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We report the structure and physical properties of a new rare-earth (RE) high-entropy boride (HEB) (Dy 0.2 Ho 0.2 Er 0.2 Tm 0.2 Lu 0.2)(Rh 0.85 Ru 0.15) 4 B 4. The as-cast HEB consists of a highly crystallized, body-centered-tetragonal phase (I 4 1 / a c d , a = 7.460 Å and c = 14.860 Å); here, all the RE elements share the same crystallographic site and are distributed uniformly on both macroscopic and microscopic scales. At high temperature, the HEB shows a paramagnetic behavior with a large effective moment p eff yet it becomes a bulk superconductor upon cooling below 6.0 K. Remarkably, a peculiar cocktail effect of properties is observed: while the lattice parameters, T c and p eff of the HEB agree reasonably well with the compositional averages of the individual pseudo-ternary counterparts, the increased RE mixing entropy tends to suppress the superconductivity even without the magnetic exchange interactions, and a reentrant resistive transition is induced at magnetic fields above 0.8 T. Our results indicate that the high-entropy design of the RE sublattice is a viable way to tune the electrical and magnetic properties in RE intermetallics. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co-recycle of spent automotive catalysts and printed circuit boards was proposed. • Co-recycle can simultaneously achieve metal enrichment and detoxification. • Slag design, pollution suppression, metal distribution and settlement were analyzed. • Influence of copper size on platinum group metals recovery rate was discussed. The traditional pyrometallurgical recycling of nano-sized platinum group metals (PGMs) from spent automotive catalysts (SACs) is an energy-intensive process that requires the addition of large quantities of copper capture and slag-forming reagents. Similarly, pyro-recycling of valuable metals from waste printed circuit boards (WPCBs) is also an energy- and reagent-intensive process that and carries a risk of pollution emissions. Based on the complementarity of composition and similarity of recycling process, synergistic pyro-recycling of SACs and WPCBs allow copper in WPCBs to capture PGMs in SACs and oxides from two waste form slag jointly, which offers benefits of enhanced metal recovery, reduced reagent and energy consumption, and suppressed pollutant emissions. However, the mechanisms of PGMs capture and pollutant transformation in co-smelting remain unknown. Here, we investigated the sub-processes mechanisms of slag formation, brominates fixation, multi-metal distribution and kinetic settlement. Oxides in both wastes support SiO 2 -Al 2 O 3 -CaO slag formation with low melting point and viscosity, where CaO suppresses the emission of brominated pollutants. Copper (50–100 μm) from WPCBs facilitates nano-sized PGMs in SACs recovery through capture and settlement. The results of demonstration experiments indicated a recovery rate of 94.6 %, 96.8 %, 97.2 %, and 98.1 % for Cu, Pt, Pd, and Rh, respectively, with a debromination efficiency exceeding 98 %. The theoretical analysis provides support for the establishment of a synergistic pyro-recycling process for SACs and WPCBs and provides insights into the potential for a greener and more efficient co-recycling of multi urban mines. [ABSTRACT FROM AUTHOR]

A series of M/NiCo-Ferrite (M: Pt, Pd, Ru, and Rh) nanoparticles were successfully synthesized, through a facile sol–gel auto-combustion followed by impregnation-reduction approach, as a catalyst for hydrogen generation from hydrolysis of NaBH4. All synthesized samples were characterized by XRD, N2 adsorption–desorption method, ICP-OES, FE-SEM, and EDX analysis. Compared to the other samples, it was observed that the Rh/NiCo-Ferrite sample exhibited higher particle distribution and surface area. To evaluate the hydrogen generation rate, the hydrolysis was carried out at a temperature of 35 °C, with an aqueous solution containing 5 wt.% NaBH4 and 3 wt.% NaOH. The experimental findings indicate that the Rh/NiCo-Ferrite sample exhibited a superior rate of hydrogen generation, with an average value of 11,667 mL/min.gcat, compared to the other samples studied. Enhanced catalytic properties may be responsible for its high activity. In addition, the activation energy of hydrolysis of sodium borohydride over the Rh/NiCo-Ferrite sample was 54.5 kJ/mol which is lower than the activation energy of many Ferrite-based catalysts. Moreover, the re-usability test of the Rh/NiCo-Ferrite sample denoted a decline in the catalytic activity after 4 recycling experiments due to the alterations in morphology and the reduction in the quantity of active phase. [ABSTRACT FROM AUTHOR]

The electrocatalytic dehydrogenation of ethylamine (EDH), owing to its high hydrogen content, holds broad prospects in electrochemical hydrogen (H2) production, H2 storage, and addressing energy issues, thus deserving wide attention. In this feature article, we first summarized the fundamentals of thermocatalytic and electrocatalytic EDH and reviewed the recent state-of-the-art advances in catalyst research, specifically platinum group metal (PGM) catalysts and non-PGM catalysts. We systematically discussed the potential applications of electrocatalytic EDH in energy storage and conversion. Finally, we provide our perspective on the key challenges and future developments in this field. We believe this feature article will offer helpful guidance for oriented design and optimization of stable and efficient catalysts for electrocatalytic EDH and related energy applications. [ABSTRACT FROM AUTHOR]

Effective solid-phase extractants (SPE) based on multi-walled carbon nanotubes (CNT) of various structures modified with an organic reagent, 2-mercaptobenzothiazole, were developed. Using scanning and transmission electron microscopy, the morphological and structural features of SPE samples and their elemental composition were determined. It was shown that the specific surface area of the modified CNT is approximately two times lower compared to the original CNT. It was revealed that the modified materials are CNT coils coated with a uniform organic shell 10−15 nm thick. The sorption capacity of the original nanotubes in 1.0 M HCl and of their modified forms (in 0.1−3.0 M HCl) at room temperature and at 80°C was determined. It was found out that in strongly acidic media, SPE based on G-183 CNT and 2-mercaptobenzothiazole, effectively sorbs Pt, Pd and Au at room temperature, and Ru and Rh at the temperature of 80°C. A possibility of the selective extraction of platinum group metals and gold with this sorbent in the presence of macroquantities of Al, Fe, Cu, Ca and Mg was assessed. [ABSTRACT FROM AUTHOR]

Platinum belongs to the technological metal group of platinum group metals, but it is finding more and more applications these days, especially in automotive catalytic converters and medicine. At the same time, the existing data on its potential toxicity both to humans and to the environment are currently rather limited, and there is also a need to increase the alternative possibilities of its chemical analysis. In this work, an attempt is made for the first time to determine platinum in aqueous samples with energy‐dispersive X‐ray fluorescence (EDXRF) at low concentrations. For this reason, selective complexing membranes were used that were produced in the context of the present research, after first testing many possible complexing agents. These membranes were fixed on the surface of thin films, immersed in the aqueous samples containing platinum at low concentrations, and after a certain period was collected and analyzed by EDXRF. In addition, other relevant factors such as the distribution of platinum on the membrane surface, the aging of the membrane, the effect of adding salts of various concentrations to the analyzed solution on the improvement of the achieved x‐ray yields, the pH, the optimal solution volume and the necessary equilibration time were also investigated. By optimizing all relevant factors, a minimum detection limit of 4 μg/L was achieved. [ABSTRACT FROM AUTHOR]

