Enrichment Of Ru Research Articles

Ru-Induced Defect Engineering in Co3O4 Lattice for High Performance Electrochemical Reduction of Nitrate to Ammonium.

Amidst these growing sustainability concerns, producing NH4 + via electrochemical NO3 - reduction reaction (NO3RR) emerges as a promising alternative to the conventional Haber-Bosch process. In a pioneering approach, this study introduces Ru incorporation into Co3O4 lattices at the nanoscale and further couples it with electroreduction conditioning (ERC) treatment as a strategy to enhance metal oxide reducibility and induce oxygen vacancies, advancing NH4 + production from NO3RR. Here, supported by a suite of ex situ and in situ characterization measurements, the findings reveal that Ru enrichment promotes Co species reduction and oxygen vacancy formation. Further, as evidenced by the theoretical calculations, Ru integration lowers the energy barrier for oxygen vacancy formation, thereby facilitating a more energy-efficient NO3RR-to-NH4 + pathway. Optimal catalytic activity is realized with a Ru loading of 10 at.% (named 10Ru/Co3O4), achieving a high NH4 + production rate (98nmols-1cm-2), selectivity (97.5%) and current density (≈100mAcm-2) at -1.0V vs RHE. The findings not only provide insights into defect engineering via the incorporation of secondary sites but also lay the groundwork for innovative catalyst design aimed at improving NH4 + yield from NO3RR. This research contributes to the ongoing efforts to develop sustainable electrochemical processes for nitrogen cycle management.

Multimode sensing and imaging platform for versatile detection of GSH based on surface modification strategy of Ru(bpy)32+ doped SiO2 nanoparticles

A multimode sensing and imaging platform based on surface modification strategy of Ru(bpy)32+ doped SiO2 nanoparticles (RuSiO2 NPs) was constructed for versatile detection of glutathione (GSH). RuSiO2 NPs as the luminophore models had outstanding fluorescence (FL) and electrochemiluminescence (ECL) signals. Furthermore, its FL signal could be captured by electrophoresis analyzer, and the ECL signal could be imaged with mobile phone to achieve visualization. So, a unique and convenient multi-mode sensing and imaging platform could be developed based on RuSiO2 NPs. SiO2 NPs could realize enrichment of Ru(bpy)32+ based on the nanoconfined effect to achieve signal amplification, and its surface was rich with abundant hydroxyl functional groups, which offered a channel for surface modification. Sulfhydryl modification on the RuSiO2 NPs was realized by using silane coupling agent, and KMnO4 was used to in situ generate MnO2 shell on the surface of RuSiO2 NPs for quenching its ECL, FL, and colorimetric (CL) signals based on resonance energy transfer (RET). Target GSH could reduce MnO2 shell to realize recovery of all signals, thus achieving the label-free multimode detection of GSH. Therefore, this work developed a multimode sensing and imaging platform without signal labels or layer-by-layer assembly of electrodes, which had the advantages of simple steps, low cost, and high detection accuracy, showing important application potential in the field of bioanalysis.

Inclusions in Placer Pt-Fe Alloy Nuggets, Northwest Ecuador: Evolution of a Ural-Alaskan Type PGE Mineralizing System (Cr-Spinel, IPGE, Sulfarsenides, and Cu-Depleted PGM)

