Topics in Catalysis最新文献

Cu-based nanocatalysts have potential applications in the selective hydrogenation of biomass-derived platform molecules. Currently, a main challenge is the poor stability of Cu catalysts under harsh reaction conditions due to metallic Cu sintering and agglomeration. Herein, a series of Cu_xFe_y/Al₂O₃ nanocomposite catalysts was prepared via controlled solution combustion synthesis (SCS) owing to its minimal reaction time and energy requirements that reduce Cu agglomeration. Among them, the Cu₅Fe₃/Al₂O₃ catalyst exhibited the most favorable structure with the smallest grain size of 2.09 nm, highest dispersion of 63.6%, and an optimal Cu⁺/Cu⁰ ratio of 1.0 than the traditional Cu/Al₂O₃ counterpart. The synergy between Fe₂O₃ and Cu inhibited the thorough reduction of Cu²⁺ to Cu⁰ and consequently facilitated H₂ dissociation and activation as well as the highly efficient activation of the ethyl levulinate’s (EL) carbonyl group. Unlike the traditional Cu/Al₂O₃ catalyst, for which activity rapidly decreased from 97% to 11% over 200 h, the Cu₅Fe₃/Al₂O₃ catalyst exhibited a high GVL yield of 85% and maintained excellent stability, attributable to the strong interaction between Cu nanoparticles and Al₂O₃ support as well as the confinement effect with barrier property of Fe doping. Therefore, the inexpensive, efficient, and stable Cu₅Fe₃/Al₂O₃ catalyst has potential applications in the selective hydrogenation of biomass-derived platform compounds.

Solution combustion synthesis was employed to prepare a Cu–Fe/Al₂O₃ nanocomposite catalyst, which exhibited excellent catalytic performance in the hydrogenation of biomass-derived ethyl levulinate to γ-valerolactone (GVL). This catalyst surpassed the performance of the traditional Cu/Al₂O₃ catalyst, particularly in terms of demonstrating a high GVL yield of 85% and maintaining stability for over 200 h. This excellent performance could be attributed to its high Cu dispersion, small grain size, and optimal Cu⁺/Cu⁰ ratio.

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Traditional electro-organic synthesis methods for sulfonamides often suffer from low catalytic efficiency, long reaction times, and the use of environmentally harmful reagents, limiting their practical applications and sustainability. This study explores the utilization of cobalt nanoparticles supported on GO enhanced with the MIL-100@Co MOF in a PAOCl as an electrolyte and SO₂ trapping agent for the electro-catalytic synthesis of sulfonamides via C-H activation reaction. The synthesized catalyst was characterized utilizing various analytical techniques, including FT-IR, BET, SEM, EDS, EDX mapping, TGA, CV, and XPS, to confirm its structural integrity and elemental composition. The catalytic performance was evaluated in terms of yield and reaction time, demonstrating an impressive 92–97%yield of sulfonamides 4(a-k) within just 45 min at ambient temperature and atmospheric pressure, using a current of 10 mA. This performance surpasses that of traditional methods employing other cathode materials, which often suffer from low yields and prolonged reaction times. The incorporation of Co nanoparticles enhances catalytic efficiency, while PAOCl serves as both an electrolyte and SO₂ trapping agent. Additionally, the MIL-100@Co MOF provides a robust support structure with a high surface area, improving reactivity in the electrochemical environment. Overall, this work highlights the potential of MIL-100@Co MOF composites in a PAOCl as effective catalytic system for sustainable sulfonamides 4(a-k) synthesis in electrochemical applications.

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The easy modulation of the first and second ligand spheres of the redox active centres in heterogenised enzyme-inspired catalysts is highly desirable for speeding up de-novo design and optimisation. In this study, we employ metal-organic framework (MOF) hosts, capable of emulating enzyme-like heterogenised Cu(I) active sites to study their catalytic performance. By leveraging on a post-synthetic modification (PSM) strategy, we modified the microenvironment around copper centres within the selected UiO-67 MOFs, thereby mimicking functionalities typical of enzymatic systems. In order to assess the feasibility of a facile modulation of the microenvironment around the active centre without recourse to organic chemistry approaches, our strategy also involved the incorporation of secondary guest molecules into the MOF matrix, such as phenol and propionamide. Through a thorough combined theoretical-experimental study, we demonstrate that the selected propionamide molecule coordinates to the redox-active cuprous centre, whereas phenol does not get adsorbed into the matrix. The synthesised materials were tested for a C–H activation reaction using cyclohexene as a model substrate and tert-butyl hydroperoxide (tBuOOH) as oxidant, under aerobic conditions. The cuprous ions coordinated to the enzyme-like motifs showed catalytic activity for cyclohexene oxidation, and in addition, showed better performance compared with its cupric counterpart. The catalytic performance of the materials modulated with propionamide however was not significantly different from the parent catalyst, on account of the swift removal of the secondary guest molecule under reaction conditions.

