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At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Enhancing electrocatalytic performance of RuO 2 -based catalysts: mechanistic insights, strategic approaches, and recent advances

Abstract Electrochemical water splitting presents the ultimate potential of hydrogen and oxygen production; however, regulating the rate and efficiency of water splitting is highly dependent on the accessibility of extremely efficient electrode materials for slow performance kinetics and large overpotential of both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Ruthenium oxide (RuO 2 ) based materials display high performance for OER and HER because of their capacity to bind oxygen, eminent catalytic activity, low cost compared to other precious metals, and stability in a wide pH range. However, there is still much space to promote the OER and HER activity and stability of RuO 2 to fulfill the necessity for practical applications in water splitting. Different researchers applied multiple approaches that boosted the catalytic performance of RuO 2 -based electrocatalysts toward overall water splitting. Herein, this review provides a comprehensive overview of recent advancements in RuO 2 -based materials in the field of water electrolysis for the generation of alternative energies. It gives a general description of water splitting in acidic and alkaline settings, including reaction mechanisms as well as common evaluation elements for the catalytic function of the materials. Most of the reviews reported based on RuO 2 materials are only focused on OER performance, but this review highlighted comprehensive ideas on different strategies like morphology design, electronic structure, electrolytes, and compositions for optimizing both electrocatalytic HER and OER functioning of RuO 2 -based electrocatalysts.

KC, Binod Raj (ORCID:0009000885806906)↗
DOE OSTI2025

Rethinking 𝛼−RuCl 3 : Parameters, models, and phase diagram

RuCl 3 was likely the first ever deliberately synthesized ruthenium compound, following the discovery of the 44 Ru element in 1844. For a long time it was known as an oxidation catalyst, with its physical properties being discrepant and confusing, until a decade ago when its allotropic form 𝛼−RuCl 3 rose to exceptional prominence. This “rediscovery” of 𝛼−RuCl 3 has not only reshaped the hunt for a material manifestation of the Kitaev spin liquid, but it has opened the floodgates of theoretical and experimental research in the many unusual phases and excitations that the anisotropic-exchange magnets as a class of compounds have to offer. Given its importance for the field of Kitaev materials, it is astonishing that the low-energy spin model that describes this compound and its possible proximity to the much-desired spin-liquid state is still a subject of significant debate ten years later. In the present study, we argue that the existing key phenomenological observations put strong natural constraints on the effective microscopic spin model of 𝛼−RuCl 3 , and specifically on its spin-orbit-induced anisotropic-exchange parameters that are responsible for the nontrivial physical properties of this material. These constraints allow one to focus on the relevant region of the multidimensional phase diagram of the 𝛼−RuCl 3 model, suggest an intuitive description of it via a different parametrization of the exchange matrix, offer a unifying view on the earlier assessments of its parameters, and bring closer together several approaches to the derivation of anisotropic-exchange models. We explore extended phase diagrams relevant to the 𝛼−RuCl 3 parameter space using quasiclassical, Luttinger-Tisza, exact diagonalization, and density-matrix renormalization-group methods, demonstrating a remarkably close quantitative accord between them on the general structure and hierarchy of the phases, with the zigzag, ferromagnetic, and incommensurate phases that are proximate to each other. As a result, one of the highlights is the detailed agreement on the nature of the incommensurate phases that realize two distinct counterrotating helical states.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Fluctuating Ru trimer precursor to a two-stage electronic transition in RuP

Superconductivity in binary ruthenium pnictides occurs proximal to and upon suppression of a non-magnetic ground state, preceded by a pseudogap phase associated with Fermi surface instability, and its critical temperature, T c , is maximized around the pseudogap quantum critical point. By analogy with isoelectronic iron based counterparts, antiferromagnetic fluctuations became ''usual suspects" as putative mediators of superconducting pairing. Here we report on a high temperature local symmetry breaking in RuP, nonsuperconducting parent of the maximum- T c branch of these novel superconductors, revealed by combined nanostructure-sensitive powder and single crystal X-ray total scattering analyses. Large local distortions of Ru chains associated with orbital-charge trimerization, further assembled into hexamers, exist above the two-stage electronic transition in RuP. In the pseudogap regime the precursors order with distortions retaining their strength, whereas they acquire spin-singlet characteristics which dramatically enhances the distortion as the nonmagnetic ground state establishes. The precursors enable the nonmagnetic ground state and presumed complex oligomerization, and the relevance of pseudogap fluctuations for superconductivity emerges as a distinct prospect. As a transition metal system in which partial d-manifold filling combined with high crystal symmetry promotes electronic instabilities, this represents a further example of local electronic precursors underpinning the macroscopic collective behavior of quantum materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Carbon-free high-performance cathode for solid-state Li-O 2 battery

