Ru Ions Research Articles

Mn-induced multiple magnetic ground states in Sr3(Ru1−xMnx)2O7

Transition-metal oxides provide an excellent platform to generate ground states by tuning the various degrees of freedom via stimuli such as chemical doping. By investigating the electrical, magnetic, and thermodynamic properties of several compositions of the bilayered ${\mathrm{Sr}}_{3}{({\mathrm{Ru}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x})}_{2}{\mathrm{O}}_{7}$ with $x$ \ensuremath{\ge} 0.36, we complete its $x$-T phase diagram and unveil a spin-glass regime. Upon Mn doping, the ground state of the system changes from the short-range antiferromagnetically (AFM) coupled metal $(0\ensuremath{\le}x\ensuremath{\le}0.05)$ to the E-type AFM-ordered insulator $(0.05<x\ensuremath{\le}0.20)$ to the spin-glass insulator $(0.20<x\ensuremath{\le}0.66)$ to the canted AFM-ordered insulator $(x\ensuremath{\sim}1.0)$. The complex evolution of the magnetic ground state results from the competition between AFM and ferromagnetic (FM) interactions. The peculiar spin-glass state between two long-range magnetically ordered states implies the significance of spin disorder induced by the intermixing of Mn and Ru ions with the lowest transition temperature for Ru : Mn \ensuremath{\sim} 1:1 ($x\ensuremath{\sim}0.5$).

Local electronic structure of rutile RuO2

Recently, rutile ${\mathrm{RuO}}_{2}$ has raised interest for its itinerant antiferromagnetism, crystal Hall effect, and strain-induced superconductivity. Understanding and manipulating these properties demands resolving the electronic structure and the relative roles of the rutile crystal field and $4d$ spin-orbit coupling (SOC). Here, we use O-K and Ru ${M}_{3}$ x-ray absorption and Ru ${M}_{3}$ resonant inelastic x-ray scattering to disentangle the contributions of crystal field, SOC, and electronic correlations in ${\mathrm{RuO}}_{2}$. The locally orthorhombic site symmetry of the Ru ions introduces significant crystal field contributions beyond the approximate octahedral coordination yielding a crystal field energy scale of $\mathrm{\ensuremath{\Delta}}({t}_{2g})\ensuremath{\approx}1\phantom{\rule{0.16em}{0ex}}\mathrm{eV}$ breaking the degeneracy of the ${t}_{2g}$ orbitals. This splitting exceeds the Ru SOC ($\ensuremath{\approx}160$ meV) suggesting a more subtle role of SOC, primarily through the modification of itinerant (rather than local) $4d$ electronic states, ultimately highlighting the importance of the local symmetry in ${\mathrm{RuO}}_{2}$. Remarkably, our analysis can be extended to other members of the rutile family, thus advancing the comprehension of the interplay among crystal field symmetry, electron correlations, and SOC in transition metal compounds with the rutile structure.

Fe3O4@MnO2 inorganic magnetic sorbent: Preparation, characterization and application for Ru(III) ions sorption

ABSTRACT In this study, inorganic magnetic core-shell sorbent Fe3O4@MnO2 was prepared and used for the adsorption of Ru(III) ions from acidic aqueous solutions. The obtained magnetic sorbent was characterized by thermogravimetric analysis (TGA), differential scanning calorimetric (DSC) and X-ray diffraction (XRD). The sorption of Ru(III) from solutions of hydrochloric and nitric acids in concentration range from 0.01 mol L−1 to 0.5 mol L−1 on Fe3O4@MnO2 was examined. The selectivity of the Ru(III) sorption in the developed system was verified by the use of other ions like Co-60, Zn-65, Cs-137,Au-198, Pt-197, Cr-51, Sc-46, La-140 and described as a separation factor (α). The effects of contact time, dosage of magnetic sorbent and sorption capacity (Q) were checked too.

