Platinum Group Research Articles

Anticancer Potential of Hemidesmus indicus-enriched Pt/Au Bimetallic Nanoparticles against Human Breast and Skin Cancer Cell Lines

Background: Worldwide, cancer has become the most disastrous disease, causing an enormous number of deaths in the population. According to GLOBOCON, in the year 2020, there were 1.93 crore cases of cancer reported and 10 million deaths caused by cancer. Methods: Metallic nanoparticles, such as gold, silver, and platinum, which possess properties of bioenvironmental stability, safety, and lower toxicity, have become preferred materials for drug delivery. Bimetallic nanoparticles, in particular, have shown enhanced optical, magnetic, electrical, catalytic, and medicinal properties compared to monometallic nanoparticles. We have developed goldplatinum PtAuBNPs containing H. indicus methanolic extract using a green synthesis approach. The PtAuBNPs were characterized by UV-visible spectroscopy, particle size analysis, zeta potential measurement, and surface characteristics using TEM, XRD, Raman spectroscopy, and DSC. The anticancer activity of PtAuBNPs was investigated using two distinctive cell lines, MCF-7 and B16F10. Results: The change in the colour of the prepared systems after incubation indicated the development of nanoparticles, as analysed by UV spectroscopy. The PtAuBNPs showed a particle size of 243.3 nm and a zeta potential of -14.4 mV. TEM analysis showed the hexagonal and cubic nature of the nanoparticles. XRD analysis indicated the crystalline nature of the nanoparticles. The bimetallic nanoparticles showed greater anticancer activity against the breast cancer cell line (MCF-7) and the skin cancer cell line (B16F10), with IC50 values of 35.52µg mL-1and 30.22 µg mL-1, respectively, which have been found to be lower than the standard 5-FU. Conclusion: The development of PtAuBNPs may pave the way for a new era of enhancing the anticancer activity of herbal extracts through the synergistic effects of gold and platinum metals. The developed PtAuBNPs have been shown to exhibit excellent anticancer activity against skin and breast cancer.

Simulating large-diameter industrial ball mills from batch-grinding tests

Phenomenological models of ball milling are routinely used to optimize size reduction operations. A usual method adopted in the minerals industry relies on batch-grinding tests to calibrate models in a population balance model formulation describing the breakage behaviour and then scale-up the breakage parameters using an energy-based relationship. Despite the important advances and application of these methods, their application in describing grinding in large-diameter (>7.5 m) mills has not been widely demonstrated. The work demonstrates the calibration of industrial-scale ball mill model parameters from laboratory milling tests on Platinum Group Metals (PGM) and Itabirite iron ores. Minor fine-tunning of a single model parameter was required to simulate the large-diameter industrial mills, demonstrating the validity of the approach for ores as distinct as PGM and Itabirite iron ores. Estimation of the Arbiter Flow Number below 4.1 showed a regular slurry transport for all mills studied. This model can then be used in optimization of the ball mill performance.

Chemical-Dealloying-Derived PtPdPb-Based Multimetallic Nanoparticles: Dimethyl Ether Electrocatalysis and Fuel Cell Application.

In this work, we report a novel multimetallic nanoparticle catalyst composed of Pt, Pd, and Pb and its electrochemical activity toward dimethyl ether (DME) oxidation in liquid electrolyte and polymer electrolyte fuel cells. Chemical dealloying of the catalyst with the lowest platinum-group metal (PGM) content, Pt2PdPb2/C, was conducted using HNO3 to tune the catalyst activity. Comprehensive characterization of the chemical-dealloying-derived catalyst nanoparticles unambiguously showed that the acid treatment removed 50% Pb from the nanoparticles with an insignificant effect on the PGM metals and led to the formation of smaller-sized nanoparticles. Electrochemical studies showed that Pb dissolution led to structural changes in the original catalysts. Chemical-dealloying-derived catalyst nanoparticles made of multiple phases (Pt, Pt3Pb, PtPb) provided one of the highest PGM-normalized power densities of 118 mW mgPGM-1 in a single direct DME fuel cell operated at low anode catalyst loading (1 mgPGM cm-2) at 70 °C. A possible DME oxidation pathway for these multimetallic catalysts was proposed based on an online mass spectrometry study and the analysis of the reaction products.

