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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Formation of open ruthenium branched structures with highly exposed active sites for oxygen evolution reaction electrocatalysis

The formation of exposed active sites that have high activity and stability for oxygen evolution reaction (OER) catalysis is a significant opportunity for improving water electrolysers. Low-index facets surface Ru can achieve both high activity and stability for OER. Here, we present a new catalyst design where low-index faceted Ru branches are grown off the corners of Pt nanocubes, forming open Ru branched nanoparticles. This open branched structure, exposing low-index facets on its length-tunable branch, enables a high electrochemically active surface area (ECSA), achieving high activity and stability for OER. This design strategy and synthetic control provide a principle for achieving high-performance OER nanocatalysts.

Xiao, Sa [The University of New South Wales, Sydne↗
DOE OSTI2026

Synergistic ruthenium single-atom and nanoparticles in nickel as cooperative catalysts for the alkaline hydrogen evolution reaction

Efficient hydrogen evolution reaction (HER) catalysts that reduce the use of noble metals and can be synthesized on a large scale are essential for advancing anion exchange membrane water electrolyzers (AEMWEs) toward commercialization. Herein, we present a composite catalyst in which Ru nanoparticles coexist with Ru single-atom alloys (SAAs) dispersed within Ni nanoparticles (Ru-SAA/Ni), creating a highly active HER electrocatalyst. Using a one-pot and scalable synthesis method, we can tune the material composition from SAA, i.e. materials containing atomically dispersed Ru atoms (with ≤0.4 at% Ru) to composite structures in which SAAs coexist with Ru NPs. Comprehensive characterization using XPS, XAS, and TEM confirms Ru-SAA formation at a low Ru content and composite structures at higher contents. Electrochemical evaluations conducted in a three-electrode setup reveal that Ru-SAA/Ni composites achieve HER performance on par with that of Pt/C. Computational insights suggest that water dissociation is significantly faster at the Ru/Ni interface compared with that on extended surfaces. These active sites are thermodynamically as active as basal planes, preventing the excessive accumulation of reaction intermediates (H*, OH*). All these results highlight the synergistic interaction between Ru SAAs and Ru nanoparticles and their potential for large-scale applications with minimal use of precious metals. Finally, the materials are processed and tested in AEMWEs, achieving 1.85 V at 0.5 A cm −2 with a total noble metal loading of only 0.1 mg cm −2 .

Khalil, Gaëlle [Université de Paris (France)]↗
DOE OSTI2024

Origin of metal-insulator transitions in the parent compounds of ruthenium-pnictide superconductors

Here we study the interplay of the structural phase transition, flat electronic band dispersion, and metal-to-insulator transition (MIT) in the parent compounds of the Ru-pnictide superconductors by using first-principles calculations. Our electron and phonon calculations reveal that Ru(P,As) undergo MIT accompanied by orthorhombic to monoclinic distortion at low temperature, but RuSb stays orthorhombic and metallic in agreement with the experimental findings. It is demonstrated that electronic correlation, as treated in DFT + U, DFT + Gutzwiller, and dynamical mean-field theory (DMFT), cannot induce MIT in the undistorted crystal structure. We find that, although small monoclinic distortion can remove the van Hove singularity at the Fermi level, it does not immediately gap out the Fermi surface and a large value of monoclinic distortion is necessary for a clear MIT, suggesting the possibility of an intermediate pseudogapped monoclinic metallic phase. Furthermore, we predict a light-induced two-step insulator-to-metal and structural transitions in the monoclinic phases of RuP and RuAs, which can be tested in future ultrafast pump-probe experiments as an alternative ideal playground to VO 2 .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1984

Intermediate phases in some rare earth-ruthenium systems

The phase equilibria and crystal structures of intermediate phases were investigated in eight representative RE-Ru systems using powder X-ray diffraction and metallographic techniques. The Fe3C, Mn5C2 and Er5Ru3 structures occur in all but the Ce-Ru systems. Phases analogous to Er5Ru3 possess an unknown crystal structure similar to Er5Rh3(I). MgCu2 and MgZn2 type Laves phases are encountered in the light rare earth and heavy rare earth systems, respectively, and RERu2 phases, where RE = Nd and Sm, possess both the Laves phase structures. An intermediate phase, NdRu, with an unknown structure, occurs only in the Nd-Ru system. A bcc structure with 40 atoms per unit cell is encountered in the phases Er3Ru2 and Y3Ru2. The behavior of cerium in Ce-Ru alloys is unique in that four unidentified structures, not encountered in other RE-Ru systems, have been encountered. Also a phase designated as Ce3Ru is found with the Th7Fe3 type structure.

