Finally, the influence of Ru NP size on HER activity is investigated by density functional theory simulations. This method provides a reliable protocol for preparing highly active HER catalysts for scale-up applications.

Ru-Embedded Highly Porous Carbon Nanocubes Derived from Metal-Organic Frameworks for Catalyzing Reversible Li2O2 Formation

Rechargeable lithium-oxygen batteries (LOBs) have attracted increasing attention due to their high energy density but highly rely on the development of efficient oxygen catalysts for reversible Li₂O₂ deposition/decomposition. Herein, highly porous carbon nanocubes with a specific surface area up to 1600 m² g^-1 are synthesized and utilized to tightly anchor Ru nanoparticles for using as the oxygen-cathode catalyst in LOBs, achieving a low charge/discharge potential gap of only 0.75 V, a high total discharge capacity of 17,632 mA h g^-1, and a superb cycling performance of 550 cycles at 1000 mA g^-1. Comprehensive ex situ and operando characterizations unravel that the outstanding LOB performance is ascribed to the highly porous catalyst structure embedding rich active sites that synergistically function in reducing overpotentials, suppressing parasitic reactions, accommodating reaction products, and promoting mass and charge transportation.

Monodispersed Ruthenium Nanoparticles on Nitrogen-Doped Reduced Graphene Oxide for an Efficient Lithium-Oxygen Battery

Lithium-oxygen batteries with ultrahigh energy densities have drawn considerable attention as next-generation energy storage devices. However, their practical applications are challenged by sluggish reaction kinetics aimed at the formation/decomposition of discharge products on battery cathodes. Developing effective catalysts and understanding the fundamental catalytic mechanism are vital to improve the electrochemical performance of lithium-oxygen batteries. Here, uniformly dispersed ruthenium nanoparticles anchored on nitrogen-doped reduced graphene oxide are prepared by using an in situ pyrolysis procedure as a bifunctional catalyst for lithium-oxygen batteries. The abundance of ruthenium active sites and strong ruthenium-support interaction enable a feasible discharge product formation/decomposition route by modulating the surface adsorption of lithium superoxide intermediates and the nucleation and growth of lithium peroxide species. Benefiting from these merits, the electrode provides a drastically increased discharge capacity (17,074 mA h g^-1), a decreased charge overpotential (0.51 V), and a long-term cyclability (100 cycles at 100 mA g^-1). Our observations reveal the significance of the dispersion and coordination of metal catalysts, shedding light on the rational design of efficient catalysts for future lithium-oxygen batteries.

Study of the Photothermal Catalytic Mechanism of CO2 Reduction to CH4 by Ruthenium Nanoparticles Supported on Titanate Nanotubes

The Sabatier reaction could be a key tool for the future of the renewable energy field due to the potential of this reaction to produce either fuels or to stabilize H₂ in the form of stable chemicals. For this purpose, a new composite made of ruthenium oxide nanoparticles (NPs) deposited on titanate nanotubes (TiNTs) was tested. Titanate nanotubes are a robust semiconductor with a one-dimensional (1D) morphology that results in a high contact area making this material suitable for photocatalysis. Small ruthenium nanoparticles (1.5 nm) were deposited on TiNTs at different ratios by Na⁺-to-Ru³⁺ ion exchanges followed by calcination. These samples were tested varying light power and temperature conditions to study the reaction mechanism during catalysis. Methanation of CO₂ catalyzed by Ru/TiNT composite exhibit photonic and thermic contributions, and their ratios vary with temperature and light intensity. The synthesized composite achieved a production rate of 12.4 mmol CH₄·g_cat⁻¹·h⁻¹ equivalent to 110.7 mmol of CH₄·g_Ru⁻¹·h⁻¹ under 150 mW/cm² simulated sunlight irradiation at 210 °C. It was found that photo-response derives either from Ru nanoparticle excitation in the visible (VIS) and near-infrared (NIR) region (photothermal and plasmon excitation mechanism) or from TiNT excitation in the ultraviolet (UV) region leading to electron–hole separation and photoinduced electron transfer.