Atomic origin of room-temperature two-dimensional itinerant ferromagnetism in an oxide-monolayer heterostructure

Materials with room-temperature two-dimensional itinerant ferromagnetism enable ultracompact device density and quantum computing in next-generation nano-spintronics. Among numerous candidates, perovskite-based heterostructures have offered an excellent platform to manipulate spin-orbital-charge coupling, unveiling a series of emergent spin-dependent phenomena. In this work, we have fulfilled a robust room-temperature soft ferromagnetism together with a metallic characteristic based on a high quality SrRuO3-monolayer-based superlattice. Further examination on this short-range ferromagnetism has been carried out by synchrotron-related spectroscopy, where charge-transfer-induced antiferromagnetic coupling between partial Ru and Ti ions have been found. Although such local antiferromagnetic coupling would break long range ferromagnetic order, it simultaneously stabilize the localized intralayer ferromagnetic order in the SrRuO3 monolayers, which is confirmed by theoretical calculations. Our study not only represents a methodological advance of achieving fantastic magnetic properties in functional oxide monolayer, but is promising to unlock new opportunities for oxide-based spintronic devices toward room-temperature applications.

Ionic chitosan Schiff bases supported Pd(II) and Ru(II) complexes; production, characterization, and catalytic performance in Suzuki cross-coupling reactions

Taking the advantage of multifunctional characteristics of chitosan (CS), we have developed new scaffolds (imidazolium-vanillyl-chitosan Schiff bases (IVCSSBs)) for supporting Pd(II) and Ru(II) ions in catalyzing Suzuki coupling reactions. The structures of new materials were described based on their elemental, spectral, thermal, and microscopic analysis. The strong interactions between the binding sites of IVCSSB ligand (OH, H-C=N, and OCH3 groups) and Pd(II) ions resulted in the formation of an excellent heterogeneous catalyst (Pd(II)IVCSSB1) with amazing catalytic activity (up to 99%) and highly stable in the reaction medium. The reusability experiments for Pd(II)IVCSSB1 revealed that there is no appreciable decrease in its catalytic activity even after five consecutive operation runs. Furthermore, this heterogeneous catalyst showed an excellent selectivity toward the cross-coupling reaction where no homo-coupling byproducts were observed in the 1H NMR spectra of the obtained products. Consequently, the present ionic catalytic system may open a new window for a novel generation of ionic bio-based catalysts for organic transformations.

Half-sandwich ruthenium(II) complexes containing 4-substituted aniline derivatives: structural characterizations and catalytic properties in transfer hydrogenation of ketones

Four half-sandwich Ru(II) complexes (1)–(4) with the general formulae [Ru(η6-p-cymene)(L)Cl2] were synthesized by the reaction of one equivalent of the Ru(II) p-cymene dimer with two equivalents of a p-substituted aniline derivative L (where L is p-methyl, p-isopropyl, p-methoxy, or p-hydroxy aniline). The structures of complexes (2)–(4) were determined by single-crystal X-ray diffraction studies. The structural analysis revealed piano-stool geometry at the Ru(II) ions which are coordinated to the η6-p-cymene, two chloride anions and the amine group of the aniline ligand. In the structure of (2)–(4), the coordinated chloride ions make intermolecular hydrogen bonding with the –NH2 group of an adjacent molecules (NH–Cl) resulting in hydrogen bond networks. The catalytic activities of the complexes in transfer hydrogenation of acetophenone were studied. Complex [Ru(η6-p-cymene)(p-methylaniline)Cl2] (1) showed the best catalytic performance in the transfer hydrogenation of acetophenone. The presence and positions of methyl and bromide groups on the acetophenone have an impact on the catalytic activity in transfer hydrogenation properties of the complex (1). Moreover, catalytic activity of the complex (1) is significantly higher in the transfers hydrogenation of cyclohexanone than 2-hexanone.