The development of a cathode for solid-state lithium-oxygen batteries has been hindered in practice by a low capacity and limited cycle life despite their potential for high energy density. Here, a previously unexplored strategy is proposed wherein the cathode delivers a specific capacity of 200 milliampere hour per gram over 665 discharge/charge cycles, while existing cathodes achieve only ~50 milliampere hour per gram and ~100 cycles. A highly conductive ruthenium-based composite is designed as a carbon-free cathode by first-principles calculations to avoid the degradation associated with carbonaceous materials, implying an improvement in stability during the electrochemical cycling. In addition, water vapor is added into the main oxygen gas as an additive to change the discharge product from growth-restricted lithium peroxide to easily grown lithium hydroxide, resulting in a notable increase in capacity. Thus, the proposed strategy is effective for developing reversible solid-state lithium-oxygen batteries with high energy density.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Visualizing the atomic-scale origin of metallic behavior in Kondo insulators

A Kondo lattice is often electrically insulating at low temperatures. However, several recent experiments have detected signatures of bulk metallicity within this Kondo insulating phase. In this study, we visualized the real-space charge landscape within a Kondo lattice with atomic resolution using a scanning tunneling microscope. We discovered nanometer-scale puddles of metallic conduction electrons centered around uranium-site substitutions in the heavy-fermion compound uranium ruthenium silicide (URu 2 Si 2 ) and around samarium-site defects in the topological Kondo insulator samarium hexaboride (SmB 6 ). These defects disturbed the Kondo screening cloud, leaving behind a fingerprint of the metallic parent state. Our results suggest that the three-dimensional quantum oscillations measured in SmB 6 arise from Kondo-lattice defects, although we cannot exclude other explanations. Finally, our imaging technique could enable the development of atomic-scale charge sensors using heavy-fermion probes.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Chemically recyclable polyolefin-like multiblock polymers

Polyolefins are the most important and largest volume plastics produced. Unfortunately, the enormous use of plastics and lack of effective disposal or recycling options have created a plastic waste catastrophe. Here in this work, we report an approach to create chemically recyclable polyolefin-like materials with diverse mechanical properties through the construction of multiblock polymers from hard and soft oligomeric building blocks synthesized with ruthenium-mediated ring-opening metathesis polymerization of cyclooctenes. The multiblock polymers exhibit broad mechanical properties, spanning elastomers to plastomers to thermoplastics, while integrating a high melting transition temperature (T m ) and low glass transition temperature (T g ), making them suitable for use across diverse applications (T m as high as 128°C and T g as low as –60°C). After use, the different plastics can be combined and efficiently deconstructed back to the fundamental hard and soft building blocks for separation and repolymerization to realize a closed-loop recycling process.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

The Effect of Material Properties on Oxygen Evolution Activity and Assessing Half-Cell Screening as a Predictive Tool in Electrolysis

Iridium-based oxygen evolution catalysts are screened in this study for activity and stability with rotating disk electrode (RDE) half-cells. This study focuses on the electrochemical and materials approaches needed to characterize oxygen evolution catalysts, and include testing for activity, stability, composition, oxide content, and structure. Findings also discuss recommendations for data interpretation and detail the difficulties of comparing catalysts across materials sets with different elemental and oxide compositions, and linking RDE activity to device-level performance. The materials evaluated are a mixture of oxides and metals, and several methods are used to quantify metal content, qualitatively assess oxide content, and determine total surface area. Oxygen evolution activities and stabilities are compared, where a wide range of results are reported. In general, higher RDE performances are found for catalysts that contained larger amounts of ruthenium and metals. Higher durability, however, is found for catalysts that only contained iridium and a higher proportion of oxides. Additionally, catalysts are evaluated for performance in membrane electrode assemblies to assess RDE as a predictive tool in electrolysis. While activity trends within individual material sets generally held between ex- and in-situ testing, RDE tends to overestimate the activity of more metallic catalysts when compared to device-level performance. These results stress the need for multiple metal/oxide baselines for mixed catalysts, to better project in-situ kinetics.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Simulated Start-Stop and the Impact of Catalyst Layer Redox on Degradation and Performance Loss in Low-Temperature Electrolysis