Abstract A Cu- and Rh-enriched magmatic ore system is defined by abundant PGM (platinum group mineral) inclusions in forty-four Pt-Fe alloy nuggets from the Camumbi River gold placer, northwest Ecuador. Isoferroplatinum is depleted in Rh, Os, and Ru compared with native platinum, suggesting most crystallized after Os-(Ir) alloy, laurite, and some Rh-PGM. Two Pt-Fe alloy nuggets have zoned hydrothermal alteration rinds, and an UM (unnamed mineral) is (Rh,Pd)4As3. Our previous work shows that silicate glass inclusions define a fractionated co-magmatic compositional series related to primitive hydrous ferrobasalt, and trace element chemistry matches their Late Cretaceous accreted volcanic arc terrane. Here we report exceptional Cr-spinel (Ural-Alaskan type) inclusions coexisting with primitive ferrobasaltic glass crystallized at highest T. Laurite inclusions also indicate high T and S saturation of early melt. Os-(Ir) inclusions are Ru-depleted while two discrete Ir-enriched osmium crystals have remarkable, extreme Ru enrichment and depletion, confirming crystallization before and after laurite. Laurite and osmium inclusions in one Pt-Fe alloy reflect concomitant crystallization and fluctuating low fS2 melt conditions. In experimental primitive Cu-bearing Pt-Pd-S-(As) melt (cf. exsolved from primitive basalt), first Cu-PGM-sulfide crystallization generates a Cu-depleted, Pt-Pd-As-(S) residual melt. At lower T immiscible melts Pt-As-(S) and later Pd-As-(S) crystallize distinctive PGM. We report analogous natural multiphase PGM inclusion assemblages in separate isoferroplatinum nuggets: (1) zoned sulfarsenides, sperrylite, and genkinite, with rare resorbed cognate xenocrystic cooperite (captured from primary sulfide melt) define a high T, Pt-enriched sub-system [Pt > Rh(Pd,Ir,Ru)As,S ≫ Sb,Bi] and (2) zoned sulfarsenides, arsenopalladinite, sperrylite, törnroosite, and gold define a lower T, fractionated Pd-enriched sub-system [(Pd > Rh ≃ Pt > Ir > Au)As,S > Te ≫ Sb,Bi]. The previously undocumented natural S-rich sperrylite (formerly “platarsite”) solid solution series and later crystallized irarsite series are discriminated in terms of Pt-Ir-Rh. Both trends fractionate toward increasing Rh (hollingworthite). The discrete PGM assemblage, sperrylite-telluropalladinite (with exsolved palladium and electrum) defines an IPGE-depleted Pd > Pt(Au > Ag)As ≥ Te ≥ Sb sub-system and records extreme fractionation. Cu-bearing multiphase PGM inclusions (some coexisting with silicate glass) derived from the fraction of Cu-bearing exsolved Pt-Pd-S-(As) melt will be reported separately.

Cold plasma-prepared Ru-based catalysts for boosting plasma-catalytic CO2 methanation

In this work, γ-Al2O3 supported Ru-based catalysts were prepared by cold plasma for boosting plasma-catalytic CO2 methanation without additional heating. CO2 conversion over plasma-prepared Ru/γ-Al2O3 (76.3%) was far superior to Ru/γ-Al2O3-C prepared by thermal reduction (52.0%) due to the high dispersion and surface enrichment of Ru induced by plasma. CoRu/γ-Al2O3 and AuRu/γ-Al2O3 prepared by plasma possessed enhanced and similar plasma-catalytic CO2 methantion activity. The sizes of the metal nanoparticles are small, and the CoRu nanoparticles showed smaller size and higher dispersion than those of AuRu. The AuRu and CoRu alloys were formed in AuRu/γ-Al2O3 and CoRu/γ-Al2O3, and the CoRu showed higher alloying degree and surface enrichment degree. Well alloyed RuCo may reduce the free energy of hydrogen adsorption at the catalysts. Small particle size can improve their atom utilization efficiency, and surface enrichment of the active species can shorten the heterogeneous reaction from 7 to 5 steps.

Novel electrochemical and electrochemiluminescence dual-modality sensing platform for sensitive determination of antimicrobial peptides based on probe encapsulated liposome and nanochannel array electrode.