Orbital effects and Affleck-Haldane-type spin dimerization in Ba4Ru3O10

${\mathrm{Ba}}_{4}{\mathrm{Ru}}_{3}{\mathrm{O}}_{10}$, the quasi-one-dimensional spin-1 ($S$ = 1) compound, has rather intricate magnetic properties. The compound consists of structural Ru trimers, which together form the zig-zag chains where the Ru has two inequivalent crystallographic sites. While at high temperature both the inequivalent Ru ions stay in the $4+$ state with effective $S=$ 1 spin state, upon lowering the temperature, the magnetic moment of the central Ru atom is completely quenched accompanied by a change in the octahedral environment. This effectively gives rise to a bond-alternating chain and provides an opportunity to study the excitation of such a spin network in a real material. We have used microscopic tools such as neutron scattering and muon spin relaxation along with the density functional theory based calculations to address the spin state of the two inequivalent Ru ions in this material. From our neutron powder diffraction, on lowering of temperature, we find a large tetragonal distortion of the central ${\mathrm{RuO}}_{6}$ octahedra of the trimer. The splitting of the ${t}_{2g}$ level of the central Ru due to this distortion is found to be significant leading to the quenching of the moment underscoring the Hund's exchange. The nonmagnetic central Ru promotes a strong antiferromagnetic superexchange between the other two Ru ions in the trimer, which gives rise to a dimeric state. The presence of spin dimers is reflected by the manifestation of a gap in the spin excitation spectra. The spin-dimer formation in ${\mathrm{Ba}}_{4}{\mathrm{Ru}}_{3}{\mathrm{O}}_{10}$ is at par with the effective model proposed by Affleck and Haldane for the $S$ = 1 bond alternating chains in the light of valence bond solid formalism. Eventually, at a lower temperature, a long-range ordered antiferromagnetic state emerges from the gapped dimer state due to the significant interdimer interactions.

Investigations on Crystalline Perfection, Raman Spectra and Optical Characteristics of Transition Metal (Ru) Co-Doped Mg:LiNbO3 Single Crystals.

Congruent lithium niobate single crystals with a Ru:Mg co-dopant have been successfully grown using the Czochralski technique from the melt containing 0.02 mol % Ru with Mg of two varied concentrations (4.0 and 6.0 mol %). The effects of Ru and Mg co-doping on the crystalline quality were determined by high-resolution X-ray diffractometry, which confirmed that the crystalline quality is good and that the dopants are statistically distributed in the crystal. The Raman scattering analysis shows no change in the lattice vibration except a slight change in the peak width and intensity due to more asymmetry in the molecular charge, which leads to enhancement of the polarizability. The optical transmission spectra indicate that both the crystals have high optical transparency in the visible region, with a shift of the absorption edge toward shorter wavelengths, as compared to un-doped LN. The weak absorption band observed below 400 nm is attributed to Ru ions. The influence of co-doping in the electronic band gap energies is calculated by the Tauc relation. The refractive index is measured by using a prism coupler at two wavelengths (532 and 1064 nm). The calculated absorption coefficients and direct and indirect band gap energies for both the samples are found to be nearly the same within experimental error. A decrease in the birefringence is observed for the Ru:Mg(6 mol %) doped sample. The observed slight reduction in refractive indices with Ru:Mg co-doping is consistent with a rise in band gap energy, which is related to the change in absorption edge to the lower wavelength. The second harmonic generation (SHG) efficiency is measured by the Kurtz and Perry powder method, and a decrease in SHG efficiency for Ru:Mg(6 mol %) is observed.

Development of a method for removal of platinum from hospital wastewater by novel ion-imprinted mesoporous organosilica

Pt(II)-imprinted thiocyanato-functionalized SBA-15 materials were prepared by co-condensation of tetraethoxysilane with various amounts of thiocyanatopropyltriethoxysilane in the presence of Pluronic123 and Pt(II) ions. The obtained materials were characterized by physicochemical methods. The adsorption behaviour of the Pt(II)-imprinted thiocyanato-functionalized SBA-15 with respect to Pt(II) ions was studied. Ion-imprinted materials were found to show a high adsorption capacity in a wide range of solution pH and fast Pt(II) adsorption rate. The maximum static adsorption capacity of the ion-imprinted sorbent synthesized of tetraethoxysilane and thiocyanatopropyltriethoxysilane in molar ratio of 18/2 for Pt(II) were 76.4 mg/g. The obtained Pt(II)-imprinted materials show a high selectivity towards Pt(II) ions in the presence of Au(III), Ru(II) and Pd(II) ions. Acidified thiourea solution was found to be the most effective medium for platinum species desorption from the synthesized ion-imprinted sorbents for 5 adsorption/desorption cycles. Each time 92% of platinum species were leached from the material in 1 mol/L thiourea solution without significantly decreasing of its adsorption capacity. The results showed that obtained ion-imprinted mesoporous organosilica could be employed as an effective material for the recovery of platinum from hospital wastewater.

