Search Results (95)

Reductive amination of cyclohexanone with NH₃ and H₂ over Rh and Rh-Ni catalysts on SiO₂ has been studied. Research has focused on the catalytic efficiency of monometallic and bimetallic catalysts in the production of cyclohexylamine, a key intermediate in the synthesis of numerous fine chemicals. Through the wet impregnation method, Rh and Rh-Ni catalysts with varying nickel loadings (1, 2, 5, and 10 wt.%) were synthesized and characterized using techniques such as N₂ physisorption, TEM, HAADF-STEM, XRD, XPS, H₂-TPR, and NH₃-TPD. The catalytic reactions were conducted under controlled conditions using a glass-coated reactor, using ammonia as nitrogen source. Rh-Ni bimetallic catalysts exhibited the highest conversion rates on reductive amination, attributed to enhanced dispersion and advantageous surface properties. High metal dispersion and small particle sizes were confirmed by TEM, HAADF-STEM, and XRD. XPS analysis confirmed the reduced state of Rh and mainly oxidized state of Ni, while H₂-TPR and NH₃-TPD results indicated improved reducibility and acidity, respectively, which are critical for catalytic activity. Monometallic Rh/SiO₂ catalyst showed 83.4% of conversion after 300 min and selectivity of 99.1% toward the desired product cyclohexylamine. The addition of nickel, a cheap and easily available metal, increases the activity without compromising selectivity. At 300 min of the reaction, the 2 wt.% NiRh/SiO₂ catalyst exhibited the highest conversion, yield, and selectivity for the desired product cyclohexylamine, 99.8%, 96.4%, and 96.6% respectively. Additionally, this catalyst is recyclable after the fourth cycle, showing 99.5% selectivity and 74.0% yield for cyclohexylamine at 75.7% conversion. Recycling tests confirmed the stability of bimetallic catalysts, maintaining performance over multiple cycles without significant deactivation. Full article

Liquid Organic Hydrogen Carriers (LOHCs) represent a promising technology for the safe storage and transport of hydrogen. Its technical development largely depends on the catalysts used in the hydrogenation and dehydrogenation processes. Typically, noble metal-based monometallic catalysts are employed, although they present limitations in terms of cost and availability. This study uses the DBT system to explore the potential of nickel (Ni) as a catalytic alternative. In dehydrogenation, its role as an additive in low-loaded Pt-based catalysts (0.25 wt%) was evaluated, showing a significant increase in activity, with dehydrogenation levels exceeding 95%, compared to 82% obtained with monometallic Pt catalysts. This improvement is attributed to the formation of Pt-Ni alloys. On the other hand, although the bimetallic systems were not effective in hydrogenation, a commercial Ni/Al₂O₃-SiO₂ catalyst was tested, achieving hydrogenation degrees of 80% in just 40 min, after pressure and catalyst loading optimization. These results position Ni as a key component in LOHC catalysis, either as an effective additive in Pt-based systems or as an active metal itself, due to its excellent performance and low cost. This paves the way for economically viable and efficient catalytic solutions for hydrogen storage applications, bridging the gap between performance and practicality. Full article

This work is devoted to the study of the effect of small Bi additives on the functional properties of Pdx:Bi/Al₂O₃ catalysts in the selective oxidation of glucose to gluconic acid. The catalysts obtained by the joint impregnation method were characterized (TEM) by high dispersion of bimetallic nanoparticles with a median diameter of 4–5 nm. The structure of the Pd-Bi solid solution was confirmed via XPS and showed a change in the valence state of Pd and Bi depending on the Bi content, as well as the fraction of the oxidized state of Bi. TPR-H₂ revealed various forms of Pd, including PdO and mixed Pd-O-Bi structures. The Pd10:Bi1/Al₂O₃ catalyst demonstrated the highest efficiency (77.2% glucose conversion, 96% sodium gluconate selectivity), which is due to the optimal ratio between Pd and Bi, ensuring the stabilization of metallic Pd and preventing its oxidation. Full article

Bimetallic catalysts can effectively enhance the catalytic degradation efficiency of peroxymonosulfate (PMS), which is usually attributed to the enhancement of electron transfer, but currently, there is no clear explanation of the mechanism of how the electron transfer is enhanced. A nitrogen-doped Fe/Mn composite biochar (FeMn-NBC) was co-constructed by hydrothermal synthesis and high-temperature calcination. The FeMn-NBC activated PMS more efficiently than the monometallic one due to the enhanced electron transfer between Fe and Mn. The FeMn-NBC/PMS system activated PMS with Mn as the active center, and the high oxidation state of Mn⁴⁺ promoted the acceleration of the PMS adsorption of the generation of Mn²⁺/Mn³⁺. This gaining effect accelerated the electron cycling between Fe²⁺/Fe³⁺ and Mn²⁺/Mn³⁺/Mn⁴⁺, which enhanced the PMS catalysis to generate free radicals (•OH, SO₄^•− and •O₂⁻) and non-radicals (¹O₂) for the efficient degradation of diisobutyl phthalate (DIBP). Benefiting from this gaining effect, the degradation rate of DIBP by the FeMn-NBC/PMS system was increased by 2.43 and 3.38 times compared to Fe-NBC and Mn-NBC. The bimetallic-enhanced electron transfer mechanism proposed in this study facilitated the development of efficient catalysts for more efficient and selective removal of organic pollutants. Full article