Stress tests are developed that focus on anode catalyst layer degradation in proton exchange membrane electrolysis due to simulated start-stop operation. Ex situ testing indicates that repeated redox cycling accelerates catalyst dissolution, due to near-surface reduction and the higher dissolution kinetics of metals when cycling to high potentials. Similar results occur in situ, where a large decrease in cell kinetics (>70%) is found along with iridium migrating from the anode catalyst layer into the membrane. Additional processes are observed, however, including changes in iridium oxidation, the formation of thinner and denser catalyst layers, and platinum migration from the transport layer. Increased interfacial weakening is also found, adding to both ohmic and kinetic loss by adding contact resistances and isolating portions of the catalyst layer. Repeated shutoffs of the water flow further accelerate performance loss and increase the frequency of tearing and delamination at interfaces and within catalyst layers. These tests were applied to several commercial catalysts, where higher loss rates were observed for catalysts that contained ruthenium or high metal content. These results demonstrate the need to understand how operational stops occur, to identify how loss mechanisms are accelerated, and to develop strategies to limit performance loss.

08 HYDROGEN↗
DOE OSTI2020

Materials Data on KHoH8RuC6(N3O2)2 by Materials Project

RuKHoC6H4(N3O)2(H2O)2 crystallizes in the orthorhombic Cmcm space group. The structure is two-dimensional and consists of four ruthenium molecules; eight water molecules; and two KHoC6H4(N3O)2 sheets oriented in the (0, 0, 1) direction. In each KHoC6H4(N3O)2 sheet, K1+ is bonded in a 2-coordinate geometry to six N3- and two equivalent O2- atoms. There are four shorter (3.08 Å) and two longer (3.14 Å) K–N bond lengths. Both K–O bond lengths are 2.93 Å. Ho3+ is bonded in a 8-coordinate geometry to six N3- and two equivalent O2- atoms. There are four shorter (2.42 Å) and two longer (2.52 Å) Ho–N bond lengths. Both Ho–O bond lengths are 2.40 Å. There are two inequivalent C+1.33+ sites. In the first C+1.33+ site, C+1.33+ is bonded in a single-bond geometry to one N3- atom. The C–N bond length is 1.18 Å. In the second C+1.33+ site, C+1.33+ is bonded in a single-bond geometry to one N3- atom. The C–N bond length is 1.18 Å. There are two inequivalent N3- sites. In the first N3- site, N3- is bonded in a 1-coordinate geometry to one K1+, one Ho3+, and one C+1.33+ atom. In the second N3- site, N3- is bonded in a distorted single-bond geometry to one K1+, one Ho3+, and one C+1.33+ atom. H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. O2- is bonded in a distorted water-like geometry to one K1+, one Ho3+, and two equivalent H1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on RuO4 by Materials Project

RuO4 is Silicon tetrafluoride-like structured and crystallizes in the monoclinic C2/c space group. The structure is zero-dimensional and consists of four ruthenium(iv) hydroxide molecules. Ru is bonded in a tetrahedral geometry to four O atoms. All Ru–O bond lengths are 1.71 Å. There are two inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one Ru atom. In the second O site, O is bonded in a single-bond geometry to one Ru atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on RuO4 by Materials Project

RuO4 is Silicon tetrafluoride-like structured and crystallizes in the cubic P-43n space group. The structure is zero-dimensional and consists of eight ruthenium(iv) hydroxide molecules. Ru is bonded in a tetrahedral geometry to four equivalent O atoms. All Ru–O bond lengths are 1.71 Å. O is bonded in a single-bond geometry to one Ru atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on H8RuC5N(ClO)3 by Materials Project

RuCl3(CH3)2NH2(CO)3 is Silicon tetrafluoride-derived structured and crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of four dimethylazanium molecules, twelve formaldehyde molecules, and four ruthenium (iii) chloride molecules.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sb4RuC6(O3F11)2 by Materials Project