Ordered Macroporous Superstructure of Nitrogen-Doped Nanoporous Carbon Implanted with Ultrafine Ru Nanoclusters for Efficient pH-Universal Hydrogen Evolution Reaction.

The electrochemical hydrogen evolution reaction (HER) is an attractive technology for the mass production of hydrogen. Ru-based materials are promising electrocatalysts owing to the similar bonding strength with hydrogen but much lower cost than Pt catalysts. Herein, an ordered macroporous superstructure of N-doped nanoporous carbon anchored with the ultrafine Ru nanoclusters as electrocatalytic micro/nanoreactors is developed via the thermal pyrolysis of ordered macroporous single crystals of ZIF-8 accommodating Ru(III) ions. Benefiting from the highly interconnected reticular macro-nanospaces, this superstrucure affords unparalleled performance for pH-universal HER, with order of magnitude higher mass activity compared to the benchmark Pt/C. Notably, an exceptionally low overpotential of only 13 mV@10mA cm-2 is required for HER in alkaline solution, with a low Tafel slope of 40.41mV dec-1 and an ultrahigh turnover frequency value of 1.6 H2 s-1 at 25mV, greatly outperforming Pt/C. Furthermore, the hydrogen generation rates are almost twice those of Pt/C during practical overall alkaline water splitting. A solar-to-hydrogen system is also demonstrated to further promote the application. This research may open a new avenue for the development of advanced electrocatalytic micro/nanoreactors with controlled morphology and excellent performance for future energy applications.

Structure, Magnetism, and First-Principles Modeling of the Na0.5La0.5RuO3 Perovskite

High-purity polycrystalline Na0.5La0.5RuO3 was synthesized by a solid-state method, and its properties were studied by magnetic susceptibility, heat capacity, and resistivity measurements. We find it to be an orthorhombic perovskite, in contrast to an earlier report, with random La/Na mixing. With a Curie–Weiss temperature of −231 K and an effective moment of 2.74 μB/mol Ru, there is no magnetic ordering down to 1.8 K. A broad hump at 1.4 K in the heat capacity, however, indicates the presence of a glassy magnetic transition, which we attribute to the influence of the random distribution of Na and La on the perovskite A-sites. Comparison to CaRuO3, a structurally ordered ruthenate perovskite with a similar A-site ionic radius and magnetic properties, is presented. First-principles calculations indicate that the Na–La distribution determines the local magnetic exchange interactions between Ru ions, favoring either antiferromagnetic or ferromagnetic coupling when the local environment is Na- or La-rich. Thus, our data and analysis suggest that mixing cations with different charges and sizes on the A-site in this perovskite results in magnetic frustration through a balance of local magnetic exchange interactions.

Comparative Analysis of DFT+U, ACBN0, and Hybrid Functionals on the Spin Density of YTiO3 and SrRuO3

We present a quantitative analysis of the theoretical spin density map of two ferromagnetic perovskites, YTiO3 and SrRuO3. We calculated the spin density using the standard density functional theory (DFT)+U method, where the Hubbard U correction is applied to the Ti and Ru ions, and with the pseudo-hybrid ACBN0 method, where the Hubbard U parameters are determined self-consistently. The ACBN0 calculations yielded a large value of the Hubbard U of the oxygen 2p orbitals. We also used the screened hybrid HSE06 functional, which is widely used to describe the electronic structure of oxides. We used the Quantum Theory of Atoms in Molecules (QTAIM) theory and integrated the spin density in the atomic basins instead of projecting on atomic orbitals. This way, our results can be compared to experimental reports as well as to other DFT calculations.

Impact of aliphatic acyl and aromatic thioamide substituents on the anticancer activity of Ru(II)-p-cymene complexes with acylthiourea ligands-in vitro and in vivo studies.