The present study reports the development of g-C₃N₄/g-C₃N₄ isotype heterojunction embedded on graphene oxide (GO) for the photodegradation of pharmaceutical waste and organic dyes. Initially, the g-C₃N₄/g-C₃N₄ isotype heterojunction was prepared by thermal treatment using two different precursors, and subsequently embedded onto GO by a sonication-assisted solvothermal method. The successful synthesis and properties of the material were confirmed by various characterization techniques, including XRD, UV-Vis DRS, FESEM, HR-TEM XPS and BET. The strong compatibility and well-aligned band structure of the g-C₃N₄/g-C₃N₄ isotype heterojunction offers a cost-effective strategy conquer the rapid recombination of photogenerated charge pairs, which is frequently observed in pristine g-C₃N₄, a potential metal-free photocatalyst. Incorporating the g-C₃N₄/g-C₃N₄ isotype heterojunctions onto GO sheets results to the formation of a ternary photocatalyst (g-C₃N₄/g-C₃N₄@GO) with high efficiency in degradation of pharmaceutical waste and organic dyes. The superior photocatalytic efficacy of hybrid ternary g-C₃N₄/g-C₃N₄@GO nanocomposite is primarily due to its enhanced surface area and improved separation of photogenerated electron-hole pairs. The study presents comprehensive synthesis, characterization and evaluation of the photocatalytic potential of the ternary isotype heterojunction, aiming to develop a metal-free catalytic approach for environmental remediations within the broader context of sustainable development.

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A spherical MoO₃–SnO₂ nanocomposite was synthesized via a precipitation–sonication approach and thoroughly characterized to evaluate its structural, optical, and catalytic properties. XRD, SEM-EDX, and HR-TEM analyses confirmed the formation of a crystalline spherical nanostructure with uniform particle distribution. DRS spectra indicated a reduced band gap of 3.25 eV compared to 3.5 eV for pure SnO₂, while photoluminescence studies revealed suppressed electron–hole recombination, confirming improved charge separation. The nanocomposite demonstrated remarkable photocatalytic performance toward the degradation of Naphthol Blue Black (NBB) dye under UV light, achieving 84% degradation within 45 min at neutral pH, significantly higher than the 59% achieved with SnO₂. The material retained 90% of its activity after four reuse cycles, highlighting excellent stability and reusability. COD analysis confirmed efficient dye mineralization with evidence of CO₂ capture. Additionally, electrochemical studies revealed enhanced anodic current and superior electrocatalytic activity in dye-sensitized solar cells, attaining an efficiency of 1.7%. Overall, the synergistic interaction between MoO₃ and SnO₂ enhances charge transfer, optical absorption, and catalytic efficiency, making this nanocomposite a versatile material for environmental remediation, green synthesis, and renewable energy applications.

In this study, NiCu and NiFe based electrocatalysts cocatalyzed with CeO₂ nanorods for ethanol electrooxidation reaction (EOR) in alkaline medium were synthesized and their electrochemical performances were investigated in detail. In all samples, the amount of CeO₂ nanorods was kept constant (20 wt%), and the ratios of Ni and second metal (Cu or Fe) were systematically changed. The obtained nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Electrochemical performance evaluations were carried out by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry (CA) methods. EOR activities of catalysts with different Ni: Cu and Ni: Fe ratios were compared and the highest performing compositions were determined for each system. According to CV analysis, NiCu-CeO_2NRs-2 had the highest current density (21.63 mA cm⁻²) and the lowest onset potential (444 mV) among Cu-containing combinations. Among Fe-containing combinations, NiFe-CeO_2NRs-2 was observed as the best performing catalyst combination with a current density of 27.71 mV cm⁻² and an onset potential of 387 mV. The effect of temperature on electrocatalytic activity was also investigated by electrochemical measurements at different temperatures on catalysts with these optimum compositions. The study reveals the effect of different metal ratios and temperature conditions on EOR performance and evaluates the performance potential of NiCu and NiFe based systems cocatalyzed with CeO₂.

This study focuses on the bacterial and chemical synthesis of CuO nanoparticles and their application in the photocatalytic degradation of high-density polyethylene (HDPE). The band gap energies of the CuO nanoparticles synthesized via bacterial and chemical methods were found to be 1.48 and 1.46 eV, respectively. The particle sizes ranged from 16 to 32 nm for the bacterially synthesised nanoparticles and 55.7 to 75.9 nm for the chemically synthesised ones. Photocatalytic degradation of the HDPE sheet, confirmed by a weight loss of 20.54 ± 0.66% after 100 h of UV irradiation, was achieved using bacterially synthesized CuO nanoparticles. Response Surface Methodology (RSM) was employed to design a statistical model using Central Composite Design (CCD). The optimal nanoparticle concentration (29.6–30 mg) and photocatalysis duration (283–300 h) yielded a desirability score of 1.0. Gas Chromatography–Mass Spectrometry (GC–MS) was used to identify the metabolites produced before and after photocatalysis, further confirming HDPE degradation. Comparison of the bacterially and chemically synthesized CuO nanoparticles revealed negligible differences in photocatalytic performance. However, bacterially synthesized nanoparticles were selected for the scale-up process due to their smaller size and environmentally friendly synthesis. To the best of our knowledge, this is the first study reporting the degradation of HDPE using both chemically and biologically synthesized CuO nanoparticles.