Search Results (85)

To address the demand for early hydrogen monitoring in power equipment insulation systems, a fiber-optic Fabry–Perot (F-P) hydrogen sensor based on a Pd–Cu alloy microcantilever is proposed. The microcantilever serves as the force-sensitive structure, with a Pd–Cu alloy film deposited as the hydrogen-sensitive layer and an Au reflective layer introduced to enhance optical reflection and suppress thermal drift. Hydrogen absorption induces volume expansion of the Pd–Cu film, causing cantilever bending and a consequent variation in the F-P cavity length, which leads to a shift in the characteristic wavelength of the reflected spectrum and enables wavelength-demodulated hydrogen detection. Finite element analysis was conducted to investigate the stress distribution and displacement response, confirming the effective amplification effect of the microcantilever structure. Sensor fabrication, packaging, and hydrogen response experiments were subsequently carried out. The results show a good linear response in the hydrogen concentration range of 0–300 ppm, with a wavelength sensitivity of approximately 20.8 pm/ppm and a limit of detection of 3.24 ppm. In a 24 h stability test, the baseline fluctuation standard deviation was 22.46 pm, indicating good stability and repeatable sensing performance. Temperature variation produced a wavelength sensitivity of approximately 0.2734 nm/°C, and environmental condition tests further demonstrated stable operation under temperature, humidity, vibration, and electromagnetic disturbances. The proposed sensor exhibits immunity to electromagnetic interference, intrinsic safety, and compatibility with miniaturized integration, showing promising potential for low-concentration hydrogen monitoring in power equipment. Full article

The magmatic Ni-Co-Cu mineralization in the Iken deposit in the central part of the Kun-Manie complex, Amur Oblast, Russia, hosted by an olivine-bearing websterite, is of a low-sulfide type. The fine-grained disseminations of base metal sulfides (BMS), dominantly pyrrhotite, pentlandite (a major source of Ni of industrial importance), and chalcopyrite, are followed by a scarce Pd-Pt-Ag mineralization. Elevated contents of Al in orthopyroxene (mean 2.78 wt.% Al₂O₃) along with Al–Na enrichment in clinopyroxene (diopside; mean 5.10 wt.% Al₂O₃) are associated with highly aluminous compositions of low-chromium members of the spinel–hercynite series. High levels of TiO₂ in kaersutite and titanian phlogopite also reflect a pronounced degree of fractionation of the ore-forming melt. Minor portions of sulfide melt are distributed evenly as a result of immiscibility at advanced stages of orthopyroxene crystallization, after the formation of olivine. Differentiated grains of droplet-like BMS largely settled in situ close to grain boundaries of orthopyroxene or occupied interstitial spaces of pyroxenes and olivine in association with spinel–hercynite and fluorapatite. A combination of late saturation in S with relatively quick cooling rates of the hypabyssal body prevented the effective settlement and accumulation of sulfide droplets in the ore zone. The well-developed lamellae of troilite (Fe₅₀S₅₀) exsolved from the host pyrrhotite Fe₄₈S₅₂ during subsolidus cooling, as a consequence of a low-temperature reaction triggered by a sudden drop in fO₂. An influx of mantle-derived fluid bearing CO₂, CO, and CH₄ with the rising magma could be the primary cause of the fO₂ reduction. Also, graphite-bearing metasedimentary rocks could have been assimilated. Tiny grains of minerals of noble metals (moncheite and merenskyite with essential amounts of melonite component, sperrylite, hessite, alloy Au_63.2Ag_36.8, and argentopentlandite) deposited late in a fluid-enriched medium under submagmatic conditions. Full article

