Iridium Content Research Articles

Widespread elevated iridium in Upper Triassic\u2013Lower Jurassic strata of the Newark Supergroup: implications for use as an extinction marker

Anomalous levels of iridium in sedimentary strata are associated with mass extinction events caused by impact events. In the case of the end-Triassic extinction event, the anomalies as well as the extinctions are linked to the eruption of the Central Atlantic Magmatic Province (CAMP) flood basalts. We report new data on concentrations of iridium in continental strata of the Fundy, Deerfield, Hartford and Newark basins, both above and below the oldest CAMP flows in these basins, that demonstrate that these anomalies are more common than previously known. We conclude that the enrichments were at least in some instances likely derived locally by concentration due to leaching directly from the lavas into sediments proximal to the CAMP flows due to post-eruptive hydrothermal activity. In other instances, the enrichments likely record the global fallout of aerosols and/or ash particles during the eruptions of the CAMP basalts. The common association of the highest levels of enrichment with organic matter suggests either redox control or stabilization by formation of organometallic complexes following post-eruptive redistribution. These findings demonstrate the importance of considering the distribution and magnitude of iridium anomalies in considering the source of the iridium and possible extinction mechanisms.

CO2-free energy circulation system—Polymer electrolyte alcohol electro-synthesis cell with a low iridium content anode based on in situ growth method

Alcohol is considered as a potential CO2-free energy carrier to replace hydrogen because of its high energy density, appropriate chemical stability and low-cost production. In this study, we describe the development of a simple in situ growth method to prepare a binder free IrOx-Ti anode with a very low IrOx loading amount (< 0.25 mg cm−2), and the obtained catalyst shows a high oxygen evolution reaction (OER) activity and durability in acidic media. The performance of a polymer electrolyte alcohol electrosynthesis cell (PEAEC) using this anode catalyst shows a better performance than that of PEAEC using a typical commercial IrO2-Ti paper anode with the loading of IrO2 = 3 mg cm−2. Furthermore, the key factors that affect the performance of the PEAEC are determined by comparing the performances of the PEAEC with different anode catalysts.

An overview on radiometric assessment and excess lifetime cancer risk of soil in Pakistan by using High Purity Germanium (HPGe) detector.

The aim of this study is to compare the natural radioactivity and excess life time cancer risk (ELCR) factor of soil in different regions of Pakistan during last decade. Soil contains various elements and compounds including naturally occurring radioactive elements (238U, 232Th, 40K and 137Cs). Human being, animals and plants are in health risk by contaminations of natural radioactivity in soil and environmental radiometric pollution. Transferring of large amount of the natural radioactive elements in human body by nutrients may cause carcinogenic effects in human body. Pakistani soil has six types as Indus Basin Soil, Bongar Soil, Khaddar Soil, Indus delta soil, Mountainous soil and Sandy Desert Soil. In some northern region of Pakistan, naturally occurring radioactive rocks like uranuium-238 and iridium concentrations present in Gharwandi, Aram, Kingri S, Vitakri Fort Munro, Dera Bugti, Kohlu and Sibbi districts. In this reviewed data, gamma rays spectroscopy used to determine the concentrations of 238U, 232Th and 40K with the help of High Purity Germanium (HPGe) detectors. Only the data of HPGe detector collected because of comparisons of different regions of Pakistan. Mostly, different gamma rays energy peaks of relevant daughter radionuclides of radioactive element were used such as the energy peak lines of daughter radionuclides 214Pb (295.21 and 352KeV) and 214Bi (609 and 1,120KeV) used for calculating the 226Ra concentration in soil. In the recent study, it is concluded that average values of concentrations of natural radioactivity in soil in central and north regions of Pakistan are higher than permissible limit but found permissible range in south region of Pakistan. Mean values of ELCR factor were found higher, equal and lower in central, north and south regions than permissible limit, respectively. Generally, no serious health hazard due to natural radioactivity in soil were found.

