Ru Clusters Research Articles

Polyaniline-coated Ru/Ni(OH)2 nanosheets for hydrogen evolution reaction over a wide pH range

How to improve the performance of ruthenium (Ru)–based catalysts for hydrogen evolution reaction (HER) to replace Pt is an interesting topic. Here, we in situ synthesize a polyaniline (PANI)-coated ultralow Ru-doped Ni(OH)2 nanosheet (RuNi-NSs@PANI) in a 3D integral electrode via a facile dissolution–precipitation strategy and electrodeposition. Results indicate that RuNi-NSs@PANI has a small overpotential of 21.9 mV at a current density of 10 mA cm−2 and a low Tafel slope of 38.54 mV dec−1 in alkaline condition, which is comparable with that of 20% Pt/C. The outstanding performance is attributed to the synergistic effects of the Ru-doped 2D Ni(OH)2 structure, active metallic Ru cluster, PANI coating and 3D integrated Ni electrode. Owing to PANI coating, RuNi-NSs@PANI shows excellent durability with the increase of 36.8% current density retention (from 52.2% for RuNi-NSs increasing to 89% for RuNi-NSs@PANI) compared to the RuNi-NSs sample without PANI coating in strong acidic medium, because the PANI coating could keep H+ from cracking the catalyst structure and therefore enhance the stability. In short, this work indicates that RuNi-NSs@PANI composite is an excellent wide pH range HER catalyst.

Properties of Negatively Charged Ruthenium Clusters in Molten Sodium Chloride

Negatively charged ruthenium clusters dispersed in molten NaCl are studied with density functional theory and molecular dynamics. The Ru clusters are charged by adding additional Na atoms to the mo...

Ruthenium Diphosphine Closo-C2B9-Carborane Clusters with Nitrile Ligands: Synthesis and Structure Determination

The interaction of 3,3-(Ph2P(CH2)4PPh2)-3-H-3-Cl-closo-3,1,2-RuC2B9H11 (1) with isopropylamine and corresponding nitrile (NCR) in dichloromethane at 40 °C yields carborane clusters of Ru(II) with nitrile ligand [3,3-(Ph2P(CH2)4PPh2)-3-NCR-closo-3,1,2-RuC2B9H11] (R = –Ph, –CH=CH2). A similar ortho-cycloboronated clusters [3-NCR-3,3,8-{(Ph2P(CH2)4PPh-μ-(C6H4-ortho)}closo-3,1,2-RuC2B9H10] were obtained from the corresponding chlorine-containing ruthenacarboranes. The novel clusters were isolated as yellow crystal solids and characterized by NMR, mass-spectroscopy and X-ray analysis. The reaction of the obtained clusters with HCl showed the chemical reversibility of dehydrohalogenation. The performed electrochemical investigation testified the ability of novel complexes to undergo reversible oxidation to Ru(III) species.

Mechanochemical Synthesis of Ruthenium Cluster@Ordered Mesoporous Carbon Catalysts by Synergetic Dual Templates.

Ruthenium (Ru)@Ordered mesoporous carbon (OMC) is a key catalyst in fine-chemical production. In general, the OMC support is prepared by a wet self-assembly requiring excessive solvent, toxic phenol-aldehyde precursors and a long reaction time, followed by post-immobilization to load Ru species. Herein, we wish to report a solid-state, rapid, and green strategy for the synthesis of Ru@OMC with biomass tannin as the precursor. The chemistry essence of this strategy lies in the mechanical-force-driven assembly, during which tannin-metal (Zn2+ and Ru3+ ) coordination polymerization and hydrogen-bonding interactions between tannin-block copolymer (PEO-PPO-PEO, F127) simultaneously occur. After thermal treatment, Ru@OMC catalysts with mesoporous channels, narrow pore-size distribution (≈7 nm), and high surface area (up to 779 m2 g-1 ) were directed by F127 micelles. Meanwhile, the Zn2+ ions dilute Ru3+ and avoid the sintering of Ru species, resulting in Ru clusters around 1.4-1.7 nm during carbonization (800 °C). Moreover, the Ru@OMC catalyst afforded a good activity (TOF: up to 4170 h-1 ) in the selective oxidation of benzyl alcohol to benzaldehyde by molecular oxygen.