Human-Machine Collaboration for Accelerated Discovery of Promising Oxygen Evolution Electrocatalysts with On-Demand Elements.

A drastically efficient method for identifying electrocatalysts with desirable functionality is a pressing necessity for making a breakthrough in advanced water-electrolyzers toward large-scale green hydrogen production and addressing the significant challenge of carbon neutrality. Despite extensive investigations over the last several centuries, it remains a time-consuming task to identify even one promising affordable electrocatalyst without platinum-group-metal (PGM) for one electrochemical reaction due to its great complexities, particularly for the key anode reaction in the water-electrolyzer of the oxygen evolution reaction (OER). In this study, we demonstrate that a human-machine collaboration based on stepwise-evolving artificial intelligence (se-AI) can significantly shorten the development period of PGM-free multimetal OER electrocatalysts with performance beyond a PGM of RuO2. We were able to reach optimized materials only after 2% experimental trials of the entire candidate pool. The best PGM-free electrocatalyst discovered exhibited excellent activity comparable to RuO2 and, surprisingly, also demonstrated superior stability with a high current density of up to 1000 mA/cm2 at even pH 9.2, which condition is a thermodynamically challenging for typical PGM-free materials. This work illustrates that human's material discovery can be significantly accelerated through collaboration with AI.

Separation of rhodium from iridium through synergistic solvent extraction

There are currently few effective processes for the solvent extraction of rhodium from hydrochloric acid streams, and none that allow rhodium to be selectively extracted over iridium. Realizing this goal could allow rhodium to be recovered earlier in a typical platinum group metal (PGM) refining flowsheet and reduce the environmental impact of PGM refining. In this work, we show that a synergistic combination of a tert-alkyl primary amine LA and various inner-sphere ligands L can be used to recover rhodium via the complex [RhCl5L].HLA2. Although we show that rhodium is extracted by several extractant combinations, it is only readily stripped from the amine/amide synergistic mixture. As this extraction relies on the inner-sphere coordination of the amide to the metal, this process also demonstrates a route to obtain preferential extraction of rhodium over more inert iridium chloridometalates under industrially relevant conditions.

Advances in E-Waste Recycling: Physical and Chemical Treatment Methods

The unprecedented rise in production and consumption of electronic devices has resulted in staggering amounts of electronic waste (e-waste). Improper recycling and disposal of e-waste can cause severe environmental and public health repercussions due to the presence of toxic substances like lead, mercury, and flame retardants. This article introduced advanced e-waste recycling technologies, focusing on physical and chemical treatment methods. Physical treatments such as gravity separation, electrostatic separation, and inverse flotation enable efficient and cost-effective recovery of precious metals like gold, silver, platinum, and rare earth metals from e-waste components. These physical processes are often environmentally friendly, scalable, and can handle diverse e-waste streams. Chemical treatments, including the dimethylformamide technique, supercritical fluid technique, and pyrolysis, allow for separating hazardous substances and recovering valuable materials not amenable to physical processes. Supercritical CO2 fluid destroys toxic organic compounds while enabling metal recovery. Pyrolysis converts plastics into liquid oil and gas products. By enhancing the separation and purification of valued materials, these physical and chemical e-waste recycling techniques provide more profitable, efficient, and sustainable solutions to ever-growing e-waste volumes.