Dehydrogenation of methylcyclohexane over Pt supported on Mg–Al mixed oxides catalyst: The effect of promoter Ir

To enhance the hydrogen release during hydrogen storage, several Pt–Ir supported on Mg–Al mixed oxide catalysts were prepared and then applied into the dehydrogenation of methylcyclohexane (MCH) in this study. The effects of iridium content, reduction temperature on the activity and stability of the catalysts were studied in detail. In the presence of Ir, metal particle size was decreased and electron transfer between Ir and Pt was observed. High reduction temperature increased the metallic Ir content but enlarged the particle size of active sites. During the dehydrogenation reaction on Pt–Ir bimetallic catalyst, MCH was efficiently converted into toluene and PtIr-5/Mg–Al-275 exhibited the highest activity. After prolonging the residence time and raising the reaction temperature to 350 °C, the conversion and hydrogen evolution rate were increased to 99.9% and 578.7 mmol·(g Pt) −1 ·min −1 , respectively. Moreover, no carbon deposition was observed in the spent catalyst, presenting a high anti-coking ability and good potential for industrial application. Hydrogen evolution rate reached up to 578.7 mmol·g Pt −1 ·min −1 in the dehydrogenation of methylcyclohexane on Pt–Ir supported on Mg–Al mixed oxide catalyst and no carbon deposition on the catalyst surface was observed after dehydrogenation reaction.

Determination of the iridium micro-concentrations using a kinetic catalytic method

The catalytic effect of iridium on the oxidation of water-soluble porphyrin — 5,10,15,20-tetrakis (4-sulfonatophenyl) porphin (TSPP) with sodium periodate is studied for the first time. A method for determination of the iridium micro-content by the catalytic effect of iridium on the oxidation of water-soluble porphyrin 5,10,15,20-tetrakis (4-sulfonatophenyl) porphin with sodium periodate in a flow-injection system is developed. The lower limit of the determined iridium concentrations is 0.2 × 10–5 μg/ml (P = 0.95), which is lower than that for the methods described in the literature. Optimal conditions for determination have been specified: pH 3; concentration of the reagents in the flows of a given hydraulic mixing scheme 0.5 × 10–5 M TSPP and 0.15 M NaIO4; room temperature for the indicator reaction. A linear calibration characteristic was obtained under chosen optimal conditions in the range of iridium concentrations (0.2 – 2.0) × 10 – 5 μg/ml. The effect of the elements accompanying iridium in industrial and natural materials was studied. Molar excesses of platinum and non-ferrous metals do not interfere with iridium determination: 20-fold Rh (III); 15-fold Pt (IV) and Fe (II); and 20-fold molar excess of Ni (II). Correctness of the results is confirmed by spike recovery tests on model iridium-containing solutions. Sr of the results of iridium determination under selected conditions at n = 3, P = 0.95 on model solutions is no more than 0.04. A comparison of the obtained results with literature data showed that the main advantages of the proposed method for iridium determination are room temperature of the reaction, more simple hardware design and lower limit of the iridium determination.

Rational Design of an Iridium-Tungsten Composite with an Iridium-Rich Surface for Acidic Water Oxidation.

Developing highly active and stable water oxidation catalysts with reduced cost in acidic media plays a critical role in clean energy technologies such as fuel cells and electrolyzers. Precious iridium-based oxides are still the only oxygen evolution reaction (OER) catalysts with reasonable activity and stability in acid. Herein, we design iridium-tungsten composites with a metallic tungsten-rich core and an iridium-rich surface by the sol-gel method followed by hydrogen reduction. The thus obtained iridium-tungsten catalyst shows much higher intrinsic water oxidation activity (100 mA/mgIr at an overpotential of 290 mV) and stability (100 h at 10 mA/cm2geom) together with reduced iridium content (33 wt % only) as compared with pure iridium oxide. An operando method using H2O2 as a probe molecule is developed to determine the relative adsorption strength of the reaction intermediates (*OH and *OOH) in the OER process. Detailed characterization shows that the tungsten-incorporated surface not only modulates the adsorption energy of oxygen intermediates on iridium but also enhances the stability of iridium species in acid, while the metallic tungsten core exhibits high electrical conductivity, all of which collectively give rise to the much enhanced catalytic performance of iridium-tungsten composite in acidic water oxidation. A single-membrane electrode assembly is further prepared to demonstrate the advantages and potential application of iridium-tungsten composite in practical proton exchange membrane electrolyzers.

