Ru Catalysts Research Articles

A hybrid Au/Ru catalyst for sequential alkyne hydration/asymmetric transfer hydrogenation reactions

A hybrid catalytic system was developed for sequential alkyne hydration/asymmetric transfer hydrogenation reactions through the confinement of an amphiphilic polymer supported ruthenium and gold catalysts within core/shell silica gel.

Coupling between two Ru(bda) catalysts bridged by a trans-dicyano complex.

We have prepared two trimetallic complexes [{Ru(bda)(DMSO)(μ-CN)}2Ru(L)4] (with bda = 2,2'-bipyridine-6,6'-dicarboxylate) where two {Ru(bda)} centers are bridged by a cyanide complex of the trans-Ru(L)4CN2 family (with L = pyridine and 4-tert-butylpyridine). The complex [{Ru(bda)(DMSO)(μ-CN)}2Ru(py)4] is fully soluble in aqueous solution and is a catalyst for the oxidation of water both chemically, using Ce(IV) at pH = 1 as the terminal oxidant, and electrochemically. Both reactions are first order in the complex and the resting state of the catalyst is the [RuVRuIII(py)4RuIV]2+ redox state. Electrochemical and spectroelectrochemical studies together with (TD)DFT calculations show that the coupling between the Ru(bda) fragments for the [RuIIIRuII(py)4RuIII]2+ and [RuIVRuII(py)4RuIV]2+ redox states is very weak, but significant for the [RuVRuII(py)4RuIV]2+ ion due to the orientation of the orbitals involved. This coupling affects the reactivity of the [RuVRuII(py)4RuIV]2+ redox state, making it a much slower catalyst towards the water oxidation reaction than [RuVRuIII(py)4RuIV]2+.

Harnessing reductive BF2-complexation via Ru(II)-catalyzed N-O cleavage of isoxazoles.

Developed here is a highly fluorescent organic N,O bidentate BF2 complex from isoxazole in the presence of a Ru(II) catalyst. Herein, the complexation proceeds via a selective N-O cleavage of the isoxazole ring. The complex shows absorption (λmax,abs) in the range of 352-363 nm with an extinction coefficient (ε) in the range of 8000-64 000 M-1 cm-1, and fluorescence emission (λmax,em) in the range of 413-485 nm with a Stokes shift of 61-125 nm having quantum yield up to 33%. Apart from the solution state, the solid BF2 complex 2u exhibits absorption at 405 nm and strong fluorescence emission at 550 nm with a quantum yield of 26.9%.

Flexible design in controllable synthesis of Ru catalyst toward enzymatic and electrochemical hydrogen peroxide performance

Ru amorphous structure is synthesized in an ice-bath atmosphere with acceptable catalytic performance in electrochemical detection and POD-like activity. Physical HIFU induced amorphous to crystalline state with an enhancement in catalytic performance.

Interfacial modulation of Ru catalysts using B, N co-doped porous carbon-confined MoC quantum dots for enhanced hydrogen evolution reaction performance

B, N-doped porous carbon confined MoC quantum dots were engineered as a facile carrier and electronic stimulator to confine Ru clusters for high-performance hydrogen evolution reaction.

Ru nanoparticle-loaded amorphous CoMoP as an efficient electrocatalyst for alkaline water/seawater hydrogen evolution

A low-cost carrier is developed and the size of Ru nanoparticles is reduced to enhance the performance of Ru catalysts used in the hydrogen evolution reaction (HER).

Influences of Ru and ZrO2 interaction on the hydroesterification of styrene.

Interfacial Lewis acid-base pairs are commonly found in ZrO2-supported metal catalysts due to the facile generation of oxygen vacancies of ZrO2. These pairs have been reported to play a crucial role in olefin hydroesterification, especially in the absence of acid promoters and ligands. In this study, a series of ZrO2-supported Ru catalysts with ruthenium(iii) chloride and ruthenium(iii) acetylacetonate as precursors were prepared for the styrene hydroesterification. The catalysts were thoroughly characterized by TPR, TEM, EPR, XPS, and FTIR. The Ru precursors significantly influenced the size and electronic properties of Ru clusters, albeit having minimal impact on oxygen vacancies. Mechanistic studies of styrene hydroesterification over ZrO2-supported Ru catalysts revealed that the carbon monoxide insertion followed the hydrogen transfer step to activated styrene. Higher activity is exhibited over ZrO2-supported Ru catalysts prepared with ruthenium(iii) chloride as a precursor, attributed to the lower adsorption strength of CO over Ru clusters, as evidenced by FTIR and DFT calculations.