With the increasing application of antimicrobial peptides (AMPs) to replace antibiotics in medicine, food and agriculture, it is highly desired to develop a fast, reliable, and convenient strategy for sensitive detection of AMPs. Herein, a novel electrochemical (EC) and electrochemiluminescence (ECL) dual-modality sensing platform was developed based on probe encapsulated liposomes and nanochannel array modified electrodes, which enables sensitive determination of nisin in food samples. The bifunctional probe with both EC and ECL signals, tris(2,2-bipyridyl) dichlororuthenium (II) (Ru(bpy)32+), was chosen to be easily encapsulated in liposomes (Ru(bpy)32+@liposome). Based on the unique sterilization mechanism that AMPs can disrupt cell membranes, Ru(bpy)32+@liposome can be destroyed by nisin and release a large number of Ru(bpy)32+ probes. Vertically-ordered mesoporous silica-nanochannel film (VMSF) modified ITO electrodes (VMSF/ITO) prepared by electrochemically assisted self-assembly (EASA) method were applied as the sensing electrode. Due to the efficient enrichment of Ru(bpy)32+ by the negatively charged nanochannel arrays, VMSF/ITO enables detection of the EC/ECL signals of the released Ru(bpy)32+ probes with ultrahigh sensitivity. In consequence, sensitive dual-modality detection of nisin was achieved by the combination of Ru(bpy)32+@liposome and VMSF/ITO. The developed sensing system can realize sensitive determination of nisin in ECL mode in the concentration range of 10 ng/ml to 50 μg/ml with a limit of detection (LOD) of 9.3 ng/ml, or in EC mode from 800 ng/ml to 100 μg/ml with a LOD of 70 ng/ml. Combined with the excellent anti-fouling and anti-interference performance of VMSF, rapid and sensitive detection of nisin in milk or egg white was also achieved by the sensor.

Unveiling the origin of alkali metal promotion in CO2 methanation over Ru/ZrO2

Alkali metals are used as promoters in a broad range of catalytic reactions involving supported metal catalysts, and the origin of their promotional effects has become one of the fundamental questions in heterogeneous catalysis. However, a thorough understanding of the promotional mechanism is still unclear. Combining experiments and theory, the effects of alkali metals on the reactivity of CO2 methanation reaction over Ru/ZrO2, a crucial reaction for CO2 utilization is explored. The conventionally assumed electron enrichment of Ru is not the decisive factor for the promotion. Rather, Na promotion facilitate the adsorption and dissociation of CO on the local interfacial Ru sites of Ru/ZrO2, which is the key step of CO2 methanation process. The feasible dissociation of CO on the alkali metal promoted Ru/ZrO2 originates from the enhanced electron back-donation from the interfacial Ru sites, which leads to more than an order of magnitude increase in CO2 conversion activity.

Light Scattering and Luminophore Enrichment-Enhanced Electrochemiluminescence by a 2D Porous Ru@SiO2 Nanoparticle Membrane and Its Application in Ultrasensitive Detection of Prostate-Specific Antigen.

Electrochemiluminescence (ECL) by virtue of its controllability and versatility has emerged as a significant tool in bioassay, but how to integrate it with other (nano)materials and further break the limit of sensitivity for ultrasensitive detection still possess tremendous potential. Herein, a close-packed Ru@SiO2 NP nanomembrane that serves as an enhanced substrate and luminophore enricher simultaneously was constructed by the liquid-liquid interface self-assembly method and applied for ECL-enhanced bioassay. The developed ECL electrode obtained ∼600-fold enhancement on ECL intensity compared with the bare ITO electrode and ∼21-fold enhancement compared with the SiO2 NP nanomembrane electrode due to the dramatic light scattering of the 2D SiO2 NPs and the enrichment of Ru(bpy)32+ molecules on the surface of the Ru@SiO2 NP nanomembrane electrode. Based on the fascinating Ru@SiO2 NP nanomembrane platform, we further constructed a label-free immunosensor for the detection of prostate-specific antigen (PSA). The as-fabricated Ru@SiO2-nanomembrane ECL immunosensor exhibited good stability and performed ultrasensitive detection with an utmost low detection limit of 0.169 fg·mL-1 (signal/noise = 3). Our work puts forward an effective solution benefiting for further improving ECL performance for ultrasensitive bioassays.