Ru(CO)6(Sb2F11)2 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of twelve formaldehyde molecules, two ruthenium molecules, and four Sb2F11 clusters. In each Sb2F11 cluster, there are two inequivalent Sb+1.50+ sites. In the first Sb+1.50+ site, Sb+1.50+ is bonded to six F1- atoms to form corner-sharing SbF6 octahedra. The corner-sharing octahedral tilt angles are 33°. There are a spread of Sb–F bond distances ranging from 1.89–2.11 Å. In the second Sb+1.50+ site, Sb+1.50+ is bonded to six F1- atoms to form corner-sharing SbF6 octahedra. The corner-sharing octahedral tilt angles are 33°. There are a spread of Sb–F bond distances ranging from 1.89–2.06 Å. There are eleven inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to one Sb+1.50+ atom. In the second F1- site, F1- is bonded in a single-bond geometry to one Sb+1.50+ atom. In the third F1- site, F1- is bonded in a single-bond geometry to one Sb+1.50+ atom. In the fourth F1- site, F1- is bonded in a single-bond geometry to one Sb+1.50+ atom. In the fifth F1- site, F1- is bonded in a single-bond geometry to one Sb+1.50+ atom. In the sixth F1- site, F1- is bonded in a bent 150 degrees geometry to two Sb+1.50+ atoms. In the seventh F1- site, F1- is bonded in a single-bond geometry to one Sb+1.50+ atom. In the eighth F1- site, F1- is bonded in a single-bond geometry to one Sb+1.50+ atom. In the ninth F1- site, F1- is bonded in a single-bond geometry to one Sb+1.50+ atom. In the tenth F1- site, F1- is bonded in a single-bond geometry to one Sb+1.50+ atom. In the eleventh F1- site, F1- is bonded in a single-bond geometry to one Sb+1.50+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sb2RuC6(OF2)6 by Materials Project

Ru(CO)6(SbF6)2 crystallizes in the tetragonal P4/mnc space group. The structure is zero-dimensional and consists of twelve formaldehyde molecules, two ruthenium molecules, and four SbF6 clusters. In each SbF6 cluster, Sb3- is bonded in an octahedral geometry to six F1- atoms. All Sb–F bond lengths are 1.92 Å. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to one Sb3- atom. In the second F1- site, F1- is bonded in a single-bond geometry to one Sb3- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cd2Ru(CN)6 by Materials Project

Ru(Cd(CN)3)2 crystallizes in the trigonal P-3 space group. The structure is two-dimensional and consists of one ruthenium molecule and one Cd(CN)3 sheet oriented in the (0, 0, 1) direction. In the Cd(CN)3 sheet, Cd2+ is bonded to six equivalent N3- atoms to form edge-sharing CdN6 octahedra. There are three shorter (2.40 Å) and three longer (2.41 Å) Cd–N bond lengths. C+1.33+ is bonded in a single-bond geometry to one N3- atom. The C–N bond length is 1.18 Å. N3- is bonded in a distorted trigonal planar geometry to two equivalent Cd2+ and one C+1.33+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mn2Ru(CN)6 by Materials Project

Ru(Mn(CN)3)2 crystallizes in the trigonal P-3 space group. The structure is two-dimensional and consists of one ruthenium molecule and one Mn(CN)3 sheet oriented in the (0, 0, 1) direction. In the Mn(CN)3 sheet, Mn2+ is bonded to six equivalent N3- atoms to form edge-sharing MnN6 octahedra. There are three shorter (2.25 Å) and three longer (2.26 Å) Mn–N bond lengths. C+1.33+ is bonded in a single-bond geometry to one N3- atom. The C–N bond length is 1.19 Å. N3- is bonded in a distorted trigonal planar geometry to two equivalent Mn2+ and one C+1.33+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on H32RuC8N4Cl7 by Materials Project

RuCl6((CH3)2NH2)2C4N2H16Cl is Silicon tetrafluoride-derived structured and crystallizes in the orthorhombic P2_12_12 space group. The structure is zero-dimensional and consists of four dimethylazanium molecules, two ruthenium(6+) hexachloride molecules, and two C4N2H16Cl clusters. In each C4N2H16Cl cluster, there are two inequivalent C2- sites. In the first C2- site, C2- is bonded to one N3- and three H1+ atoms to form corner-sharing CH3N tetrahedra. The C–N bond length is 1.49 Å. There is two shorter (1.09 Å) and one longer (1.10 Å) C–H bond length. In the second C2- site, C2- is bonded to one N3- and three H1+ atoms to form corner-sharing CH3N tetrahedra. The C–N bond length is 1.49 Å. All C–H bond lengths are 1.10 Å. N3- is bonded in a tetrahedral geometry to two C2- and two H1+ atoms. There is one shorter (1.04 Å) and one longer (1.06 Å) N–H bond length. There are eight inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one N3- and one Cl1- atom. The H–Cl bond length is 2.04 Å. In the eighth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. Cl1- is bonded in a bent 150 degrees geometry to two equivalent H1+ atoms.

36 MATERIALS SCIENCE↗