Six different acylthiourea ligands (L1-L6) and their corresponding Ru(II)-p-cymene complexes (P1-P6) were designed to explore the structure-activity relationship of the complexes upon aliphatic chain and aromatic conjugation on the C- and N-terminals, respectively. The compounds were synthesized and adequately characterized using various analytical and spectroscopic techniques. The structures of P2-P6, solved using single crystal X-ray diffraction (XRD), confirmed the neutral monodentate coordination of the S atoms of the acylthiourea ligands to Ru(II) ions. In silico studies showed an increase of lipophilicity for the ligands with an increase in alkyl chain length or aromatic conjugation at the C- or N-terminal, respectively. Subsequently, mitogen-activated protein kinases (MAPK) were predicted as one of the primary targets for the complexes, which showed good binding affinity towards extracellular signal-regulated kinases (ERK1, ERK2 and ERK5), c-Jun N-terminal kinase (JNK) and p38 of the MAPK pathway. Henceforth, the complexes were tested for their anticancer activity in lung carcinoma (A549) and cisplatin-resistant lung carcinoma (cisA549R) cells and human umbilical vein epithelial normal cells (HUVEC). Interestingly, an increase in chain length or aromatic conjugation led to an increase in the activity of the complexes, with P5 (7.73 and 13.04 μM) and P6 (6.52 and 14.45 μM) showing the highest activity in A549 and cisA549R cells, which is better than the positive control, cisplatin (8.72 and 44.28 μM). Remarkably, we report the highest activity yet observed for complexes of the type [(η6-p-cymene)RuIICl2(S-acylthiourea)] in the tested cell lines. Aqueous solution studies showed that complexes P5 and P6 are rapidly hydrolyzed to produce solely aquated species that remained stable for 24 h. Staining assays and flow cytometric analyses of P5 and P6 in A549 cells revealed that the complexes induced apoptosis and arrested the cell cycle predominantly in the S phase. In vivo studies demonstrated the higher toxicity of cisplatin and a comparatively higher survival rate of mice injected with the most active complex P6. Histological analyses revealed that treatment with P6 at high doses of up to 8 mg kg-1 did not cause any palpable damage to the tested organs.

A hydrothermal synthesis of Ru-doped LiMn1.5Ni0.5O4 cathode materials for enhanced electrochemical performance.

An Ru-doped spinel-structured LiNi0.5Mn1.5O4 (LNMO) cathode has been prepared via a simple hydrothermal synthesis method. The as-prepared cathode is characterized via Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), laser particle size distribution analysis, X-ray photoelectron spectroscopy (XPS) and electrochemistry performance tests. The FTIR spectroscopy and XRD analyses show that the Ru-doped LNMO has a good crystallinity with a disordered Fd3̄m space group structure. The disordered structure in the cathode increased and the LixNi1−xO impurity phase decreased when Ru addition increased. SEM shows that all samples are octahedral particles with homogeneous sizes distribution, and the particle size analysis shows that the Ru-doped samples have smaller particle size. XPS confirms the existence of Ru ions in the sample, and reveals that the Ru induce to part of Mn4+ transfers to Mn3+ in the LNMO. The electrochemical property indicated that the Ru-doped cathode exhibits better electrochemical properties in terms of discharge capacity, cycle stability and rate performance. At a current density of 50 mA g−1, the discharge specific capacity of the Ru-4 sample is 140 mA h g−1, which is much higher than that of the other samples. It can be seen from the rate capacity curves that the Ru-doped samples exhibit high discharge specific capacity, particularly at high current density.

Structural elucidation, spectroscopic, and metallochromic studies of 2-(2-hydroxy phenyl)-1-H–benzimidazole complexes: Metal ions sensing, DNA binding, and antimicrobial activity evaluation