Ru-M (M = Fe or Co) Catalysts with high Ru surface concentration for Fischer-Tropsch synthesis

Ru-Co/Al2O3 and Ru-Fe/Al2O3 have been prepared by the reduction-deposition method. This approach favours the interaction between Ru and Fe or Co in the final catalysts, while increasing surface enrichment of Ru. Their performance for the Fischer-Tropsch Synthesis (FTS) has been evaluated in a fixed bed reactor. Ru-Co/Al2O3 displays the highest activity in the series, doubling the steady-state CO conversion rate of a Ru/Al2O3 catalyst with 3 times higher Ru loading. Ru-Fe/Al2O3 displays higher initial CO conversion and -CH2- productivity than Ru/Al2O3, but its activity declines during operation reaching lower conversion rates than Ru/Al2O3. In addition to CO2, Ru-Fe/Al2O3 produces oxygenated products, mainly alcohols. To a lesser extent, the formation of oxygenates over Ru-Co/Al2O3 and Ru/Al2O3 is also observed, and ascribed to the small crystallite size of the Ru particles. The evolution of CO2 during time on stream indicates that Fe is segregated to the surface of this catalyst during the FTS.

Atomic-Scale View into the Degradation of Ir-Ru Alloys during Anodic Oxygen Evolution

Hydrogen is likely to play a key role as central energy carrier in the world’s transition towards a more sustainable future. Electricity from renewable sources can be used to power water electrolyzers to generate carbon-neutral hydrogen [1]. ‘Green’ hydrogen can then, for example, be used for the synthesis of carbon-neutral fuels, in the transportation sector to power H2 fuel-cell fitted vehicles, as a carbon-neutral agent for the direct reduction of metals from ores, or to re-generate electricity in time of high demand. However, the technological upscaling of proton exchange membrane water electrolysis (PEM) devices is currently hindered by the low reactivity and instability of most catalyzing materials for the anodic oxygen evolution reaction (OER). The development of electrocatalysts with superior performance requires a detailed understanding of how their surfaces evolve during OER, ideally at the atomic scale [2,3]. The identification of the role of individual atoms in different chemical and structural environments in the near-surface region of the catalyst is crucial to understand the electrochemical performance and degradation processes.Here, we provide atomic scale insights into the degradation mechanism of an Ir-Ru model alloy during electrochemical oxygen evolution. Ir-Ru alloys are promising candidates for PEM electrolysis combining the stability of Ir and high activity of Ru towards OER. The changes in electronic state of the catalysts induced by OER are studied by X-ray photoelectron spectroscopy (XPS), while an in-situ activity-stability analysis was performed online using an inductively coupled plasma mass spectrometer. Atom probe tomography (APT) was used to reveal the structure and composition of the first few atomic layers of the catalyst in three dimensions.APT reveals strong compositional differences between intragranular and grain boundary regions in the pristine alloy, resulting from significant Ru segregation to crystalline defects during the deposition process [4,5]. Significant Ru dissolution occurs during the OER, as revealed by online dissolution measurements, resulting in a few surface layers enriched in Ir, consistent with XPS results. APT further shows that the entire near-surface region affected by the oxidation exhibits signs of Ru dissolution. In addition, oxides formed in Ru-rich regions across the catalyst´s surface, i.e. in the proximity of grain boundaries, generally exhibit a higher oxygen content, compared to oxides on top of intergranular regions. Our data suggests that the defect structure of the material governs the enrichment of Ru in grain boundaries with consecutive preferential oxidation of these regions. This preferential oxidation potentially contributes to an accelerated, localized formation of volatile RuO4 species during the OER, leading to an enhanced Ru leaching along defect regions, eventually resulting in the deterioration of the overall reactivity of the material.Finally, using the new insights gained by this study, we discuss potential design strategy improvements of Ir-Ru alloys, to engineers an OER catalyst with a higher performance and longer durability. With this work we stress the need to investigate processes in catalytic materials with a combination of independent methods and at the near-atomic scale. Only the combination of insights enables the establishing of reliable structure-function relationships of electrocatalytic materials.