Ruthenium (Ru) is an important platinum group metal for the manufacture of advanced materials owing to its chemical and physical properties. Generally, it is extremely difficult to dissolve Ru metal by using acidic solutions containing strong oxidizing agents. Therefore, pretreatments like alkali fusion roasting at high temperature are practiced to render the Ru metal soluble in aqueous solution. In this work, a simple procedure was proposed to dissolve Ru metal at room temperature without any pretreatments. The dissolution procedure consisted of two steps: (i) oxidation of Ru metal to RuO4– by using pure NaClO solution; (ii) reduction of RuO4– to stable Ru2OCl104– by using HCl as a reducing agent. The role of NaClO and HCl in the dissolution of Ru metal was discussed on the basis of the potential-pH diagram and the corresponding oxidation and reduction reactions. The effect of several parameters like the concentration of NaClO and HCl, temperature, time, and pulp density was investigated. Optimum conditions were obtained to completely dissolve Ru metal by using NaClO and HCl solution without alkali fusion. [ABSTRACT FROM AUTHOR]

Promoting the hydrogen oxidation reaction (HOR) activity and poisoning tolerance of electrocatalysts is crucial for the large‐scale application of hydrogen‐oxygen fuel cell. However, it is severely hindered by the scaling relations among different intermediates. Herein, lattice‐contracted Pt−Rh in ultrasmall ternary L12‐(Pt0.9Rh0.1)3V intermetallic nanoparticles (~2.2 nm) were fabricated to promote the HOR performances through an oxides self‐confined growth strategy. The prepared (Pt0.9Rh0.1)3V displayed 5.5/3.7 times promotion in HOR mass/specific activity than Pt/C in pure H2 and dramatically limited activity attenuation in 1000 ppm CO/H2 mixture. In situ Raman spectra tracked the superior anti‐CO* capability as a result of compressive strained Pt, and the adsorption of oxygen‐containing species was promoted due to the dual‐functional effect. Further assisted by density functional theory calculations, both the adsorption of H* and CO* on (Pt0.9Rh0.1)3V were reduced compared with that of Pt due to lattice contraction, while the adsorption of OH* was enhanced by introducing oxyphilic Rh sites. This work provides an effective tactic to stimulate the electrocatalytic performances by optimizing the adsorption of different intermediates severally. [ABSTRACT FROM AUTHOR]

Properties of high‐entropy alloys are currently in the spotlight due to their promising applications. One of the least investigated aspects is the affinity of these alloys to hydrogen, its diffusion, and reactions. In this study, high pressure is applied at ambient temperature and stress‐induced diffusion of hydrogen is investigated into the structure of high‐entropy alloys (HEA) including the famous Cantor alloy as well as less known, but nevertheless important platinum group (PGM) alloys. By applying X‐ray diffraction to samples loaded into diamond anvil cells, a comparative investigation of transition element incorporating HEA alloys in Ne and H2 pressure‐transmitting media is performed at ambient temperature. Even under stresses far exceeding conventional industrial processes, both Cantor and PGM alloys show exceptional resistance to hydride formation, on par with widely used industrial grade Cu–Be alloys. The observations inspire optimism for practical HEA applications in hydrogen‐relevant industry and technology (e.g., coatings, etc), particularly those related to transport and storage. [ABSTRACT FROM AUTHOR]

HHO gas is an alternate source of fuel that can be used in automobiles as a clean fuel with reduced carbon emissions, replacing the conventional hydrocarbon fuels being used today. Many different methods are involved in the production of this gas. Among these methods, alkaline water electrolysis is one of the easiest and most reliable methods for production. Though there are many limitations in the storage of Hydrogen, the HHO gas has been produced on-site using alkaline water electrolysis. This article mainly focuses on the production of HHO gas for different operating parameters and conditions, such as change of electrolyte, electrode material coating, effect of temperature and the surface area of the electrode. The electrolytes used in the electrolyser are sodium hydroxide (NaOH) and potassium hydroxide (KOH). The electrode material is titanium coated with two different materials namely Mixed Metal Oxide (MMO) and Platinum (Pt) respectively. A maximum yield of 0.9 LPM of HHO gas has been generated when supplying 40 amps of current to the electrolyser unit coated with MMO and KOH as electrolyte. Use of KOH electrolyte results in higher production rate when compared to NaOH. MMO coated titanium electrode produces more HHO gas when compared to platinum coated electrode. • Enhanced HHO gas generation of 0.9 LPM. • Increase in HHO production of 4.4 %. • Design and analysis of platinum and mixed metal oxide coated titanium-based electrolyser. • Effect temperature and current on HHO gas production. • Effect of different Electrolytes on HHO production rate. [ABSTRACT FROM AUTHOR]

The presented research is the seed of a vision for the development of a waste-for-product strategy. Following this concept, various synthetic solutions containing low concentrations of platinum group metals were used to model their recovery and to produce catalysts. This is also the first report that shows the method for synthesis of a pyramid-like structure deposited on activated carbon composed of Pd and Pt. This unique structure was obtained from a mixture of highly diluted aqueous solutions containing both metals and chloride ions. The presence of functional groups on the carbon surface and experimental conditions allowed for: the adsorption of metal complexes, their reduction to metal atoms and enabled further hierarchical growth of the metal layer on the carbon surface. During experiments, spherical palladium and platinum nanoparticles were obtained. The addition of chloride ions to the solution promoted the hierarchical growth and formation of palladium nanopyramids, which were enriched with platinum nanoparticles. The obtained materials were characterized using UV–Vis, Raman, IR spectroscopy, TGA, SEM/EDS, and XRD techniques. Moreover, Pd@ROY, Pt@ROY, and Pd-Pt@ROY were tested as possible electrocatalysts for hydrogen evolution reactions. [ABSTRACT FROM AUTHOR]

Talc is a gangue mineral of most platinum group metals and base metal ores commonly found in the Southern African mineral repository. It is naturally hydrophobic, and invariably, the depression of talc is paramount and challenging in the flotation of these ores. This paper introduced alkaline gelatinised cassia tora gum (CTG) and locust bean gum (LBG) as novel talc depressants. The adsorption densities, thermochemical properties, and talc depression of these depressants were studied using adsorption, zeta potential and microflotation studies. Talc flotability in the absence of the depressant was 89%, which implied that the talc used in this study was naturally floatable. Adsorption studies revealed that CTG yielded the highest talc adsorption density, followed by LBG and carboxymethyl cellulose (CMC), and their adsorption densities were 5.8 mg/m2, 4.6 mg/m2 and 3.5 mg/m2, respectively. PGM flotation occurs at pH 9. Therefore, the zeta potential results at this pH were given more attention in the present study. The zeta potentials at pH 9 were −5.75 mV for LBG and CTG and −15 mV for CMC. In addition, the percentage of talc depression achieved in the microflotation studies decreased in the order of LBG > CTG > CMC; their respective values were 72% > 56% > 51%. Therefore, the zeta potential values agree with the adsorption and microflotation results observed in this study, i.e. LBG and CTG depressed talc more effectively than CMC. Finally, bench flotation results revealed that LBG had the greatest effect on talc depression at 100 g/t; while, CTG had the greatest effect on talc depression at 25 g/t. Thus, these results agreed with thermodynamic theory, viz. a low molecular weight polymer is effective at low dosages where the surface is unsaturated. In contrast, a high molecular weight polymer is effective at high dosages because there is enough quantity to cover the surface adequately. [ABSTRACT FROM AUTHOR]