A novel citric acid-assisted in situ reduction method has been developed for the synthesis of bimetallic AuPd alloy nanoparticles supported on amine–phosphate-functionalized carbon nanotubes (AuPd/NH₂-P-CNTs). In this strategy, formic acid acts not only as the reducing agent for reducing metal precursors, but also as the hydrogen source for the subsequent catalytic dehydrogenation. The introduction of citric acid significantly accelerates the reduction kinetics and promotes the uniform formation of ultrafine AuPd nanoparticles (∼1.8 nm). As a result, the optimized Au_0.5Pd_0.5/NH₂-P-CNTs exhibit an extraordinary catalytic activity and 100% H₂ selectivity during hydrogen generation from FA with sodium formate as an additive, affording a remarkable initial turnover frequency of 5663.94 mol H₂ mol Pd⁻¹ h⁻¹ at 303 K. The experimental results reveal that the -NH₂ and -P functional groups on the support are crucial for stabilizing and uniformly dispersing the alloy nanoparticles. Furthermore, the enhanced reaction rate can be attributed to the strong metal–support interaction established between AuPd nanoparticles and -NH₂-P-CNT supports. This work provides a new perspective on the design of highly efficient Pd-based catalysts for hydrogen production from formic acid. Full article

Bimetallic nanoparticles have garnered significant attention in scientific literature due to their diverse applications and unique properties. Concurrently, green synthesis methodologies have emerged as environmentally friendly alternatives, reducing the ecological footprint of nanoparticle production. In this study, the efficient synthesis of Au-Pd bimetallic nanoparticles is presented, utilizing Aspalathus linearis (Burm.f.) R. Dahlgren, commonly known as green rooibos (GR), and its pure bioactive compound, Aspalathin (ASP). Integrating ASP as a pure compound into the green synthesis process offers precise control over nanoparticle characteristics, including size, morphology, and composition. Interestingly, the total extract forms an Au-Pd nanoparticle alloy, while aspalathin forms core–shell nanoparticles. Furthermore, cytotoxicity testing was carried out on selected cell lines to assess their impact on cell viability. The cytotoxicity test on cell lines and cellular uptake analysis demonstrated that none of the tested samples exhibited significant cytotoxic effects. ASP-conjugated bimetallic increased the uptake of the NPs by the cells more than the total extract. The results demonstrated that the Au-Pd bimetallic nanoparticles hold promise for biomedical applications, owing to their enhanced biocompatibility and tailored properties. Full article

The ethanol oxidation reaction (EOR) is a key process for direct ethanol fuel cells (DEFCs), offering a high-energy-density and carbon-neutral pathway for sustainable energy conversion. However, the practical implementation of DEFCs is significantly hindered by the EOR due to its sluggish kinetics, complex multi-electron transfer pathways, and severe catalyst poisoning by carbonaceous intermediates. This review provides a comprehensive and mechanistically grounded overview of recent advances in EOR electrocatalysts, with a particular emphasis on the structure–activity relationships of noble metals (Pt, Pd, Rh, Au) and non-noble metals. The effects of catalyst composition, surface structure, and electronic configuration on C–C bond cleavage efficiency, product selectivity (C1 vs. C2), and CO tolerance are critically evaluated. Special attention is given to the mechanistic distinctions among different metal systems, highlighting how these factors influence reaction pathways and catalytic behavior. Key performance-enhancing strategies—including alloying, nanostructuring, surface defect engineering, and support interactions—are systematically discussed, with mechanistic insights supported by in situ characterization and theoretical modeling. Finally, this review identifies major challenges and emerging opportunities, outlining rational design principles for next-generation EOR catalysts that integrate high activity, durability, and scalability for real-world DEFC applications. Full article

In a previous article, an estimation procedure for calculating the liquidus and solidus lines of binary equilibrium phase diagrams was presented. In this article, keeping the thermodynamic basics, the estimation method for the approximate calculation of the liquidus and solidus surfaces of ternary phase diagrams was further developed. It is shown that the procedure has a hierarchical structure, and the ternary functions contain the binary functions. The applicability of the method is checked by calculating the liquidus and solidus surfaces of the Ag-Au-Pd isomorphous ternary equilibrium phase diagram. The application of each level of the developed four-level procedure depends on the data available and the aim. It is shown that in the case of a concentration range close to the base alloy pure element, the liquidus and solidus surfaces of the ternary equilibrium phase diagram can be calculated from the liquidus and solidus functions of the binary equilibrium phase diagrams with a few K errors, which is 0.2 at% at 10 K/at% slope. The equilibrium phase diagrams were available in graphical form, so the data obtained via digitalisation of the diagrams for the calculations was used. The functions describe the slope of the surfaces, and the approximate method developed for the calculation of the partition ratios is also shown. Full article