Mechanochemically Assisted Synthesis of Ruthenium Clusters Embedded in Mesoporous Carbon for an Efficient Hydrogen Evolution Reaction

AbstractRuthenium (Ru) clusters are reported as efficient electrocatalysts for the hydrogen evolution reaction (HER). However, a precise and facile synthetic protocol for preparing Ru clusters is still a challenge. Herein, a facile mechanochemically assisted strategy was proposed to synthesize ruthenium clusters embedded in mesoporous carbon (Ru‐CN/MC). Importantly, for the synthesis of Ru‐CN/MC, melamine was utilized not only as a capping agent to stabilize Ru clusters, but also to provide N sites for the carbon support. The well‐designed Ru‐CN/MC exhibits impressive HER performance in 1 M KOH, which shows an extremely low overpotential of 17 mV at a current density of 10 mA cm−2. More importantly, excellent long‐term electrochemical stability in both alkaline and acid electrolyte was achieved for Ru‐CN/MC. Therefore, the developed synthesis method for Ru clusters and the subsequent insightful investigations on the HER performance shed light on new opportunities for exploring highly efficient and renewable HER electrocatalysts.

Synergetic Effect of Ultrasmall Metal Clusters and Zeolites Promoting Hydrogen Generation.

Taking advantage of the synergetic effect of confined ultrasmall metal clusters and zeolite frameworks is an efficient strategy for improving the catalytic performance of metal nanocatalysts. Herein, it is demonstrated that the synergetic effect of ultrasmall ruthenium (Ru) clusters and intrinsic Brønsted acidity of zeolite frameworks can significantly promote the hydrogen generation of ammonia borane (AB) hydrolysis. Ultrasmall Ru clusters are embedded onto the silicoaluminophosphate SAPO‐34 (CHA) and various aluminosilicate zeolites (MFI, *BEA, and FAU) with tunable acidities by a facile incipient wetness impregnation method. Evidenced by high‐resolution scanning transmission electron microscopy, the sub‐nanometric Ru clusters are uniformly distributed throughout the zeolite crystals. The X‐ray absorption spectroscopy measurements reveal the existence of Ru‐H species between Ru clusters and adjacent Brønsted acid sites of zeolites, which could synergistically activate AB and water molecules, significantly enhancing the hydrogen evolution rate of AB hydrolysis. Notably, the Ru/SAPO‐34‐0.8Si (Si/Al = 0.8) and Ru/FAU (Si/Al = 30) catalysts with strong acidities afford high turnover frequency values up to 490 and 627 min−1, respectively. These values are more than a 13‐fold enhancement than that of the commercial Ru/C catalyst, and among the top level over other heterogeneous catalysts tested under similar conditions.

A universal synthesis strategy for single atom dispersed cobalt/metal clusters heterostructure boosting hydrogen evolution catalysis at all pH values

The development of a stable, efficient and economic catalyst for hydrogen evolution reaction (HER) of water splitting is one of the most hopeful approaches to confront the environmental and energy crisis. A two-step method is employed to obtain metal clusters (Ru, Pt, Pd etc.) combining single cobalt atoms anchored on nitrogen-doped carbon (Ru/Pt/Pd@Co-SAs/N-C). Based on the synergistic effect between Ru clusters and single cobalt atoms, Ru@Co-SAs/N-C exhibits an outstanding HER electrocatalytic activity. Specifically, Ru@Co-SAs/N-C only needs 7 mV overpotential at 10 mA cm-2 in 1 M KOH solution, which is much better than commercial 20 wt% Pt/C (40 mV) catalyst. Density functional theory (DFT) calculations further reveal the synergy effect between surface Ru nanoclusters and Co-SAs/N-C toward hydrogen adsorption for HER. Additionally, Ru@Co-SAs/N-C also exhibits excellent catalytic ability and durability under acidic and neutral media. The present study opens a new avenue towards the design of metal clusters/single cobalt atoms heterostructures with outstanding performance toward HER and beyond.