Throughout history, metal-based coordination compounds have been used for medical purposes, including the treatment of various illnesses like cancer. Since the discovery of cisplatin in 1965, many other metal coordinating complexes have been developed and evaluated, involving metals such as platinum, iron, zinc, ruthenium, gold, silver, titanium, and copper. The goal behind these efforts is to create effective and safe medications. At the moment, there are a lot of studies talking about the use of cytostatic metal complexes, mainly on promising platinum- and non-platinum-based drugs in both preclinical and clinical trials. However, there is a lack of recent comprehensive studies that cover both the chemical and biological aspects of metal-based coordinating molecules in the context of cancer therapy. This review aims to provide a thorough analysis of the coordination chemistry of existing and innovative cytostatic substances. It will include a description of their design and synthesis, as well as a summary of the biochemical reactivity and physicochemical features of potential metal-containing complexes. [ABSTRACT FROM AUTHOR]

The Nagaland-Manipur ophiolites (NMO), part of the Phanerozoic (538.8–0 Ma) Tethyan ophiolites, occur in the NNE-SSW trending Indo-Myanmar Orogenic Belt (IMOB), northeast India. The NMO hosts both high-Al (0.46 < Cr# < 0.53) and high-Cr chromitites (0.71 < Cr# < 0.79). These chromitite bodies are hosted in lherzolite, harzburgite, and dunite and show various textures, including massive, disseminated, nodular, and granular. The high-Al chromitite compositions in conjunction with the calculated Al2O3[melt] (15.66–16.39 wt.%), TiO2[melt] (0.65–0.94 wt.%), and FeO/MgO[melt] (0.65–0.83 wt.%) values indicate that they were derived from the tholeiitic melt that formed at the mid-ocean ridge centre through low-degree partial melting. In contrast, the high-Cr chromitites, coupled with the Al2O3[melt] (11.24–12.99 wt.%), TiO2[melt] (0.21–0.33 wt.%), and FeO/MgO[melt] (0.58–1.54) values show similar geochemical affinities to those derived from boninitic melts produced by partial melting of already depleted mantle due to the subduction of oceanic plate in a supra-subduction zone environment. The total platinum group element (PGE) contents (60–190 ppb) of high-Al chromitites are lower than the total PGE contents (118–2341 ppb) in high-Cr chromitites. Chondrite-normalized PGE patterns in high-Al chromitites are flat from Os to Rh and negatively sloping from Rh to Pd, whereas high-Cr chromitites show strongly fractionated chondrite-normalized PGE patterns. Total PGE contents and low Pd/Ir ratios (0.02–0.64) of chromitites are consistent with typical ophiolitic chromitites. Mineral chemistry and PGE systematics suggest that NMO chromitites were generated in two separate tectonic settings. Thus, we argue that the upper mantle of the NMO of the IMOB has been modified by a substantial amount of supra-subduction zone components after initially being formed in a mid-ocean ridge tectonic environment. [ABSTRACT FROM AUTHOR]

Dry reforming of methane (DRM) is considered one of the most promising technologies for efficient greenhouse gas management thanks to the fact that through this reaction, it is possible to reduce CO2 and CH4 to obtain syngas, a mixture of H2 and CO, with a suitable ratio for the Fischer–Tropsch production of long-chain hydrocarbons. Two other main processes can yield H2 from CH4, i.e., Steam Reforming of Methane (SRM) and Partial Oxidation of Methane (POM), even though, not having CO2 as a reagent, they are considered less green. Recently, scientists' challenge is to overcome the many drawbacks of DRM reactions, i.e., the use of precious metal-based catalysts, the high temperatures of the process, metal particle sintering and carbon deposition on the catalysts' surfaces. To overcome these issues, one proposed solution is to implement photo-thermal dry reforming of methane in which irradiation with light is used in combination with heating to improve the efficiency of the process. In this paper, we review the work of several groups aiming to investigate the pivotal promoting role of light radiation in DRM. Focus is also placed on the catalysts' design and the progress needed for bringing DRM to an industrial scale. [ABSTRACT FROM AUTHOR]

The elemental and isotopic properties of garnet pyroxenites can yield information on lithospheric mantle composition, thermal state, and evolution. The 34Ma Kakanui Mineral Breccia in New Zealand contains spectacular but little-studied mantle peridotite and pyroxenite xenoliths that yield new insights into the evolution of a portion of the underlying mantle lithosphere of a former Gondwana margin. The moderately depleted and metasomatized spinel peridotites, as judged from spinel and olivine compositions and bulk rock major and platinum group element abundances, give mineral equilibration temperatures <1020°C and are derived from the middle to shallow (~35 to 50 km) lithospheric mantle when projected onto a 70 mW∙m−2 geotherm. These residues have low Re/Os and Re-depletion 187Os/188Os model ages that range from Eocene (0.05 Ga) to Paleoproterozoic (1.9 Ga), consistent with extraction from a lithospheric mantle comprising fragments with complex depletion histories. Although the peridotites have restricted δ18O (olivine +5.2 to 6.2), evidence for an isotopically heterogeneous mantle column in addition to the 187Os/188Os is seen in clinopyroxene 87Sr/86Sr (0.70244 to 0.70292), εNd (+4.1 to 18.8), 206Pb/204Pb (17.8 to 20.3), and εHf (+10 to +101). Higher metamorphic equilibrium temperatures of the garnet pyroxenites (Fe–Mg exchange of >1150°C) compared to the peridotites indicate their Eocene extraction was from towards the base of this isotopically heterogeneous mantle lithosphere. Pyroxenite bulk compositions point to cumulate origins, and the mineral isotope ratios of 87Sr/86Sr (0.70282 to 0.70294), εNd (+5.5 to 8.0) and 206Pb/204Pb (18.1 to 19.3) match many of the Zealandia metasomatized mantle peridotite xenoliths as well as the primitive intraplate basalts but not the garnet pyroxenite host magmas. In contrast to many global pyroxenite studies, the garnet pyroxenite 87Sr/86Sr and δ18O (+5.2 to 5.8) data provide no evidence for subducted crustal material in the primary magma source region, and Sm–Nd and Lu–Hf isotope data yield mid-Cenozoic ages that are probably related to isotope closure during eruption. An exception is one sample that yields a Lu–Hf isochron age of 111.9 ± 9.1 Ma, which corresponds to the convergence of the Lu–Hf isotope evolution curves of three other samples. Liquids calculated to have been in equilibrium with these cumulates have trace element compositions comparable to primitive alkaline intraplate basalts like those found at the surface of Zealandia. The new data, therefore, indicate that a pulse of intraplate magmatism occurred during or directly after the cessation of long-lived subduction on the former Zealandia Early Cretaceous forearc Gondwana margin, despite any volcanic surface exposure having been long eroded away. The lower lithospheric mantle emplacement of the garnet pyroxenites suggests that the source of the alkaline parent magmas was probably the convecting mantle, which supports conclusions that intraplate magmas in Zealandia have asthenospheric and lithospheric mantle sources. [ABSTRACT FROM AUTHOR]