Bimetals—materials composed of two metal components with dissimilar standard reduction–oxidation (redox) potentials—offer unique electronic, optical, and catalytic properties, surpassing monometallic systems. These materials exhibit not only the combined attributes of their constituent metals but also new and novel properties arising from their synergy. Although many reviews have explored the synthesis, properties, and applications of bimetallic systems, none have focused exclusively on iron (Fe)- and aluminum (Al)-based bimetals. This systematic review addresses this gap by providing a comprehensive overview of conventional and emerging techniques for Fe-based and Al-based bimetal synthesis. Specifically, this work systematically reviewed recent studies from 2014 to 2023 using the Scopus, Web of Science (WoS), and Google Scholar databases, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, and was registered under INPLASY with the registration number INPLASY202540026. Articles were excluded if they were inaccessible, non-English, review articles, conference papers, book chapters, or not directly related to the synthesis of Fe- or Al-based bimetals. Additionally, a bibliometric analysis was performed to evaluate the research trends on the synthesis of Fe-based and Al-based bimetals. Based on the 122 articles analyzed, Fe-based and Al-based bimetal synthesis methods were classified into three types: (i) physical, (ii) chemical, and (iii) biological techniques. Physical methods include mechanical alloying, radiolysis, sonochemical methods, the electrical explosion of metal wires, and magnetic field-assisted laser ablation in liquid (MF-LAL). In comparison, chemical protocols covered reduction, dealloying, supported particle methods, thermogravimetric methods, seed-mediated growth, galvanic replacement, and electrochemical synthesis. Meanwhile, biological techniques utilized plant extracts, chitosan, alginate, and cellulose-based materials as reducing agents and stabilizers during bimetal synthesis. Research works on the synthesis of Fe-based and Al-based bimetals initially declined but increased in 2018, followed by a stable trend, with 50% of the total studies conducted in the last five years. China led in the number of publications (62.3%), followed by Russia, Australia, and India, while Saudi Arabia had the highest number of citations per document (95). RSC Advances was the most active journal, publishing eight papers from 2014 to 2023, while Applied Catalysis B: Environmental had the highest number of citations per document at 203. Among the three synthesis methods, chemical techniques dominated, particularly supported particles, galvanic replacement, and chemical reduction, while biological and physical methods have started gaining interest. Iron–copper (Fe/Cu), iron–aluminum (Fe/Al), and iron–nickel (Fe/Ni) were the most commonly synthesized bimetals in the last 10 years. Finally, this work was funded by DOST-PCIEERD and DOST-ERDT. Full article

Marine biofouling causes significant economic losses, and conventional antifouling methods are often associated with environmental pollution. Hydrogen peroxide (H₂O₂), as a clean energy source, has gained increasing attention in recent years. Meanwhile, electrocatalytic 2e⁻ oxygen reduction reaction (ORR) for H₂O₂ production has received growing interest. However, the majority of current studies are conducted on acidic or alkaline electrolytes, and research on 2e⁻ ORR in neutral NaCl solutions remains rare. Here, a bimetallic Zn-Cd zeolitic imidazolate framework (ZnCd-ZIF) is rationally designed to achieve chloride-resistant 2e⁻ ORR catalysis under simulated seawater conditions (pH 7.5, 3.5% Cl⁻). Experimental results demonstrate that the ZnCd-ZIF catalyst exhibits an exceptional H₂O₂ selectivity of 70% at 0.3 V_RHE, surpassing monometallic Zn-ZIF (60%) and Cd-ZIF (50%). Notably, H₂O₂ production reaches 120 mmol g⁻¹ in a Cl⁻-containing neutral electrolyte, exhibiting strong resistance to structural corrosion and Cl⁻ poisoning. This work not only pioneers an effective strategy for designing ORR catalysts adapted to marine environments but also advances the practical implementation of seawater-based electrochemical H₂O₂ synthesis. Full article

