Ru Atoms Research Articles

Quantitative study on Ru local atomic structure in Ni-Al-Ru ternary alloys

The synchrotron radiation X-ray absorption fine structure (XAFS) technique is used to study the local structure of the key atom Ru in a series of Ni-Al-Ru ternary alloys with different Ru contents and heat treatments. All the investigated alloys consist of two phases, γ and γ', and especially Ru exists as an atom coordinated by 12 Ni atoms in the first shell without Ru clusters or intermetallic compounds. In γ phase Ru resides on the Ni lattice site introducing an outward relaxation of the neighboring atoms, while in the γ' phase Ru replaces the Al lattice site causing an inward relaxation. The interatomic distance of Ru–Ni bond and Debye-Waller factor are mainly affected by the composition and increase with the increasing Ru content. While the effect of heat treatment is obvious when the Ru content is higher than 6 at%. The variation of Ru local atomic structure can greatly influence the microstructural evaluation and deformation mechanism by changing the lattice misfit and the vacancy formation energy to control the creep properties of Ni-Ru-Al ternary alloys.

Ultrasmall Ruthenium Nanoparticles with Boosted Antioxidant Activity Upregulate Regulatory T Cells for Highly Efficient Liver Injury Therapy.

Nanozymes exhibiting antioxidant activity are beneficial for the treatment of oxidative stress-associated diseases. Ruthenium nanoparticles (RuNPs) with multiple enzyme-like activities have attracted growing attention, but the relatively low antioxidant enzyme-like activities hinder their practical biomedical applications. Here, a size regulation strategy is presented to significantly boost the antioxidant enzyme-like activities of RuNPs. It is found that as the size of RuNPs decreases to ≈2.0nm (sRuNP), the surface-oxidized Ru atoms become dominant, thus possessing an unprecedentedly boosted antioxidant activity as compared to medium-sized (≈3.9nm) or large-sized counterparts (≈5.9nm) that are mainly composed of surface metallic Ru atoms. Notably, based on their antioxidant enzyme-like activities and ultrasmall size, sRuNP can not only sustainably ameliorate oxidative stress but also upregulate regulatory T cells in late-stage acetaminophen (APAP)-induced liver injury (ALI). Consequently, sRuNPs perform highly efficient therapeutic efficiency on ALI mice even when treated at 6h after APAP intoxication. This strategy is insightful for tuning the catalytic performances of nanozymes for their extensive biomedical applications.

Biaxially Compressive Strain in Ni/Ru Core/Shell Nanoplates Boosts Li-CO2 Batteries.

Regulating surface strain of nanomaterials is an effective strategy to manipulate the activity of catalysts, yet not well recognized in rechargeable Li-CO2 batteries. Herein, biaxially compressive strained nickel/ruthenium core/shell hexagonal nanoplates (Ni/Ru HNPs) with lattice compression of ≈5.1% and ≈3.2% in the Ru {10-10} and (0002) facets are developed as advanced catalysts for Li-CO2 batteries. It is demonstrated that tuning the electronic structure of Ru shell through biaxially compressive strain engineering can boost the kinetically sluggish CO2 reduction and evolution reactions, thus achieving a high-performance Li-CO2 battery with low charge platform/overpotential (3.75V/0.88V) and ultralong cycling life (120 cycles at 200mA g-1 with a fixed capacity of 1000 mAh g-1 ). Density functional theory calculations reveal that the biaxially compressive strain can downshift the d-band center of surface Ru atoms and thus weaken the binding of CO2 molecules, which is energetically beneficial for the nucleation and decomposition of Li2 CO3 crystals during the discharge and charge processes. This study confirms that strain engineering, though constructing a well-defined core/shell structure, is a promising strategy to improve the inherent catalytic activity of Ru-based materials in Li-CO2 batteries.

Metal-Decorated Phthalocyanine Monolayer as a Potential Gas Sensing Material for Phosgene: A First-Principles Study.