Selective methanation of CO over HZSM-5 supported Ni and Ni–Ru catalysts

Under the synergistic effect of acid sites and active metal sites, Ni/HZSM-5 and Ni–Ru/HZSM-5 performed excellent CO removal properties and CO methanation selectivity.

Direct amination of poly(p-phenylene oxide) to substituted anilines over bimetallic Pd–Ru catalysts

We demonstrate a novel route for the upcycling of poly(phenylene oxide) (PPO) into dimethylanilines using a bimetallic Pd7Ru3/CNT catalyst. This represents the first successful transformation of PPO into nitrogen-containing compounds.

Reversible hydrogen spillover at the atomic interface for efficient alkaline hydrogen evolution

Ru1–Mo2C, a novel dual-site synergistic catalyst, demonstrated exceptional performance for the alkaline hydrogen evolution reaction (HER) through a reversible hydrogen spillover mechanism.

Construction of Cu–Ru bimetallic catalyst for the selective catalytic transfer hydrogenation of carbonyl (C[dbnd]O) in biomass-derived compounds

The catalytic transfer hydrogenation (CTH) of levulinate ester to γ-valerolactone is one of the important reactions for production of renewable fuels from biomass. An efficient and robust bimetallic Cu–Ru catalyst were developed for the hydrogenation of biomass-derived ethyl levulinate to γ-valerolactone. A series of bimetallic catalysts were prepared and characterized in detail. Subsequently, the as-prepared catalysts were evaluated in the hydrogenation system of ethyl levulinate. The results showed that Cu–Ru/ZrO2–SO3–SiO2-450 catalyst provided 100 % GVL yield in 12 h at 180 °C. Meanwhile, it also exhibited high catalytic hydrogenation activity for the various biomass-derived carbonyl compounds. The structure-reactivity relationship of catalysts was investigated in detail, and the results show the interaction between support and metal sites played an important role in the hydrogenation activity. The sulfur species could tune the electronic states of metallic sites to gain optimal activity. Besides, the Cu–Ru/ZrO2–SO3–SiO2-450 catalyst performed excellent recyclability in five reaction runs without an obvious loss of activity.

Catalytic oxidation of propane over nanorod-like TiO2 supported Ru catalysts: Structure-activity dependence and mechanistic insights

Nanorod-like titanium dioxide (TiO2-Rod) supported ruthenium catalysts with variable metal loadings (designated as x-Ru/TiO2-Rod, x = 0.1, 0.5, 1.0 and 1.5 wt.%) were prepared for the catalytic oxidation of propane. The unique nanorod-like structure and high specific surface area of TiO2-Rod support was favorable for the surface distribution of ruthenium nanoparticles, constructing highly active redox sites for propane oxidation. Light-off experimental results indicated that the x-Ru/TiO2-Rod catalysts exhibited diverse catalytic activities for propane oxidation, giving a volcanic sequence of 0.1-Ru/TiO2-Rod < 0.5-Ru/TiO2-Rod < 1.5-Ru/TiO2-Rod < 1.0-Ru/TiO2-Rod with the increasing ruthenium content. Additionally, the optimal 1.0-Ru/TiO2-Rod delivered adequate catalytic stability and CO2/water resistant ability under complex industrial conditions. Characterization results revealed that the metallic Ru0 and the surface lattice oxygen species from the Ru-TiO2 interface were demonstrated to be the catalytic active components, which played an essential role in the reaction. In situ DRIFTs analysis verified the formation of acetate, acetone and formate species as the predominant organic intermediates in propane oxidation, which may result from two plausible reaction pathways depending on the activation of terminal methyl group (–CH3) and the central methylene (CH2) group in propane molecule. This work provides fundamental guidance for the development of Ru-based catalysts and the reaction mechanism understanding for light alkanes oxidation.

