Topics in Catalysis最新文献

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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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.

The storage and distribution of H₂ represent major challenges for its widespread utilization. Liquid organic hydrogen carriers (LOHC), such as methylcyclohexane (MCH), offer a promising alternative by enabling H₂ delivery through dehydrogenation to toluene. Although Pt-based catalysts are the state of the art for this process, this study investigates Ni–Cu catalysts as non-noble metal alternative. For this purpose, two γ-Al₂O₃–supported bimetallic Ni-Cu catalysts were prepared at Cu/Ni atomic ratios of 0.25 and 0.56 and their activity and selectivity towards toluene were evaluated and compared with monometallic Pt (0.6 wt%), Ni (12.8 wt%) and Cu (20.0 wt%) γ-Al₂O₃–supported catalysts. The experimental evaluation was carried out in a fixed-bed reactor at a temperature and pressure of 320 °C and 1.5 bara respectively, and at a weight hourly space velocity of 2.2 h⁻¹. Characterization of the synthesized Ni–Cu catalysts indicated the absence of alloy formation under the synthesis conditions. Experimental results indicated that the bimetallic catalysts exhibited increased activity and selectivity to toluene compared to the monometallic counterparts (i.e. Ni, Cu). A positive correlation was observed between copper addition and MCH conversion, with the Ni–Cu catalyst having a Cu/Ni ratio of 0.56 exhibiting a sevenfold increase compared to the monometallic Ni (7% compared to 1%) at the studied conditions. Nevertheless, the performance remained considerably lower than that of Pt-based catalysts, which achieved 33% MCH, under the conditions studied. Moreover, the selectivity towards toluene was observed to increase with time on stream stream, initially reaching 88% for Cu/Ni = 0.56, comparing with 60% and 85% for Ni/γ-Al₂O₃ and Pt/γ-Al₂O₃ respectively. This results suggests that Cu addition can inhibit the hydrodealkylation of toluene, thereby suppressing the dehydrogenation selectivity of unpromoted Pt catalysts. The enhancement in activity of NiCu catalysts is plausibly attributed to the Ni–Cu interactions at the interface, wehreas the improvement in selectivity is considered to arise from the preferential occupation of the C–C cleavage sites on Ni by Cu. However, catalyst stability was not improved by Cu addition with the deactivation rate being positively correlated with Cu content.

Aimed to enhance the electrocatalytic efficiency of the Electrocatalytic hydrogen evolution reaction (HER) by synthesizing TiO₂/Co₃O₄ composites as highly efficient HER electrocatalysts through a two-step hydrothermal reaction method. Addressing the limitations of conventional TiO₂ materials, such as poor electrical conductivity and limited adsorption/desorption ability of hydrogen intermediates, our strategy used the superior electrical conductivity and catalytic activity of Co₃O₄. Furthermore, this method significantly increased the surface roughness of TiO₂ microspheres, thereby exposing a greater number of electrocatalytic active sites. The resulting TiO₂/Co₃O₄/CC composites exhibited remarkable performance in the HER process, achieving a current density of 10 mA·cm⁻² at a low overpotential of only 150 mV. This outcome indicates fast reaction kinetics and significantly enhanced electrocatalytic activity. Notably, the composite demonstrated robust stability during long-term electrolysis experiments, maintaining stable operation at a current density of 10 mA·cm⁻² for 20 h. These findings provide valuable insights for the design of cost-effective catalysts and the optimization of HER performance.

Hydrodeoxygenation (HDO) is a critical process for upgrading biomass-derived feedstocks. It enables the removal of oxygen, which improves stability, energy density, and compatibility with existing fuel infrastructure. This study examines the catalytic performance of titania-supported noble metals (ruthenium [Ru], rhodium [Rh], palladium [Pd], silver [Ag], iridium [Ir], platinum [Pt], and gold [Au]) in the HDO of anisole, a model compound for lignin-derived oxygenates. The catalysts were prepared via incipient wetness impregnation and characterized using X-ray fluorescence (XRF), nitrogen physisorption (N₂-physisorption), X-ray diffraction (XRD), carbon monoxide (CO) chemisorption, thermogravimetric reduction (TPR), ammonia-temperature-programmed desorption (NH₃-TPD), hydrogen-temperature-programmed desorption (H₂-TPD), and transmission electron microscopy (TEM). The results reveal that metal-support interactions significantly influence metal dispersion, activity, and selectivity. Rh and Pt catalysts exhibited the highest anisole conversion and benzene selectivity due to their small particle sizes, high dispersion, and strong hydrogen spillover effects. Conversely, Ag and Au catalysts demonstrated limited activity: Ag induced a phase transition in TiO₂, and Au formed large particles. Residual chlorine from precursor salts notably affected the performance of Ru/TiO₂ and Ir/TiO₂. Reducible TiO₂ support was found to enhance demethoxylation activity synergistically compared to SiO₂, highlighting the importance of support reducibility for HDO. This work provides insights into the structure-function relationships of noble metal/TiO₂ catalysts.

In this work, ZnO (zinc oxide) nanostructures were electrodeposited onto a glassy carbon electrode (GCE) using a simple, environmentally friendly, and low-cost electrochemical method. The electrocatalytic oxidation of uric acid (UA) was investigated at this ZnO/GCE. Electrochemical oxidation of uric acid in 0.1 M phosphate buffer solution PBS (0.1M K₂HPO₄ + 0.1 M KH₂PO₄) at pH = 7 was examined by cyclic voltammetry. The formation and structure of the ZnO/GCE were systematically characterized by SEM, EDX and XRD. These analyses showed that the synthetized ZnO nanostructures possessed good-crystallinity with well-defined nanorod morphology and favorable characteristics. The electrochemical response of the as-prepared ZnO-based sensor toward uric acid in PBS was further evaluated by linear sweep voltammetry (LSV) and chronoamperometry. The results confirmed that ZnO-modified GCE exhibited high electrocatalytic activity toward uric acid oxidation. Furthermore, the sensor demonstrated a high sensitivity of 28.4 µA µM⁻¹ cm⁻² and a low limit of detection (LOD) of 10.778 µM. The calibration curves were linear in the concentration range 0.125 to 3.0 mM (R² = 0.99) for UA. Kinetic analysis revealed an electron transfer coefficient (α) of 0.390 and a diffusion coefficient (D) of D = 2.130 10⁻⁶ cm² s⁻¹. In addition, the ZnO/GCE demonstrated good repeatability and operational stability for uric acid detection. It also showed negligible interference from common biological species such as glucose and ascorbic acid. Overall, these results indicate that ZnO nanostructures on GCE represent a promising candidate material for electrochemical sensing of uric acid and potentially other analytes.