The thermal stability of bimetallic nanoparticles plays a crucial role in their performance in applications in catalysis, biotechnology, and materials science. In this study, we employ molecular dynamics simulations to investigate the melting behavior of Au-Pd nanoparticles with cuboctahedral, icosahedral, and decahedral geometries. Using a tight-binding potential, we systematically explore the effects of particle size and composition on the melting transition. Our analysis, based on caloric curves, Lindemann coefficients, and orientational order parameters, reveals distinct premelting behaviors influenced by geometry. Larger particles exhibit a coexistence of a pseudo-crystalline core and a partially melted shell, but, in decahedra and icosahedra, melting of the core occurs unevenly, with twin boundaries promoting the melting of one or two of the tetrahedral subunits before the rest of the particle. Notably, icosahedral nanoparticles display higher thermal stability, while both icosahedral and decahedral structures exhibit localized melting within twin boundaries. Additionally, we generate HAADF-STEM simulations to aid the interpretation of in situ electron microscopy experiments. Full article

Ammonia (NH₃) emissions from mobile sources pose significant environmental challenges, contributing to air pollution, ecosystem degradation, and climate change. The selective catalytic oxidation of NH₃ (NH₃-SCO) offers a sustainable solution by converting NH₃ into nitrogen and water, yet designing catalysts that balance high efficiency, selectivity, and stability under operational conditions remains a critical challenge. This review provides a comprehensive overview of zeolite-based catalysts, renowned for their high surface area, tunable pore structures, and exceptional hydrothermal stability, which make them ideal for NH₃-SCO applications. The review synthesizes recent advancements in catalyst design, emphasizing innovative architecture, the role of zeolite frameworks in active site dispersion, and strategies for optimizing catalytic architectures. Key insights include an enhanced understanding of NH₃-SCO reaction mechanisms, progress in mitigating catalyst deactivation caused by poisoning and sintering, and the development of bimetallic and core-shell catalysts to improve performance and durability. Current limitations, including the sensitivity of catalysts to operational environments and scalability issues, are critically analyzed, and potential strategies for overcoming these barriers are proposed. This review highlights the state-of-the-art in zeolite-based NH₃-SCO catalysis, offering valuable insights into the fundamental and applied aspects of catalyst design. The findings presented here provide a roadmap for future innovations in environmental catalysis, paving the way for more efficient and robust solutions to ammonia emission control. Full article

A novel sequential one-pot bimetallic catalytic system combining Fe(III)-catalyzed alkynylation and a Rh(I)-catalyzed [2+2+2] reaction was successfully developed. The σ-Lewis acid properties of iron (III) and the π-Lewis acid properties of rhodium (I) catalysts were unified in an unprecedented intermolecular alkynylation/cyclotrimerization one-pot process. Using this unique Fe/Rh bimetallic relay catalytic system, a variety of benzo and pyrridinoisoindolinone derivatives were obtained under mild conditions from easily available N-(propargyl) hydroxy aminals, as the simplest N-acyliminium ion precursors, and several alkynes. Full article

Palladium-doped silver nanoclusters (NCs) have been highlighted for their unique physicochemical properties and potential applications in catalysis, optics, and electronics. Anion-directed synthesis offers a powerful route to control the morphology and properties of these NCs. Herein, we report a novel Pd-doped Ag NC, [Pd(H)Ag₁₃(S){S₂P(OⁱPr)₂}₁₀] (PdHAg₁₃S), synthesized through the inclusion of sulfide and hydride anions. This NC features a unique linear S-Pd-H axis enclosed in a 4-5-4 stacked arrangement of silver atoms. The distinctive hydride environment was characterized by NMR spectroscopy, and the total structure was determined by single-crystal X-ray diffraction (SCXRD) and supported by computational studies. Mass spectrometry and X-ray photoelectron spectroscopy (XPS) further confirmed the assigned composition. This unique construct exhibits promising hydrogen evolution reaction (HER) activity. Our findings highlight the potential of anion-directed synthesis for creating novel bimetallic NCs with tailored structures and catalytic properties. Full article

Direct light olefin synthesis from bio-syngas hydrogenation is a promising pathway to decarbonize the chemical industry. The present study is devoted to the investigation of co-hydrogenation of carbon oxides in the presence of complex systems with the perovskite structure GdBO₃ (B = Fe, Mn, Co). The catalyst samples were synthesized by sol-gel technology and characterized by XRD, XPS, BET and TPR. It was found that the Fe/Mn-containing samples exhibited efficient catalysis of the hydrogenation of simulated bio-syngas to light hydrocarbons. The GdMnO₃ catalyst exhibits selectivity for C₂–C₃ light olefins of up to 37% among C1+ hydrocarbons, with a maximum olefin/paraffin ratio. GdMnO₃ also exhibits high conversion of CO and CO₂, reaching up to 70–75% at 723 K. However, the GdFeO₃ catalyst shows a lower selectivity of (${\mathit{C}}_{2-3}^{=}$ = 22%, while it exhibits a higher conversion of CO₂, up to 95%, at the same temperature. Herein, we established a catalyst structure–performance relationship as a function of chemical composition. Oxygen mobilities and ratios of surface (O_s) to lattice (O_l) oxygen, forms of hydrogen adsorption, formation of -CH_x- radicals and their subsequent recombination to olefins are influenced by the nature of the element in the B position. This work provides valuable insights for the rational design of bimetallic catalysts for bio-syngas hydrogenation. 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