Enhanced ruthenium selectivity for the conversion of FAMEs to diesel-range alkanes by surface decoration of FeOx species

Ruthenium-based catalysts have been widely used in the lignin depolymerization and polystyrene hydrogenolysis reactions due to its superior hydrogenolysis activity for C-O and C-C bonds. However, serious cleavage of C-C bonds at high temperatures greatly limits its application in the production of green biodiesel from the conversion of natural oils and bio-derived fatty esters. In this work, we found that introducing a suitable second less-reactive metal (e.g., Fe, Zn) can effectively suppress the hydrogenolysis activity of ruthenium (Ru) metal for C-C bonds and exhibit a high selectivity (>90 %) to diesel-range alkanes (C15-C18 alkanes) in the conversion of fatty acid methyl esters (FAMEs) even at high reaction temperature (250 °C) over the Ru1Fe0.5 catalyst, while an obvious cracking reaction was observed from 210 °C over the monometallic Ru catalyst. Detailed characterization and theoretical calculation results reveal that the introduction of Fe species in the RuFe catalysts weakens the interaction between catalyst and the resulting alkanes, which inhibits the cracking of alkanes. Specifically, adding Fe species breaks the ensemble of Ru atoms and decreases the binding affinity of metallic Ru for H2, which suppresses the activity of Ru metal for the hydrogenolysis of C-C bonds and exhibits a high selectivity to diesel-range alkanes. This research provides valuable information for improving the hydrodeoxygenation (HDO) selectivity of Ru-based catalysts while inhibiting its high hydrogenolysis activity for C-C bonds.

Performance of a Small PEMFC Stack Operated with CO/H2 Mixtures

Hydrogen produced by reforming processes may include sulfur (S),carbon monoxide (CO) and other impurities.. Presence of ppm level impurities in hydrogen may adsorp onto Pt catalyst and lower performance and lifetime. There are efforts to overcome cost and performance issues by reducing Pt amount and utilizing new catalyst and support materials, more tolerant to CO. Ru catalyst are often added to oxidize CO before poisoning Pt. Ti0.7Mo0.3O2 was investigated as an alternative support material for anode catalyst. It has been shown that the stoichiometric ratio between Ti and Mo have significant impact on the CO tolerance. Ti0.8Mo0.2O2 was synthesized and used as anode electrode in PEM fuel cell testing. In this paper, titanium/molybdenum alloy on carbon (Ti0.8Mo0.2O2-C) is evaluated as catalyst support to prevent performance decay by CO poisoning. 3-cell stack was developed and tested for performance and degradation issues. Cell hardware with 15 cm2 active area was used for fuel cell measurements. Cathode was loaded with 0.6 mgPt/cm2 (20 wt.% Pt/C) and anode with 0.5 mgPt/cm2 (40 wt.% Pt/Ti0.8Mo0.2O2-C) onto Sigracet 29BC GDL by painting. Bipolar plates for single cell and stack were designed using Solid Works. End plates, anode bipolar plate and cathode bipolar plate with cooling channels on the other surfaces were designed and produced from graphite composite in-house. Seals from silicon was also designed and produced in-house. MEA had active area of 15 cm2. Figure 1 shows stack formation with all components put together in order. Stack was conditioned under 100% humidified hydrogen. There was no effect of stack orientation on performance. Performance for 2-cell stack was better going from atmospheric pressure to 2 bar. When polarization was 0.6V, pressurized operation provided improvement in current density going from 1300 mA/cm2 (no pressure) to 2000 mA/cm2 (15 psig). When this 2-cell stack was subjected to different concentrations of CO, polarization values of Figure 2 was obtained. Increasing concentration of CO caused decrease in current densities. Utilizing a DC/DC converter, stack has provided power to charge a cell phone. More details will be shared for 2, 3 cell stack operation under CO conditions. Figure 1