This study provides a comprehensive literature review of the distribution, the platinum- group elements (PGE) composition, and mineral chemistry of chromitites associated with Mesozoic Tethyan ophiolites in the Mediterranean Basin. These suites outcrop in the northern Italian Apennines, the Balkans, Turkey, and Cyprus. Most chromitites occur in depleted mantle tectonites, with fewer found in the mantle-transition zone (MTZ) and supra-Moho cumulates. Based on their Cr# = (Cr/(Cr + Al)) values, chromitites are primarily classified as high-Cr, with a subordinate presence of high-Al chromitites. Occasionally, high-Al and high-Cr chromitites co-exist within the same ophiolite complex. High-Cr chromitites are formed in supra-subduction zone (SSZ) environments, where depleted mantle interacts with high-Mg boninitic melts. Conversely, high-Al chromitites are typically associated with extensional tectonic regimes and more fertile peridotites. The co-existence of high-Al and high-Cr chromitites within the same ophiolite is attributed to tectonic movements and separate magma intrusions from variably depleted mantle sources, such as mid-ocean ridge basalts (MORB) and back-arc basin basalts. These chromitites formed in different geodynamic settings during the transition of the oceanic lithosphere from a mid-ocean ridge (MOR) to a supra-subduction zone (SSZ) regime or, alternatively, within an SSZ during the differentiation of a single boninitic magma batch. Distinct bimodal distribution and vertical zoning were observed: high-Cr chromitites formed in the deep mantle, while Al-rich counterparts formed at shallower depths near the MTZ. Only a few of the aforementioned chromitites, particularly the high-Cr ones, are enriched in the refractory IPGE (iridium-group PGE: Os, Ir, Ru) relative to PPGE (palladium-group PGE: Rh, Pt, Pd), with an average PPGE/IPGE ratio of 0.66, resulting in well-defined negative slopes in PGE patterns. The IPGE enrichment is attributed to their compatible geochemical behavior during significant degrees of partial melting (up to 30%) of the host mantle. It is suggested that the boninitic melt, which crystallized the high-Cr chromitites, was enriched in IPGE during melt-rock reactions with the mantle source, thus enriching the chromitites in IPGE as well. High-Al chromitites generally exhibit high PPGE/IPGE ratios, up to 3.14, and strongly fractionated chondrite-normalized PGE patterns with positive slopes and significant enrichments in Pt and Pd. The PPGE enrichment in high-Al chromitites is attributed to the lower degree of partial melting of their mantle source and crystallization from a MOR-type melt, which contains fewer IPGE than the boninitic melt above. High-Al chromitites forming at higher stratigraphic levels in the host ophiolite likely derive from progressively evolving parental magma. Thus, the PPGE enrichment in high-Al chromitites is attributed to crystal fractionation processes that consumed part of the IPGE during the early precipitation of co-existing high-Cr chromitites in the deep mantle. Only a few high-Al chromitites show PPGE enrichment due to local sulfur saturation and the potential formation of an immiscible sulfide liquid, which could concentrate the remaining PPGE in the ore-forming system. [ABSTRACT FROM AUTHOR]

Chalcones are a class of naturally occurring flavonoid compounds associated to a variety of biological and pharmacological properties. Several reviews have been published describing the synthesis and biological properties of a vast array of analogues. However, overviews on the reactivity of chalcones has only been explored in a few accounts. To fill this gap, a systematic survey on the most recent developments in the transition metal‐catalyzed transformation of chalcones was performed. The chemistry of copper, palladium, zinc, iron, manganese, nickel, ruthenium, cobalt, rhodium, iridium, silver, indium, gold, titanium, platinum, among others, as versatile catalysts will be highlighted, covering the literature from year 2000 to 2023, in more than 380 publications. [ABSTRACT FROM AUTHOR]

The Ririwai anorogenic alkaline complex harbours extensive rare metal (Nb-Zr-Sn-Zn) mineralization. However, uncertainty still surrounds their origin and magmatic-hydrothermal processes responsible for their rare metal mineralization. The complex is composed of peralkaline arfvedsonite ± albite-bearing granites, mildly peralkaline fayalite-bearing granite porphyries, and weakly peraluminous biotite-bearing granites, all of which show diagnostic A1-type characteristics. Zircon U-Pb dating reveals emplacement ages between 181.4 ± 0.81 and 188.6 ± 7 Ma for the three rock units. Sm-Nd and Pb isotopes (εNd (t) = –0.6 to −5.4, 206Pb/204Pb = 17.68–17.93) constrained the Ririwai A-type granites to represent highly fractionated products of enriched mantle-derived magmas. Mass-balance modelling suggests that magma evolution was fuelled by extensive fractional crystallization of 50 ~ 60 vol.% K-feldspar, 30 ~ 35 vol% fayalite, 5 ~ 10 vol.% amphibole, and ~ 5 vol.% apatite under reduced and water-undersaturated (ΔFMQ = –1.55; logfo2 = –18.63; H2O = <2.0 wt.%) conditions and assimilation of ~ 50 vol.% crust. Whole rock and amphibole compositions revealed an increasing degree of fractionation from the fayalite-bearing granite porphyries through biotite-bearing granites to the arfvedsonite ± albite-bearing granites. This extended fractionation at the late stage of magma differentiation, facilitated by fluorine dissolution and concentration of excess HFSE and REE as alkali-fluorocomplexes in the fluorine-rich silicate melt, allowed the accumulation of economic rare metal pyrochlore and columbite mineralizations in the highly fractionated arfvedsonite± albite- and biotite-bearing granites, respectively. Nonetheless, the metasomatic reaction rim textures around the magmatic pyrochlore, coupled with the M-type lanthanide tetrad effect (TE1,3 >1.10) indicate the subsequent effect of hydrothermal processes. Tectonically, reactivated shear fractures and transcurrent faults following lithospheric stresses in a transtensional regime allowed magma uprising and emplacement of A-type granites in the Ririwai complex. [ABSTRACT FROM AUTHOR]

One of the main causes of atmospheric pollution comes from mobile sources that emit noxious gases from internal combustion engines. For the suppression of toxic exhaust gases, a catalytic converter is used as an anti-pollution device, because it catalyzes or accelerates the degradation of emissions making them less harmful. In the catalytic converter, platinum (Pt), palladium (Pd) and rhodium (Rh) catalysts are normally used for their excellent performances. However, these metals are expensive, rare, and scarce in the earth's crust. These precious metals thus emphasized the importance of developing efficient recycling practices. For the recycling of these precious metals, a very fast, easy, economical, environmentally friendly and high-safety electric pulse discharge method was used to separate the Pd and Rh from the spent metal-honeycomb (MH) catalytic converter consisting of p as the catalyst carrier. To standardize the precious metals recycling process and attain the highest level of separation of Pd and Rh, electric pulse shots ranging from 120-240 and standoff distances (gap width between the positive electrode and the sample surface) ranging from 5-10mm were applied. During this process, an electrical explosion occurred within the honeycomb structures through the electric shock. After the electrical explosion, the particles are collected, then sieved and physical characterizations are performed. Scanning electron microscope (SEM) and energy dispersive spectroscopy (EDX) analyses revealed that the most separated particles are highly pure, and dispersed homogeneously without destroying particle structures. In this article, we first report about 87.91% of Pd and 90.77% of Rh are separated from each catalytic converter using the electric pulse discharge method that can overcome challenges and achieve ambitious recycling targets in the recycling industry. The effects of the discharge energies and the shock energy determined by varying electric pulse shots and standoff distance, respectively, are discussed. These findings provide insight into the recovery of precious metals for electric pulse discharge and play a role in developing a very effective recycling method not only for the catalytic converter but also for other devices. [ABSTRACT FROM AUTHOR]