Solution‐Processed Polymer Solar Cells with over 17% Efficiency Enabled by an Iridium Complexation Approach

AbstractThe commercially available PM6 as donor materials are used widely in highly efficient nonfullerene polymer solar cells (PSCs). In this work, different concentrations of iridium (Ir) complexes (0, 0.5, 1, 2.5, and 5 mol%) are incorporated carefully into the polymer conjugated backbone of PM6 (PM6‐Ir0), and a set of π‐conjugated polymer donors (named PM6‐Ir0.5, PM6‐Ir1, PM6‐Ir2.5, and PM6‐Ir5) are synthesized and characterized. It is demonstrated that the approach can rationally modify the molecular aggregations of polymer donors, effectively controlling the corresponding blend morphology and physical mechanisms, and finally improve the photovoltaic performance of the PM6‐Irx‐based PSCs. Among them, the best device based on PM6‐Ir1:Y6 (1:1.2, w/w) exhibits outstanding power conversion efficiencies (PCEs) of 17.24% tested at Wuhan University and 17.32% tested at Institute of Chemistry, Chinese Academy of Sciences as well as a certified PCE of 16.70%, which are much higher than that of the control device based on the PM6‐Ir0:Y6 blend (15.39%). This work affords an effective approach for further break through the reported champion PCE of the binary PSCs.

Evidence of Cosmic Impact at Abu Hureyra, Syria at the Younger Dryas Onset (~12.8 ka): High-temperature melting at >2200\u2009\xb0C

At Abu Hureyra (AH), Syria, the 12,800-year-old Younger Dryas boundary layer (YDB) contains peak abundances in meltglass, nanodiamonds, microspherules, and charcoal. AH meltglass comprises 1.6 wt.% of bulk sediment, and crossed polarizers indicate that the meltglass is isotropic. High YDB concentrations of iridium, platinum, nickel, and cobalt suggest mixing of melted local sediment with small quantities of meteoritic material. Approximately 40% of AH glass display carbon-infused, siliceous plant imprints that laboratory experiments show formed at a minimum of 1200°–1300 °C; however, reflectance-inferred temperatures for the encapsulated carbon were lower by up to 1000 °C. Alternately, melted grains of quartz, chromferide, and magnetite in AH glass suggest exposure to minimum temperatures of 1720 °C ranging to >2200 °C. This argues against formation of AH meltglass in thatched hut fires at 1100°–1200 °C, and low values of remanent magnetism indicate the meltglass was not created by lightning. Low meltglass water content (0.02–0.05% H2O) is consistent with a formation process similar to that of tektites and inconsistent with volcanism and anthropogenesis. The wide range of evidence supports the hypothesis that a cosmic event occurred at Abu Hureyra ~12,800 years ago, coeval with impacts that deposited high-temperature meltglass, melted microspherules, and/or platinum at other YDB sites on four continents.

Platinum-group elements link the end-Triassic mass extinction and the Central Atlantic Magmatic Province

Elevated concentrations of iridium (Ir) and other platinum-group elements (PGE) have been reported in both terrestrial and marine sediments associated with the end-Triassic mass extinction (ETE) c. 201.5 million years ago. The source of the PGEs has been attributed to condensed vapor and melt from an extraterrestrial impactor or to volcanism. Here we report new PGE data for volcanic rocks of the Central Atlantic Magmatic Province (CAMP) in Morocco and show that their Pd/Ir, Pt/Ir and Pt/Rh ratios are similar to marine and terrestrial sediments at the ETE, and very different from potential impactors. Hence, we propose the PGEs provide a new temporal correlation of CAMP volcanism to the ETE, corroborating the view that mass extinctions may be caused by volcanism.