Communication—Dissolution and Passivation of a Ni-Cr-Fe-Ru-Mo-W High Entropy Alloy by Elementally Resolved Electrochemistry

The formation and dissolution of the passive film on a novel NiCrFeRuMoW high entropy alloy in H2SO4 was measured with atomic emission spectroelectrochemistry. Passivation involved Cr and Ru enrichment, whether passivation was achieved spontaneously at open circuit or by potentiostatic step into the passive domain. The other elements, Ni, Fe, Mo, and W, dissolved at rates approximately proportional to their bulk concentrations. The air formed film showed only a Cr enrichment. Excellent corrosion resistance properties were indicated by spontaneous passivation, the low passive current in the polarization curve, and the absence of detectable elemental dissolution during the active peak.

Ophiolite-related associations of platinum-group minerals at Rudnaya, western Sayans and Miass, southern Urals, Russia

ABSTRACTWe describe similar assemblages of minerals found in two placers in Russia, both probably derived from an ophiolitic source. The first is located along the River Rudnaya in the western Sayan province, Krasnoyarskiy kray, and the second pertains to the Miass placer zone, Chelyabinsk oblast, in the southern Urals. The platinum-group element (PGE) mineralization in both cases is mostly (at least 80%) represented by alloy minerals in the system Ru–Os–Ir, in the order of occurrence osmium, ruthenium and iridium. The remainder consists of Pt–Fe alloys and species of PGE sulfides, arsenides, sulfarsenides, etc. The associated olivine and amphiboles are supermagnesian, and the chromian spinel has a high Cr# value. The observed enrichment in Ru, typical of an ophiolitic source, may be due to high-temperature hydrothermal equilibration and mobilization in the ophiolite, as is the enrichment in Mg and Cr. Low-temperature replacement of the alloys led to the development of laurite, sulfoarsenides and arsenides. Some placer grains in both suites reveal unusual phases of sulfo-arsenoantimonides of Ir–Rh, e.g. the unnamed species (Rh,Ir)SbS and (Cu,Ni)1+x(Ir,Rh)1–xSb, wherex= 0.2, and rhodian tolovkite, (Ir,Rh)SbS. Two series of natural solid-solutions appear to occur in the tolovkite-type phases. Among the oddities in the Rudnaya suite are globules of micrometric PGE sulfides, crystallites of platinum-group minerals, amphibole, and chalcopyrite bearing skeletal micrometric monosulfide-like compounds (Cu,Pt,Rh)S and (Pd,Cu)S1–x. Pockets of fluxed evolved melt seem to have persisted well below the solidus of the host Pt3Fe-type alloy.

Redox Cycling in Nanogap Electrochemical Cells. The Role of Electrostatics in Determining the Cell Response

Ion transport near interfaces is a fundamental phenomenon of importance in electrochemical, biological, and colloidal systems. In particular, electric double layers in highly confined spaces have implications for ion transport in nanoporous energy storage materials. By exploiting redox cycling amplification in lithographically fabricated thin-layer electrochemical cells comprising two platinum electrodes separated by a distance of 150–450 nm, we observed current enhancement during cyclic voltammetry of the hexaamineruthenium(III) chloride redox couple (Ru(NH3)63/2+) at low supporting electrolyte concentrations, resulting from ion enrichment of Ru(NH3)63/2+ in the electrical double layers and an enhanced ion migration contribution to mass transport. The steady-state redox cycling was shown to decrease to predominately diffusion controlled level with increasing supporting electrolyte concentration. Through independent biasing of the potential on the individual Pt electrodes, the voltammetric transport limit...

AuRu/AC as an effective catalyst for hydrogenation reactions.

AuRu bimetallic catalysts have been prepared by sequential deposition of Au on Ru or vice versa obtaining different nanostructures: when Ru has been deposited on Au, a Au(core)-Ru(shell) has been observed, whereas the deposition of Au on Ru leads to a bimetallic phase with Ru enrichment on the surface. In the latter case, the unexpected Ru enrichment could be attributed to the weak adhesion of Ru on the carbon support, thus allowing Ru particles to diffuse on Au particles. Both structures result very active in catalysing the liquid phase hydrogenolysis of glycerol and levulinic acid but the activity, the selectivity and the stability depend on the structure of the bimetallic nanoparticles. Ru@Au/AC core-shell structure mostly behaved as the monometallic Ru, whereas the presence of bimetallic AuRu phase in Au@Ru/AC provides a great beneficial effect on both activity and stability.