Highly Stable and Active Ru Clusters Supported on Boron Carbon Nitride for Acidic Water Oxidation

In recent years, metal oxides, such as IrO2, have been widely used in proton exchange membrane water electrolysis (PEMWE) because of their excellent catalytic activity and long-term stability [1]. However the high price and scarcity of these catalysts were not enough to meet the requirements of PEMWE [2]. Therefore, it is significant to explore novel electrochemically active, stable, and low-cost catalysts.In this paper, a uniformly dispersed Ru confined on boron carbon nitride support was synthesized and studied. The surface chemical states of Ru were tuned by the interaction between Ru and the active N in boron carbon nitrogen (BCN), forming a highly stable Ru-N bond. Benefiting from a graphene-like structure, the BCN-0.5Ru catalyst exhibited greater conductivity than RuO2. The strong interaction between Ru and the BCN support also allowed for accelerated charge transfer at the electrode interface.Transmission electron microscopy (TEM) investigations revealed that Ru clusters were uniformly dispersed on BCN (Figure 1a), and the particle size distributions (Figure 1b) showed that the Ru clusters possessed an average particle size of 4 nm. It suggests that the Ru nanoclusters on the BCN support had small particle sizes and a narrow particle size distribution. These results demonstrated that the BCN support helped disperse the Ru metal nanoclusters more homogeneously than what occurred when RuO2 was prepared via direct RuCl3 annealing. The electrochemical performance of oxygen evolution reaction (OER) for BCN-xRu catalysts in O2-saturated 0.5 M H2SO4 solution was evaluated. The BCN-0.5Ru catalyst demonstrates a low overpotential of 164 mV at a current density of 10 mA cm–2 and remains stable for 12 h in acidic electrolyte (Figure 1c). In contrast, RuO2 without any support fails in only 1 h (Figure 1c). We propose that the surface chemical states of Ru supported by BCN may play an important role in enhancing stability. This study provides insights into designing and synthesizing high-performance electrocatalysts for acidic OER.

Tungsten Oxide-Based Materials as Catalyst Support for Oxygen Evolution Reaction

The high cost of iridium (Ir) is a major concern for the large scale deployment of polymer electrolyte membrane water electrolysis (PEMWE). To mitigate its impact, the usage of Ir on the anode must be significantly reduced. Down-sizing the catalyst particle is a straight forward strategy but requires the use of appropriate support materials to disperse and anchor fine Ir nanoparticles. We have investigated the use of tungsten oxide-based materials as support for the oxygen evolution reaction (OER) Ir and ruthenium (Ru) catalyst. The synthesis of nanostructured substoichiometric tungsten oxide and the subsequent loading of ultrafine Ir/Ru-based nanoparticles is thoroughly studied. Due to the successful loading, the mass activity of the tungsten oxide-supported Ir/Ru-based catalyst shows significant improvements under rotating disk electrode (RDE) conditions compared with commercially available Ir/Ru-blacks. Furthermore, non-destructive depth profiling by synchrotron-based X-ray photoelectron spectroscopy (XPS) has revealed the strong catalyst-support interaction which suppressed the oxidation of the supported Ir/Ru-based catalysts, leading to much enhanced durability under accelerated durability testing conditions. To verify its performance under practical PEM electrolysis conditions, the tungsten oxide-supported OER catalyst is directly coated onto a polymer electrolyte membrane, i.e., forming a catalyst coated membrane (CCM), and tested under single cell testing conditions without pressure differential. The voltage dependent chemical state of the supported catalyst is also probed in-situ by synchrotron-based XPS where a potential dependent electron transfer between the catalyst and tungsten-oxide support is discovered. Our discovery is anticipated to aid the development of cost effective PEM electrolysis anodes.