Theoretical insights into nonprecious oxygen-evolution active sites in Ti–Ir-Based perovskite solid solution electrocatalysts

A novel core/shell-type material model, where an iridium-free STO core is covered with a single-layered-thick STIO shell, is overall suggested to achieve highly active oxygen evolution electrocatalysts with an ultralow iridium content.

Structure and properties of a-C films modified with Ir nanoparticles

In this work, thin amorphous carbon films modified with iridium nanoparticles (a-C <Ir>) synthesized by magnetron ion-plasma co-sputtering in an argon atmosphere are considered.The morphology and structure of a-C <Ir> films were studied using atomic-force microscopy and Raman spectroscopy. The dispersion of the G peak showed structural changes of a-C with increasing Ir concentration in the films, which is more clearly manifested in the films synthesized on silicon substrates. The optical and electrical properties of a-C <Ir> films were studied. A change in the band gap with increasing Ir concentration additionally showed a structural transition from a diamond-like to a graphite-like matrix. A percolation transition of conductivity at Ir concentration of ∼0.2 at.% in a-C <Ir> films was detected and an increase in conductivity by 107 when the concentration of iridium was increased by 0.7 at.%.

Tailored mesoporous Ir/TiOx: Identification of structure-activity relationships for an efficient oxygen evolution reaction

The depletion of fossil resources coupled with an increasing demand in both sustainable and renewable energy sources further strengthen the development of highly efficient electrocatalytic water splitting catalysts. Iridium oxide is well known for its excellent activity and stability during acidic oxygen evolution reaction (OER). However, high prices and rare abundance demand the most efficient utilization.We report a new synthesis approach for iridium/titanium-based mixed oxides with a tailored mesopore structure employing iridium acetate and titanium chloride as precursors. The new Ir/TiOx system outperforms OER catalysts based on other titanium precursors by a factor of up to two. The material is used as a model system to investigate the impact of synthesis and structural parameters on OER performance.We find that calcination temperature and iridium content are the main synthesis parameters to achieve tailored structures and superior electrochemical activity. The highest surface area and OER-activity are attained for samples with a fully developed mesoporous network and small crystallite sizes obtained by a moderate calcination around 400 °C. A minimum content of iridium is required to achieve sufficient electrical conductivity, whereas at higher iridium content the OER performance scales approximately linearly.

Characterization of binary Ce–Ir alloy photocathodes

Binary Ce–Ir alloys nominally containing 83, 78, 75, and 67 at% Ir were grown via arc melting in order to clarify the optimum composition for a Ce–Ir system to be used as photocathode material. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) analysis were employed to characterize the microstructure and phase composition of these alloys. The results of the XRD analyses and SEM/EDX measurements indicated that single-phase homogeneous crystals composed of CeIr2 grains were successfully grown in the sample with an iridium content amounting to 67 at%. Through quantum efficiency (QE) measurements, it was revealed that the QE of the Ce-67 at% Ir alloy (CeIr2 phase) is a few times higher than that of the other Ce–Ir alloys.

Ni0.6-xMo0.4-xIrx-oxide as an electrode material for supercapacitors: investigation of the influence of iridium content on the charge storage/delivery

Ni0.6-xMo0.4-xIrx-oxide coatings were fabricated with the purpose of investigating the influence of Ir content on their charge storage/delivery capability when used as an electrode for electrochemical supercapacitor. Experimental work in alkaline medium confirmed that the amount of Ir in the Ni-Mo-oxide significantly influences the material’s charge storage capacity. The highest overall capacitance (108 ± 2 mFcm−2 at 1 mA cm−2) was obtained for the composition containing 40 mol% of Ir (Ni0.36Mo0.24Ir0.4-oxide), while the best candidates in terms of the intrinsic (surface area–independent) charge storage/delivery are the compositions containing 20 and 40 mol% of Ir (no statistical difference). Ni0.36Mo0.24Ir0.4-oxide was found to retain ca. 86% of its initial capacitance after 2500 charge-discharge cycles, at 1 mA cm−2.