Sharifrazi, P.↗
NASA NTRS1986

The barium iron ruthenium oxide system

In the system BaFe(1-x)Ru(x)O(3-y), three phases, separated by immiscibility gaps, are present: an Fe-rich phase (x = 0 to 0.75) with hexagonal BaTiO3 structure (6H; sequence (hcc)2), a Ru-rich phase (x = 0.9) of hexagonal 4H-type (sequence (hc)2), and the pure Ru compounds BaRuO3 with rhombohedral 9R structure (sequence (hhc)3). By vibrational spectroscopic investigations in the 6H phase a transition from n-type semiconduction (Fe-rich compounds with complete O lattice) can be detected. The 4H and 9R stacking polytypes are good, metal-like conductors. The lattice parameters are given.

Kemmler-Sack, S.↗
NASA NTRS2000

Ruthenium Oxide Electrochemical Super Capacitor Optimization for Pulse Power Applications

Electrical actuator systems are being pursued as alternatives to hydraulic systems to reduce maintenance time, weight and costs while increasing reliability. Additionally, safety and environmental hazards associated with the hydraulic fluids can be eliminated. For most actuation systems, the actuation process is typically pulsed with high peak power requirements but with relatively modest average power levels. The power-time requirements for electrical actuators are characteristic of pulsed power technologies where the source can be sized for the average power levels while providing the capability to achieve the peak requirements. Among the options for the power source are battery systems, capacitor systems or battery-capacitor hybrid systems. Battery technologies are energy dense but deficient in power density; capacitor technologies are power dense but limited by energy density. The battery-capacitor hybrid system uses the battery to supply the average power and the capacitor to meet the peak demands. It has been demonstrated in previous work that the hybrid electrical power source can potentially provide a weight savings of approximately 59% over a battery-only source. Electrochemical capacitors have many properties that make them well-suited for electrical actuator applications. They have the highest demonstrated energy density for capacitive storage (up to 100 J/g), have power densities much greater than most battery technologies (greater than 30kW/kg), are capable of greater than one million charge-discharge cycles, can be charged at extremely high rates, and have non-explosive failure modes. Thus, electrochemical capacitors exhibit a combination of desirable battery and capacitor characteristics.

Merryman, Stephen A.↗
NASA NTRS1994

Supported transition metal catalysts for para- to ortho-hydrogen conversion

The main goal of this study was to develop and improve on existing catalysts for the conversion of ortho- to para-hydrogen. Starting with a commercially available Air Products nickel silicate, which had a beta value of 20, we were trying to synthesize catalysts that would be an improvement to AP. This was accomplished by preparing silicates with various metals as well as different preparation methods. We also prepared supported ruthenium catalysts by various techniques using several metal precursors to improve present technology. What was also found was that the activation conditions prior to catalytic testing was highly important for both the silicates and the supported ruthenium catalysts. While not the initial focus of the research, we made some interesting observations into the adsorption of H2 on ruthenium. This helped us to get a better understanding of how ortho- to para-H2 conversion takes place, and what features in a catalyst are important to optimize activity. Reactor design was the final area in which some interesting conclusions were drawn. As discussed earlier, the reactor catalyst bed must be constructed using straight 1/8 feet OD stainless steel tubing. It was determined that the use of 1/4 feet OD tubing caused two problems. First, the radius from the center of the bed to the wall was too great for thermal equilibrium. Since the reaction of ortho- to para-H2 is exothermic, the catalyst bed center was warmer than the edges. Second, the catalyst bed was too shallow using a 1/4 feet tube. This caused reactant blow-by which was thought to decrease the measured activity when the flow rate was increased. The 1/8 feet tube corrected both of these concerns.