DEVELOPMENT OF A REACTOR FOR LOW-TEMPERATURE CATALYTIC REDUCTION OF NITROGEN OXIDE EMISSIONS AT NITROGEN-FERTILIZER ENTERPRISES

The article presents the development of a more efficient use of the processes of catalytic reduction of nitrogen oxides of gas emissions for industrial use. The advantages of plate catalyst blocks with a deposited active substance in comparison with industrial granular aluminum-vanadium catalysts are presented. Chemical and kinetic regularities of this process are shown. It is noted that the use of plate deposited catalysts based on noble metals is a more effective means of reducing nitrogen oxides than granular ones due to the presence of low hydraulic resistance and increased activity. On the basis of experimental data of laboratory and pilot studies of the developed catalyst obtained by impregnating the applied metal carrier based on TiO2 with salts of platinum group metals, physicochemical and kinetic calculations of the process of reduction of nitrogen oxides using ammonia were carried out. Graphical dependencies of the activity of the developed catalysts on the process temperature and volume velocity are given. The optimal values of these indicators have been determined. It is shown that the effect of temperature is explained by the growth of the reaction rate constant in proportion to the temperature according to Arrhenius' law, and the effect of the volumetric velocity is associated with a change in the duration of contact of the reacting components with the active surface of the catalyst. The calculation of the Reynolds criterion was carried out, which showed that this process in the conditions of industrial technologies is characteristic of the laminar regime. It is noted that the use of the developed catalyst in production provides an expansion of the temperature range of the emission purification process, it is more suitable for operation in industry in accordance with the determined optimal conditions of its application.

Amino- and sulfur-containing POSS for highly efficient and selective extraction of platinum group elements from acidic solution

As the platinum group elements (PGEs) are very important, expensive, and scarce in the earth's crust, the selective extraction and recovery of these elements from electronic wastes is an efficacious strategy to address the increasing demands for these elements' resources. This study reports the design and execution of a novel amino- and sulfur-containing polyhedral oligomeric silsesquioxane (POSS–S-DETA) for highly efficient and selective extraction of precious PGEs such as Pd(II) (PdCl42−) and Pt (IV) (PtCl62−) from acidic aqueous medium. The developed material shows not only very high adsorption efficacies of 505.4 ± 18.1 mg g for Pd(II) and 433.9 ± 13.9 mg/g for Pt (IV), but also proficient selectivity for these PGEs in presence of various interfering metal ions such as Mg(II), Zn(II), Cu(II), Pb(II), Cd(II), and Fe(III). The sorptions of these PGEs accord with the Langmuir isotherm, pseudo-second-order, aswellas intraparticle diffusion kinetic models. The thermodynamic data demonstrates that the sorptions of these PGEs are endothermic and spontaneous. Density functional theory (DFT) calculation shows that strong binding energies are involved among POSS-S-DETA and these PGEs during adsorption. The adsorption mechanism is found to be the electrostatic interaction, hydrogen bonding, and chelate bond formation among the active functional sites of POSS-S-DETA and the used PGEs. The developed material not only demonstrates proficient acid-resistance at pH 1, but also shows excellent repeatability for these PGEs up to eight consecutive cycles. So, these results suggest that the developed POSS-S-DETA has high potential for practical application in the selective adsorptive elimination of PGEs from acidic solution.

Environmental and material criticality assessment of hydrogen production via anion exchange membrane electrolysis

The need to drastically reduce greenhouse gas emissions is driving the development of existing and new technologies to produce and use hydrogen. Anion exchange membrane electrolysis is one of these rapidly developing technologies and presents promising characteristics for efficient hydrogen production. However, the environmental performance and the material criticality of anion exchange membrane electrolysis must be assessed. In this work, prospective life cycle assessment and criticality assessment are applied, first, to identify environmental and material criticality hotspots within the production of anion exchange membrane electrolysis units and, second, to benchmark hydrogen production against proton exchange membrane electrolysis. From an environmental point of view, the catalyst spraying process heavily dominates the ozone depletion impact category, while the production of the membrane represents a hotspot in terms of the photochemical ozone formation potential. For the other categories, the environmental impacts are distributed across different components. The comparison of hydrogen production via anion exchange membrane electrolysis and proton exchange membrane electrolysis shows that both technologies involve a similar life-cycle environmental profile due to similar efficiencies and the leading role of electricity generation for the operation of electrolysis. Despite the fact that for proton exchange membrane electrolysis much less material is required due to a higher lifetime, anion exchange membrane electrolysis shows significantly lower raw material criticality since it does not rely on platinum-group metals. Overall, a promising environmental and material criticality performance of anion exchange membrane electrolysis for hydrogen production is concluded, subject to the expected technical progress for this technology.