Photochemically Synthesized Ruthenium Nanoparticle-Decorated Carbon-Dot Nanochains: An Efficient Catalyst for Synergistic Redox Reactions

Ruthenium nanoparticle (NP)-decorated carbon dots (Ru/C-dots) were fabricated as a potential catalyst in the application of both oxidation and reduction. The photochemical method was used to synthesize Ru/C-dot nanohybrids. The as-prepared Ru/C-dots exhibited a core-shell-based nanochain structure, in which the spherical nature of C-dots further evolved to a layer structure to homogeneously encapsulate Ru NPs. Such Ru/C-dots have excellent catalytic properties, which were demonstrated in the oxidation of flavonoids and concomitantly reduction of inorganic complex and organic dyes, each yielding a high catalytic rate constant. We also proposed an appropriate catalytic mechanism for each reaction. Higher catalytic activity was achieved by the synergistic effect of the encapsulated Ru NPs and the C-dots layer. Further, this nanohybrid was successfully applied to inspect a real aqueous sample. We anticipated that Ru/C-dots nanohybrid may open up a broad platform for the design of efficient multifunctional catalysts.

High-Performance Ru@C4N Electrocatalyst for Hydrogen Evolution Reaction in Both Acidic and Alkaline Solutions

We report a high-performance Ru@C₄N electrocatalyst for the hydrogen evolution reaction (HER) in both acidic and alkaline solutions. This catalyst is synthesized by annealing a complex of a covalent organic framework compound coordinated with ruthenium synthesized by a "one-pot" solvothermal method. This Ru@C₄N catalyst shows excellent electrocatalytic activity toward the hydrogen evolution reaction (HER) in both acidic and alkaline solutions with very low overpotentials at 10 mA/cm² (6 mV in 0.5 M H₂SO₄ solution; 7 mV in 1.0 M KOH solution), which outperforms the commercial catalyst Pt/C. The Ru@C₄N electrocatalyst also exhibits high HER turnover frequencies of 0.93 H₂ per s in 0.5 M H₂SO₄ and 0.65 H₂ per s in 1.0 M KOH solutions at 25 mV as well as superior performance stability.

Light-Induced Thermal Gradients in Ruthenium Catalysts Significantly Enhance Ammonia Production

Industrial scale catalytic chemical synthesis demands both high reaction rates and high product yields. In exothermic chemical reactions, these conflicting objectives require a complex balance of optimized catalysts, high temperatures, high pressures, and multiple recycling steps, as in the energy-intensive Haber-Bosch process for ammonia synthesis. Here we report that illumination of a conventional ruthenium-based catalyst produces ammonia with high reaction rates and high conversion yields. Indeed, using continuous wave light-emitting diodes that simulate concentrated solar illumination, ammonia is copiously produced without any external heating or elevated pressures. The possibility of nonthermal plasmonic effects are excluded by carefully comparing the catalytic activity under direct and indirect illumination. Instead, thermal gradients, created and controlled by photothermal heating of the illuminated catalyst surface, are shown to be responsible for the high reaction rates and conversion yields. This nonisothermal environment enhances both by balancing the conflicting requirements of kinetics and thermodynamics, heralding the use of optically controlled thermal gradients as a universal, scalable strategy for the catalysis of many exothermic chemical reactions.

Indirect CO2 Methanation: Hydrogenolysis of Cyclic Carbonates Catalyzed by Ru-Modified Zeolite Produces Methane and Diols

We report a ruthenium-modified zeolite which efficiently transforms propylene carbonate to propylene glycol and methane, under solvent-free conditions. The catalyst achieved high product selectivity and no significant ageing effect was observed after multiple cycles. The resulting liquid product (water-containing glycol) can be directly used as anti-freeze solution and the gas phase can directly be used as an energy carrier in the form of H₂ -enriched methane. This process efficiently bridges energy storage and an important chemical synthesis under sustainable (CO₂ consuming) conditions.

Atomic Layer Deposition of Ruthenium Nanoparticles on Electrospun Carbon Nanofibers: A Highly Efficient Nanocatalyst for the Hydrolytic Dehydrogenation of Methylamine Borane

We report the fabrication of a novel and highly active nanocatalyst system comprising electrospun carbon nanofiber (CNF)-supported ruthenium nanoparticles (NPs) (Ru@CNF), which can reproducibly be prepared by the ozone-assisted atomic layer deposition (ALD) of Ru NPs on electrospun CNFs. Polyacrylonitrile (PAN) was electropsun into bead-free one-dimensional (1D) nanofibers by electrospinning. The electrospun PAN nanofibers were converted into well-defined 1D CNFs by a two-step carbonization process. We took advantage of an ozone-assisted ALD technique to uniformly decorate the CNF support by highly monodisperse Ru NPs of 3.4 ± 0.4 nm size. The Ru@CNF nanocatalyst system catalyzes the hydrolytic dehydrogenation of methylamine borane (CH₃NH₂BH₃), which has been considered as one of the attractive materials for the efficient chemical hydrogen storage, with a record turnover frequency of 563 mol H₂/mol Ru × min and an excellent conversion (>99%) under air at room temperature with the activation energy ( E_a) of 30.1 kJ/mol. Moreover, Ru@CNF demonstrated remarkable reusability performance and conserved 72% of its inherent catalytic activity even at the fifth recycle.