An organometallic ruthenium nanocluster with conjugated aromatic ligand skeleton for explosive sensing

Abstract 9-Ethynylphenanthrene (EPT) bound to highly monodispersed Ruthenium (Ru) nanocluster (Ru:EPT) with mean diameter of \(1.5\pm 0.2\,\hbox {nm}\) and mol wt. of \({\sim }\)8600 Da was synthesized via a facile and high yield biphasic ligand exchange protocol using similar sized ethylene glycol (EG)-stabilized Ru clusters (Ru:EG) as precursor. The synthesized organometallic nanocluster was meticulously analyzed to understand its size distribution, oxidation state, crystallinity, optical and luminescence behavior and metal–ligand interfacial structure. Contrary to the extensive quenching of ligand emission by metalcore as usually observed, the ruthenium core here acts as a conductor, which conjugates surface ligands with strong emission property courtesy to an unusual vinylidene-binding motif. Thus, the synthesized nanocluster shows good luminescence property (\(\upphi = \,{\sim }\, 7\%\)) originated from the ligand skeleton and the spherical metal core restricts lateral overlap of phenanthrene moiety to cause any excimer emission. This nanocluster showed high sensitivity for solution phase detection of nitroaromatic explosives through luminescence quenching method (\(\hbox {K}_{\mathrm{SV}}\) up to \(4.98 \times 10^{4}\,\hbox {M}^{-1})\) and mimic the mechanism like conjugated organic polymer. We propose that dynamic \(\uppi -\uppi \) interaction between Ru bound phenanthrene moiety and nitroaromatic compounds followed by photoinduced electron transfer (PET), as well as Förster Resonance Energy Transfer (FRET), are the possible mechanisms behind this luminescence quenching.Graphical abstract SYNOPSIS An organometallic ruthenium nanocluster with \(\sim 8.6 \hbox { kDa mol. wt. }\) was synthesized, where aromatic phenanthrene ligands were inter-molecularly conjugated through Ru core. The Ru nanocluster showed excellent sensing performance for detection of nitroaromatic explosive molecules through luminescence quenching strategy.

Nanoporous Carbon: Liquid-Free Synthesis and Geometry-Dependent Catalytic Performance.

Nanostructured carbons with different pore geometries are prepared with a liquid-free nanocasting method. The method uses gases instead of liquid to disperse carbon precursors, leach templates, and remove impurities, minimizing synthetic procedures and the use of chemicals. The method is universal and demonstrated by the synthesis of 12 different porous carbons with various template sources. The effects of pore geometries in catalysis can be isolated and investigated. Two of the resulted materials with different pore geometries are studied as supports for Ru clusters in the hydrogenolysis of 5-hydroxymethylfurfural (HMF) and electrochemical hydrogen evolution (HER). The porous carbon-supported Ru catalysts outperform commercial ones in both reactions. It was found that Ru on bottleneck pore carbon shows a highest yield in hydrogenolysis of HMF to 2,5-dimethylfuran (DMF) due to a better confinement effect. A wide temperature operation window from 110 to 140 °C, with over 75% yield and 98% selectivity of DMF, has been achieved. Tubular pores enable fast charge transfer in electrochemical HER, requiring only 16 mV overpotential to reach current density of 10 mA·cm-2.

Boosting hydrogen evolution activity in alkaline media with dispersed ruthenium clusters in NiCo-layered double hydroxide

Herein, we report a hybrid electrocatalyst consisting of Ru clusters trapped in NiCo-layered double hydroxide (NiCo-LDH) as the basis for an efficient hydrogen evolution reaction (HER) in alkaline media. Benefiting from the fast water dissociation kinetics on NiCo-LDH and favorable H recombination on Ru, the resultant Ru-NiCo-LDH shows an extremely low HER overpotential of 28 mV at a current density of 10 mA cm−2 with a small Tafel slope of 42 mV dec−1. This superior catalytic activity can be ascribed to its high charge transfer ability and to the synergistic effect of the highly dispersed Ru and the NiCo-LDH. Moreover, we also found that the oxidized Ru incorporated in NiCo-LDH was entirely reduced to Ru0 under hydrogen-evolution conditions, which suggests that Ru0 is the true catalytically active phase responsible for the outstanding HER performance.