Electrodeposited mesh-type dimensionally stable anode for oxygen evolution reaction in acidic and alkaline media

A mesh-type dimensionally stable anode (DSA) consisting of ruthenium and iridium with low catalyst loading was prepared as an oxygen evolution reaction catalyst in acidic and alkaline media. The electrodeposition (ED) conditions, i.e., applied current density and total cycle number, and ED solutions with different precursor ratios of ruthenium to iridium are examined to fabricate various DSAs with a uniform thickness, and the effect of the iridium content on the catalytic activity is investigated. Among various DSA electrodes, the DSA electrode without iridium exhibits the highest activity and stability in the acidic medium owing to the high ratio of ruthenium. Conversely, the DSA electrode obtained using the ED solution with the ratio of 8:2 exhibits the highest performance in the alkaline medium. This is because the DSA electrode without iridium showed low stability, which is attributed to the dissolution of ruthenium oxide in the alkaline medium. In addition, two large-scale DSA electrodes optimized in the acidic and alkaline electrolytes show excellent performance, indicating the feasibility of the application of this electrode in practical electrolysis.

On a link of rare earth-rare metal and gold-ore mineralizationwith fault-block tectonics of the Ukrainian shield. 2

In the second article of the cycle «On a link of rare earth-rare metal and gold-ore mineralization with fault-block tectonics of the Ukrainian shield» [Nechaev et al., 2018] the internal structure, kinematics, age and metallogeny of the faults of the Gaivoron-Zavaliev section of the Pobuzhie mining region (PMR) of the Ukrainian shield (USh) have been considered. It is shown that the Gaivoron zone of faults with a width of up to 10 km consists of five shear zones of the latitudinal stretch, which make up the boundary between the Bug and Ros in megablocks of the USh. The kinematic shear zones are laid out as left shifts in the field of stresses σ 1 45°, σ 3 315°, σ 2 ∟ (West-Ingulets stage). The youngest stage of their activization is the Subbotsk-Moshorin (σ 1 312°, σ 3 42°, σ 2 ∟ — right shift). The actual Gaivoron shear zone is characterized by widespread lamprophyres with rare earth mineralization of La, Ce, Y, as well as increased content of Ti, Mn, Ba, Cr. Within the Khaschevat shear zone the Solomievsk deposit of aqueous phosphates with yttrium composition of ores and an iron-manganese deposit with a priority triad of Y, Yb, Ge, as well as Au are known among tectonites. The granitoids of the Ustye-Stavsk shear zone are characterized by an abnormally high monazite content. For the first time the internal structure and kinematics of the Zavaliev fault zone, the width of which is at least 4 km, is studied in detail. It is shown that it consists of two shear zones — the latitudinal actually Zavaliev and northeastern Peschanaya-Zhakchik. Both shear zones are observed in the Zavaliev graphite pit. The yformed, as the Gaivoron zone of faults, at the West-Ingulets stage, and the last phase of activіzation took place in the Subbotsk-Moshorin stage. The opinion that the Zavaliev structure is not a synclinal fold, as was supposed to be, but an intrafault lens of hydrothermalites-metasomatites. These include graphite-biotite gneisses and shales, ore and ore-free quartzites, calciphyres and skarnoids. In addition to the world’s reserves of graphite, elevated concentrations of gold, silver, platinum, and iridium are widely represented in the zone of faults (in zones of silicification and sulfidization of graphite-biotite gneisses).

Optical properties of zinc-iridium oxide thin films

We present the results of an investigation of ultraviolet, visible, near-infrared (UV-Vis-NIR) and X-ray absorption spectroscopy absorption spectra for zinc-iridium oxide (Zn-Ir- O) thin films with various iridium concentrations deposited by reactive DC magnetron sputtering. It is found that the absorption spectra of zinc-iridium oxide thin films contain a broad band with maxima at 446 nm and 710 nm in the visible region, bands with maxima at about 1100 nm and 3300 nm, and a low-intensity absorption band at 1570 nm in the near-infrared region. The obtained absorption bands are associated with iridium ions at valences of Ir3+, Ir4+ and Ir5+. Changes in the oxidation state of iridium ions from 5+ to 4+ are observed.