Metal oxide-based electrocatalysts are promising alternatives to platinum group metals for water splitting due to their low cost, abundant raw materials, and impressive stability. This review covers recent progress in various metal oxides tailored for hydrogen and oxygen evolution reactions, discussing their crystal structure, composition, and surface modification influence on performance. Strategies like surface engineering, doping, and nanostructuring are evaluated for enhancing catalytic activity and stability. The key considerations for commercialization are highlighted, emphasizing ongoing research, innovation, and future scope to drive widespread adoption of water-splitting technology for a cleaner and sustainable future. [ABSTRACT FROM AUTHOR]

Abstract\nKEY POINTSPlatinum group elements (PGEs) are commonly hosted by base metal sulfides (BMSs, e.g. chalcopyrite or pentlandite) or platinum group minerals (PGMs). PGE-bearing phases are generally small, ranging from tens of nanometres to a few micrometres. In addition, PGEs can be hosted in PGMs, either intimately associated with BMSs or spatially separated. This poses a difficulty in their detection and analysis, and leads to uncertainty in identification of their mineral hosts. Their erratic occurrence introduces a substantial nugget effect in bulk rock assays, used to evaluate deposit economics on a larger scale. Knowledge of PGE hosts has a direct influence on resource management and extraction efficiency, making the understanding of mineral distribution important for processing. The Eastman Ultramafic Intrusion is a layered mafic–ultramafic intrusive complex in the Eastern Kimberley of Western Australia. Samples from Cu–Co–Ni–PGE exploration drilling at Eastman were bulk-assayed and found to contain up to 2.39 ppm PGEs. The rocks have been strongly altered and no longer represent their primary magmatic mineral assemblage and textures. To better understand the Eastman PGE mineralogy, we applied a multi-method approach of quantitative analytical electron microscopy, 3D scanning and in situ mass spectrometry. We find that Pt is primarily hosted in sperrylite, whereas Pd is mainly associated with kotulskite, pseudomertieite, testibiopalladite, sudburyite and michenerite. Additionally, minor Pt and Pd occur in solid solution within cobaltite, as well as Rh-rich cobaltite (hollingworthite). Spatially, PGMs and cobaltite are mostly clustered on a millimetric scale, and BMSs on a micrometric scale.Three-dimensional computed tomography scanning is a valuable tool for understanding PGM distribution, nugget effect scale and narrowing down interest areas for sample analysis.Guided by 3D scanning, combined quantitative analytical electron microscopy and i mass spectrometry are effective for finding and identifying PGEs.Platinum is overwhelmingly hosted in the arsenide sperrylite, whereas palladium is mostly hosted in various bismuthides and tellurides. Cobaltite contains minor Pt and Pd.The Eastman mineralisation is primarily orthomagmatic, and later reequilibration at low temperature redistributed palladium but not platinum. [ABSTRACT FROM AUTHOR]

Metal-catalyzed highly Markovnikov-type selective hydrofunctionalization of terminal alkynes provides a straightforward and atom-economical route to access 1,1-disubstituted alkenes, which have a wide range of applications in organic synthesis. However, the highly Markovnikov-type selective transformations are challenging due to the electronic and steric effects during the addition process. With the development of metal-catalyzed organic synthesis, different metal catalysts have been developed to solve this challenge, especially for platinum group metal catalysts. In this perspective, we review homogeneous metal-catalyzed Markovnikov-type selective hydrofunctionalization of terminal alkynes according to the classified element types as well as reaction mechanisms. Future avenues for investigation are also presented to help expand this exciting field. [ABSTRACT FROM AUTHOR]

Here, we report the systematical synthesis of zeolite‐templated carbon (ZTC) supported Ru and Rh mono‐ or bi‐metallic electrocatalysts towards hydrogen evolution reaction (HER). The zeolite A or ZSM‐5 derived ZTC supports and metal sites were adjusted, and all electrocatalysts outperformed the commercial Pt/C electrocatalyst for HER performance. In particular, the RhRu/(ZTC/ZSM5) sample exhibited superior catalytic performance with the overpotential of 24.8 mV@10 mA ⋅ cm−2, and outstanding stability with 1 mV drop after 20000 cyclic voltammetry circles. This work offers a simple impregnation method for the synthesis of highly performed HER electrocatalysts supported on porous zeolite‐templated carbon. [ABSTRACT FROM AUTHOR]

Alkaline anion‐exchange membrane water electrolyzers (AEMWEs) for green hydrogen production have received intensive attention due to their feasibility of using earth‐abundant platinum group metal (PGM)‐free catalysts. Herein, the third metal is incorporated into NiFe‐based catalysts to regulate their electronic structures and morphologies, aiming to achieve sufficient oxygen evolution reaction (OER) activity and performance in AEMWEs. The ternary NiFeM (M: Cu, Co, or Mn) catalysts are featured with multiple layered structures and nanofoam network morphologies, consisting of highly OER‐active amorphous Ni‐rich oxide shells and electrically conductive metallic alloy cores. The physical and electronic perturbations to the NiFe induced by a third element lead to a fine‐tuning of the redox ability of the metal sites at the reaction centers, which breaks the scaling relationship between OH* and O* intermediates at the reaction centers. Thus, the unique structural configuration and electronic regulation simultaneously benefit catalytic activity and performance improvements. These NiFeM nanofoam catalysts demonstrated promising anode performance in actual AEMWEs, comparable to the IrO2 reference, especially at high current densities. Notably, using various electrolytes (e.g., KOH solution or pure water) for AEMWEs exhibited a different performance trend among studied NiFeM catalysts, likely due to dynamic changes of catalysts under various OER environments. [ABSTRACT FROM AUTHOR]

Manganese is currently experiencing a great deal of attention in homogeneous catalysis as a sustainable alternative to platinum group metals due to its abundance, affordable price and low toxicity. While homogeneous nitrogen fixation employing well‐defined transition metal complexes has been an important part of coordination chemistry, manganese derivatives have been only sporadically used in this research area. In this contribution, the authors systematically cover manganese organometallic chemistry related to N2 activation spanning almost 60 years, identify apparent pitfalls and outline encouraging perspectives for its future development. [ABSTRACT FROM AUTHOR]