Research into a gas sensing material with excellent performance to detect or remove toxic phosgene (COCl2) is of great significance to environmental and biological protection. In the present work, the adsorption performance of COCl2 on pristine phthalocyanine (Pc) and metal-decorated Pc (MePc, Me = Cu, Ga, and Ru) monolayers was studied by first-principles calculations. The results show that the absorption process of COCl2 on pristine Pc and CuPc both belong to physisorption, indicating that they are not suitable gas sensing materials for COCl2. When Pc sheets are decorated by Ga and Ru atoms, the adsorption of COCl2 is changed into chemisorption, and the corresponding adsorption energies are −0.57 and −0.50 eV for GaPc and RuPc, respectively. The microcosmic mechanism between COCl2 and adsorbents (GaPc, RuPc) was clarified by the analysis of the density of states, the charge density difference, and the Hirshfeld charge. In addition, the COCl2 adsorption results in a significant conductivity variation of the RuPc monolayer, demonstrating it exhibits a high sensitivity to the COCl2 molecule. Meanwhile, quick desorption processes were noticed at various temperatures for the COCl2/RuPc system. Consequently, the RuPc monolayer can be considered as a potential candidate for phosgene sensors because of the moderate adsorption strength, high sensitivity, and fast desorption speed.

Platinum-Ruthenium Single Atom Alloy as a Bifunctional Electrocatalyst toward Methanol and Hydrogen Oxidation Reactions.

The precise regulation for the structural properties of nanomaterials at the atomic scale is an effective strategy to develop high-performance catalysts. Herein, a facile dual-regulation approach was developed to successfully synthesize Ru1Ptn single atom alloy (SAA) with atomic Ru dispersed in Pt nanocrystals. High-angle annular dark-field scanning transmission electron microscopy and X-ray absorption fine structure demonstrated that Ru atoms were dispersed in Pt nanocrystals as single atoms. Impressively, the Ru1Ptn-SAA exhibited an ultrahigh specific activity (23.59 mA cm-2) and mass activity (2.805 mA/μg-PtRu) for methanol oxidation reaction (MOR) and exhibited excellent exchange current density activity (1.992 mA cm-2) and mass activity (4.71 mA/μg-PtRu) for hydrogen oxidation reaction (HOR). Density functional theory calculations revealed that the introduction of Ru atoms greatly reduced the reaction free energy for the decomposition of water molecules, which promoted the removal of CO* in the MOR process and adjusted the Gibbs free energy of hydrogen and hydroxyl adsorption to promote the HOR. Our work provided an effective idea for the development of high performance electrocatalysts.

Dissociation of Bipyridine and Coordination with Nitrosyl: Cyclometalated Ruthenium Nitrosyl Complex.

A novel family of ruthenium nitrosyl complexes [Ru(bpy)(C∧N)(MeCN)NO](PF6)2 (2a-2e, bpy = 2,2'-bipyridine, HC∧N = 2-phenylpyridine and its derivatives) has been prepared by reacting cyclometalated ruthenium complexes [Ru(bpy)2(C∧N)][PF6] (1a-1e) with NO+, which were comprehensively characterized by mass, IR, NMR, and UV-vis spectra as well as the single-crystal X-ray structure determinations. Herein, the coordination geometry of Ru atoms in 2a-2e is a distorted octahedron and {RuII-NO+}6 is present in these complexes. Theoretical calculations suggest that the reactions involving dissociation of one bipyridine and coordination with NO+ proceed spontaneously (ΔG < 0) and the transformation from 1a-1e to the intermediates is dominated by substituents (ΔGRI varies from -1.19 to -1.53 eV), which influence the binding energy between Ru(II) and NO+ in complexes 2a-2e (-89.42 to -101.17 kcal/mol) and thus control the photorelease of NO on a certain scale. The weak absorption bands in the visible region could be attributed to the contribution of dπ(RuII) → π*(NO+), which were enhanced greatly under light, indicating the possible release of NO. The photoinduced NO, as well as singlet oxygen (1O2), was then confirmed by EPR spectra, and the amount of NO released from 2a-2e was estimated via Griess reagent assay. The cytotoxicity of these complexes with or without visible light irradiation was also investigated using an MTT assay.