Brooks, Christopher J.↗
NASA NTRS2005

Improved Anode for a Direct Methanol Fuel Cell

A modified chemical composition has been devised to improve the performance of the anode of a direct methanol fuel cell. The main feature of the modified composition is the incorporation of hydrous ruthenium oxide into the anode structure. This modification can reduce the internal electrical resistance of the cell and increase the degree of utilization of the anode catalyst. As a result, a higher anode current density can be sustained with a smaller amount of anode catalyst. These improvements can translate into a smaller fuel-cell system and higher efficiency of conversion. Some background information is helpful for understanding the benefit afforded by the addition of hydrous ruthenium oxide. The anode of a direct methanol fuel cell sustains the electro-oxidation of methanol to carbon dioxide in the reaction CH3OH + H2O--->CO2 + 6H(+) + 6e(-). An electrocatalyst is needed to enable this reaction to occur. The catalyst that offers the highest activity is an alloy of approximately equal numbers of atoms of the noble metals platinum and ruthenium. The anode is made of a composite material that includes high-surface-area Pt/Ru alloy particles and a proton-conducting ionomeric material. This composite is usually deposited onto a polymer-electrolyte (proton-conducting) membrane and onto an anode gas-diffusion/current-collector sheet that is subsequently bonded to the proton-conducting membrane by hot pressing. Heretofore, the areal density of noble-metal catalyst typically needed for high performance has been about 8 mg/cm2. However, not all of the catalyst has been utilized in the catalyzed electro-oxidation reaction. Increasing the degree of utilization of the catalyst would make it possible to improve the performance of the cell for a given catalyst loading and/or reduce the catalyst loading (thereby reducing the cost of the cell). The use of carbon and possibly other electronic conductors in the catalyst layer has been proposed for increasing the utilization of the catalyst by increasing electrical connectivity between catalyst particles. However, the relatively low density of carbon results in thick catalyst layers that impede the mass transport of methanol to the catalytic sites. Also, the electrical conductivity of carbon is less than 1/300th of typical metals. Furthermore, the polymer-electrolyte membrane material is acidic and most metals are not chemically stable in contact with it. Finally, a material that conducts electrons (but not protons) does not contribute to the needed transport of protons produced in the electro-oxidation reaction.

Valdez, Thomas↗
NASA NTRS2005

Sol-Gel Process for Making Pt-Ru Fuel-Cell Catalysts

A sol-gel process has been developed as a superior alternative to a prior process for making platinum-ruthenium alloy catalysts for electro-oxidation of methanol in fuel cells. The starting materials in the prior process are chloride salts of platinum and ruthenium. The process involves multiple steps, is time-consuming, and yields a Pt-Ru product that has relatively low specific surface area and contains some chloride residue. Low specific surface area translates to incomplete utilization of the catalytic activity that might otherwise be available, while chloride residue further reduces catalytic activity ("poisons" the catalyst). In contrast, the sol-gel process involves fewer steps and less time, does not leave chloride residue, and yields a product of greater specific area and, hence, greater catalytic activity. In this sol-gel process (see figure), the starting materials are platinum(II) acetylacetonate [Pt(C5H7O2)2, also denoted Pt-acac] and ruthenium(III) acetylacetonate [Ru(C5H7O2)3, also denoted Ru-acac]. First, Pt-acac and Ru-acac are dissolved in acetone at the desired concentrations (typically, 0.00338 moles of each salt per 100 mL of acetone) at a temperature of 50 C. A solution of 25 percent tetramethylammonium hydroxide [(CH3)4NOH, also denoted TMAH] in methanol is added to the Pt-acac/Ruacac/ acetone solution to act as a high-molecular-weight hydrolyzing agent. The addition of the TMAH counteracts the undesired tendency of Pt-acac and Ru-acac to precipitate as separate phases during the subsequent evaporation of the solvent, thereby helping to yield a desired homogeneous amorphous gel. The solution is stirred for 10 minutes, then the solvent is evaporated until the solution becomes viscous, eventually transforming into a gel. The viscous gel is dried in air at a temperature of 170 C for about 10 hours. The dried gel is crushed to make a powder that is the immediate precursor of the final catalytic product. The precursor powder is converted to the final product in a controlled-atmosphere heat treatment. Desirably, the final product is a phase-pure (Pt phase only) Pt-Ru powder with a high specific surface area. The conditions of the controlled- atmosphere heat are critical for obtaining the aforementioned desired properties. A typical heat treatment that yields best results for a catalytic alloy of equimolar amounts of Pt and Ru consists of at least two cycles of heating to a temperature of 300 C and holding at 300 C for several hours, all carried out in an atmosphere of 1 percent O2 and 99 percent N2. The resulting powder consists of crystallites with typical linear dimensions of <10 nm. Tests have shown that the powder is highly effective in catalyzing the electro-oxidation of methanol.