Gatifloxacin (GAT), an antibiotic belonging to the fluoroquinolone (FQ) class, is a toxicant that may contaminate food products. In this study, a method of ultrasensitive immunochromatographic detection of GAT was developed for the first time. An indirect format of the lateral flow immunoassay (LFIA) was performed. GAT-specific monoclonal antibodies and labeled anti-species antibodies were used in the LFIA. Bimetallic core@shell Au@Ag nanoparticles (Au@Ag NPs) were synthesized as a new label. Peroxidase-mimic properties of Au@Ag NPs allowed for the catalytic enhancement of the signal on test strips, increasing the assay sensitivity. A mechanism of Au@Ag NPs-mediated catalysis was deduced. Signal amplification was achieved through the oxidative etching of Au@Ag NPs by hydrogen peroxide. This resulted in the formation of gold nanoparticles and Ag⁺ ions, which catalyzed the oxidation of the peroxidase substrate. Such “chemical enhancement” allowed for reaching the instrumental limit of detection (LOD, calculated by Three Sigma approach) and cutoff of 0.8 and 20 pg/mL, respectively. The enhanced assay procedure can be completed in 21 min. The enhanced LFIA was tested for GAT detection in raw meat samples, and the recoveries from meat were 78.1–114.8%. This method can be recommended as a promising instrument for the sensitive detection of various toxicants. Full article

Catalysis is a fundamental process in chemistry and industry, driving the transformation of reactants into valuable products while minimizing energy input and waste generation. The quest for efficient and selective catalysts has led to the emergence of cyclodextrin metal–organic frameworks (CD-MOFs), a unique class of porous materials combining the advantages of cyclodextrins and metal–organic frameworks. CD-MOFs are gaining recognition for their distinctive capabilities in catalysis, offering benefits in terms of catalytic activity, selectivity, and sustainability. This paper presents an overview of current research on CD-MOFs in catalysis, emphasizing their application as hosts for catalytic materials and as catalysts themselves. The exploration includes studies on the confinement of redox-active monomers within CD-MOFs, resulting in controlled polymerization and enhanced electrical conductivity. Additionally, the paper discusses the encapsulation of photocatalysts in CD-MOFs, leading to stable and active hybrid materials for selective reduction processes. Further investigations focuses into the nanoconfined environment of CD-MOFs, showcasing their ability to influence the regio- and stereoselectivity of photodimerization reactions. The synthesis of bimetallic nanoparticles within CD-MOFs is also explored, highlighting their potential in catalytic applications with enhanced stability and recyclability. Despite significant progress, research gaps persist, urging a deeper understanding of the structure–function relationships within CD-MOFs. Mechanistic insights into catalytic processes, scalable synthesis methods, stability under catalytic conditions, recyclability, and diversification of catalytic functions are identified as critical areas for future exploration. The paper concludes by envisioning the future of CD-MOFs in catalysis, emphasizing tailored structures for specific reactions, multifunctionality, sustainability, industrial integration, and the exploration of novel catalytic frontiers in challenging environments. The catalytic prowess of CD-MOFs holds the promise of contributing to sustainable and efficient chemical processes, ushering in a new era of innovation at the intersection of materials science and catalysis. Full article

With the excessive use of fossil fuels, atmospheric carbon dioxide (CO₂) concentrations have risen dramatically in recent decades, leading to serious environmental and social issues linked to global climate change. The emergence of renewable energy sources, such as solar, tidal, and wind energy, has created favorable conditions for large-scale electricity production. Recently, significant attention has been drawn to utilizing renewable energy to catalyze the conversion of CO₂ into fuels, producing substantial industrial feedstocks. In these CO₂ conversion processes, the structure and performance of catalysts are critical. Metal-organic frameworks (MOFs) and their derivatives have emerged as promising electrocatalysts for CO₂ reduction, offering advantages such as high surface area, porosity, exceptional functionality, and high conversion efficiency. This article provides a comprehensive review of structural regulation strategies for copper-based MOFs, highlighting innovative mechanisms like synergistic bimetallic catalysis, targeted doping strategies, and the construction of heterostructures. These novel approaches distinguish this review from previous studies, offering new insights into the electrocatalytic performance of copper-based MOFs and proposing future research directions for improved catalyst design. Full article