CO2 hydrogenation: Selectivity control of CO versus CH4 achieved using Na doping over Ru/m-ZrO2 at low pressure

By doping 1%Ru/m-ZrO2 with sodium, selectivity tuning between CO and CH4 during CO2 hydrogenation was achieved by controlling the relative rates of reverse water-gas shift and CO methanation. By increasing basicity through Na loading: (1) the formate C-H bond is weakened in DRIFTS of adsorbed CO, accelerating C-H bond formation of formate and promoting CO formation at the Ru/m-ZrO2 interface; and (2) the coverage of Na increases on ensembles of Ru atoms responsible for methanation. Increasing Na content shifts selectivity from CH4 (useful for synthetic natural gas) to CO, which can be used for Fischer-Tropsch synthesis or methanol-to-gasoline. Electronic modification of formate is likely due to enhanced basicity (strengthening bonding between catalyst and the -CO2 function of formate and weakening C-H). No electron transfer from Na to Ru was detected in XANES. DRIFTS as a function of time and XPS results showed that Na exacerbates site blocking and deactivation.

Stabilizing single-atomic ruthenium by ferrous ion doped NiFe-LDH towards highly efficient and sustained water oxidation

Single-atom catalysts (SAC) possesses the potentials of developing cost-effective water splitting devices; however, the active sites tend to form high valence state and dissolve into electrolyte at the anode during long-term oxidation process, leading to severe stability issue. Herein, we anchored single atomic Ru on Fe2+ ions doped NiFe layered double hydroxides, affording a strong electronic interaction between Ru and Fe2+, which lowered the oxidation state of Ru and meanwhile enhanced the Fe-O bond strength, thus resulting in significantly improved activity and stability of both the Ru sites and NiFe-LDH substrates. With 1.32 wt% Ru loading, the Ru/NiFe2+Fe-LDH catalyst showed a low overpotential of 194 mV at 10 mA / cm2 and a small Tafel slope of 36 mV / dec, which outperformed most of the Ru and NiFe based alkaline OER catalysts reported so far. In addition, the catalyst did not show obvious performance decay and dissolution after 100 h stability test at 100 mA / cm2, attributing to the strong electronic coupling between the single atomic Ru and the NiFe2+Fe-LDH, as evidenced by the X-ray absorption spectroscopy and density function theory calculation results that Fe2+ transferred 1.54 e- to Ru.

Strongly anisotropic electronic and magnetic structures in oxide dichlorides RuOCl2 and OsOCl2

Here, using density functional theory and density matrix renormalization group methods, we investigate the electronic and magnetic properties of RuOCl$_2$ and OsOCl$_2$ with $d^4$ electronic configurations. Different from a previous study using VOI$_2$ with $d^1$ configuration, these systems with $4d^4$ or $5d^4$ do not exhibit a ferroelectric instability along the $a$-axis. Due to the fully-occupied $d_{xy}$ orbital in RuOCl$_2$ and OsOCl$_2$, the Peierls instability distortion disappears along the $b$-axis, leading to an undistorted I${\rm mmm}$ phase (No. 71). Furthermore, we observe strongly anisotropic electronic and magnetic structures along the $a$-axis. The large crystal-field splitting energy (between $d_{xz/yz}$ and $d_{xy}$ orbitals) and large hopping between nearest-neighbor Ru and Os atoms suppresses the spin-orbital effect in $M$OCl$_2$ ($M$ = Ru or Os) with electronic density $n = 4$, resulting in a spin-1 system instead of a $J = 0$ singlet ground state. Moreover, we find staggered antiferromagnetic order with $\pi$ wavevector along the $M$-O chain direction ($a$-axis) while the magnetic coupling along the $b$-axis is weak. Based on Wannier functions from first-principles calculations, we calculated the relevant hopping amplitudes and crystal-field splitting energies of the $t_{2g}$ orbitals for the Os atoms to construct a multi-orbital Hubbard model for the $M$-O chains. Staggered AFM with $\uparrow$-$\downarrow$-$\uparrow$-$\downarrow$ spin structure dominates in our DMRG calculations, in agreement with DFT calculations.

The Effect of Ru on the Evolution of the γ' Phase in Ni-Al-Ru Alloys.

