Search Results (1,756)

Platinum (Pt) and palladium (Pd) are crucial in hydrogen energy technologies, especially in fuel cells, due to their high catalytic activity and chemical stability. Pt-Pd nanoparticles, produced through various methods, enhance catalytic performance based on their size, shape, and composition. These nanocatalysts excel in direct methanol fuel cells (DMFCs) and direct ethanol fuel cells (DEFCs) by promoting alcohol oxidation and reducing CO poisoning. Pt-Pd catalysts are also being explored for their oxygen reduction reaction (ORR) on the cathodic side of fuel cells, showing higher activity and stability than pure platinum. Molecular dynamics (MD) simulations have been conducted to understand the structural and surface energy effects of PdPt nanoparticles, revealing phase separation and chemical ordering, which are critical for optimizing these catalysts. Pd migration to the surface layer in Pt-Pd alloys minimizes the overall potential energy through the formation of Pd surface monolayers and Pt-Pd bonds, leading to a lower surface energy for intermediate compositions compared to that of the pure elements. The potential energy, calculated from MD simulations, increases with a decreasing particle size due to surface creation, indicating higher reactivity for smaller particles. A general contraction of the average distance to the nearest neighbour atoms was determined for the top surface layers within the nanoparticles. This research highlights the significant impact of Pd segregation on the structural and surface energy properties of Pt-Pd nanoparticles. The formation of Pd monolayers and the resulting core–shell structures influence the catalytic activity and stability of these nanoparticles, with smaller particles exhibiting higher surface energy and reactivity. These findings provide insights into the design and optimization of Pt-Pd nanocatalysts for various applications. Full article

The transformation of biomass into renewable fuels and chemicals has gained remarkable attention as a sustainable alternative to fossil-based resources. Metal-based catalysts, encompassing transition and noble metals, are crucial in these transformations as they drive critical reactions, such as hydrodeoxygenation, hydrogenation, and reforming. Transition metals, including nickel, cobalt, and iron, provide cost-effective solutions for large-scale processes, while noble metals, such as platinum and palladium, exhibit superior activity and selectivity for specific reactions. Catalytic advancements, including the development of hybrid and bimetallic systems, have further improved the efficiency, stability, and scalability of biomass transformation processes. This review highlights the catalytic upgrading of lignocellulosic, algal, and waste biomass into high-value platform chemicals, biofuels, and biopolymers, with a focus on processes, such as Fischer–Tropsch synthesis, aqueous-phase reforming, and catalytic cracking. Key challenges, including catalyst deactivation, economic feasibility, and environmental sustainability, are examined alongside emerging solutions, like AI-driven catalyst design and lifecycle analysis. By addressing these challenges and leveraging innovative technologies, metal-based catalysis can accelerate the transition to a circular bioeconomy, supporting global efforts to combat climate change and reduce fossil fuel dependence. Full article

The pursuit of carbon neutrality has accelerated advancements in sustainable hydrogen production and storage methods, increasing the importance of methanol steam reforming (MSR) technology. Catalysts are central to MSR technology and are primarily classified into copper-based and noble metal-based catalysts. This review begins with an examination of the active components of these catalysts, tracing the evolution of the understanding of active sites over the past four decades. It then explores the roles of various supports and promoters, along with mechanisms of catalyst deactivation. To address the diverse perspectives on the MSR reaction mechanism, the existing research is systematically organized and synthesized, providing a detailed account of the reaction mechanisms associated with both catalyst types. The discussion concludes with a forward-looking perspective on MSR catalyst development, emphasizing strategies such as anti-sintering methods for copper-based catalysts, approaches to reduce byproduct formation in palladium-based catalysts, comprehensive research methodologies for MSR mechanisms, and efforts to enhance atomic utilization efficiency. Full article