Three novel chelates, [Ru(L)3]2H2O, C1, [NiL(H2O)3(AcO)]H2O, C2, and [CuL(H2O)(AcO)], C3, derived from 2-(2-hydroxy phenyl)-1-H –benzimidazole) HL, have been designed. The structures of the isolated compounds have been elucidated by elemental analysis, molar conductance, thermal analysis, spectral data (UV–Vis, mass spectra, IR, fluorescence), thermal analysis (TGA) and magnetic moment measurements. The IR spectral data ascertained that the HL compound acts as a monobasic bidentate ligand via the O and N atoms of the OH and C=N groups of the benzimidazole moiety, respectively. The spectral and magnetic measurements implied octahedral structures for C1 and C2 and square planar geometry for C3. The kinetic and thermodynamic parameters of the thermal decomposition stages have been evaluated. Molecular orbital calculations have been performed. The metallochromic behavior of the investigated free ligand was studied in the presence of Ru(III), Ni(II) and Cu(II) ions. The observed spectral changes indicated the ability of HL to act as potential optical sensor for probing these metal ions. Interaction of the investigated compounds with CT-DNA was studied via electronic absorption and emission spectroscopy, as well as ethidium bromide displacement. The results suggested that all compounds interact through intercalative mode. The binding behavior and binding constants have been evaluated and discussed. The CT-DNA-binding constants confirmed the strong intercalation between the investigated ligand and metal complexes with the CT-DNA, suggesting that the investigated compounds can be used as promising therapeutic drug. Finally, the antimicrobial activities of the metal complexes have been screened.

Morphological and magnetic features of Ru(III) doped magnetite ultrafine nanoparticles

Magnetite nanoparticles constitute a class of nanoparticles which is easily manipulated using a magnetic field. Magnetite nanoparticles doped with ruthenium (Ru) ions [RuxFe(3−x)O4] were synthesized via co-precipitation method where 0.0 ≤ x ≤ 0.5 with step 0.1. The obtained nanopowder was investigated via x-ray diffraction, FTIR, FESEM. It was shown that Ru ions were incorporated successfully into a magnetite structure with a slight influence on the value of the lattice parameter which increased from 8.354 Å at x = 0.0 to be 8.403 Å at x = 0.3, while crystallite size deteriorated from 20.1 nm at x = 0.0 to be around 3 nm at x = 0.3. In addition, the surface roughness average was influenced by the dopant content, where it decreased from 35.6 nm at the pure magnetite to be 25.87 nm at x = 0.3. The ICP examination indicated that the measured contents of Ru ions through competitions were around 41 ppm and increased to 190 ppm comparing with 43 and 199 ppm as a theoretical value both x = 0.1 and 0.5. Regarding magnetic properties, the coercivity raised from 40.11 Oe and raised 44.66 Oe for x = 0.0 and 0.5, respectively. This manipulated behavior of magnetite due to dopant suggests that desired properties could be achieved via the dopant strategy to be used for several applications.

Doping and temperature evolutions of optical response of Sr3(Ir1-xRux)2O7

We report on optical spectroscopic study of the Sr3(Ir1-xRux)2O7 system over a wide doping regime. We find that the changes in the electronic structure occur in the limited range of the concentration of Ru ions where the insulator–metal transition occurs. In the insulating regime, the electronic structure associated with the effective total angular momentum Jeff = 1/2 Mott state remains robust against Ru doping, indicating the localization of the doped holes. Upon entering the metallic regime, the Mott gap collapses and the Drude-like peak with strange metallic character appears. The evolution of the electronic structure registered in the optical data can be explained in terms of a percolative insulator–metal transition. The phonon spectra display anomalous doping evolution of the lineshapes. While the phonon modes of the compounds deep in the insulating and metallic regimes are almost symmetric, those of the semiconducting compound with x = 0.34 in close proximity to the doping-driven insulator–metal transition show a pronounced asymmetry. The temperature evolution of the phonon modes of the x = 0.34 compound reveals the asymmetry is enhanced in the antiferromagnetic state. We discuss roles of the S = 1 spins of the Ru ions and charge excitations for the conspicuous lineshape asymmetry of the x = 0.34 compound.