Carbon-Quantum-Dots-Loaded Ruthenium Nanoparticles as an Efficient Electrocatalyst for Hydrogen Production in Alkaline Media

Highly active, stable, and cheap Pt-free catalysts for the hydrogen evolution reaction (HER) are facing increasing demand as a result of their potential use in future energy-conversion systems. However, the development of HER electrocatalysts with Pt-like or even superior activity, in particular ones that can function under alkaline conditions, remains a significant challenge. Here, the synthesis of a novel carbon-loaded ruthenium nanoparticle electrocatalyst (Ru@CQDs) for the HER, using carbon quantum dots (CQDs), is reported. Electrochemical tests reveal that, even under extremely alkaline conditions (1 m KOH), the as-formed Ru@CQDs exhibits excellent catalytic behavior with an onset overpotential of 0 mV, a Tafel slope of 47 mV decade^-1 , and good durability. Most importantly, it only requires an overpotential of 10 mV to achieve the current density of 10 mA cm^-2 . Such catalytic characteristics are superior to the current commercial Pt/C and most noble metals, non-noble metals, and nonmetallic catalysts under basic conditions. These findings open a new field for the application of CQDs and add to the growing family of metal@CQDs with high HER performance.

Nanoceria-Supported Ruthenium(0) Nanoparticles: Highly Active and Stable Catalysts for Hydrogen Evolution from Water

Ruthenium(0) nanoparticles supported on nanoceria (Ru⁰/CeO₂) were prepared by reduction of Ru³⁺ ions on the surface of ceria using aqueous solution of NaBH₄. The Ru⁰/CeO₂ samples were characterized by advanced analytical tools and employed as electrocatalysts on the glassy carbon electrode (GCE) in hydrogen evolution from water. The GCE, modified by Ru⁰/CeO₂ (1.86 wt % Ru), provides an incredible electrocatalytic activity with a high exchange current density of 0.67 mA·cm^-2, low overpotential of 47 mV at j = 10 mA·cm^-2, and small Tafel slope of 41 mV·dec^-1. Moreover, this modified GCE provides an unprecedented long-term stability without changing the onset potential (33 mV) even after 10 000 scans in acidic water splitting at room temperature. The hydrogen gas, evolved during the water splitting using the Ru⁰/CeO₂ (1.86 wt % Ru) electrocatalyst, was also collected. The amount of the evolved H₂ gas matches well with the calculated value, which indicates the achievement of nearly 100% Faradaic efficiency.

Pompon-like RuNPs-Based Theranostic Nanocarrier System with Stable Photoacoustic Imaging Characteristic for Accurate Tumor Detection and Efficient Phototherapy Guidance

Even though numerous therapeutic methods exist for cancer treatment, many fail to achieve ideal outcomes or have severe side effects. Here, we describe a theranostic nanocarrier system with improved tumor vasculature detection and tumor margin quantification that increases the accuracy and guidance efficiency of phototherapy. Novel pompon-like RuNPs with superb photothermal properties and high encapsulation efficiency were first synthesized via the polyol reducing method. Based on these RuNPs, we then developed a multifunctional theranostic system, pRu-pNIPAM@RBT, composed of poly(N-isopropylacrylamide) as the thermal-response switch and of [Ru(bpy)₂(tip)]²⁺ as the photosensitizer of PDT and the contrast agent of biomedical imaging. We demonstrate that the pRu-pNIPAM@RBT can generate intracellular hyperthermia and reactive oxygen species (ROS) for simultaneous photothermal therapy (PTT) and photodynamic therapy (PDT) by laser activation. In contrast to other studies, our work highlights the integration of quantitative analysis of infrared thermal imaging and PA imaging data, which can distinguish between tumor and healthy tissues and guide the destructive but precise phototherapy and decrease nonspecific tissue injury. Considering the excellent in vivo antitumor phototherapeutic effects, this strategy may help preclinical researchers gain insight into theoretical as well as practical aspects of precision cancer therapy.