With the development and wide application of nickel-based single-crystal superalloys, the effect of Ru on the microstructure stability and high-temperature properties of superalloys is becoming increasingly important. In this study, the effect of Ru on the evolution of the γ′ phase in Ni-Al-Ru ternary alloys during aging treatment was analyzed, using a scanning electron microscope and transmission electron microscope, combined with energy-dispersive spectroscopy. The relationship between chemical partition behavior and γ/γ′ lattice misfit was investigated in detail. During the aging process, Ru addition suppressed the growth rate and rafting process of γ′ precipitates, while the effect of Ru on hindering γ′ phase growth was reduced when the Ru content was over 3 at%. Ru preferentially partitioned to the γ phase, and its partitioning ratio to the γ phase increased with a variation in Ru content from 1 at% to 3 at% and decreased for the NiAl6Ru alloy. Additionally, the lattice misfit of all alloys was positive and reduced with the increase in Ru content, which hindered the Ru atoms to diffuse into the γ phase and promoted the shape of γ′ precipitates to change from cubic to spherical.

Efficient conversion of low-concentration nitrate sources into ammonia on a Ru-dispersed Cu nanowire electrocatalyst.

Electrochemically converting nitrate ions, a widely distributed nitrogen source in industrial wastewater and polluted groundwater, into ammonia represents a sustainable route for both wastewater treatment and ammonia generation. However, it is currently hindered by low catalytic activities, especially under low nitrate concentrations. Here we report a high-performance Ru-dispersed Cu nanowire catalyst that delivers an industrial-relevant nitrate reduction current of 1 A cm-2 while maintaining a high NH3 Faradaic efficiency of 93%. More importantly, this high nitrate-reduction catalytic activity enables over a 99% nitrate conversion into ammonia, from an industrial wastewater level of 2,000 ppm to a drinkable water level <50 ppm, while still maintaining an over 90% Faradaic efficiency. Coupling the nitrate reduction effluent stream with an air stripping process, we successfully obtained high purity solid NH4Cl and liquid NH3 solution products, which suggests a practical approach to convert wastewater nitrate into valuable ammonia products. Density functional theory calculations reveal that the highly dispersed Ru atoms provide active nitrate reduction sites and the surrounding Cu sites can suppress the main side reaction, the hydrogen evolution reaction.

Adsorption and Sensing for SF6 Decomposition Products by Ru–MoTe2 Monolayer

In this work, the adsorption of SF6 decomposition products (SO2, SOF2, and SO2F2) on Ru–MoTe2 monolayer is investigated based on density‐functional theory (DFT) calculations. The doping structure, band structure, adsorption structure, adsorption energy, charge transfer, density of states (DOS), and molecular orbital are analyzed to better analyze the interaction mechanism between gas molecules and Ru–MoTe2 system. In the results, it is shown that the conductivity of MoTe2 monolayer can be greatly increased by doping Ru atom. Pristine MoTe2 shows a weak adsorption capacity for SO2, SOF2, and SO2F2 gases, which belongs to physical adsorption. When Ru atom is doped on MoTe2, the adsorption capacity of the doping system for these three gases is obviously improved. The adsorption capacity of Ru–MoTe2 monolayer to the gases is ranked as SO2F2 &gt; SOF2 &gt; SO2. Moreover, the strong interaction between gas molecules and Ru–MoTe2 surfaces leads to the rise of the conductivity of all adsorption systems to varying degrees, and the degree of the rise of conductivity influenced by gas molecules is ranked as SO2F2 &gt; SO2 &gt; SOF2. Herein, a theoretical basis for the preparation of gas sensors or adsorbers based on Ru–MoTe2 is provided for detecting and absorbing SF6 decomposition products.

Phase transformation pathway and microstructural refinement by feathery transformation of Ru-containing γ-TiAl alloy

The phase transformation sequence and transition temperatures of Ti–48Al–4Nb–2Cr-0.3Ru alloy are studied by using in-situ synchrotron radiation high energy X-ray diffraction, which was confirmed as α → α+γ → α/α2+β/B2+γ. The α transus and β/B2 solvus temperatures are located at 1390 °C and 1300 °C, respectively. Significantly, the acceleration of Ru element on the precipitation of metastable massive and feathery microstructures was found for the first time. Based on that, a multi-step heat treatment consisting of homogenization treatment, cyclic air-cooling heat treatment, γ equiaxed treatment and lamella reprecipitation treatment was designed to optimize the Ti–48Al–4Nb–2Cr-0.3Ru alloy. The coarse microstructure after homogenization was refined by feathery microstructure during cyclic air-cooling heat treatment. Finally, a fine duplex microstructure with γ grain and lamellar colony sized approximately 25 μm and 40 μm, respectively, was achieved. First-principles calculation revealed that the interfacial energies can be decreased when Ru atom occupies the Al sublattice position of true twin and Σ5 coincidence site lattice boundaries, which promote the occurrence of metastable transformations. Comparing with the initial microstructure, the tensile properties of the duplex microstructure were highly improved both at room temperature and 800 °C.