Airborne geophysics, petrophysics, geochemistry and geology of Ni-Cu (Co-Au-PGE) footprints to define exploration targets in mafic-ultramafic rocks

The correlation between various prospecting methodologies plays a pivotal role in achieving substantial outcomes in the pursuit of mineral deposits. The use of these methodologies within prospecting programs is widely implemented across diverse geological settings. The purpose of this research was to develop a prospective model for Ni–Cu–Co–Au-PGE (Nickel–Copper–Cobalt–Gold–Platinum Group Elements) within a mafic-ultramafic intrusion known as the Barra do Gameleira Intrusion (BGI), located in Tocantins, Brazil. To achieve it, publicly available data were employed, including airborne geophysics and geochemical data obtained from stream sediments and pan concentrate. Additionally, newly obtained, and unpublished results from lithogeochemical sampling and semi-detailed geological mapping were used. According to what was found, three potential targets were identified based on geophysical and geochemical anomalies. The magnetic results proved a robust correlation between magnetization intensity and anomalous elemental contents in geochemistry. Radiometric data were employed to see the inverse correlation between the concentration of radioelements and geochemical anomalies, particularly with respect to potassium, which exhibited null values in petrophysical measurements. Furthermore, both anomalous potassium and anomalous uranium enhancements showed a strong correlation with the presence of ultramafic rocks. Finally, the geological mapping confirmed that mineralization occurrences are associated with lithologies composed of ultramafic rocks.

Hydrogen oxidation reaction catalysts derived from Co, Ni-coordination compounds and polymers (MOFs)

Aiming to obtain catalysts for the Hydrogen Oxidation Reaction (HOR) and to construct fuel cells completely free of noble metals, two Ni-MOFs, a Ni-coordination polymer, and a Ni-complex were synthesized, together with their corresponding Co and NiCo analogs. The following N-heterocyclic ligands were employed: 2-Methylimidazolate, imidazolate, nicotinate, 2,3-pyrazinedicarboxylate and pyrazinecarboxylate. These precursor compounds were pyrolyzed at 700 °C obtaining metallic nanoparticles embedded within N-doped mesoporous carbons. These materials were characterized by different physical and electrochemical techniques. The catalysts exhibited HOR activities (jη = 50 mv) comparable to the best-reported materials, i.e.: 1.3 and 0.6 mA cm−2disk for the Ni imidazolate and Ni nicotinate derived materials respectively. The results are relevant for the design of new catalysts and to construct alkaline anion exchange membrane fuel cells completely free of platinum group metals.

The search for plausible economic mineral deposits in the central parts of Tanzania; insight from stream sediment geochemistry, multivariate statistics and geostatistics

Exploration success relies heavily on the data obtained, but, significantly on the type of analytical methods deployed and the interpretation reached. A poorly analyzed data may obscure the true reflectivity of the data, and thus, compromised the decision made. A combined data processing approach of descriptive statistics, enrichment-depletion data normalization, geospatial elemental distribution, and stacked overlayed comparison of elements have been used in this study. The prime purpose was to demonstrate potential elemental anomalies, and predict areas of higher degree of confidence for subsequent exploration and mineral resource evaluation. One-hundred and sixty-six stream sediment samples from the Dodoma Region of the Tanzania Craton have been examined; to reveal potential elements or mineral commodity that warrant further exploration. Forty-three elements of target were examined, as this craton is globally known for its rich earth mineral commodity. Our result indicates an enrichment of transition metals (TMs) (Cu, Ni, Co, Cr, Mn and Zn), High Field Strength Elements (Y, Th, U, Zr, Nb, Hf, Ta and Pb), Large Ion Lithophile Elements (Ba and Rb) and Rare-Earth Elements (La and Ce), Platinum Group Element (Pd and Pt) and other metals (Au, As, Bi, W, Mo and Li).Obtained results point to a likely poly-metallic sources and processes; as the underlain geology is marked largely by pegmatite and migmatites, and moderate proportion of fine clastic sedimentary rocks, and minor volcanic rocks mostly to the northern domain. Theoretically, the Large Ion Lithophile Elements (LILEs), Rare-Earth Elements (REEs) and Platinum Group Elements (PGEs) are associated with felsic rocks or variable stages of plutonic granitization. Although, the TMs are often associated with mafic-ultramafic rocks, the linkage of such metals with organic-rich shales been reported elsewhere. These rocks may equally contribute to the occurrence of other metals as stated in this paper. Its intriguing to note a strong positive correlation of Li with TMs, possibility of Li control by mafic minerals in pegmatite bodies. This work proposes a polymetallic enrichment controlled by the area geology. To suggest an alluvial mining potential of the above elements in the area, resource evaluation is a requirement. The geospatial maps reveal areas worth focusing for subsequent exploration. The adopted geostatistical methods and other approach utilized in this research are effective, indicative of handling bulk exploration data for decision and subsequent exploration.