Sodium borohydride (NaBH 4) has been generally studied as a source of hydrogen (H 2) due to its important advantages with the development of support materials and catalysts for H 2 release in the energy sector. In this context, we carry out molecular dynamics (MD) simulations by using extended tight-binding (xTB) model Hamiltonian based on density functional theory (DFT) and analyze the Ca 12 Al 14 O 33 functional material doped X metals (X = Co, Ru, Rh) as a catalyst with [Co(III)(N 3) 3 (C 9 H 8 N 2) 2 ] as complex compound with amine ligand from NaBH 4 hydrolysis for H 2 production. The use of a functional material doped by X metals causes to the high rate in H 2 production when compared to without functional material doped by X metals. The increase of complex compound with amine ligand facilitates H 2 production. Rh on the functional material displays the best catalytic performance compared to Ru and Co to increase the H 2 production rate. Also, the increment of temperature has a positive effect on the H 2 production rate with functional material doped Co, Ru and Rh metals. Thus, Ca 12 Al 14 O 33 support material doped with noble metals appears promising as an innovative catalyst for H 2 production. [Display omitted] • X metals on the Ca 12 Al 14 O 33 functional material and complex compound are designed. • Addition of complex compound with amine group leads to increase of 13% on H 2. • Addition of Rh catalyst on the Ca 12 Al 14 O 33 supplies the H 2 increasing of 25%. • Rh-doped Ca 12 Al 14 O 33 increases 6 times to H 2 production rate. • MD simulations confirm the formation of H 2 bonding using the NABH 4 hydrolysis. [ABSTRACT FROM AUTHOR]

The hydroxide exchange membrane fuel cells (HEMFCs) are promising but lack of high‐performance anode hydrogen oxidation reaction (HOR) electrocatalysts. The platinum group metals (PGMs) have the HOR activity in alkaline medium two to three orders of magnitude lower than those in acid, leading to the high required PGMs amount on anode to achieve high HEMFC performance. The mechanism study demonstrates the hydrogen binding energy of the catalyst determines the alkaline HOR kinetics, and the adsorbed OH and water on the catalyst surface promotes HOR. Iridium (Ir) has a unique advantage for alkaline HOR due to its similar hydrogen binding energy to Pt and enhanced adsorption of OH. However, the HOR activity of Ir/C is still unsatisfied in practical HEMFC applications. Further fine tuning the adsorption of the intermediate on Ir‐based catalysts is of great significance to improve their alkaline HOR activity, which can be reasonably realized by structure design and composition regulation. In this concept, we address the current understanding about the alkaline HOR mechanism and summarize recent advances of Ir‐based electrocatalysts with enhanced alkaline HOR activity. We also discuss the perspectives and challenges on Ir‐based electrocatalysts in the future. [ABSTRACT FROM AUTHOR]

In this work, a granular expanded vermiculite (GEV) is employed as a sorbent to remove Platinum group metals (PGMs) such as Pt (IV), Rh (III), Ru (III) and Ir (III). Batch adsorption experiments included factors such as metal concentration, pH, GEV dosage and contact time; whereas in a continuous system, the bed height and the desorption process were also investigated. Pseudo-second order was the rate equation that accurately described the adsorption kinetic and adsorption isotherms that were adequately simulated by the Langmuir and Freundlich model. Maximum sorption capacities of GEV in a batch system for Pt (IV), Rh (III), Ru (III) and Ir (III) were 73.01 μg g−1, 157.03 μg g−1, 147.12 μg g−1 and 47.91 μg g−1 at optimal pH values, respectively. Additionally, the adsorption capacities obtained in continuous adsorption experiments for Pt (IV), Rh (III), Ru (III) and Ir (III) were 48.78 μg g−1, 50.11 μg g−1, 51.88 μg g−1 and 37.96 μg g−1. The elution step was accomplished efficiently (71.9-82.5%) using an HCl solution. Hence, the GEV adsorbent could be used as a profitable alternative to remove and recover PGMs from solutions. [ABSTRACT FROM AUTHOR]

Previous studies on bimetallic paddlewheel compounds have established a direct correlation between metal–metal distance and ligand torsion angles, leading to the rule that higher torsion results in longer metal‐metal bond distances. Here, the new discovery based on diarylformamidinate Ru₂⁵⁺ paddlewheel compounds [Ru2Cl(DArF)4] that show an opposite behavior is reported: higher torsions lead to shorter metal–metal distances. This discovery challenges the assumption that internal rotation solely impacts the δ bond. By combining experimental and theoretical techniques, it is demostrated that this trend is associated with previously overlooked π metal‐ligand interactions. These π metal‐ligand interactions are a direct consequence of the paddlewheel structure and the conjugated nature of the bidentate ligands. This findings offer far‐reaching insights into the influence of equatorial ligands and their π‐conjugation characteristics on the electronic properties of paddlewheel complexes. That this effect is not exclusive of diruthenium compounds but also occurs in other bimetallic cores such as ditungsten or dirhodium is demonstrated, and with other ligands showing allyl type conjugation. These results provide a novel approach for fine‐tuning the properties of these compounds with significant implications for materials design. [ABSTRACT FROM AUTHOR]

Water electrolyzers powered by renewable energy are emerging as clean and sustainable technology for producing hydrogen without carbon emissions. Specifically, anion exchange membrane (AEM) electrolyzers utilizing non‐platinum group metal (non‐PGM) catalysts have garnered attention as a cost‐effective method for hydrogen production, especially when integrated with solar cells. Nonetheless, the progress of such integrated systems is hindered by inadequate water electrolysis efficiency, primarily caused by poor oxygen evolution reaction (OER) electrodes. To address this issue, a NiFeCo─OOH has developed as an OER electrocatalyst and successfully demonstrated its efficacy in an AEM electrolyzer, which is powered by renewable electricity and integrated with a silicon solar cell. [ABSTRACT FROM AUTHOR]

Iron–nitrogen co-doped carbon (Fe/N/C) catalysts derived from zinc-based zeolite imidazole frameworks (ZIF-8) have been ideal alternatives to platinum group metals (PGM) and shown great potential to catalyze oxygen reduction reaction (ORR). Unfortunately, the ORR performance is seriously suppressed by the insufficient density and accessibility of the electrochemical active Fe–N sites. The precise regulation of ZIF-8 to the formation of Fe/N/C catalysts with the desired Fe–N sites for ORR is a critical challenge. Herein, a citric acid assisted reconstitution strategy is proposed to design Fe doped ZIF-8 frameworks and construct multi-dimensional Fe/N/C catalysts composed of inner concave and entangled carbon nanotubes outer moieties for efficient acid-resistant ORR reaction. The introduction of citric acid imparts Fe/N/C catalysts with dense accessible active sites and highly opened multi-dimensional mass transfer pathways. Therefore, the optimized Fe/N/C catalysts dominant half-wave potential of 0.785 V and great acid stability were obtained in 0.5 M H2SO4 with a high number of transferred electrons and a low yield of H2O2 ( n ¯ = 3.97 and average yield = 4%). This work provides a novel and feasible approach to design and tailoring of Fe/N/C catalysts with improved distribution density and accessibility of the Fe–N active sites. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cyano group (CN)'s monomer-specific affinity determines the rapid Pd-Pt separation. • MnHCF can adsorb 90.30 % of Pd(Ⅱ) with ∼ 5 min at low initial concentrations of 10 ppm. • Electron-losing of C and N jointly contributes to the formation of N -Pd coordination bonds. • The strong and direct coordination between CN and Pd(Ⅱ) drives the rapid and selective adsorption. Rapid separation of low concentration palladium (Pd) from Pd-Platinum (Pt) coexisting systems remains a formidable challenge, primarily due to the undifferentiated substitution of ligands in Pd/Pt complexes by adsorption sites. The development of an adsorbent featuring monomer-specific affinity adsorption sites for Pd/Pt could mitigate this drawback. Herein, Manganese hexacyanoferrate (MnHCF) possessing the sensitivity and specificity to Pd ions (Pd(II)) was synthesized via the facile co-precipitation method. MnHCF could rapidly and selectively capture 90.30 % of Pd(II) from a 10 ppm Pd-Pt coexisting system within just 5 min. Spectroscopic analyses and density functional theory (DFT) calculations indicated that cyano-group (CN) in MnHCF exhibited the monomer-specific affinity for targeted capturing Pd via the direct and strong coordination interaction (Fe-CN-PdCl 2), which was co-determined by the electron-losing of C (0.06 e) and N (0.07 e) atom. At the same time, CN could neither react directly with the fully coordinated [PtCl 6 ]2− species nor substitute the Cl− ligand, both of which contributed to the non-adsorption of Pt, thus triggering the Pd-Pt separation. This study provides a promising candidate adsorbent for practical applications in platinum group metals recovery by the design of adsorption sites with monomer-specific affinity. [ABSTRACT FROM AUTHOR]