Mechanistic details of C[sbnd]O bond activation in and H-addition to guaiacol at water-Ru cluster interfaces

Catalytic pathways of guaiacol and hydrogen (H2) reactions on dispersed Ru clusters in the aqueous medium and the associated kinetic requirements for COCH3 bond cleavage and H-addition steps are established based on kinetic and isotopic investigations. Time-dependent kinetic measurements in a gradientless semi-batch reactor reveal that guaiacol reacts with H2 via two independent routes of COCH3 bond cleavage and H-addition; the former leads to phenol, cyclohexanone, cyclohexanol, and cyclohexane and latter to 2-methoxy-cyclohexanol. During catalysis, an adsorbed guaiacol undergoes a single, quasi-equilibrated H-adatom (H*) addition on its aromatic ring, forming a partially-hydrogenated intermediate, before the sequential kinetically relevant COCH3 cleavage or H* addition steps on Ru cluster surfaces nearly saturated with deprotonated guaiacol. Increasing the H* coverage promotes the overall turnovers but decreases the selectivity towards the COCH3 bond cleavage, because H* addition event not only activates guaiacol but also promotes H-addition without breaking its CO bond.

New molecular architectures containing low-valent cluster centres with di- and trimetalated 2-vinylpyrazine ligands: synthesis and molecular structures of Ru5(CO)15(μ5-C4H2N2CH[double bond, length as m-dash]CH)(μ-H)2 and Ru8(CO)24(μ7-C4H2N2CH[double bond, length as m-dash]C)(μ-H)3.

Reaction of 2-vinylpyrazine with Ru3(CO)12 results in multiple C–H bond activations to afford penta- and octa-ruthenium clusters, Ru5(CO)15(μ5-C4H2N2CHCH)(μ-H)2 (2) and Ru8(CO)24(μ7-C4H2N2CHC)(μ-H)3 (3), in which a Ru3 sub-unit is linked to Ru2 and Ru5 centres via di- and tri-metalated 2-vinylpyrazine ligands, exhibiting novel coordination modes including the loss of ring aromaticity in 2. The bonding of 2 and the mechanism for the fluxional behaviour of the hydrides have been examined by electronic structure calculations.

MoS2 Polymorphic Engineering Enhances Selectivity in the Electrochemical Reduction of Nitrogen to Ammonia

The electrochemical N2 reduction reaction (NRR) offers a direct pathway to produce NH3 from renewable energy. However, aqueous NRR suffers from both low Faradaic efficiency (FE) and low yield rate. The main reason is the more favored H+ reduction to H2 in aqueous electrolytes. Here we demonstrate a highly selective Ru/MoS2 NRR catalyst on which the MoS2 polymorphs can be controlled to suppress H+ reduction. A NRR FE as high as 17.6% and NH3 yield rate of 1.14 × 10–10 mol cm–2 s–1 are demonstrated at 50 °C. Theoretical evidence supports a hypothesis that the high NRR activity originates from the synergistic interplay between the Ru clusters as N2 binding sites and nearby isolated S-vacancies on the 2H-MoS2 as centers for hydrogenation; this supports formation of NH3 at the Ru/2H-MoS2 interface.

Transformation of a μ3-Benzyne Ligand into Phenol on a Cationic Triruthenium Cluster Supported by a μ3-Sulfido Ligand