Hydrogen peroxide (H₂O₂) is an important industrial chemical that is widely applied in many areas. The direct synthesis of H₂O₂ from H₂ and O₂ has proved to be a green and economic pathway. Pd-based bimetallic catalysts, due to their superior catalytic performances in this reaction, have attracted intensive attention. Herein, Tetrakis(hydroxymethyl)phosphonium chloride (THPC) was adopted as the protective ligand to immobilize Pd-Au alloy nanoparticles onto activated carbon (AC). The varied Pd/Au molar ratios demonstrated homogeneously distributed Pd-Au nanoalloys with average particle sizes ranging from 3.51 to 5.75 nm. The optimal ratio was observed over the Pd₃Au₁/AC-THPC catalyst with a maximum H₂O₂ productivity of 165 mol/(kg_Pd·h) and selectivity of 82.3% under ambient pressure. The relationship between the electronic structure and catalytic activity indicated Pd⁰ was the active site, while the presence of Au inhibited H₂O₂ degradation rate. This research could help in the design efficient bimetallic catalysts for the direct synthesis of H₂O₂. Full article

Electrochemical nitrogen reduction reaction (NRR) has emerged as a promising approach for sustainable ammonia synthesis under ambient conditions, offering a low-energy alternative to the traditional Haber–Bosch process. However, the development of efficient and sustainable electrocatalysts for NRR remains a significant challenge. Noble metals, known for their exceptional chemical stability under electrocatalytic conditions, have garnered considerable attention in this field. In this study, we report the successful synthesis of nanoporous CuAuPtPd quasi-high-entropy alloy (quasi-HEA) prism arrays through “melt quenching” and “dealloying” techniques. The as-obtained alloy demonstrates remarkable performance as an NRR electrocatalyst, achieving an impressive ammonia synthesis rate of 17.5 μg h⁻¹ mg⁻¹ at a potential of −0.2 V vs. RHE, surpassing many previously reported NRR catalysts. This work not only highlights the potential of quasi-HEAs as advanced NRR electrocatalysts but also provides valuable insights into the design of nanoporous multicomponent materials for sustainable energy and catalytic applications. Full article

Ammonia (NH₃) represents a promising zero-emission fuel in hydrogen fuel cells. Membrane reactors for NH₃ decomposition based on Pd-alloys have demonstrated high NH₃ conversion, high hydrogen diffusivity, and high hydrogen selectivity, which allows for the production of high-purity H₂ without the need for gas separation or purification. However, it is observed that Pd-alloy membranes are to a various degree prone to H₂ flux inhibition in the presence of NH₃. Hence, finding proper means to tailor the surface adsorption properties through, e.g., alloying is imperative to further improve the technology. In the current work, hydrogen and ammonia co-adsorption phenomena on M(1 1 1) and Pd₃M(1 1 1) (M = Pd, Ru, Ag, Au, Cu) surfaces are studied using density functional theory calculations. It is shown that the surface adsorption properties are strongly dependent on the surface composition, which can be linked to the corresponding electronic structure at the membrane surface. Full article