Highly Reversible Anionic Redox without Voltage Decay

IntroductionHigh-capacity positive electrode materials are needed to further increase energy density of rechargeable lithium batteries. Recently, Li-enriched materials, Li2 MO3-type layered materials (M = transition metal ions), classified as a cation-ordered rocksalt-type structure, have been extensively studied as advanced positive electrode materials. Among the series of Li2 MO3-type oxides, Li2MnO3 and its derivatives, e.g., Li1.2Ni0.13Co0.13Mn0.54O2, have been the most widely studied, and Li1.2Ni0.13Co0.13Mn0.54O2, delivers a large initial discharge capacity, over 250 mA h g-1 originating from anionic redox. Nevertheless, oxygen is irreversibly released on charge, leading to voltage decay on continuous electrochemical cycles.In this study, Li2RuO3 which possesses the same crystal structure with Li2MnO3, is targeted as a model material with highly reversible anionic redox. Ru ions have a much a higher covalent nature with oxide ions, and moreover chemical stability with higher oxidation states is relatively high when compared with 3d-transition metal ions. Therefore, unfavorable charge transfer from oxygen to Ru ions on charge is effectively suppressed, resulting in highly reversible anionic redox.1 Through the detailed study on Li2RuO3, the design concept of next generation high capacity Li-excess positive electrode materials with anionic redox is discussed.ExperimentalLi2RuO3 were prepared by conventional calcination method from a mixture of Li2CO3, and RuO2. Acetylene black (HS-100, Denka) was mixed with Li2RuO3 and used as a conductive material. PVdF (#1100, Kureha) was used as a binder. A mixture of Li2RuO3, acetylene black, and PVdF was casted on aluminum foil. Electrochemical properties of the composite electrodes were evaluated in a two-electrode cell. (Type TJ-AC, Tomcell, Japan).Results and discussionX-ray diffraction patterns of Li2RuO3 and Li1.2Ni0.13Co0.13Mn0.54O2 are compared in Fig. 1. Both samples were classified as the cation-ordered rocksalt-type structure with a monoclinic symmetry. Electrochemical properties of Li2RuO3 and Li1.2Ni0.13Co0.13Mn0.54O2 in Li cells are also compared in Fig. 2. A characteristic feature of Li1.2Ni0.13Co0.13Mn0.54O2 is found as a voltage plateau associated with anionic redox during an initial charge. An initial discharge capacity of Li1.2Ni0.13Co0.13Mn0.54O2 exceeds >300 mA h g-1 at 50 oC. However, voltage decay is clearly observed on continuous cycles, which presumably associated with gradual and irreversible oxygen loss.Similarly, Li2RuO3 with the 4d-transition metal ion exhibits a large reversible capacity of >300 mA h g-1, which corresponds to >90% of the theoretical capacity. Moreover, in contrast to Li1.2Ni0.13Co0.13Mn0.54O2, voltage decay is not observed even at 50 oC. This observation indicates high reversibility of anionic redox even at elevated temperatures. From these experimental results of Li1.2Ni0.13Co0.13Mn0.54O2 and Li2RuO3, factors affecting reversibility of anionic redox are discussed in detail.Reference Yabuuchi, Chem. Rec., 19, 692 (2019). Figure 1

A Low-Current and Analog Memristor with Ru As Mobile Species

The switching parameters and device performance of memristors are predominately determined by their mobile species and matrix materials. Devices with oxygen or oxygen vacancies as the mobile species usually exhibit a great retention but also need a relatively high switching current (e.g., >30 µA), while devices with Ag or Cu as cation mobile species do not require a high switching current but usually show a poor retention. Here, Ru is studied as a new type of mobile species for memristors to achieve low switching current, fast speed, good reliability, scalability, and analog switching property simultaneously. An electrochemical metallization-like memristor with a stack of Pt/Ta2O5/Ru is developed. Migration of Ru ions is revealed by energy-dispersive X-ray spectroscopy mapping and in situ transmission electron microscopy within a sub-10 nm active device area before and after switching. The results open up a new avenue to engineer memristors for desired properties.

Complex magnetic structure in Ba5Ru3O12 with isolated Ru3O12 trimer

We report detailed magnetic, transport, heat-capacity, and neutron diffraction measurements of Ba5Ru3O12, a compound consisting of isolated Ru3O12 trimers. We show that this system develops long-range antiferromagnetic ordering at 60 K (TN) without structural distortion and metal-insulator-type transition, which is in sharp contrast to other Barium Ruthenate trimer systems such as 9R-BaRuO3 and Ba4Ru3O10. A complex magnetic structure is revealed which is attributable to the magnetic frustration due to competing exchange interactions between Ru ions on different crystallographic sites within the Ru3O12 trimer.