Impacts of PTL coating gaps on cell performance for PEM water electrolyzer

The anode porous transport layer (PTL) is a critical component of polymer electrolyte membrane (PEM) water electrolyzers, providing electrical conduction and water/oxygen transport to the anode catalyst layer. Platinum group metal (PGM) coatings are applied to titanium PTLs to prevent oxidation and preserve conductivity. To implement PEM water electrolysis on a large scale, it is essential to minimize the cost of mass-manufactured cell components while ensuring that defects in materials and components do not adversely affect the performance of the cell. In this study, we created gaps in the Pt coatings that are typically applied to PTLs to understand their effects on cell performance and inform on fabrication tolerances. The PTL coatings were fabricated by sputter deposition of Pt, intentionally leaving uncoated regions in either large patches or thin strips. For either geometry, the cell performance decreased with the increasing fraction of the uncoated regions. However, PTLs containing multiple thin uncoated strips caused a less severe performance effect than PTLs with continuous uncoated regions of the same relative total area. Through analysis of cell performance, impedance, and 3D charge transport modelling, we demonstrate that both the anode catalyst layer and membrane play a role in distributing current to mitigate the impact of coating defects at a short length scale. These results allow to draw conclusions about the tolerance requirements with regards to PTL coating uniformity in terms of both the size and total area of defects.

Electrochemical Evolution of Ru-Based Polyoxometalates into Si,W-Codoped RuOx for Acidic Overall Water Splitting.

Despite intensive studies over decades, the development of electrocatalysts for acidic water splitting still relies on platinum group metals, especially Pt and Ir, which are scarce, expensive, and poorly sustainable. Because such problems can be alleviated, Ru-based bifunctional catalysts such as rutile RuO2 have recently emerged. However, RuO2 has a relatively low activity for hydrogen evolution reactions (HER) and low stability for oxygen evolution reactions (OER) under acidic conditions. In this study, the synthesis of a RuOx -based bifunctional catalyst (RuSiW) for acidic water splitting via the electrochemical evolution from Ru-based polyoxometalates at cathodic potentials is reported. RuSiW consists of the nanocrystalline RuO2 core and Si,W-codoped RuOx shell. RuSiW exhibits outstanding HER and OER activity comparable to Pt/C and RuO2 , respectively, with high stability. Computational analysis suggests that the codoping of RuOx with W and Si synergistically improves the HER activity of otherwise poor RuO2 by shifting the d-band center and optimizing atomic configurations beneficial for proper hydrogen adsorption. This study provides insights into the design and synthesis of unprecedented bifunctional electrocatalysts using catalytically inactive and less explored elements, such as Si and W.