This research aims to employ a first-principles approach based on density functional theory (DFT) to predict the structural, electronic, and magnetic attributes of CdMX compounds, where M represents Ru , Rh , or Pd , and X represents either S or Se . We utilized the modified Beck-Johnson potential, combined with the generalized gradient approximation ( mBJGGA ), to scrutinize the electronic and magnetic features of these compounds. The results reveal robust magnetic ground states for M -doped CdX . The analysis of spin-polarized band structures and densities of states indicates that CdRuX and CdPdX compounds exhibit half-metallic ferromagnetism, characterized by complete spin polarization of 100% at the Fermi level. Conversely, CdRhX compounds exhibit the properties of ferromagnetic semiconductors. For Ru , Rh , and Pd -doped CdX , an integer-integrated total magnetic moment is observed, corresponding to 4, 3, and 2 μ B , respectively, with the primary contribution stemming from the doping atom and its four nearest neighboring X atoms. This ferromagnetic behavior is attributed to the strong p - d hybridization occurring between the states of the host X ions and the M impurity ion. Consequently, the outcomes of our study render these alloys as suitable materials for possible spintronic devices. [ABSTRACT FROM AUTHOR]

The giant Jiaodong gold deposits represent one of the largest gold provinces (>5000 tons of Au) in the North China Craton of eastern China. They formed ~1.7 b.y. after high-grade metamorphism of the crust. The metasomatized subcontinental lithospheric mantle (SCLM) has been increasingly proposed as the main source of such gold mineralization, but the direct geochemical links remain scarce. Here, we present a comprehensive d34S dataset of sulfides from fresh lamprophyres (130-121 Ma) that formed from the metasomatized SCLM that is spatially and temporally associated with the Jiaodong gold deposits (ca. 120 Ma). Due to the negligible effects of crustal contamination and magmatic degassing, the consistently high d34S (4‰-6‰, n = 73) of lamprophyres from variable localities reveals d34S-enriched mantle sources relative to the asthenospheric mantle (-1.3‰ ± 0.3‰). Combined with the radiogenic Sr-Nd-Pb isotope signatures of these lamprophyres, we determined that such high d34S signatures could have resulted from a period of mantle metasomatism related to subducted continental materials. The lamprophyres share d34S (4.4‰ ± 0.8‰) and Sr-Nd-Pb isotopes with coeval gold-mineralized diorites (ca. 120 Ma) beneath the ore field (d34S: 5.4‰ ± 2.5‰), which were interpreted to have sampled the magma chamber underlying the auriferous fluid systems. The lamprophyres and diorites consistently indicate the key control of metasomatized SCLM, although these mantle-derived magmas followed different pathways from source to crust. These relatively primitive and evolved magmas all show S and Pb isotopes similar to ore-related sulfides from the Jiaodong gold deposits, particularly those formed in the deep parts and at the early stage of the Jiaodong auriferous fluid system (d34S: 5‰-7‰). Such results suggest that the primary auriferous fluids are genetically linked to the magmas derived from the metasomatized SCLM. Combined with radiogenic isotopes, our study on the sulfur isotopes of mantle-derived magmas identifies the metasomatized mantle source of the gold and provides new evidence for establishing a geochemical link between metasomatized SCLM, derivative magmas, and the giant gold deposits, supporting the model that subduction-related metasomatism plays a key role in the enrichment of volatiles and gold in the SCLM for large-scale gold mineralization. [ABSTRACT FROM AUTHOR]

Alkene hydrosilylation is one of the most concise and atom-economical methods to synthesize organosilicon molecules. Herein, we reported the precise immobilization of metal single atoms (M-SAs; M = Ru, Rh, Ir, Pd, Pt, and Au) into a porphyrinic metal-organic framework (MOF) of PCN-222 (PCN = porous coordination network), and then applied the resultant MOF composites of M-SAs@PCN-222 to alkene hydrosilylation. Under solvent-free conditions, Pt-SAs@PCN-222 displayed an especially high catalytic efficiency with the turnover frequency up to 119 s−1 and the maximum turnover number of 906,250 at room temperature. Experimental and theoretical studies revealed that there existed strong interactions between Pt-SAs@PCN-222 and the substrates, which helped to condense the substrates in the cavities of the porous catalysts. Further density functional theory calculations and molecular dynamics simulations disclosed that PCN-222 could transfer electrons to Pt-SAs to enhance the silane oxidative addition and drive the reaction to proceed smoothly via Chalk–Harrod pathway. [ABSTRACT FROM AUTHOR]

We assessed the hydrochemistry of 15 watersheds in the Halton Region, southern Ontario, in high resolution (n > 500 samples across n > 40 streams) to characterize water quality dynamics and governing controls on major and trace element concentrations in this rapidly urbanizing region. In 2022, major water quality parameters were generally in line with historic monitoring data yet significantly different across catchments, e.g., in specific conductance, turbidity, phosphate and chloride, and trace element concentrations. Distinct hydrochemical signatures were observed between urban and rural creeks, with urban stream sections and sites near the river mouths close to Lake Ontario having consistently higher chloride (up to 700 mg/L) and occasional enrichment in nutrients levels (up to 8 and 20 mg/L phosphate and nitrate, respectively). Particularly upper reaches exhibited hydrochemical signatures that were reflective of the catchment surface lithologies, for instance through higher dissolved Ca to Mg ratios. Unlike for chloride and phosphate, provincial water quality guidelines for trace elements and heavy metals were seldom surpassed (on < 10 occasions for copper, zinc, cadmium, and uranium). Concentrations of other trace elements (e.g., platinum group elements or rare earth elements) were expectedly low (< 0.3 µg/L) but showed spatiotemporal concentration patterns and concentration-discharge dynamics different from those of the major water quality parameters. Our results help improve the understanding of surface water conditions within Halton's regional Natural Heritage Systems and demonstrate how enhanced environmental monitoring can deliver actionable information for watershed decision-making. [ABSTRACT FROM AUTHOR]