PGE geochemical constraints on the origin of the Ni-Cu-PGE sulfide mineralization in the Suoi Cun intrusion, Cao Bang province, Northeastern Vietnam

The Permian (266–262 Ma) Suoi Cun intrusion in the Song Hien Rift Zone (NE Vietnam) consists of a sulfide-bearing mafic-ultramafic unit and a sulfide-free mafic unit. The Cu-Ni-PGE mineralization is represented by disseminated sulfides throughout the sulfide-bearing unit containing ~0.5 wt.% Ni, ~0.05 wt.% Cu, and ~0.2 ppm PGE. The sulfide schlieren have a limited distribution and contain ~2.6 wt.% Ni, ~0.5 wt.% Cu, and ~2.6 ppm PGE. The Suoi Cun rocks containing disseminated sulfides display moderately fractionated mantle-normalized PGE patterns with positive Pd and negative Ru anomalies. In contrast, the sulfide schlieren show enrichment in Ru with lower contents of other PGE except Pd. The low Cu/Pd ratios (1,385–11,529) throughout the intrusion indicate that all sulfides were separated from a PGE-undepleted magma as a result of a single sulfide segregation event. We suggest that sulfides segregated from Mg-rich basaltic magmas in a deep-seated magma chamber due to crustal contamination with country rocks. Then, the sulfide liquid along with early crystallizing olivines and Cr-spinels were pushed out upwards into an upper magma chamber by new pulses of magma. Two processes were important for understanding the PGE distribution: 1) fractionation of the sulfide liquid gave rise to PGE distribution observed in the disseminated ore and, 2) the interaction of oxidized silicate melts with the sulfide liquid was the responsible for the low PGE contents in the sulfide schlieren due to PGE transfer from the oxidized sulfide liquid to the silicate melt.

Platinum-group element (PGE) geochemistry of Mesoarchean ultramafic–mafic cumulate rocks and chromitites from the Nuasahi Massif, Singhbhum Craton (India)

The Mesoarchean Nuasahi Massif in eastern India comprises a lower ultramafic and an upper gabbro unit. The lower unit consists of orthopyroxenite, harzburgite, dunite and three chromitite bands. All these rocks are characterized by adcumulate textures. The upper unit consists of gabbro with magnetite layers. At the contact between the eastern orthopyroxenite and the lower part of the upper gabbro, a sulfide-rich breccia zone with platinum-group-element (PGE) mineralization is present. Detailed studies of major-, trace- and PGE abundances suggest that the ultramafic-mafic cumulate rocks, chromitites and breccias are genetically linked. The chondrite-normalized U-shaped rare earth element (REE) patterns of the harzburgite resemble those of Phanerozoic boninite. The overall U-shaped REE patterns of the ultramafic rocks indicate derivation of the parental magma from a metasomatized depleted mantle source. The upper gabbros have higher relative abundances of trace elements than the lower ultramafic rocks, due to crystallization from a fractionated magma. Whole-rock geochemistry suggests that the lower ultramafic cumulate rocks with chromitites crystallized from a boninitic parental magma, whereas the upper gabbros with magnetite bands may be formed from residual boninitic magma that was contaminated by more tholeiitic-like magmas. The boninitic parental magma that crystallized to form the lower ultramafic unit was most likely generated by second-stage melting of a depleted metasomatized mantle source in a supra-subduction zone (SSZ) setting and emplaced into crustal sequences. The PGE abundances in the Nuasahi rocks provide additional constraints on their geochemical evolution during the Mesoarchean. Primitive-mantle-normalized PGE diagrams show (1) Ru enrichment in chromitites (Pd/Ru = 0.17 - 0.64), (2) Pd/Pt fractionation in both chromitites (Pd/Pt = 3.1) and ultramafic rocks (Pd/Pt = 0.62), (3) marked Ir depletion in ultramafic rocks (Pd/Ir = 6.3) and (4) overall PGE enrichment in chromitites (PGEtotal = 142 – 502 ppb). The large Ir depletion in the ultramafic rocks, and the overall Ir-depleted character of other rocks from the Nuasahi Massif, may be related to multiple episodes of melt extraction from the mantle source, giving it a subchondritic character.