The effect of additional nitrogen source on iron phthalocyanine-based nanocarbon catalysts for oxygen reduction reaction in acidic media

The focus in the development of catalysts doped with transition metals aims to replace platinum group metal catalysts in fuel cells. However, these non-precious metal catalysts exhibit limited performance in acidic environment for the oxygen reduction reaction (ORR) due to issues such as metal agglomeration and the subsequent loss of active sites. Herein, we synthesised catalysts doped with iron and nitrogen on a composite material consisting of carbide-derived carbon (CDC) and graphene (G), employing an additional nitrogen source dicyandiamide (DCDA), denoted as FeN-CDC/G/DCDA. Our physico-chemical analysis unveiled that the inclusion of DCDA was effective in mitigating metal agglomeration during the synthesis process and increasing the presence of Fe-Nx sites in the catalysts. Notably, the FeN-CDC/G/DCDA catalyst exhibited enhanced ORR activity in acid media with half-wave potential (E1/2) of 0.76 V, surpassing the performance of the FeN-CDC/G catalyst, which had an E1/2 value of 0.70 V. Furthermore, the rotating ring-disk electrode results indicated a reduced formation of hydrogen peroxide when employing the FeN-CDC/G/DCDA catalyst. The findings from this study represent a significant step towards the development of efficient catalysts for fuel cells, underscoring the pivotal role of additional nitrogen doping and its positive impact on the ORR performance.

Geospatial Insights into Ophiolitic Complexes in the Cimmerian Realm of the Afghan Central Block (Middle Afghanistan)

Ophiolites are remnants of oceanic crust that have been thrust onto continental crust due to tectonic processes. They are composed of mostly mafic and ultramafic rocks, which are genetically associated with gold, silver, platinum group element (PGE), chrome, manganese, titanium, cobalt, copper, and nickel deposits. The main objective of this research was to identify the spatial distribution of Mesozoic ophiolitic complexes within the Central Afghan Block in Middle Afghanistan using optical remote sensing data and spectral analyses. Distinct algorithms, such as false color composite (FCC), proposed band ratios (PBR), principal component analysis (PCA), and spectral angle mapper (SAM), were used to map the targeted ophiolitic complexes. New band ratios were proposed in this study based on the spectral properties of mafic-ultramafic minerals and rocks, which showed high efficiency. Based on the results, four different ophiolitic complexes were delineated within this study area. These complexes are consistent with previous studies. The accuracy assessment of this study showed an overall accuracy of 72.2%. The findings of this study can significantly contribute to further studies on the emplacement mechanism and paleo-Tethys history of Middle Afghanistan. Also, the spatial distribution of the ophiolitic complexes identified in this study can be used to constrain models of the tectonic evolution of the Central Afghan Block. Additionally, the identification of new band ratios for mapping ophiolitic complexes can be used in future studies of other ophiolite-bearing regions.

Continuous Unsteady-State De-NOx System via Tandem Water-Gas Shift, NH3 Synthesis, and NH3-SCR under Periodic Lean/Rich Conditions.

The development of urea-free and platinum group metal (PGM)-free catalytic systems for automotive emission control is a challenging task. Herein, we report a new de-NOx system using cyclic feeds of rich and lean gas mixtures with PGM-free catalysts. Initial catalyst screening tests showed that Cu/CeO2 with 5 wt % Cu loading was the most suitable for the water-gas shift reaction (WGS, CO + H2O → CO2 + H2), followed by the selective NH3 synthesis by the NO + H2 reaction. The unsteady-state system under alternating feeds of rich (0.1% NO + 0.5% CO + 1% H2O) and lean (0.1% NO + 2% O2 + 1% H2O) gas mixtures over a mixture of Cu/CeO2 and Cr-exchanged mordenite (CrMOR) showed higher NOx conversion than the steady-state (0.1% NO + 0.35% CO + 0.6% O2 + 1% H2O) reaction between 200 and 500 °C. The de-NOx mechanism under periodical rich/lean conditions was studied by operando infrared (IR) experiments. In the rich period, the WGS reaction on the Cu/CeO2 catalyst yield H2, which reduces NO to NH3 on the Cu/CeO2 catalyst. NH3 is then captured by the Brønsted acid sites of CrMOR. In the subsequent lean period, the adsorbed NH3 acts as a reductant for the selective catalytic reduction of NOx catalyzed by the Cr sites of CrMOR. This study demonstrates a new urea-free and PGM-free catalytic system that can provide an alternative de-NOx technology for automotive catalysis under periodic rich/lean conditions.