This study investigates the electrochemical conversion of methane to methanol using fuel-cell-type reactors with palladium- and lanthanum-based catalysts supported on antimony-doped tin oxide (ATO). The combination of these elements demonstrated promising characteristics for selective methanol production. Transmission electron microscopy (TEM) analysis revealed the impact of lanthanum addition on palladium nanoparticles, influencing size distribution and clusters. Polarization curves and power density plots highlighted the Pd₅₀La₅₀/ATO catalyst, indicating an optimal palladium/lanthanum ratio for methanol optimization. FTIR analysis confirmed the presence of methanol in the reaction products, while the methanol production rate showcased the superior performance of the Pd₅₀La₅₀/ATO catalyst compared to other compositions. The synergistic effects between lanthanum’s water activation capability and the carbophilic nature of PdO emerged as crucial factors for the catalyst’s success. Full article

A pyridine-fused triazapentalene shows weak fluorescence in solution and is readily accessible via nitrene-mediated cyclization. In this study, a modified Cadogan reaction was used to synthesize HetATAP 1. Palladium-catalyzed reactions have been used as post-functionalization methods. Interestingly, modified Suzuki cross-couplings with various boronic acids resulted in poor to moderate yields of HetATAPs 2–5 which were arylated at the azole moiety. Direct CH arylation of HetATAP 1 gave the products with the same regiochemistry in satisfactory yields. The structures of HetATAPs 2–5 were confirmed using NMR analysis. In addition, the photophysical properties of HetATAPs 1–5 were studied under various conditions. Particularly, the emission of HetATAPs 2–5 is enhanced in the solid and aggregate state. Full article

In this paper, the clean high yielding, synthesis, and structure of the tetraphosphine ligand, 1,1′,2,2′-tetrakis-(di-isopropyl-phosphino)ferrocene, (tdipf), is described. In addition, improved synthesis methods for 1,1′,2,2′-tetrakis(diphenylphosphino)ferrocene, (tppf), and 2,2′-bis-(diphenylphosphino)-1,1′-dibromoferrocene are also reported, and the synthetic method is generalised to include the synthesis of 3,3′-bis-(diphenylphosphino)-1,1′,2,2′-tetrabromoferrocene. The related ligands 2,2′-bis-(iso-propylphosphino)-1,1′-bis-diphenylphosphinoferrocene (diprdppf) and 2,2′-bis-(di-isopropylphosphino)-dibromoferrocene have also been prepared and characterised. The crystal structure of the square planar bimetallic nickel (II) dichloride of tdipf is also described, together with a brief NMR study investigating the synthesis of this and related metal complexes. The crystal structures of the palladium and platinum dichloride complexes of 2,2′-bis-(di-isopropylphosphino)-1,1′-dibromoferrocene, bpdbf, are also discussed in the context of comparison with previously known crystal structures in the same general family. A general discussion on the synthetic methodology is given, along with indications for future research that other researchers might explore. Full article

Zwitterionic π-allenyl palladium species are newly developed intermediates. A substrate-controlled step existed in the cycloaddition of zwitterionic π-allenyl palladium species with tropsulfimides or tropones. With the assistance of previously experimental studies, zwitterionic allenyl/propargyl palladium species was provenly found by HRMS. Further DFT calculation studies show that zwitterionic π-allenyl palladium species are generated through the oxidative addition of Pd(0), which can be promoted by Lewis acid like Yb(OTf)₃, and the cycloaddition more likely undergoes through an outer sphere nucleophilic attack. The isomerization is caused by the difference of dissociation energy between the cycloaddition intermediation of tropsulfimides and tropones, forming the substrate-controlled specificity. Full article

The emergence of RNA viruses driven by global population growth and international trade highlights the urgent need for effective antiviral agents that can inhibit viral replication. Nucleoside analogs, which mimic natural nucleotides, have shown promise in targeting RNA-dependent RNA polymerases (RdRps). Starting from protected 5-iodouridine, we report the synthesis of hitherto unknown C5-substituted-(1,3-diyne)-uridines nucleosides and their phosphoramidate prodrugs. The modifications at C5 include 4-(trifluoromethyl)benzene (a), 4-pentyl-benzene (b), 3,5-dimethoxy-benzene (c), 4-(trifluoromethoxy)benzene (d), 3-aniline (e), 4-pyridine (f), 3-thiophene (g), C₆H₁₃ (h), 2-pyrimidine (i), cyclopropyl (j), and phenyl (k) groups. These compounds were synthesized using Sonogashira palladium-catalyzed reactions and nickel–copper-catalyzed C-H activation between various alkynes, yielding between 25% and 67%. The antiviral activities of obtained compounds were measured through HTS against RNA viruses including influenza H1N1 and H3N2, human respiratory syncytial virus (RSV), SARS-CoV-2, Zika, hepatitis C virus (HCV), Hepatitis E virus (HEV), as well as against coronavirus (HCoV-229E). Unfortunately, none of them showed promising antiviral activity, with less than 85% inhibition observed in the cell viability screening of infected cells. Full article