Effect of the amount of reducing agent on surface structures, electrochemical activity and stability of PtRu catalysts

The effect of the amount of reducing agent used in the synthesis of PtRu alloy catalysts on their surface structure was investigated, and the prepared catalysts were characterized using transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, cyclic voltammetry, and potential cycling. The alloying degree of the catalysts was essentially the same for all of the catalysts studied, despite the use of different amounts of reducing agent. Varying the amount of reducing agent resulted in changes in the surface composition of the catalysts, wherein the surfaces were found to be composed of several PtRu domains that differed in local inhomogeneity and hence showed differences in activity for CO ad oxidation. The highest activity for methanol oxidation was obtained when there was moderate Ru enrichment of the catalyst. The electrochemical stability of the catalysts was also investigated via potential cycling in a methanol-containing electrolyte solution. The electrochemical stability under methanol oxidation was enhanced by Ru-enrichment at the catalyst surface, because the Ru-rich surface had sufficient Ru atoms near the Pt atoms to act as a bifunctional catalyst, even though the Ru atoms were leached out by potential cycling. The most Ru-rich catalyst exhibited an increase in methanol oxidation current in the middle of potential cycling whereas the other catalysts showed a monotonic decrease.

Process intensification in extraction by liquid emulsion membrane (LEM) process: A case study; enrichment of ruthenium from lean aqueous solution

Process intensification in extraction as a unit operation can be realized through liquid emulsion membrane (LEM) process by combining extraction and stripping in one stage eliminating the need of stripper. LEM technique is very useful to enrich very lean aqueous phase containing precious metal to aid the recovery process. The technique is illustrated by applying the same to enrich platinum group noble metal, ruthenium (Ru) from its aqueous solution. The liquid membrane phase consisted of extractant (trioctylamine) dissolved in liquid paraffin modified with 1-octanol and the surfactant used was Monemul 80. The strip phase found to be very effective was perchloric acid. To facilitate extraction tin(II) chloride was added to the aqueous feed phase containing Ru at 20 ppm level. Various process parameters affecting the performance of LEM process such as extractant, surfactant, strip phase concentrations, the batch extraction time, the treat ratio and the speed of agitation were studied at bench scale to aid process development. The maximum enrichment of Ru, obtained was almost 10.3 times, in the internal strip phase (2 mol L −1 of perchloric acid), from the feed phase containing Ru at 20 ppm level.

Iridium, ruthenium and rhodium in komatiites: Evidence for iridium alloy saturation

A large body of new data (over 400 samples) on platinum-group element (PGE) concentrations in Yilgarn Craton komatiites is combined with all available high-quality literature data, to reveal trends in a spectrum of komatiite lithologies ranging from spinifex-textured rocks to pure olivine and olivine–chromite adcumulates. The data set is restricted to Carius Tube-isotope dilution analyses, and high-precision nickel sulfide fire-assay-ICP-MS analyses, and we demonstrate good agreement between the two methods. Only S-poor samples are considered, and the data set is filtered to eliminate the effects of addition of cumulus chromite, and addition or segregation of magmatic sulfide liquid. The residual trends indicate that Ir, Ru and Rh are decoupled from one another and from Pt and Pd. Rhodium behaves more like Pt and Pd, whereas Ru is intermediate between Ir and Rh. Rhodium and Ru both show indications of olivine control with partition coefficients less than unity. The maximum Ir whole-rock content is a roughly linear positive function of MgO, but the minimum is constant, sub-1 ppb and independent of MgO. Ruthenium shows some evidence for limited control by chromite, but anomalous Ru enrichment is also found in some olivine cumulate samples with no evidence for accumulated chromite or sulfide. Neither Rh nor Ir shows evidence for any detectable control by chromite. The distribution of Ir, and to a lesser degree Ru and Rh, cannot be adequately explained by olivine control, and a major influence of an Ir-rich phase is strongly indicated. The pattern of Ir variance in relation to MgO bears some important similarities to that of Cr. This similarity arises from the fact that both elements are controlled by a temperature-dependent solubility limit: the chromite saturation surface in the case of Cr, and saturation in Ir (or Ir–Os) alloy in the case of Ir. Combining this effect with moderate compatibility in olivine allows us to successfully model the entire range of Ir data. The upper limit of Ir concentration in olivine cumulates, in an exact analogy to that for Cr, is interpreted as the cotectic ratio of olivine to alloy, as determined by the average slope of the tangent to the alloy solubility curve. Sulfide-undersaturated mantle melts of a wide range of compositions are likely to be Ir alloy saturated. Experimental predictions of very low Ir solubilities in magmas are borne out, with the further implication that true thermodynamic sulfide–silicate liquid partition coefficients, at least for Ir and by inference for the other PGEs, are of the order of 10 7 or even higher.