Micro-tailored g-C3N4 enables Ru single-atom loading for efficient photocatalytic H2 evolution

Loading single atom (SA) cocatalysts onto semiconductors offers great potential for improving the photocatalytic performance. Here, we report a simple micro-tailoring strategy that cuts g-C3N4 into small pieces and oligomers. Defects, boundaries, dopants and terminal groups created could confine Ru SAs stably onto the framework, ensuring uniform dispersion of Ru SAs on the tailored g-C3N4. The as-prepared composite, the tailored g-C3N4 loaded with Ru SAs, showed a dramatic increase photocatalytic activity for H2 evolution (4052.1 μmol h−1 g−1) compared to the composite of the non-tailored g-C3N4 loaded with Ru (394.3 μmol h−1 g−1). The enhanced catalytic activity was achieved by the metal-support interaction between the Ru atoms and the tailored g-C3N4, which could manipulate local charge distribution, thus promoting the adsorption of intermediates and enabling efficient charge transfer. In addition, atomic Ru-sites could provide directional charge transfer channels and targeting sites to facilitate rapid photo-introduced charge transfer and water reduction reaction. The proposed strategy provides a facile and feasible way for the construction of atomically dispersed catalysts for efficient photocatalytic H2 evolution and other reactions.

Insight into the critical role of strong interaction between Ru and Co in RuCo single-atom alloy structure for significant enhancement of ammonia synthesis performance

Rational design of efficient catalysts for ammonia (NH3) synthesis at mild conditions is of paramount importance for the development of electrolysis driven Haber-Bosch (eHB) process. Ammonia synthesis is a structure sensitive reaction, and any small change of electronic structure could result in dramatic change of catalytic activity, especially for the Ru-based NH3 synthesis catalysts. Electronic structure modulation of the Ru-based catalysts could provide desirable catalytic activity. Herein, we explore a class of Ru-Co single-atom alloy catalysts (marked as RuxCo1 SAA, x stands for Ru/Co molar ratio), in which Co single atoms are located on Ru nanoclusters to form Co-Ru coordination, and then electronic structure of RuxCo1 SAA could be effectively tuned by regulating the Ru/Co molar ratio. Our studies show that a moderate ratio of Ru/Co (1.7:1) favors superior NH3 synthesis rate and low activation energy. Using a suite of elaborate characterizations, we have observed that the outstanding performance over Ru1.7Co1 SAA can be attributed to the electron redistribution between Ru and Co atom, resulting in an upshift of d band center and lowering of work function. However, there is decrease of NH3 synthesis rate when Ru/Co molar ratio is 2, due to the partial detachment of Ru entities from SAA structure, and the formed individual Ru nanoparticles (NPs) overlay the surface of catalyst. In such a case, N2 activation behavior over Ru2Co1 is alike that of Ru NPs catalysts. The present study demonstrates that the Ru/Co ratio in SAA structure can effectively regulate the electronic structure of catalyst for NH3 synthesis rate enhancement.

Performance descriptors of nanostructured metal catalysts for acetylene hydrochlorination.

Controlling the precise atomic architecture of supported metals is central to optimizing their catalytic performance, as recently exemplified for nanostructured platinum and ruthenium systems in acetylene hydrochlorination, a key process for vinyl chloride production. This opens the possibility of building on historically established activity correlations. In this study, we derived quantitative activity, selectivity and stability descriptors that account for the metal-dependent speciation and host effects observed in acetylene hydrochlorination. To achieve this, we generated a platform of Au, Pt, Ru, Ir, Rh and Pd single atoms and nanoparticles supported on different types of carbon and assessed their evolution during synthesis and under the relevant reaction conditions. Combining kinetic, transient and chemisorption analyses with modelling, we identified the acetylene adsorption energy as a speciation-sensitive activity descriptor, further determining catalyst selectivity with respect to coke formation. The stability of the different nanostructures is governed by the interplay between single atom-support interactions and chlorine affinity, promoting metal redispersion or agglomeration, respectively.