A triruthenium complex containing μ3-η2(||)-benzyne and μ3-sulfido ligands, [(Cp*Ru)3(μ3-S){μ3-η2(||)-C6H4}(μ-H)] (2), was synthesized by the reaction of [(Cp*Ru)3(μ3-S)(μ-H)3] (1) with benzene. Although 2 was stable toward oxygen and water, two-electron oxidation of 2 with a Ag(I) salt in the presence of water afforded the dicationic μ-hydroxo complex [(Cp*Ru)3(μ3-S){μ3-η2(||)-C6H4}(μ-OH)]2+ (3). Treatment of 3 with amine resulted in the deprotonation of the μ-hydroxo ligand, and an unsaturated monocationic complex, [(Cp*Ru)3(μ3-S)(μ3-OC6H4-κO,κC)]+ (4), which possesses a μ3-cyclohexadienonediyl ligand, was formed via reductive C–O bond formation between the μ3-benzyne and transient μ-oxo ligands. Phenol was extruded from the Ru3 cluster upon the hydrogenation of 4 via the formation of a μ3-phenoxo complex, [(Cp*Ru)3(μ3-S){μ3-OPh}(μ-H)]+ (5). The cyclic voltammogram of 2 shows two reversible one-electron redox waves, and a dicationic μ3-benzyne complex, [(Cp*Ru)3(μ3-S){μ3-η2:η2(⊥)-C6H4}(μ-H)]2+(8), was s...

The coordination and activation of azobenzene by Ru5(μ5-C) cluster complexes

The reaction of Ru5(μ5-C)(CO)15, 1 with azobenzene, PhN = NPh, yielded the pentaruthenium carbido cluster compound Ru5C(CO)13(C6H4N=NC6H5)[μ-H], 4 containing a chelating ortho-metalated azobenzene ligand on one of the ruthenium atoms in a opened square-pyramidal Ru5C cluster. Compound 4 is electronically unsaturated and it readily adds one CO ligand at 25 °C to yield the electronically saturated complex Ru5C(CO)14(C6H4N=NC6H5)[μ-H], 5. Ru5C(CO)13(μ-η2-Ph)[μ-Au(NHC)], 3 reacts with azobenzene to yield the azobenzene complex Ru5C(CO)13(μ−η2−PhN = NPh)(η1−Ph)[μ−Au(NHC)], 6, NHC = 1,3-bis(2,6-diisopropylphenyl-imidazole-2ylidene), which contains a novel bridging di-σ-η2-N,N-coordinated azobenzene ligand across an open edge of an Ru5C cluster. Compound 6 eliminated benzene and was transformed to the new compound Ru5C(CO)13(C6H4N=NC6H5)[μ−Au(NHC)], 7 when heated to 105 °C for 3 h. Compound 7 is similar to 4 except that it has an Au(NHC) group in the place of the bridging hydrido ligand in 4. Compound 7 is also formally electronically unsaturated like 4. All of the new compounds were characterized by single-crystal X-ray diffraction analyses. The structures, bonding and reactivity of the complexes are discussed.

Energy‐Efficient Nitrogen Reduction to Ammonia at Low Overpotential in Aqueous Electrolyte under Ambient Conditions

AbstractInvited for this month's cover is the group of Prof. Douglas R. MacFarlane at Monash University. The Cover picture depicts the electrocatalytic synthesis of ammonia on Ru clusters supported on carbon. The Full Paper itself is available at 10.1002/cssc.201801632.

CH activations in aldehydes in reactions with Ru5(μ5-C)(CO)15

The reaction of Ru5(μ5-C)(CO)15, 1 with benzaldehyde yielded two new pentaruthenium carbido cluster compounds: Ru5(μ5-C)(CO)14[η2-O=C(H)C6H4](μ-H), 2 and Ru5(μ5-C)(CO)14(μ-η2-O=CPh)(μ-H), 3 containing open Ru5C cluster complexes formed by the activation of two different C-H bonds of the benzaldehyde molecule. Compound 2 contains a chelating, ortho-metallated benzaldehyde ligand coordinated to an open Ru5C cluster that is coordinated by the aldehyde oxygen atom and one of the ortho-positioned carbon atoms of the phenyl ring that was formed by loss of a CO ligand and an oxidative addition of the ortho-C-H bond of the phenyl ring to the metal atom. Compound 3 is an isomer of 2 that contains an O=C-coordinated, η2-bridging benzoyl ligand across the open edge of the Ru5C cluster formed by C-H activation at the aldehyde formyl group. The reaction of 1 with trans-cinnamaldehyde yielded two complexes: Ru5(μ5-C)(CO)14[η2-O=C(H)CH=CPh](μ-H), 4 and Ru5(μ5-C)(CO)14[μ-η2-O=CC(H) = C(H)Ph](μ-H), 5. Compound 4 contains an open Ru5 cluster with a chelating cinnamoyl ligand formed by coordination of the aldehyde oxygen atom and the β–carbon atom of the alkene double bond formed by a C-H activation at the alkene atom. Compound 5 contains a η2-bridging, O=C coordinated cinnamoyl group formed by C-H activation at the aldehyde formyl group. The reactions of 1 with furfural and 5-hydroxymethylfurfural yielded similar complexes: Ru5(μ5-C)(CO)14(μ-η2-O=CC4OH3)(μ-H), 6 and Ru5(μ5-C)(CO)14[μ-η2-O=CC4OH2(CH2OH)](μ-H), 7, respectively with each one containing bridging, O=C coordinated acyl ligand formed by C-H activation at the aldehyde formyl group. All of the new compounds were characterized by single-crystal X-ray diffraction analyses.