Anion exchange membrane fuel cells (AEMFCs) are versatile power generation devices that can be fed by both gaseous (H₂) and liquid fuels. The development of sustainable, efficient, and stable catalysts for the oxidation of hydrogen (HOR) and oxygen reduction (ORR) under alkaline conditions remains a challenge currently facing AEMFC technology. Reducing the loading of PGMs is essential for reducing the overall cost of AEMFCs. One strategy involves exploiting the synergistic effects of two metals in bimetallic nanoparticles (NPs). Here, we report that the activity for the HOR and the ORR can be finely tuned through surface engineering of carbon-supported PdAu-PVA NPs. The activity for both ORR and HOR can be adjusted by subjecting the material to heat treatment. Specifically, heat treatment at 500 °C under an inert atmosphere increases the crystallinity and oxophilicity of the nanoparticles, thereby enhancing anodic HOR performance. On the contrary, heat treatment significantly lowers ORR activity, highlighting how reduced surface oxophilicity plays a major role in increasing active sites for ORR. The tailored activity in these catalysts translates into high power densities when employed in AEMFCs (up to 1.1 W cm⁻²). Full article

The reliability of GaN-based devices operating under high temperatures is crucial for their application in extreme environments. To identify the fundamental mechanisms behind high-temperature degradation, we investigated GaN-on-sapphire Schottky barrier diodes (SBDs) under simultaneous heating and electrical biasing. We observed the degradation mechanisms in situ inside a transmission electron microscope (TEM) using a custom-fabricated chip for simultaneous thermal and electrical control. The pristine device exhibited a high density of extended defects, primarily due to lattice mismatch and thermal expansion differences between the GaN and sapphire. TEM and STEM imaging, coupled with energy-dispersive X-ray spectroscopy (EDS), revealed the progressive degradation of the diode with increasing bias and temperature. At higher bias levels (4–5 V) and elevated temperatures (300–455 °C), the interdiffusion and alloying of the Au/Pd Schottky metal stack with GaN, along with defect generation near the interface, resulted in Schottky contact failure and catastrophic device degradation. A geometric phase analysis further identified strain localization and lattice distortions induced by thermal and electrical stresses, which facilitated diffusion pathways for rapid metal atom migration. These findings highlight that defect-mediated electrothermal degradation and interfacial chemical reactions are critical elements in the high-temperature failure physics of GaN Schottky diodes. Full article

Upgrading the bio-derived platform chemical 5-hydroxymethylfurfural (HMF) into the high value-added bioplastic monomer 2,5-furandicarboxylic acid (FDCA) is a promising pathway for biomass conversion. In this work, the natural and abundant available mineral vermiculite was employed as a carrier for loading a Au-Pd bimetal catalyst. Due to the high dispersion of bimetallic nanoparticles, this synthesized vermiculite-supported Au-Pd bimetal catalyst revealed excellent catalytic performance for the aerobic oxidation of HMF to FDCA. By adjusting the ratio of Au and Pd metals, the catalytic performance of the catalyst can be optimized. Finally, 100% HMF conversion and 99.9% FDCA yield could be obtained under the conditions of Au/Pd = 2/1, 2 h, 2 MPa O_2, and 100 °C. The catalyst revealed good stability, and the FDCA yield can be maintained at 90.1% after five recycle usages. The physicochemical properties of the synthesized catalysts were characterized by various characterization methods. It could be concluded that the high dispersion and alloying effect of bimetallic nanoparticles promoted the activation of reactants and intermediates, resulting in the effective production of FDCA. This study could provide ideas and references for the development and utilization of natural minerals and also offer a new way to realize the efficient conversion of HMF to FDCA under green conditions. Full article

This article conducts wire bonding tests and cold/hot-cycle tests using φ 0.025 mm Ag-Au alloy wires and Ag-Au-Pd alloy wires with different specifications. The results show that, due to the addition of the alloying element Pd, under the same bonding parameters, the fracture strength and ball-bonded point shear force of the Ag-Au-Pd alloy wires are significantly higher than those of the Ag-Au alloy wires. After the cold/hot-cycle tests, the failure probability of the Ag-Au-Pd alloy wires is approximately half that of the Ag-Au alloy wires. Among Ag-Au-Pd alloy wires, 92% break at the ideal positions, while 77% of the Ag-Au alloy wires break at the necks. As the Au content increases, the Free Air Ball (FAB) morphology of the Ag-Au-Pd alloy wires becomes more and more regular, gradually transitioning from a pointed ball to an ellipsoid and finally presenting a spherical shape. Full article