Narayanan, Sekharipuram↗
DOE OSTI2025

Capture of volatile RuO 4 from oxidized simulated used nuclear fuel solutions

Ruthenium is a challenging fission product in used nuclear fuel (UNF) reprocessing due to its complex redox chemistry, variable speciation in nitric acid, partial extractability, and volatility. This work presents a strategy for Ru removal based on the volatilization of RuO 4 using the strong oxidant sodium bismuthate, followed by RuO 2 deposition onto various substrates. Among the materials tested, polymer-based substrates such as polyolefin wax film (Parafilm®), exhibited superior performance, achieving up to near-quantitative Ru removal from solution. After dissolution of the substrate, 99.6% of the Ru was recovered as RuO 2 . The deposition mechanism onto the polyolefin wax film involves both physisorption and chemical reaction through oxidative cleavage of olefinic bonds within the polymer. In contrast, on inorganic substrates such as Al foil, RuO 4 undergoes incomplete surface adsorption and reduction, as confirmed by FTIR and XPS analyses. This approach remains effective under conditions of simulated oxidation of UNF solutions, selectively removing Ru while leaving other fission products in solution. As a result, capture of RuO 4 offers a practical and efficient strategy for ruthenium decontamination and recovery, offering a route for integration into existing UNF reprocessing flowsheets to enhance overall process safety and performance.

Ruthenium↗
DOE OSTI2026

Phase Transformation and Water Adsorption Behavior of As‐Deposited and Annealed Ru Metal Thin Films Prepared by Atomic Layer Deposition

ABSTRACT Surfaces play a central role in catalytic processes, and understanding the transformation of ruthenium metal into ruthenium oxide during annealing is essential for tailoring functional catalytic interfaces. In this study, we systematically investigate ≈22 nm thick Ru metal films deposited by atomic layer deposition (ALD) at 300°C, focusing on their chemical composition, structural evolution, and surface hydration behavior following post‐deposition annealing in air from 400 to 600°C. Lab‐based and synchrotron X‐ray photoelectron spectroscopy (XPS) reveal a gradual conversion from metallic Ru to fully oxidized Ru 4+ with increasing annealing temperature, accompanied by a corresponding increase in lattice oxygen. X‐ray diffraction (XRD) shows amorphous Ru oxide phases at 400°C and 500°C that evolve into crystalline RuO 2 at 600°C, while atomic force microscopy (AFM) indicates enhanced grain growth and surface roughening upon annealing. Ambient‐pressure XPS (AP‐XPS) under controlled H 2 O vapor environments (1–17 Torr) demonstrates that samples annealed at 400°C and 500°C exhibit initially high hydroxyl coverage that decreases with increasing water vapor pressure, concurrent with a rise in molecular H 2 O adsorption. In contrast, the crystalline RuO 2 surface formed at 600°C maintains stable hydroxylation and supports increased water uptake. Overall, this work provides fundamental insight into Ru oxide–H 2 O interactions and establishes design principles for engineering oxide surfaces optimized for electrocatalytic applications.

APXPS↗
DOE OSTI2025

Regeneration of Benzimidazole-Based Organohydrides Mediated by Ru Catalysts

Benzimidazole-based organohydrides (BIHs) are versatile hydride, electron, and proton donors in a variety of artificial photosynthetic systems for the generation of solar fuels. Currently, BIHs are often used in stoichiometric rather than catalytic processes. The catalytic regeneration of BIHs from their oxidized form (BI + ) is an urgent necessity in order to allow the development of recyclable systems and devices, but viable examples are scarce and require large overpotentials. Here, in this study, we report the electrocatalytic regeneration of a series of BIHs with varying hydricities, promoted by a ruthenium half-sandwich complex, [(HMB)Ru(bpy)(H)]+ (HMB = η 6 -C 6 Me 6 , bpy = 2,2′-bipyridine), in the presence of tributylammonium (HNBu 3 + ) as a proton source. This metal hydride was generated in situ from the 2e - reduction/protonation of the corresponding solvento-complex. In comparison to the direct cathodic reduction of BI + in the presence of HNBu 3 + , the use of this ruthenium catalyst allowed efficient regeneration of BIHs at less negative potentials, with Faradaic efficiencies up to 80% and significantly higher conversion yields due to the circumvention of the dimerization pathway and the stepwise reduction and protonation reactions. Finally, the thermodynamic challenges involved in the regeneration of very hydridic BIHs mediated by Ru hydride catalysts were examined.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