Catalyst Screening and Development for HI Decomposition in Sulfur-iodine Thermochemical Cycle for Hydrogen Production

The intrinsic activities of six important transition metals for HI decomposition were identified by kinetic study. Ru showed high activity and a low apparent activation barrier, indicating a good activity at low temperature. Ru/AC (Ru clusters supported on activated carbon) was designed and proved to be a highly active, cost-effective, and long-term durable catalyst for HI decomposition. The present work could contribute to catalyst development for the industrialization of the sulfur-iodine thermochemical cycle for hydrogen production.

Electronic Structure-Reactivity Relationship on Ruthenium Step-Edge Sites from Carbonyl 13C Chemical Shift Analysis.

Ru nanoparticles are highly active catalysts for the Fischer-Tropsch and the Haber-Bosch processes. They show various types of surface sites upon CO adsorption according to NMR spectroscopy. Compared to terminal and bridging η1 adsorption modes on terraces or edges, little is known about side-on η2 CO species coordinated to B5 or B6 step-edges, the proposed active sites for CO and N2 cleavage. By using solid-state NMR and DFT calculations, we analyze 13C chemical shift tensors (CSTs) of carbonyl ligands on the molecular cluster model for Ru nanoparticles, Ru6(η2-μ4-CO)2(CO)13(η6-C6Me6), and show that, contrary to η1 carbonyls, the CST principal components parallel to the C-O bond are extremely deshielded in the η2 species due to the population of the C-O π* antibonding orbital, which weakens the bond prior to dissociation. The carbonyl CST is thus an indicator of the reactivity of both Ru clusters and Ru nanoparticles step-edge sites toward C-O bond cleavage.

Dissolution Induced Self-Selective Zn- and Ru-Doped TiO2 Structure for Electrochemical Generation of KClO3

We demonstrate an electrochemical approach to prepare a highly active and stable (Zn, Ru)-doped TiO2 (Ru0.26Ti0.73Zn0.01Ox) for electrochemical generation of KClO3. The essential ingredients of this approach consists of (1) co-electrodeposition of Ru, Ti and Zn as metallic alloy and then annealing it to oxide (2) dissolution under electrochemically oxidative acidic environment of Ru and Zn-rich surface clusters having high selectivity towards oxygen evolution reaction (OER) leaving Ti-enriched structure that is more selective to chlorine evolution reaction (CER) and (3) using this electrocatalyst for KClO3 production under near-neutral pH conditions. Dissolution of Ru- and Zn enriched surfaces result in porous structure with higher electrochemical surface area and roughness. Furthermore, this electrochemical dissolution of (Zn, Ru)-rich surface results in electrocatalytic structure that is self-selective towards KClO3 formation with higher specific activity. The co-electrodeposition of Zn aids (1) the formation of roughened and porous surface structure through surface dissolution of Zn- or ZnO clusters and (2) the enhancement of conductivity of electrocatalyst through formation of oxygen vacancies. The obtained structure has been found to show higher specific activity, activity and stability towards KClO3 production in comparison to untreated (Zn, Ru)-doped TiO2 or Ru-doped TiO2 or RuO2.