Palladium (Pd) is a 4d transition metal with electronic configuration [Kr] 4d¹⁰ 5s⁰, and it is one of the most widely studied metals in the periodic table due to its versatile catalytic role in organic synthesis. The choice of ligands that can coordinate with Pd sites plays a crucial role in the progress of the reaction. Due to the coexistence of multiple oxidation states (Pd(0)/Pd(II)), the active Pd sites of the catalysts can participate in various stages of the coupling reaction. The Pd-catalyzed C-C coupling reactions proceed through four steps: (1) oxidative addition of the reactant to the catalytic site, (2) transmetallation, (3) rearrangements of ligand centers and (4) reductive elimination to the coupling products. For the heterogeneous Pd nanocatalysts, active Pd sites are often strongly bound (chelated) with the solid catalyst surfaces. In this review, we have highlighted the advancements made in the heterogeneous Pd nanocatalysts with an emphasis on the types of different classes of porous solids, which could ligate with the Pd centers via strong covalent bonds. The high specific surface areas and small Pd sites of these nanocatalysts provide a larger number of catalytic sites and thus facilitate the reaction. Mechanistic aspects of the C-C cross-coupling reactions are discussed in the context of the structure–reactivity relationship. Full article

Meriolins (3-(pyrimidin-4-yl)-7-azaindoles) are synthetic hybrids of the naturally occurring alkaloids variolin and meridianin and display a strong cytotoxic potential. We have recently shown that the novel derivative meriolin 16 is highly cytotoxic in several lymphoma and leukemia cell lines as well as in primary patient-derived lymphoma and leukemia cells and predominantly targets cyclin-dependent kinases (CDKs). Here, we efficiently synthesized nine novel 2-aminopyridyl meriolin congeners (3a–3i), i.e., pyrimeriolins, using a one-pot Masuda borylation-Suzuki coupling (MBSC) sequence, with eight of them bearing lipophilic alkoxy substituents of varying length, to systematically determine the influence of the alkoxy sidechain length on the biological activity. All the synthesized derivatives displayed a pronounced cytotoxic potential, with six compounds showing IC₅₀ values in the nanomolar range. Derivatives 3b–3f strongly induced apoptosis and activated caspases with rapid kinetics within 3–4 h in Jurkat leukemia and Ramos lymphoma cells. The induction of apoptosis by the most potent derivative 3e was mediated by the intrinsic mitochondrial death pathway, as it was blocked in caspase-9 deficient and Apaf-1 knockdown Jurkat cells. However, as recently shown for meriolin 16, derivative 3e was able to induce apoptosis in the Jurkat cells overexpressing the antiapoptotic protein Bcl-2. Since tumor cells often inactivate the intrinsic mitochondrial apoptosis pathway (e.g., by overexpression of Bcl-2), these meriolin congeners represent promising therapeutic agents for overcoming therapeutic resistance. 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