Anion exchange membrane fuel cells (AEMFCs) have been hailed as a promising hydrogen energy technology due to high energy conversion efficiency, zero carbon emission and the potential independence on scare and expensive noble metal electrocatalysts. A variety of platinum group metal (PGM)‐free catalysts has been developed with superior catalytic performance to noble metal benchmarks toward cathodic oxygen reduction reactions (ORR). However, PGM electrocatalysts still dominate the anodic catalyst research because the kinetics of hydrogen oxidation reaction (HOR) are two or three orders of magnitude slower than in that acidic media. Therefore, it is urgently desirable to improve noble metal utilization efficiency and/or develop high‐performance PGM‐free electrocatalysts for HOR, thus promoting the real‐world implementation of AEMFCs. In this review, the current research progress of electrocatalysts for HOR in alkaline media is summarized. We start with the discussion on the current HOR reaction mechanisms and existing controversies. Then, methodologies to improve the HOR performance are reviewed. Following these principles, the recently developed HOR electrocatalysts including PGM and PGM‐free HOR electrocatalysts in alkaline media are systematically introduced. Finally, we put forward the challenges and prospects in the field of HOR catalysis. [ABSTRACT FROM AUTHOR]

The development of cost-effective components for Proton Exchange Membrane (PEM) electrolyzers plays a crucial role in the transformation of renewable energy into hydrogen. To achieve this goal, two main issues should be addressed: reducing the Platinum Group Metal (PGM) content present on the electrodes and finding a large-scale electrode manufacturing method. Magnetron sputtering could solve these hurdles since it allows the production of highly pure thin films in a single-step process and is a well-established industrial and automated technique for thin film deposition. In this work, we have developed an ultra-low 0.1 mg cm−2 Pt loading electrode using magnetron sputtering gas aggregation method (MSGA), directly depositing the Pt nanoparticles on top of the carbon substrate, followed by a complete evaluation of the electrochemical properties of the sputtered electrode. These ultra-low Pt content electrodes have been thoroughly characterized and tested in a real electrolyzer cell. They demonstrate similar efficiency to commercial electrodes with a Pt content of 0.3 mg/cm2, achieving a 67% reduction in Pt loading. Additionally, durability tests indicate that these electrodes offer greater stability compared to their commercial counterparts. Thus, magnetron sputtering has been proven as a promising technology for manufacturing optimum high-performance electrodes at an industrial scale. [ABSTRACT FROM AUTHOR]

We systematically explored NO activation at metal/oxide interfaces by the combination of Sr3Ti2O7, Sr3Fe2O7, CeO2, anatase-TiO2, ZrO2, and γ-Al2O3 supports and the platinum-group metal cluster (Pd4, Pt4, and Rh4) using slab-model density functional theory calculations. These metal clusters can be strongly adsorbed at these metal oxide surfaces. The Pt4 and Rh4 clusters show larger adsorption energies than the Pd4 cluster, yet the γ-Al2O3(100) surface shows smaller adsorption energies than other metal oxide surfaces. One oxygen vacancy close to the metal cluster was constructed to evaluate the NO activation at those metal/oxide interfaces. The O atom of NO refills the oxygen vacancy after NO dissociation, while the N adatom is left on the metal cluster. The exothermic process was identified for the NO activation except for the Sr3Fe2O7 case, indicating the significant role of the interplay between the metal cluster and oxygen vacancy. [ABSTRACT FROM AUTHOR]

This study explored, on a laboratory scale, how matte separates from the gangue in the black top of a PGM smelter. Two PGM concentrates, one with high sulfide content (17.3 mass%, Platreef concentrate) and the other with low sulfide content (1.3 mass%, UG-2 concentrate), were studied in the temperature range of 800°C to 1480°C, which is the temperature gradient across the black top. The results showed that effective matte separation occurs at temperatures when the matte is completely molten, and a substantial amount of liquid silicate phase has formed. The main matte separation mechanism is the coalescence of sulfide prills and their gravitational settling through the continuous path created by the liquid silicate phase. Complete matte separation occurs at lower temperatures in Platreef concentrate (1400°C in Platreef concentrate vs. 1480°C in UG-2 concentrate), due to the higher concentration of liquid silicate phase of lower viscosity, as well as the higher amount of sulfide minerals in this concentrate. PGMs already dissolve and collect in a nickel-iron-based alloy associated with the matte at temperatures as low as 900°C. [ABSTRACT FROM AUTHOR]

The quality of in situ XAS of electrochemical systems is highly sensitive to electrode disturbances, such as gas evolution and gas consumption at an electrolyte/catalyst interface. A novel in situ spectro‐electrochemical X‐ray absorption spectroscopy (SPEC‐XAS) cell is presented as a new tool for the characterisation of gas evolving and consuming electrocatalysts at high overpotentials. By utilising a thin, porous membrane with efficient electrolyte and gas circulating loops, an improved three phase interface is established that enabled efficient gas supply and minimised the interference from bubble formation. X‐ray absorption spectroscopy (XAS) measurements were conducted in fluorescence mode with three experiments selected to demonstrate the cell's performance. The first two reactions; an in‐situ study of a highly active amorphous iridium oxide catalyst during the oxygen evolution reaction (OER) and an in‐situ study of copper oxide during the carbon dioxide reduction reaction (CO2RR) are used to exemplify the XAS data quality achieved under operational conditions. Thirdly, a detailed XAS investigation of a highly dispersed platinum catalyst during the oxygen reduction reaction (ORR) is presented, along with comparative data in nitrogen. These measurements show the retention of oxygen on the surface of the platinum metal particles down to 0.48 V (vs. RHE), well below the platinum oxide reduction peak. [ABSTRACT FROM AUTHOR]

Calcium-aluminum-rich inclusions (CAIs) are the first formed solids in our solar system. Information regarding their formation and alteration is imprinted within their crystal structures, and so analysis of CAIs can provide insight into the early stages of solar system formation. Here we report on micrometer-sized metal grains that occur inside of fluffy type A (FTA) CAIs in the NWA 8323 and Leoville CV3 chondrites. Transmission electron microscopy (TEM) shows that the ultra-refractory metal assemblages contain subhedral grains of crystalline alloys of Pt, Os, Ir, Ru, Fe, Ni, and Mo, with minor amounts of oxides and silicates inclusions. These assemblages occur in melilite and are surrounded by or adjacent to spinel and perovskite. TEM analysis shows that the majority of the alloys present in the assemblages are significantly enriched in Pt-group elements, with compositions of 75 wt % Pt in some Fe-Ni-Pt grains, and >90 wt % Pt-group elements in Os-Ir-Ru grains. Electron diffraction shows that the alloys occur predominantly in a hexagonal (HCP) structure, with a minority of the grains exhibiting cubic (FCC) and tetragonal lattices. To support these findings, we present a thermodynamic model for the formation of hexagonal (HCP) and cubic (BCC and FCC) ultra-refractory alloys. We use an Fe-Os-Ir ternary system to approximate the various compositions and crystal structures observed in the metal grains. Modeling results indicate a condensation temperature for the alloys as high as 1831 K (HCP, 10−4 bar), placing them well above those predicted for the major CAI phases that surround them. Based on the spatial relationships of the refractory metal grains to their host CAIs, our thermodynamic predictions, and prevailing astrophysical models of the solar protoplanetary disk, the data imply that the grains could have formed inward of the regions where CAI materials condensed. We hypothesize that the refractory metal grains were transported radially outward to the part of the disk where CAIs formed and provided a nucleation site for the condensation of CAI phases such as melilite, hibonite, perovskite, and spinel. [ABSTRACT FROM AUTHOR]