Improving the Anticancer Efficacy of Laminin Receptor-Specific Therapeutic Ruthenium Nanoparticles (RuBB-Loaded EGCG-RuNPs) via ROS-Dependent Apoptosis in SMMC-7721 Cells

Functionalization can promote the uptake of nanoparticles into cancer cells via receptor-mediated endocytosis, enabling them to exert their therapeutic effects. In this paper, epigallocatechin gallate (EGCG), which has a high binding affinity to 67 kDa laminin receptor (67LR) overexpressed in HCC cells, was employed in the present study to functionalized ruthenium nanoparticles (RuNPs) loaded with luminescent ruthenium complexes to achieve antiliver cancer efficacy. [Ru(bpy)2(4-B)] (ClO4)2·2H2O (RuBB)-loaded EGCG-RuNPs (bpy = 2,2'-bipyridine) showed small particle size with narrow distribution, better stability, and high selectivity between liver cancer and normal cells. The internalization of RuBB-loaded EGCG-RuNPs was inhibited by 67LR-blocking antibody or laminin, suggesting that 67LR-mediated endocytosis played an important role in the uptake into HCC cells. Moreover, transmission electron microscopy and confocal microscopic images showed that RuBB-loaded EGCG-RuNPs accumulated in the cytoplasm of SMMC-7721 cells. Furthermore, our results indicated that the EGCG-functionalized nanoparticles displayed enhanced anticancer effects in a target-specific manner. Concentrations of RuBB-loaded EGCG-RuNPs, nontoxic in normal L-02 cells, showed direct reactive oxygen species-dependent cytotoxic, pro-apoptotic, and anti-invasive effects in SMMC-7721 cells. Furthermore, in vivo animal study demonstrated that RuBB-loaded EGCG-RuNPs possessed high antitumor efficacy on tumor-bearing nude mice. It is encouraging to conclude that the multifunctional RuNPs may form the basis of new strategies on the treatment of liver cancer and other malignancies.

Hydrogenation of Carbon Dioxide to Methane by Ruthenium Nanoparticles in Ionic Liquid

The efficient transformation of carbon dioxide into fuels can be an excellent alternative to sequestration. In this work, we describe CO2 hydrogenation to methane in imidazolium-based ionic liquid media, using ruthenium nanoparticles prepared in situ as catalyst. The best yield of methane (69 %) was achieved using 0.24 mol % ruthenium catalyst (in [omim][NTf2 ], 1-octyl-3-methylimidazolium bistrifluoromethanesulfonylimide, at 40 bar of hydrogen pressure plus 40 bar of CO2 pressure, and at 150 °C.

Dihydrogen Phosphate Stabilized Ruthenium(0) Nanoparticles: Efficient Nanocatalyst for The Hydrolysis of Ammonia-Borane at Room Temperature

Intensive efforts have been devoted to the development of new materials for safe and efficient hydrogen storage. Among them, ammonia-borane appears to be a promising candidate due to its high gravimetric hydrogen storage capacity. Ammonia-borane can release hydrogen on hydrolysis in aqueous solution under mild conditions in the presence of a suitable catalyst. Herein, we report the synthesis of ruthenium(0) nanoparticles stabilized by dihydrogenphosphate anions with an average particle size of 2.9 ± 0.9 nm acting as a water-dispersible nanocatalyst in the hydrolysis of ammonia-borane. They provide an initial turnover frequency (TOF) value of 80 min⁻¹ in hydrogen generation from the hydrolysis of ammonia-borane at room temperature. Moreover, the high stability of these ruthenium(0) nanoparticles makes them long-lived and reusable nanocatalysts for the hydrolysis of ammonia-borane. They provide 56,800 total turnovers and retain ~80% of their initial activity even at the fifth catalytic run in the hydrolysis of ammonia-borane at room temperature.

Highly active metastable ruthenium nanoparticles for hydrogen production through the catalytic hydrolysis of ammonia borane

Late transition metal nanoparticles (NPs) with a favorably high surface area to volume ratio have garnered much interest for catalytic applications. Yet, these NPs are prone to aggregation in solution, which has been mitigated through attachment of surface ligands, additives or supports; unfortunately, protective ligands can severely reduce the effective surface area on the NPs available for catalyzing chemical transformations. The preparation of 'metastable' NPs can readily address these challenges. We report herein the first synthesis of monodisperse metastable ruthenium nanoparticles (RuNPs), having sub 5 nm size and an fcc structure, in aqueous media at room temperature, which can be stored for a period of at least 8 months. The RuNPs can subsequently be used for the catalytic, quantitative hydrolysis of ammonia-borane (AB) yielding hydrogen gas with 21.8 turnovers per min at 25 °C. The high surface area available for hydrolysis of AB on the metastable RuNPs translated to an Ea of 27.5 kJ mol(-1) , which is notably lower than previously reported values for RuNP based catalysts.