Currently, the main limitations of Pd-coated Nb-TiFe dual-phase alloys include insufficient hydrogen permeability, susceptibility to hydrogen embrittlement (HE), and poor tolerance of H₂S poisoning. To address these issues, this study proposes a series of improvements. First, a novel Nb₁₅Ti₅₅Fe₃₀ alloy composed of a well-aligned Nb-TiFe eutectic was successfully prepared using directional solidification (DS) technology. After deposition with a Pd catalytic layer, this alloy exhibits high hydrogen permeability of 3.71 × 10⁻⁸ mol H₂ m⁻¹ s⁻¹ Pa^−1/2 at 673 K, which is 1.4 times greater than that of the as-cast counterpart. Second, to improve the H₂S corrosion resistance, a new Pd₈₈Au₁₂ catalytic layer was deposited on the surface using a multi-target magnetic control sputtering system. Upon testing in a 100 ppm H₂/H₂S mixture, this membrane exhibited better resistance to bulk sulfidation and a higher permeance recovery (ca. 58%) compared to pure Pd-coated membrane. This improvement is primarily due to the lower adsorption energies of the former with H₂S, which hinders the formation of bulk Pd₄S. Finally, the composition region of the Pd-Au catalytic membrane with high comprehensive performance was determined for the first time, revealing that optimal performance occurs at around 12–18 at.% Au. This finding explains how this composition maintains a balance between high H₂ permeability and excellent sulfur resistance. The significance of this study lies in its practical solutions for simultaneously improving hydrogen permeability and resistance to H₂S poisoning in Nb-based composite membranes. Full article

Variations in the recovery of platinum group metals (PGMs) are often attributed to mineralogical and other natural ore-type variations. To increase the recovery of PGMs by the flotation process, a comprehensive understanding of gangue and valuable minerals is essential for optimising the extraction and processing of metals. Recoveries may be improved if the questions of how, where, and why losses occur can be answered with a certain degree of confidence. A requirement is the availability of statistically reliable mineralogical data. The PGMs of MG-1–4 chromite tailings dumps of the western limb of the Bushveld complex (BC) were studied in detail to unravel the PGMs and the nature of the platinum group minerals in the sample. Characterisation of the chromite tailings via deportment analysis revealed that the sample contained a significant amount of 3E PGM + Au (Pt, Pd, Ru, and Au) and was concentrated in the -25 µm fraction. The results of automated mineralogical analysis showed that the sample was composed of the PGE-sulphides group, comprising 63.6 vol%, PGE-sulfarsenides 10.4 vol%, PGE-arsenides 1.3 vol%, PGE-bismuth tellurides 3.3 vol%, PGMs-alloy 4.1 vol%, and Laurite comprising 17.3 vol% of the total PGE population. The sample was composed of 66.5 vol% of liberated PGMs, 0.2 vol% attached to liberated BMS, 27.3 vol% of PGMs attached to or locked within silicate or oxide gangue composite particles, 0.2 vol% of PGMs associated with BMS attached to silicate or oxide gangue particles, and a low proportion (5.8 vol%) of PGMs reported being locked within gangue or oxide particles. The majority of PGM grains observed were reported in the fast-floating category (64.4 vol%), 27.6 vol% in the slow-floating 1 category, 2.2 vol% in the slow-floating 2 category, and 5.8 vol% to the non-floating category. The results of the study revealed that the PGMs of MG 1–4 chromite tailings were liberated; however, the low liberation index (<0.2) suggested that a significant portion of PGMs remained trapped within gangue, hindering their recovery. This highlights the need for effective comminution (crushing and grinding) to achieve better liberation. The sample contained fine particles that were more prone to being lost in the tailings and to lowering recovery due to the slimes coating valuable minerals. The recovery of the PGMs from this complex’s polymetallic bodies of low-grade and complex mineralogy will be insufficient with traditional methods and thus innovation is needed. Innovation like advanced comminution, novel flotation equipment or reagents, selective leaching and bioprocessing can overcome these challenges. Full article