Energy consumption in buildings is linked to lighting technology. Light-emitting diode (LED) technology includes lamps and luminaires for general lighting applications. Due to their structure, LED lamps are expected to generate specific waste electrical and electronic equipment (WEEE) streams. LEDs are the main source of luminous flux, and their elemental composition is of particular interest to the recycling sector. In this study, surface-mount device (SMD) LEDs from six types of LED lamps (E27, E14, G9, R7S, GU10, and MR16) were removed, collected, separated by correlated colour temperature (CCT) (2700 K, 3000 K, 4000 K, and 6500 K), and characterised for the presence of rare earth elements and precious metals. They were digested with HNO₃, aqua regia, and HF in a hot plate and characterised by inductively coupled plasma mass spectrometry (ICP-MS). The concentration of each element as a function of CCT ranged as follows: lanthanum, 242–1840 mg/kg; cerium, 132–284 mg/kg; europium, 15–69 mg/kg; gadolinium, 1.9–3.8 mg/kg; terbium, 0.1–0.4 mg/kg; lutetium, 29–6381 mg/kg; yttrium, 4804–11,551 mg/kg; silver, 2712–5262 mg/kg; gold, 502–956 mg/kg; and palladium, 32–110 mg/kg. These results indicate the need for selective removal and separate recycling processes of SMD LEDs from LED lamps. Full article

The recovery of palladium from aqueous solutions is important due to its critical role in various industrial applications and the growing demand for sustainable resource management. This study investigates the potential of hybrid materials composed of Mg₃Al layered double hydroxides (LDHs), chitosan, and ionic liquids (methyl trialchil ammonium chloride) for the efficient adsorption of palladium ions from low-concentration aqueous solutions. Comprehensive characterization techniques, including X-ray diffraction (RX), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and thermogravimetric analysis (TG), were employed to elucidate the structural and compositional properties of the hybrid materials. The results of the batch adsorption experiments demonstrate that each component contributes synergistically to the adsorption process, significantly enhancing the overall efficacy of palladium recovery. Furthermore, the method of preparing the adsorbent material was found to impact the effectiveness of palladium recovery. Among the materials tested, the chitosan/Mg₃Al/IL hybrid exhibited the highest adsorption capacity (q_max = 98 mg/g), suggesting that the ionic liquid functionalization is most beneficial when applied during the hybrid material synthesis, rather than during the LDH synthesis process. This research underscores the viability of hybrid materials as a sustainable approach to palladium recovery, contributing to advancements in environmental remediation technologies. Full article

In this work, for the first time, the sorption behaviour of platinum and palladium on polyethylene microplastics (PE-MP) was studied. To simulate natural conditions, part of PE-MP was subjected to the ageing process in lake water under the influence of solar radiation. The original and aged PE-MP was characterised using elemental analysis, FT-IR, SEM-EDX, and nitrogen porosimetry methods. The studies on Pt and Pd sorption on PE-MP were carried out in batch mode in natural lake water at pH 7.6. It was found that the ageing process led to the degradation of the surface of the PE-MP and the formation of a biofilm. The sorption process of Pt and Pd on PE-MP particles proceeds according to pseudo-second-order kinetics. A good fit of the experimental data to the Freundlich and Langmuir isotherm model indicates the mixed nature of Pt and Pd sorption on PE-MP. It was clearly indicated that Pt and Pd sorption from natural waters can occur on the surface of inert polyethylene particles, which can lead to the preconcentration of these elements, even from waters with a very low content, and transferring them over longer distances. This poses a threat to the health of living organisms and humans. Full article

This study investigates the synthesis, characterization, and potential applications of silver–copper (AgCu) alloy powders produced from co-precipitated carbonates. The Cu/Ag carbonate samples were analyzed using EDXRF, TGA-DSC, XRD, SEM, and electrical conductivity tests to examine their composition, thermal behavior, structure, and morphology. The results showed slight deviations from the theoretical Cu/Ag ratios in the carbonates, attributed to equilibrium effects during precipitation. Thermal analysis indicated that the reduction process of carbonates with hydrogen was completed at 300 °C, while alloy formation was confirmed by endothermic peaks around 780 °C. XRD and SEM analyses revealed that AgCu alloys formed a solid solution, with smaller crystallite sizes observed at higher Cu contents. Electrical conductivity tests demonstrated that while pure Ag and Cu powders exhibited conductivity increases with compaction, the AgCu alloy showed stable conductivity without a significant decrease. In Pd(II) cementation experiments, AgCu alloys demonstrated higher efficiency in Pd(II) recovery than pure Ag and Cu. These findings suggest that AgCu alloys, particularly with a balanced composition, may offer improved performance for metal recovery applications, providing a promising approach for industrial cementation processes. Full article