THE SYNTHESIS, STUDY OF PHYSICOCHEMICAL PROPERTIES, AND EVALUATION OF CATALYTIC ACTIVITY OF A THREE-WAY CATALYST MODIFIER CONTAINING EUROPIUM (III) OXIDE

Modification of the applied Pt-containing catalysts with rare-earth metals is one of effective ways to increase their activity and resistance to thermal deactivation, which is associated with both an increase in thermal stability of the texture and structure of the carrier material and an increase in the degree of dispersion and resistance to sintering of the applied platinum metals (PM) when exposed to high temperatures. Conflicting data make it difficult to select a suitable modifier for the use as part of a three-way catalyst in the exhaust treatment system of gasoline-powered cars, whose function is to simultaneously convert CO, CxHy and NOx. In this work, the effect of europium-modified Pt-containing γ-Al2O3 -based catalyst on its physicochemical properties and activity in the oxidation of CO, CxHy, and NOx reduction processes was evaluated. The catalytic activity was evaluated by passing a gas mixture simulating the exhaust of a gasoline-powered car through the catalyst applied onto the surface of a cylindrical honeycomb block with simultaneous measurement of the degree of conversion of toxic components into relatively non-toxic CO2, N2 and H2O in the temperature range from 1000C to 4000C. The modification of the Pt/γ-Al2O3 catalytic system with europium was shown to enhance the activity in all three reactions studied, indicating a great potential for the use as a modifier of a three-way catalyst

Influence of antisite defects on two-dimensional polymeric material for improved hydrogen evolution reaction

Two-dimensional materials (2D) supported by single atom catalysis have emerged as effective catalysts for H2 production at large scale by Hydrogen Evolution Reaction (HER). While there is a research surge on utilizing inexpensive metals as catalysts to replace Platinum (Pt) and other related noble metals, their practical limitations such as oxidation issues remain a concern. In this work, we report electrochemical HER activity of a recently synthesized metal-free 2D Polyaramid (2DPA) using Density Functional Theory (DFT) calculations. Pristine 2DPA exhibits remarkable HER performance in terms of active sites availability for hydrogen adsorption and the lowest Gibb's free energy change (−0.06 eV) close to that of benchmark Pt/C catalyst (−0.09 eV). Furthermore, introduction of antisite defects by substituting carbon for nitrogen (CN) and nitrogen for carbon (NC) in pristine 2DPA depicts enhanced HER activity. CN and NC defects tune the electronic properties by reducing the band gap resulting improved conductivity. Low formation energies calculated for obtaining antisite defects confirm their feasibility of synthesis while ab initio molecular dynamics (AIMD) simulations ensure their thermal stability at room temperature. The change in Gibb's free energy (ΔGH) values for CN-defective and NC-defective 2DPA are computed to be −0.13 eV and −0.11 eV, respectively. Both CN-defective and NC-defective 2DPA favor H2 evolution via Heyrovsky reaction pathways due to their relatively lower activation energy, 0.64 eV and 0.51 eV, respectively. Our findings encourage design and development of a novel 2D metal-free electrocatalyst for enhanced HER.

Occurrence of Native Platinum and PGE-bearing Pyrite in the Porphyry-Skarn-Epithermal Ore Complex at Recsk, Hungary

In this short report we present the first detection of a platinum group element (PGE) mineral and Cu-bearing native platinum in a hydrothermal breccia pipe in the intermediate sulfidation mineralization of the Recsk ore complex in Hungary. Trace element analyses of pyrite provide further insights into the enrichment of PGE in the mineralized complex.The occurrence of native platinum is associated with one of the highest observed Pt contents in pyrite, as well as with other ore minerals such as Sn- and Pt-bearing native copper, pure native copper, and Ag-bearing tenorite. Crocoite and vanadinite were identified by SEM-EDS as secondary minerals possibly from the same paragenesis. Our new results suggest that the Recsk complex might contain economic PGE resources.