Regulating the Electronic Structure of IrO x /SnO y with NaCl for Efficient Proton Exchange Membrane Water Electrolysis

Hydrogen has been considered as a promising energy carrier because of its high gravimetric energy density. However, most hydrogen has been produced by steam methane reforming, which releases significant amounts of CO2 during the process. In contrast, water electrolysis (WE) offers the most sustainable way to produce hydrogen without carbon emissions. Especially, proton exchange membrane water electrolysis (PEMWE) technique has attracted much attention due to its high efficiency, compact design, and fast response to load fluctuations, enabling the integration of renewable energy. However, the inevitable use of precious metal (Ir, Ru) catalyst due to the sluggish kinetics of oxygen evolution reaction (OER) has hindered the practical implementation of PEMWE. In this regard, developing low-content Ir-based catalysts with high activity is critical for enhancing the cost efficiency of PEMWE. This presentation will propose a synthesis strategy for tin oxide-supported iridium oxide (IrO x /SnO y _NaCl) catalyst prepared using NaCl as a sacrificial template. This approach allows uniform dispersion of Ir particles and regulation of its valence states to favor the OER. The synthesized IrO x /SnO y _NaCl catalyst exhibited high OER activity and mass activity comparable to the state-of-the-art Ir-based OER catalysts. Electrochemical and X-ray spectroscopic analyses demonstrated that the use of NaCl template can improve the catalytic activity of IrO x by tuning the valence state ratio (Ir3+/Ir4+). Moreover, IrO x /SnO y _NaCl catalyst showed a high single-cell performance of PEMWE, achieving mass activity 2.6 times higher than commercial IrO2.

Ru Perovskites with Enhanced Activity and Durability for the OER in Acid Media

Iridium- and Ruthenium based catalysts are the only feasible ones for the oxygen evolution reaction (OER) in acidic media. The high price and scarcity of Ir is a major hurdle to realize electrolysis in the GW-scale. Ru-based catalysts can be suitable candidates to replace Ir, since they are more active for the OER than Ir. However, Ru catalysts lack sufficient stability during the OER. This is because, Ru tends to form soluble upper oxides e.g. RuO4 at high voltages (> 1.4 V). Previous studies reveal that Na- or K-doping can increase Ru’s durability during the OER.1,2 However, recent studies demonstrate that Ru’s activity and stability depends on the structure and composition of the Ru-based catalyst.3 In this work, we report a series of Ru double perovskites, namely R2NiRuO6 (R = Pr, Nd, Tb, Dy, Y, Ho and Er)4 with low ruthenium content and high OER activity in acidic electrolyte. The oxides have been synthesized by wet-chemistry and thoroughly characterized by XRD (Rietveld refinement), TEM and XPS.The OER was studied in the rotating ring disk (RDE) configuration in 0.1 M HClO4. Due to the absence of Sr or alkali metals in their structure, in addition to displaying high initial OER activity, the perovskites are stable during OER cycles between 1.1 and 1.7 V, with Dy2NiRuO6 being stable at least during 500 consecutive cycles (see Figures 1a and 1b).Characterization results reveal that Ru-O distances in the perovskites follow the order Dy<Er<Y<Ho<Tb<Nd<Pr. As shown in Figure 1c, the OER activity, i.e., the potential recorded at 10 mA·cm-2, follows the same trend. Also, the durability of the catalysts follows the same trend.The smaller Ru-O distance indicates a higher oxidation state of Ru atoms in Dy2NiRuO6. In addition, the gives symmetry and order to the structure. perovskite, making it more stableXPS and TEM-EDS post-mortem studies of Dy2NiRuO6 reveal a loss of Ni after 500 OER cycles and the presence of Ru3+ cations, being the main cause of the loss of OER activity.The R2NiRuO6 double perovskites reported in this work are the first example of highly active and stable Ru-based perovskites for the OER in acidic electrolyte that can opens the way for the replacement of Ir from state of the art PEMWEs.(1) Retuerto, M.; Pascual, L.; Calle-Vallejo, F.; Ferrer, P.; Gianolio, D.; Pereira, A. G.; García, Á.; Torrero, J.; Fernández-Díaz, M. T.; Bencok, P.; Peña, M. A.; Fierro, J. L. G.; Rojas, S. Na-Doped Ruthenium Perovskite Electrocatalysts with Improved Oxygen Evolution Activity and Durability in Acidic Media. Nat. Commun. 2019, 10 (1), 2041. https://doi.org/10.1038/s41467-019-09791-w.(2) Rodríguez-García, I.; Galyamin, D.; Pascual, L.; Ferrer, P.; Peña, M. A.; Grinter, D.; Held, G.; Abdel Salam, M.; Mokhtar, M.; Narasimharao, K.; Retuerto, M.; Rojas, S. Enhanced Stability of SrRuO3 Mixed Oxide via Monovalent Doping in Sr1-XKxRuO3 for the Oxygen Evolution Reaction. J. Power Sources 2022, 521, 230950. https://doi.org/10.1016/j.jpowsour.2021.230950.(3) Paoli, E. A.; Masini, F.; Frydendal, R.; Deiana, D.; Malacrida, P.; Hansen, T. W.; Chorkendorff, I.; Stephens, I. E. L. Fine-Tuning the Activity of Oxygen Evolution Catalysts: The Effect of Oxidation Pre-Treatment on Size-Selected Ru Nanoparticles. Catal. Today 2016, 262, 57–64. https://doi.org/10.1016/j.cattod.2015.10.005.(4) Kayser, P.; Alonso, J. A.; Muñoz, A.; Fernández-Díaz, M. T. Structural and Magnetic Characterization of the Double Perovskites R2NiRuO6 (R = Pr-Er): A Neutron Diffraction Study. Acta Mater. 2017, 126, 114–123. https://doi.org/10.1016/j.actamat.2016.12.024. Figure 1