Atomic Layer Deposited TiO2–IrOx Alloys Enable Corrosion Resistant Water Oxidation on Silicon at High Photovoltage

We synthesized by atomic layer deposition (ALD) TiO2–IrOx alloys that enable high photovoltages and catalyze water oxidation on silicon metal–insulator–semiconductor (MIS) photoanodes. The ratio of TiO2 to IrOx was precisely controlled by varying the number of ALD cycles for each precursor. Silicon with a 2 nm surface SiO2 layer was coated with TiO2–IrOx alloys ranging in composition from 18 to 35% iridium relative to the sum of titanium and iridium concentrations. IrOx catalyzed oxygen evolution and imparted a high work function to the TiO2–IrOx alloys, enabling photovoltages during water oxidation that exceeded 600 mV. TiO2 imparted stability and inhibited corrosion of the underlying silicon light absorber. After annealing in forming gas (5% H2/95% N2), TiO2–IrOx alloys were stable for 12 h of continuous water oxidation in 1 M H2SO4. Key properties of the MIS junction affecting electrochemical operation were also extracted by electrochemical impedance spectroscopy. This work demonstrates that alloying b...

Hierarchically Structured Ultraporous Iridium‐Based Materials: A Novel Catalyst Architecture for Proton Exchange Membrane Water Electrolyzers

AbstractIridium oxide is the gold‐standard catalyst for the oxygen evolution reaction (OER) in acidic media due to its unmatched activity and stability. Here, a new catalyst architecture comprising a nanoneedle network of iridium‐containing oxides assembled into macroporous micrometric particles with ≈75% of porosity is reported. The rationally designed porous hierarchical structure optimizes the accessibility of reactants and products to the surface of the nanoparticles and maximizes catalyst activity. The materials are easily prepared from aqueous solutions by an industrially viable spray‐drying route through an evaporation self‐assembly mechanism. The versatility of the process enables the preparation of mixed oxides with low iridium content, particles with tunable crystallinity, and various iridium surface species with high electrochemical activity. Highly porous Ir0.7Ru0.3O2 outperforms commercial iridium oxide. These materials also represent an ideal platform to assess the reactivity of the iridium and oxygen species involved in the oxygen evolution reaction. Furthermore, it is demonstrated that these highly porous particles are optimal building blocks to be integrated into catalyst layers, without the drawbacks associated with the use of discrete nanoparticles. Fresh‐ and end‐of‐test membrane–electrode assemblies' characterization shows that their particular architecture is preserved upon catalyst layer preparation and after operation in a proton‐exchange membrane electrolysis cell.

Iridium substitution in nickel cobaltite renders high mass specific OER activity and durability in acidic media

Oxygen evolution reactions being kinetically sluggish and highly expensive remains bottleneck in high pressure hydrogen production from acidic solution water electrolysis. Process economization is mostly affected due to larger consumption of precious iridium as an anodic catalyst. Therefore, effective utilization of noble metal remains a major challenge to be overwhelmed. Comprehensive theoretical and experimental studies show electronic dependency on different structural motifs of IrOx. However, due to lack of suitable non-noble host structures for iridium substitution there is hindrance in implementation. In current study, we explored inverse spinel, nickel cobaltite, as a host structure that provides OER beneficial structural motif to iridium sites on account of relatively higher IrO6 edge sharing than in rutile IrO2. Compact presence of octahedras in host structure reduces IrIr bond length for neighboring IrO6 octahedral units in it that further intrinsically improves the iridium sites due to electronic modulations. Specifically, composite comprising 20 mol% iridium in NiCo2-xO4 rendered acid stable 15 folds enhancement in mass specific OER activity relative to IrO2 resulting in substantial reduction of iridium content. Fabricated composite displayed an onset potential and tafel slope of 1.425 V and 40.4 mV dec−1, respectively in relative to 1.475 V and 68.1 mV dec−1 for pure IrO2. Current approach for effectively utilizing precious metal will lead in future for economizing hydrogen production via water splitting.