PtRu Nanoparticle Electrocatalyst with Bulk Alloy Properties Prepared through a Sonochemical Method

Properties of PtRu nanoparticles prepared using high-intensity sonochemistry are reported. Syntheses were carried out in tetrahydrofuran (THF) containing Ru3+ and Pt4+ in a fixed mole ratio of either 1:10 or 1:1. X-ray diffraction measurements confirmed sonocation produces an alloy phase and showed that the composition of the nanometer scale metal particles is close to the mole fraction of Ru3+ and Pt4+ in solution with deviations that tend toward Ru enrichment in the alloy phase. The materials gave responses that are similar in terms of peak potential and current density, referenced to the catalyst active surface area, to those of bulk alloys in voltammetry experiments involving CO stripping and CH3OH electrochemical oxidation in 0.1 M H2SO4. The results show that sonochemical methods have the potential to produce nanometer scale bimetallic electrocatalysts that possess alloy properties. The materials have application in mechanistic studies of fuel cell reactions and as platforms for the development of CO tolerant fuel cell catalyst.

Activation of Nanoparticle Pt−Ru Fuel Cell Catalysts by Heat Treatment: A 195Pt NMR and Electrochemical Study

(195)Pt NMR spectroscopic and electrochemical measurements were carried out on commercial Pt-Ru alloy nanoparticle samples to investigate the effect of high-temperature annealing in different vacuum/gas-phase environments. Samples annealed at 220 degrees C in Ar gas, or in a vacuum, did not show any demonstrable change in catalytic activity vs electrochemically reduced, room-temperature samples. In contrast, annealing at 220 degrees C in H(2) gas led to a 3-fold increase in reactivity toward methanol oxidation (per surface site). NMR experiments show that annealing at 220 degrees C (in both Ar and H(2)) leads to a slight reduction in the Fermi level local density of states (E(F)-LDOS) at the Pt sites, which we attribute to surface enrichment of Ru. This electronic effect alone, however, appears to be too small to account for the increase in the catalytic activity observed for the H-treated catalyst. By comparing the electrochemical and NMR data of the H- and Ar-treated samples, we conclude that annealing at 220 degrees C in the hydrogen atmosphere reduces surface Ru oxides into metallic Ru, and consequently, the presence of metallic Ru and its enrichment on the surface are essential for the enhanced catalytic activity. In contrast, heat treatment at 600 degrees C in both vacuum and argon atmosphere increases the particle size and reduces the amount of platinum on the nanoparticle surface, thereby increasing the surface Ru content beyond the optimum surface composition values. This causes a large reduction in catalytic activity. Our results suggest that optimizing the amount of surface Ru by heat treatment at temperatures near 200 degrees C, in a hydrogen atmosphere, can be utilized to produce Pt-Ru alloy nanoparticles with high methanol oxidation activity. Finally, our NMR and electrochemical data, taken together with the lattice parameter measurements, lead to a novel model of Pt-Ru alloy nanoparticles having a Ru-rich core and a Pt-Ru alloy overlayer.