Hot-electron-induced CO2 hydrogenation on Au@AuRu/g-C3N4 plasmonic bimetal–semiconductor heterostructure

Hot-electron-induced CO2 hydrogenation is a promising pathway for solar-to-chemical energy conversion under mild conditions. Herein, we designed a unique “antenna–reactor” architecture with surface alloyed Au@AuRu plasmonic nanoparticles (NPs) loaded on g-C3N4 (Au@AuRu/g-C3N4) to achieve high-efficiency CO2 methanation under light-heat dual activation. Remarkably, Au@AuRu/g-C3N4 exhibits a high CH4 production rate (103 μmol/g/h) with 98.4% selectivity under light at 150 °C. The activity is 11 times higher than that in dark, and also 12 and 2.6 times that of Au/g-C3N4 and Au@Ru/g-C3N4, respectively. The modified Ru atoms significantly boost the H2, CO2 and CO adsorption capacity, facilitating the selective transformation of CO2 to CH4. In situ DRIFT analysis indicated that CO2 is converted to CO and then adsorbed on the metal surface for further hydrogenation to CH4. The femtosecond transient absorption spectroscopic study further reveals that the synergy between the surface structure and the metal–semiconductor heterojunction provides a longer time window for hot electrons to promote the chemical reaction. This work provides new insights for plasmonic nanostructures to efficiently activate CO2 at low temperatures.

Surface hydroxyl dependent adsorption of ruthenium on SiO2(0 0 1) – Understanding metal–support interaction

To understand the metal–support interaction of oxide supported transition metal catalysts, we computed the adsorption structures and energies of ruthenium on the idealized SiO2(001) surfaces with full (OH, 100%), partial (OH, 50%) surface hydroxyl and without surface hydroxyl (OH, 0%) at different ruthenium loading. On the fully (up to 9Ru) and partially (up to 6Ru) hydroxylated surfaces, ruthenium adsorption prefers surface O-H oxidative addition and forms regularly distributed Ru(H)2 species. After the reductive and re-combinative desorption of H2, the adsorbed ruthenium atoms prefer structures with aggregated 2Ru dimeric units on the fully hydroxylated surface, while structures of remote and dispersed singly adsorbed Ru atoms on the partially hydroxylated surface. On the hydroxyl free surface (up to 6Ru), the adsorbed ruthenium atoms prefer three-dimensional aggregated structures, which become more stable with the increase of ruthenium loading. This indicates the surface hydroxyl dependent ruthenium adsorption on SiO2 (001), and this finding is important for understanding the structure, stability and activity of silica supported ruthenium catalysts and catalysis.

Structure and electronic properties of a μ-oxo ruthenium bromide

The crystal structure of potassium μ-oxo-bis[pentabromoruthenate] K4Ru2OBr10, determined from synchrotron X-ray powder diffraction, is described. Each Ru atom is surrounded by five Br atoms and one O atom. Magnetic measurements show the complex to be diamagnetic as a result of strong Ru–Ru interactions facilitated by the linear Ru–O–Ru linkage.

Synthesis, characterization, and multielectron redox property of pyridine‐coordinated tetra‐Ru‐oxo core sandwich‐type silicotungstate, [(γ‐SiW10O36)2({Ru(IV)(pyridine)}4O4(OH)2]10−

AbstractA pyridine‐coordinated tetra‐Ru‐oxo core sandwich‐type silicotungstate, [(γ‐SiW10O36)2({Ru(IV)(pyridine)}4O4(OH)2]10−, in which four Ru atoms are coordinated by pyridine molecules, was prepared and characterized by single‐crystal X‐ray structure analysis, 1H nuclear magnetic resonance spectroscopy (1H NMR), high‐resolution electrospray ionization mass spectrometry (HR‐ESI‐MS), infrared (IR) spectroscopy, and elemental analysis. Cyclic voltammetry and ultraviolet–visible (UV‐Vis) electrospectroscopy indicated that the molecule showed multielectron redox processes over a wide pH range (1–12).