Nb2AlC MAX Nanosheets Supported Ru Nanocrystals as Efficient Catalysts for Boosting pH-Universal Hydrogen Production.

MAX phase combines both ceramic and metallic properties, which exhibits widespread application prospects. 2D MAX nanosheets have more abundant surface-active sites, being anticipated to improve the performance of surface-related applications. Herein, for the first time, 2D Nb2AlC nanosheets (NSs) as novel supports anchored with Ru catalysts for overall water splitting are developed. The optimized catalyst of Ru@Nb2AlC NSs exhibit Pt-comparable kinetics and superior catalytic activity toward hydrogen evolution reaction (HER) (low overpotentials of 61 and 169mV at 10 and 100mAcm-2, respectively) with excellent durability (5000 cycles or 80h) in alkaline media. In particular, Ru@Nb2AlC NSs achieve a mass activity of ≈4.8 times larger than the commercial Pt/C (20wt.%) catalyst. The post-oxidation resultant catalyst of RuO2@Nb2AlC NSs also exhibit boosting HER and oxygen evolution reaction activities and ≈100% Faraday efficiency for overall water splitting with a cell voltage of 1.61V to achieve 10mAcm-2. Therefore, the novel category of 2D MAX supports anchored with Ru nanocrystals offers a novel strategy for designing a wide range of MAX-supported metal catalysts for the renewable energy field.

Interplay between surface structure, reaction condition and mechanism for ammonia decomposition on Ru catalyst

Ammonia decomposition provides a potential route for the production of COx-free hydrogen. Despite numerous studies, the active sites and reaction mechanism remain in debate. To date, only N-N recombination mechanism, in which N2* is formed by the N* atoms recombination, is investigated on the archetypical Ru catalyst and Ru B5 site has been identified as the active site. Combined density functional theory calculation and microkinetic modeling, we show that the N2Hy* (y > 0) dehydrogenation mechanism, which involves the stepwise N2Hy* dehydrogenation to N2*, is important and even dominant on Ru defect sites at low temperatures, elevated PNH3 or PH2 where the coverage of vacant sites is low so that the NHx (x = 1–3) dehydrogenation is suppressed. Regardless of reaction conditions, Ru A4 and kink sites show higher activity than the conventional B5 site, with the rate-determining steps of NH3 adsorption and H2 desorption. Inhibition of the ammonia decomposition rate by the hydrogen produced originates from the low dissociation barrier of hydrogen. This work reveals the interplay between surface structure, reaction condition and mechanism for ammonia decomposition on Ru catalyst, and the insights can enrich the design principles of catalysts for the ammonia decomposition and other important reactions of technological interest.